BFG Quality????

[Marauderjack]

I, like a bunch of others, am about 8000 miles into my second set of rears....fronts are still fine?? :confused:

I checked the middle tread on the rears today and much to my amazement....ONE IS WORN MUCH WORSE THAN THE OTHER!!! :mad2:

I have been checking pressure every week or so and wonder if BFG has merely had some KNOWN quality issues with these rear tires and sold them to Ford for our Marauders just to get rid of them?? :confused: It is very apparent that my two replacements are vastly different from a wear point of view.....and how come the fronts still look new and will probably outlast the rears 4 to 1????? :confused:

Would one side on the rear wear faster than the other?? If so which one would and I'll tell ya which is which. :rolleyes:

BTW....This car has plenty of power but it WILL NOT SPIN THE TIRES FROM A STAND STILL AND I HAVE NEVER HEARD A "CHIRP" AT THE 1-2 SHIFT!!! :(

Ideas??

I personally think BFG is getting rid of "Off Spec" tires by selling them to us!! :censor:

Marauderjack :cool4:

[drobin]

I contacted BFG awhile back and all I received was BS and denied having a potential problem with this tire. Let's face it, they don't intend to admit having a problem and will continue to deny receiving complaints from un-happy consumers. If enough complain, they may step up and do something for us....


drobin
"Donald"

[RF Overlord]

Let's face facts...NO major corporation will EVER admit anything is EVER wrong, EVER. The potential for litigation is just too great.

Especially since the Firestone/Explorer fiasco, I would have been mighty surprised if BFG acknowledged any tire problems, although I don't believe they are knowingly pawning off defective tires on us...Goodyear, yes.

[martyo]

I contacted BFG awhile back and all I received was BS and denied having a potential problem with this tire. Let's face it, they don't intend to admit having a problem and will continue to deny receiving complaints from un-happy consumers. If enough complain, they may step up and do something for us....


drobin
"Donald"

On a tire that was almost purpose built just for our cars??? Don't hold your breath....

[Marauderman]

BTW....This car has plenty of power but it WILL NOT SPIN THE TIRES FROM A STAND STILL AND I HAVE NEVER HEARD A "CHIRP" AT THE 1-2 SHIFT!!! :(

Marauderjack :cool4:

....If you would ever slow down long enough to tell me when your in town, like I have asked you, you can drive #7 and hear all the chirps you want....Tom

[Marc]

I just put my snow tires on for the year and took a good look at my new (just put on in July) tires. No noticable wear on the front, but uneven center wear on the rears. Same problem as the OEM's.

Honestly, what can we do? No one else makes the size. I'll try to reduce tire pressure when I put them back on and see if that helps, but BFG will not do anything in this instance.

[Marauderman]

I, like a bunch of others, am about 8000 miles into my second set of rears....fronts are still fine?? :confused:

I checked the middle tread on the rears today and much to my amazement....ONE IS WORN MUCH WORSE THAN THE OTHER!!! :mad2:

I have been checking pressure every week or so and wonder if BFG has merely had some KNOWN quality issues with these rear tires and sold them to Ford for our Marauders just to get rid of them?? :confused: It is very apparent that my two replacements are vastly different from a wear point of view.....and how come the fronts still look new and will probably outlast the rears 4 to 1????? :confused:

Marauderjack :cool4:
..I finally realized from the guys in Alt last week that it's the air thingy--keep more air in --just do the opposite from we knew as the old rule of thumb-....Tom

[TripleTransAm]

..I finally realized from the guys in Alt last week that it's the air thingy--keep more air in --just do the opposite from we knew as the old rule of thumb-....Tom


Very interesting... what was the reasoning for this? I'm in discussion with my own dealer over this, and would very much like to get some feedback on this approach.

[TAF]

I've got a new set of the BFGoodrich KDW NEW tread on the way. Going with OEM size on the fronts and 255/55/18 on the rears. I like the looks of these MUCH better and I'm hoping to get much more wear out of these over the OEM - KDWS. These will go on after I burn through my current rears next Saturday @ SSHS4...and I'll be glad to report/take pics on what I and others think of them. (Why do you think the OEMs are only going for $80 on TireRack??!! These are $130)

Click HERE to learn more about the NEW BFG's (http://www.tirerack.com/tires/tires.jsp?tireMake=BFGoodrich&tireModel=g-Force+T%2FA+KDW+2&vehicleSearch=false&partnum=555VR8GFTAKDW2RF&fromCompare1=yes)

http://www.tirerack.com/images/tires/bfg/bfg_gforce_ta_kdw2_ci2_l.jpght tp://www.tirerack.com/images/tires/bfg/bfg_gforce_ta_kdw2_ci1_l.jpght tp://www.tirerack.com/images/tires/bfg/bfg_gforce_ta_kdw2_ci3_l.jpg

[Bigdogjim]

At 22,000 miles my tires are wearing like iron.
Thanks to carfixer I corrected a problem with the fronts:) and reports no other issues.

Go figure?

[TAF]

Another sidebar:

On one of my trips up through the lovely state of South Carolina about 5 months ago, I decided to stop in and talk to someone at the Michelin/BFG N.A. HQs about what we could do about getting some BFG Drag Radials to fit Legal Knevil (you never know who you might get just walking in the door and asking)...well, I got Todd Brant, who runs the Racing Division. I got him to walk out and look at the BFGs on my car...his comment..."Those are snow-tires...not high performance tires." He told me about the new tread design, explained why I'd want to do those...and now the opportunity has presented itself.

As for the BFG Drag Radials...there was no current product or interest in making any that would fit our parameters...so we went with the Nittos.

BTW...yes Logan...I did by these through TireRack and I did get there through the banner here. :up:

[duhtroll]

I have a set of the KDWs as well, but they won't go on until at least next summer. I have not worn through my first set of OEMs yet. I use the winter wheels/tires and only have about 14K on my oriignal set of BFGs.

I'm expecting a bit harder ride from the new ones but better dry traction and better wear.

-A

[jstevens]

Instructions to chirp tires: install 4.10's

Instructions to spin a lot: install s/c

[TripleTransAm]

his comment..."Those are snow-tires...not high performance tires."


He obviously hasn't driven on any such tires...

Knowing full well the precarious grip I'd have on a snow-covered (but previously plowed) road surface, I *very* carefully attempted to execute a U-turn at what must have been no more than 2 or 3 mph last January. I gracefully drifted right into a snow bank...
(no damage, wasn't going fast enough...)
If it wasn't for the traction control, I'd have never made it back up the slight incline of my driveway.

I've driven many many winters with my last RWD winter vehicle (1985 Parisienne, equipped with 225mm-wide all seasons up front and 225mm-wide winter tires in back) and I can assure you the KDWS are useless in the slightest snow accumulation.

I really don't know what possesses people to make comments like that...
:shake:

[jgc61sr2002]

I, like a bunch of others, am about 8000 miles into my second set of rears....fronts are still fine?? :confused:

I checked the middle tread on the rears today and much to my amazement....ONE IS WORN MUCH WORSE THAN THE OTHER!!! :mad2:

I have been checking pressure every week or so and wonder if BFG has merely had some KNOWN quality issues with these rear tires and sold them to Ford for our Marauders just to get rid of them?? :confused: It is very apparent that my two replacements are vastly different from a wear point of view.....and how come the fronts still look new and will probably outlast the rears 4 to 1????? :confused:

Would one side on the rear wear faster than the other?? If so which one would and I'll tell ya which is which. :rolleyes:

BTW....This car has plenty of power but it WILL NOT SPIN THE TIRES FROM A STAND STILL AND I HAVE NEVER HEARD A "CHIRP" AT THE 1-2 SHIFT!!! :(

Ideas??

I personally think BFG is getting rid of "Off Spec" tires by selling them to us!! :censor:

Marauderjack :cool4:



IMO Under normal acceleration the power is applied to one rear tire and that is causing the additional wear. The posi only kicks in when one wheel starts to spin.

[FiveO]

Just received a new set of OEM BFG's....the old or current style.

$80 each.

Hoping I can burn 'em down at SSHS4 next weekend :) 1 day at the track...1 set of tires. Not bad!

[SergntMac]

Hey, y'all...I got a set of (2) OEM rear BFGs for sale, good condition, 2K miles...125 bucks buys both with UPS shipping to your front door. Drop me a note at SergntMac@aol.com Meanwhile, some notes to keep in mind?

BFGs are known to be a quiet tire, they slip a lot before you hear the squeal.

When the MM was scheduled for production, there were no tires in 18" that would support the MM's gross weight or speed rating, and they were a new development for this car. Early versions may suffer from inappropriate tread design, or, composition, welcome to the world of beta testing. I recall that the tires on my first MM, a May '02 build, were not designated as KDWS on the sidewall, just "all season radial." I think it's safe to say that there are a few "versions" of the BFG for our MMs.

Today, there are dozens of selections in our base tire group, but not in our specific size, so, dare to be different next time around? There a lots of great tires from Pirelli, Kuhmo, Yokohama, Dunlop, Falken and others, and you can change sizes with no loss to OEM rake, or, complications with ABS/traction control, with just a little attention to the math. You can even run the same size on all four corners, and maintain your rake by adjusting the rear air suspension. Shop around?

Traction-Loc (POSI) doesn't function until it detects slip, so, if you're just crusing around town, only your right rear tire is pushing. Rotate side to side every 5K or so, you'll get much more even wear.

Tire pressure is critical, and trusty formulas are failing us today. I run 36 PSI at all four corners, and I'll step it up to 40 PSI for OTR driving. I know this backwards from conventional thinking, but it's working for me, go figure.

Yes, 20K miles sounds like a short life, but keep this in mind too? Traction in rain and snow is dependent on tread depth, and critical in emergency conditions, i.e. panic stops and avoiding a collision. Chances are that your opportinity for a collision is greater in the rain and snow than not, and once you cross the half-worn-out point, traction, grip and control just get progressively worse. I'm happy to get 20K from any tire on any car, and once I cross that mileage mark, I'll start shopping, because I don't want to find out the hard way that my ability to maintain control is dependent on tires that are more than half worn out...Think about it?

[Marauderjack]

Thanks Mac and all who have responded!! :D

The tire with the most wear was on the right side and I suspected it would be the "Drive Wheel" under most casual conditions plus "climbing the highway crown" more than the left?? :confused: I moved it to the left side and will see how the better one wears on the right side.

Marauderman....I seldom stay around Charlotte....I had 20+ years of the ridiculous traffic around there and try to program my travels to go up I-77 at 10:00 AM or 2:30 PM even though that can get testy at times...I had a punk point a 9MM at me on the Woodlawn ramp several years ago...just for kicks!! :mad2: Email me your phone # again as I dropped the cell phone I had it programmed into......in the river!!!! :mad2: I'll call ya when I'm passing through. Thanks for the offer to drive your BEAST!! I plan to talk to Dennis about the ProCharger after he evaluates it!! :banana2:

TAF....I like the looks of the 2 series BFG's and may get a complete set next time....If I do I will have 2 brand new OEM rears for sale if anyone is interested??

Regardless of poor tire wear and some of the problems associated with our cars, I have to say it is still the BEST NEW CAR I HAVE EVER BOUGHT!!!! :beer:

Kinda sad FMC is so DUMB!!! :(

Marauderjack :cool4:

[MSR7878]

IMO
The reason the right rear tire wears more is because in the USA we drive on the right side of the road, therefore when you make a normal right turn it is much sharper that a normal left turn therefore the difference in speed between the right and left tire is much greater so the right tire 'spins' a little because we have a limited slip diff which engages at a certain difference in speed plus the application of torque. If no wheel is spinning (slipping) equal power is applied to both sides.
just my theory

[Marauderjack]

MSR7878....

That makes perfect sense...Maybe my better tire will last about as long as the one on the left then?? :confused:

Marauderjack :beer:

[mrjones]

[QUOTE=TAF]I've got a new set of the BFGoodrich KDW NEW tread on the way. Going with OEM size on the fronts and 255/55/18 on the rears. I like the looks of these MUCH better

Please let us know how you are liking the new tires when you get them on. I'm planning on getting either those, or a set of the Kumho's in the 255/55 size all the way around. I really like the tread pattern on the new BFG's though. I think I can get the Kumhos through one of my suppliers pretty cheap. It may come down to that.

[teamrope]

I'm at 22.5K and the original pasenger side is ok. (I had a blowout in Barstow on the BOA tour)

I'm running around 35 PSI cold, and the center is wearing a little faster than the sides, but not down to the wear bars yet.

[TAF]

Please let us know how you are liking the new tires when you get them on. I'm planning on getting either those, or a set of the Kumho's in the 255/55 size all the way around. I really like the tread pattern on the new BFG's though. I think I can get the Kumhos through one of my suppliers pretty cheap. It may come down to that.
I will...but, keep in mind I won't get these mounted till after SSHS4 (Nov.8th)...but I'll have lots of folks drive my car and give you feedback here. :up:

[mtnh]

As far as I know, the limited slip diff in our cars provides full time power to both wheels. That idea of sensing traction loss and locking the rear diff is what GM's idea of limited slip had become when I ordered a 1988 K5 Blazer. What a pile of crap that was. You'd hear the ratcheting noises and you could feel the mechanical lock-up, which would stay on for some time after activation, possibly due to torque holding pawls that don't let go until you let off the gas or hit the brakes. When that would happen, the truck did not want to turn, very tight entering turns. The marauder is nothing like that. The tip off on the real limited slip differential is the need to add friction modifier to the gear oil, which we do. That is for the clutches in a real limited slip differential. Also note that if you get a flat tire and place the spare into service, the two rear wheels will activate constant slip in the rear diff clutches due to dissimilar rotating, and a prolonged drive like that would cook your clutches and you then get an open diff situation.


I think that our resident nuke has it right about tire scrub on tight right hand turns. ( I really looked up to you guys from down in MCC on the boomers)

The center tread wear is due to centrifugal expansion of the tire, at high speeds. That is the only real working contact patch when cruising down the highway. Too little air in the tires makes it easier to expand, so that is why you pump them up harder, so they stay flatter by the sidewalls pulling the tread tighter across the contact patch area. Both my MM and my LS do this to rear tires, but the effect is reduced by running 36-38 psi.

Mike FTB1 (SS) 1974-1980

[Marauderjack]

Well....

I just pulled out of the gas station (hard right) and actually heard the RR tire slipping!! I normally wouldn't hear it but the radio was turned down since I had been on the phone.

I believe the RR "scrubbing" on right turns is the answer!! :o

I still don't understand how the fronts can last so long and most of us replace the rears in under 20K miles?? My fronts will probably go 50K plus?? :confused:

If I didn't have the anti-lock brakes and traction control to contend with I'd run the fronts all around!! Wonder what the speedo error would be??

Marauderjack :cool:

[michburt]

Hey Guys,

I currently own a 02 Honda VTX 1800R. It's a motorcycle to those that think that looks Greek. A Cruiser. Honda recommended to inflate the tires to 36psi. After awhile comparing notes on the VTXOwners Board is was discovered that tire wear was an issue. It was soon discovered that ramping the pressure up to the max that was stamped on the tire prevented such wear. I have put the air pressure up to the max on the Marauder and at 11,000 miles I have note no abnormal tire wear.

Mike:party:

[SergntMac]

If I didn't have the anti-lock brakes and traction control to contend with I'd run the fronts all around!
I know for sure that same size all four corners is not a complication for the ABS system, I've tested it myself for over 500 miles, take it to the bank.

I can't say the same for the Traction Control, I don't have it. It would be nice to have two MM owners with Traction Control to hook up, swap tires and test the Traction Control as well, and put this question to sleep once and for all. I'd also like to know if Traction Control operates off it's own sensor (meaning MMs with TC have two wheels sensors) or share the single sensor feeding the ABS. If this is so, sharing the same sensor with same size on all four corners would not complicate Traction Contron either.

How about it, members, anyone game?

[TripleTransAm]

I believe we've already had 300B (or 2004 A) members who have had their tires swapped during 'rotation' and have had the TC freak on them. I wonder if having 4 same sizes all around would do the same... I don't know what the computer's threshold is before thinking the car is majorly slipping.

[chicago_cop]

I, like a bunch of others, am about 8000 miles into my second set of rears....fronts are still fine?? :confused:

I checked the middle tread on the rears today and much to my amazement....ONE IS WORN MUCH WORSE THAN THE OTHER!!! :mad2:

I have been checking pressure every week or so and wonder if BFG has merely had some KNOWN quality issues with these rear tires and sold them to Ford for our Marauders just to get rid of them?? :confused: It is very apparent that my two replacements are vastly different from a wear point of view.....and how come the fronts still look new and will probably outlast the rears 4 to 1????? :confused:

Would one side on the rear wear faster than the other?? If so which one would and I'll tell ya which is which. :rolleyes:


BTW....This car has plenty of power but it WILL NOT SPIN THE TIRES FROM A STAND STILL AND I HAVE NEVER HEARD A "CHIRP" AT THE 1-2 SHIFT!!! :(

Ideas??

I personally think BFG is getting rid of "Off Spec" tires by selling them to us!! :censor:

Marauderjack :cool4:

I have 12K mi on mine, and notice not difference back to front. They look almost new. You may threaten a class action suit, but if the other cars are moded they can say you spun the tires.
chicago_cop .........................

[RF Overlord]

"Majorly slipping"? /Steve, that's not well English...even for someone who speaks it as a third language... :P

[Bradley G]

Traction control uses the same wheel(speed) sensor as the Antilock braking system.I will test T/C with another
I know for sure that same size all four corners is not a complication for the ABS system, I've tested it myself for over 500 miles, take it to the bank.

I can't say the same for the Traction Control, I don't have it. It would be nice to have two MM owners with Traction Control to hook up, swap tires and test the Traction Control as well, and put this question to sleep once and for all. I'd also like to know if Traction Control operates off it's own sensor (meaning MMs with TC have two wheels sensors) or share the single sensor feeding the ABS. If this is so, sharing the same sensor with same size on all four corners would not complicate Traction Contron either.

How about it, members, anyone game?

[SergntMac]

I believe we've already had 300B (or 2004 A) members who have had their tires swapped during 'rotation' and have had the TC freak on them. I wonder if having 4 same sizes all around would do the same... I don't know what the computer's threshold is before thinking the car is majorly slipping.
Swapping, or, rotating front to rear results in size differences greater than the 1.05" tolerance, alarms will sound. All four same size, no matter the size will not affect ABS, prpbably will not affect TC if they share the one sensor at the wheel.

[TripleTransAm]

"Majorly slipping"? /Steve, that's not well English...even for someone who speaks it as a third language... :P

Be thankful I didn't ask any question in Fortran...

[TripleTransAm]

Swapping, or, rotating front to rear results in size differences greater than the 1.05" tolerance, alarms will sound. All four same size, no matter the size will not affect ABS, prpbably will not affect TC if they share the one sensor at the wheel.


That would be VERY interesting, if the TC would not freak out if all four tires were of the same size... screw the rake, if I could get away with 4 winter tires of the same size, I wouldn't be worrying about no special Arctic Alpin winter tire package!!!

I'm dying to get confirmation of this being the case... (and after all the trouble I went to just to pick up a lightly used set of MM-package winter tires and wheels... :mad2: )

[RF Overlord]

Be thankful I didn't ask any question in Fortran...

I've got a nice IBM System/360 I'll sell you, cheap...one owner...only used on Sundays to calculate the square root of Pi... :type: :arcade:

[TripleTransAm]

I've got a nice IBM System/360 I'll sell you, cheap...one owner...only used on Sundays to calculate the square root of Pi... :type: :arcade:

No thanks, I already got one, powering my doorbell's operating system. And when I don't have company for a while, I keep it busy by making it divide stuff by zero...

[EbonyMarauder03]

I just got a snow tire package from the TireRack. I did this because at 18,000 miles my back tires are done. The center is down to 1 or 2/32's over the wear bar. Since I live in Pa. this won't do for the winter. I have a new set of OEM tires waiting for the spring. It looks like I did well in the wear department.

[hitchhiker]

I've got a nice IBM System/360 I'll sell you, cheap...one owner...only used on Sundays to calculate the square root of Pi... :type: :arcade:

No problem, I do FORTRAN! :P

[ultravorx]

I've got a new set of the BFGoodrich KDW NEW tread on the way. Going with OEM size on the fronts and 255/55/18 on the rears. I like the looks of these MUCH better and I'm hoping to get much more wear out of these over the OEM - KDWS. These will go on after I burn through my current rears next Saturday @ SSHS4...and I'll be glad to report/take pics on what I and others think of them. (Why do you think the OEMs are only going for $80 on TireRack??!! These are $130)

Click HERE to learn more about the NEW BFG's (http://www.tirerack.com/tires/tires.jsp?tireMake=BFGoodrich&tireModel=g-Force+T%2FA+KDW+2&vehicleSearch=false&partnum=555VR8GFTAKDW2RF&fromCompare1=yes)

http://www.tirerack.com/images/tires/bfg/bfg_gforce_ta_kdw2_ci2_l.jpght tp://www.tirerack.com/images/tires/bfg/bfg_gforce_ta_kdw2_ci1_l.jpght tp://www.tirerack.com/images/tires/bfg/bfg_gforce_ta_kdw2_ci3_l.jpg
These are the exact same tires im geting in the spring, but im doing the 255/55/18 on all 4 corners.
Frank

[Silver03MM]

15k and rotated the rear and front tired but yeah the right rear tire wore so much more than the left, I am going to need new rear tires.

[Krytin]

15k and rotated the rear and front tired but yeah the right rear tire wore so much more than the left, I am going to need new rear tires.
Could be the clutches in your rear are shot - mine were toast @ 22k miles!

[jgc61sr2002]

Could be the clutches in your rear are shot - mine were toast @ 22k miles!


Paul - The posi/limited slip only kicks in when one tire loses traction. Under normal operation the power is applied to only one wheel causing the excessive ware to the right rear tire.

[Krytin]

Main > Auto > Under the Hood

How Differentials Work
by Karim Nice
On Thin Ice
The open differential always applies the same amount of torque to each wheel. There are two factors that determine how much torque can be applied to the wheels: equipment and traction. In dry conditions, when there is plenty of traction, the amount of torque applied to the wheels is limited by the engine and gearing; in a low traction situation, such as when driving on ice, the amount of torque is limited to the greatest amount that will not cause a wheel to slip under those conditions. So, even though a car may be able to produce more torque, there needs to be enough traction to transmit that torque to the ground. If you give the car more gas after the wheels start to slip, the wheels will just spin faster.

If you've ever driven on ice, you may know of a trick that makes acceleration easier: If you start out in second gear, or even third gear, instead of first, because of the gearing in the transmission you will have less torque available to the wheels. This will make it easier to accelerate without spinning the wheels.

Now what happens if one of the drive wheels has good traction, and the other one is on ice? This is where the problem with open differentials comes in.

Remember that the open differential always applies the same torque to both wheels, and the maximum amount of torque is limited to the greatest amount that will not make the wheels slip. It doesn't take much torque to make a tire slip on ice. And when the wheel with good traction is only getting the very small amount of torque that can be applied to the wheel with less traction, your car isn't going to move very much.

Off Road
Another time open differentials might get you into trouble is when you are driving off-road. If you have a four-wheel drive truck, or an SUV, with an open differential on both the front and the back, you could get stuck. Now, remember -- as we mentioned on the previous page, the open differential always applies the same torque to both wheels. If one of the front tires and one of the back tires comes off the ground, they will just spin helplessly in the air, and you won't be able to move at all.

The solution to these problems is the limited slip differential (LSD), sometimes called positraction. Limited slip differentials use various mechanisms to allow normal differential action when going around turns. When a wheel slips, they allow more torque to be transferred to the non-slipping wheel.

The next few sections will detail some of the different types of limited slip differentials, including the clutch-type LSD, the viscous coupling, locking differential and Torsen differential.


Clutch-Type Limited Slip
The clutch-type LSD is probably the most common version of the limited slip differential.

This type of LSD has all of the same components as an open differential, but it adds a spring pack and a set of clutches. Some of these have a cone clutch that is just like the synchronizers in a manual transmission.

The spring pack pushes the side gears against the clutches, which are attached to the cage. Both side gears spin with the cage when both wheels are moving at the same speed, and the clutches aren't really needed -- the only time the clutches step in is when something happens to make one wheel spin faster than the other, as in a turn. The clutches fight this behavior, wanting both wheels to go the same speed. If one wheel wants to spin faster than the other, it must first overpower the clutch. The stiffness of the springs combined with the friction of the clutch determine how much torque it takes to overpower it.

Getting back to the situation in which one drive wheel is on the ice and the other one has good traction: With this limited slip differential, even though the wheel on the ice is not able to transmit much torque to the ground, the other wheel will still get the torque it needs to move. The torque supplied to the wheel not on the ice is equal to the amount of torque it takes to overpower the clutches. The result is that you can move forward, although still not with the full power of your car.

The above is from "howstuffworks" website.
From above:
"Both side gears spin with the cage when both wheels are moving at the same speed, and the clutches aren't really needed -- the only time the clutches step in is when something happens to make one wheel spin faster than the other, as in a turn. The clutches fight this behavior, wanting both wheels to go the same speed. If one wheel wants to spin faster than the other, it must first overpower the clutch. The stiffness of the springs combined with the friction of the clutch determine how much torque it takes to overpower it."

When the clutches burn out - the posi turns into an open diff & the first wheel to loose traction will be the one that spins/burns rubber. Note that RWD open diffs favor torque transmission to the right rear wheel in forward & left rear wheel in reverse - try it and see!
A burned out posi will wear the right rear tire out faster if do all your "launches" in forward (not that anyone is doing "reverse" burnouts).

[Paul T. Casey]

I must have got a good set last time. I am up over 40K on the fronts and probably 20-25K on the rears. It will sonn be time for a complete new set, but IMHO these are great numbers considering the way I drive. I guess I'm just lucky.

[JACook]

The posi/limited slip only kicks in when one tire loses traction. Under normal operation the power is applied to only one wheel causing the excessive ware to the right rear tire.Krytin is right on the mark.

All differentials, whether RWD or FWD, open or limited slip, Detroit Locker, Torsen or viscous, will always apply the same amount of torque to both drive wheels under normal traction conditions.

Your MM's right rear receives exactly the same drive torque as the left rear.
The differences only show up when traction is lost to one of the drive wheels.

Clutch-type limited slip units, like what's in the MM, keep both rear wheels locked together until the breakaway torque, AKA preload, is exceeded. This can cause some undesirable handling effects, particularly in FWD applications. They can also chatter, especially in units with lots of preload, and as they age, the breakaway torque value decreases.

Detroit Lockers use a ratchet mechanism in place of the clutches. The ratchet mechanism comes into play when there is a speed difference between the axles. No breakaway torque required. These can be noisy, though, so you normally will only find these in truck applications.

The Torsen is a "torque biasing" differential, that uses no ratchets or clutches, but rather a combination of spur and worm gears. Different designs are available with different bias ratios, ranging from around 2:1 to 3.5:1. The bias ratio describes the torque that will be available to the non-spinning wheel. Torsens are very smooth in their torque transfer, but can be a bit fragile. They're better suited to road course duty than to drag strips. Great unit for FWD.

A viscous LSD uses a stack of perforated discs in a bath of a special silicone fluid that effectively goes solid when it's shear limit has been exceeded. The amount of allowable shear is determined by the properties of the fluid, and the layout of the holes or slots in the discs. Viscous LSDs are more abrupt than a Torsen, but are smoother than clutch or locker types. Like the Torsen, VLSDs are better suited to road courses than to drag strips. And like the Torsen, VLSDs are well suited to FWD applications.

Other less common differential types are the ARB Air Locker, Eaton E-Locker, and Gerotor designs. The Air Locker and E-Locker are both essentially open differentials, with a mechanism that allows the differential to be locked by pushing a button. When locked, they behave just like a spool.

The Gerotor design uses the difference in wheel speed to operate a gerotor style oil pump, and then uses the pressure from the pump to actuate clutches, effectively locking the drive wheels together. All the advantages of a clutch-style LSD, but without the preload, and the aging problems. The downside is complexity, and the need for a significant amount of slip to be present before the clutch pack locks up. This gives a rather nonlinear application curve that can upset handling.

Probably more than anyone really wanted to know... :-)

[SergntMac]

Krytin is right on the mark.
Your MM's right rear receives exactly the same drive torque as the left rear.
The differences only show up when traction is lost to one of the drive wheels.
No, he's not "right on the mark." Krytin's CC from "How Things Work" is a simplistic interpretation of what's going on, yes, but it left me feeling like I was reading software manual written by someone who doesn't have a good grasp of what they are writing about, and just because it's posted on the Internet doesn't make it correct.

HSW has been wrong before, and it's wrong here when it explains that "The open differential always applies the same amount of torque to each wheel." This a generalization of theory, and impractical here. "Open" vs. "locked" means that only one wheel is getting power until it is detected that traction has been lost. Otherwise, the differential would be a full time "locker," would it not? Moreover, both of you have missed the point of this question in this thread.

The point here is tire wear, not differential designs and how they work on paper. The gentleman noticed more wear to his right rear tire than his left, and asked why. If you redirect your focus to the relationship between the tire and the ground, the suggestion is slip between the two surfaces, tire and ground, as just one of the explanations offered.

The right rear tire slips on the ground more than the left, thus it will wear out sooner than the right, and this has been the rationale for tire rotation since the dawn of inflated tires. Limited slip/posi-traction/locker devices reduce the loss of traction by transfering (enhancing) power to the left rear, however, not until slip is detected, or unusual power is applied, i.e. WOT.

However small this window, however brief this slip, the right rear tire carries the burder of traction over the left rea tire, and it slips on the ground more than the left rear tire, even when properly inflated and driven under normal circumstances.

[MSR7878]

Not trying to cause trouble but I still think in a tight turn, like a 90 degree right, the DIFFERENCE IN SPEED between the left and right is enough to cause the right rear to spin. To put it in terms like the explanations of diffs, the left rear goes much further than the right rear in the same amount of time, thus it spins faster, just like it would if it slipped, so the clutches engage, or however you want to think of it, but basically the diff tries to make them spin at the same rate so the inside one spins some

[JACook]

The point here is tire wear, not differential designs and how they work on paper. The gentleman noticed more wear to his right rear tire than his left, and asked why. If you redirect your focus to the relationship between the tire and the ground, the suggestion is slip between the two surfaces, tire and ground, as just one of the explanations offered.

The right rear tire slips on the ground more than the left, thus it will wear out sooner than the right, and this has been the rationale for tire rotation since the dawn of inflated tires. Limited slip/posi-traction/locker devices reduce the loss of traction by transfering (enhancing) power to the left rear, however, not until slip is detected, or unusual power is applied, i.e. WOT.

However small this window, however brief this slip, the right rear tire carries the burder of traction over the left rea tire, and it slips on the ground more than the left rear tire, even when properly inflated and driven under normal circumstances.OK, I'm not relying on HSW or "on paper" knowlege here. Personally built (and broke) many a rearend over the years.

Yes, the right rear slips more, and that's why it wears more, but your understanding of why this is, and of how a LSD works is flawed, unless we're talking about a Locker, Viscous, or Gerotor design. You can not lump these all together, as they are all very different approaches to the problem, and operate very differently. My post was an effort to explain the differences, and in doing so, reduce some confusion about the LSD used in the MM.

The MM uses a clutch-type LSD, and in these, there is NO delay when a wheel loses grip. In a clutch-type LSD, both wheels are locked together until the wheels need to turn at different speeds. When this happens, the clutch pack's breakaway torque value is exceeded, and the wheels are (grudgingly) allowed to spin at different rates.

It is in this understanding of the MM rearend that you will find the answer to why one rear tire wears sooner than the other. There are two factors at work here. First, because the clutch pack is only locked until the breakaway torque value is exceeded, the LSD cannot always deliver the driveline's full torque to both wheels. As in any live-axle RWDer, the twist of the driveline will attempt to lighten the right-rear tire, reducing it's traction. It's why live-axle RWD cars with open rears tend to spin the right rear (while IRS cars typically do not). The clutch-type LSD in the MM can keep some power diverted to the left-rear, but only to a point. What that point is, is determined by the surface area and spring preload in the clutch pack. With a clutch-type or Torsen LSD, you will always get some right-rear spin. Only locking-type differentials are able to route 100% of the driveline torque to a single wheel.

The other factor is the breakaway torque itself. I don't recall who it was, but I recall in an earlier post, one person suggested the right-rear tire wears faster because we drive on the right side of the road. This is not far from the truth, though it is not the full story.

Because the MM's rear wheels are effectively locked together by the clutch pack, the LSD will always fight speed differences between the rear wheels. When turning, the LSD will initially try to scrub the rear tires, and in the case of a right turn, the combination of weight transfer and the aforementioned driveline twist conspire to make the right-rear give up more slip than the left-rear. Acceleration out of the turn amplifies these effects. In left turns, the right-rear is disproportionately loaded vs the left-rear, and the turn radius is greater, lessening the scrub forces vs a right turn. Even an open-differential RWDer won't spin the right-rear coming off a left turn.

Again, I don't disagree that the tires wear at different rates, it's the lack of understanding of how clutch-type LSDs work that prompted me to post.

[MSR7878]

JACook,
So, by your explanation if I lifted my car off the ground and spun one of the tires by hand the other one would turn the SAME? way?

[JACook]

JACook,
So, by your explanation if I lifted my car off the ground and spun one of the tires by hand the other one would turn the SAME? way?
Absolutely. Provided that the parking brake is off, and the transmission is out of "park". With the trans in park, neither wheel will want to turn at all, unless you're strong, and/or your LSD is worn out. Once you overcome the LSD, still with the trans in park, the opposite wheel will turn in the opposite direction, same as an open diff. The amount of force it takes to make that happen is the breakaway torque, or preload, that I referred to.

[RF Overlord]

JACook,
So, by your explanation if I lifted my car off the ground and spun one of the tires by hand the other one would turn the SAME? way?

Yes. When my buddy and I used to build (well, more like cobble-up) muscle cars for friends, that was one of the ways to find a "posi" in a junkyard...spin one wheel and see which way the other goes...if it was the same, it was a posi...

[SergntMac]

OK, I'm not relying on HSW or "on paper" knowlege here. Personally built (and broke) many a rearend over the years.
Likewise...And if I wanted to be a geekysmartazz here, I could craft a reply that turns your "been here, did this" remark against you. However, I am not like this, and do not like it when I see others here do this.

Every component of this mystical (yet simple too) MM has been (and will continue to be) examined inside and out, upside and down. It's a side effect of us all dealing with the exact same hardware and it's associated issues, but dealing with it from many different perspectives, such as age, location, driving habits, professional background, education, expertise, mods, and even including how we talk about it all in this one-dimensional medium connecting us. We all know what we mean to say, and to ask, and we're usually correct in our efforts, but we do screw it up in the sharing.

Yes, the right rear slips more, and that's why it wears more, but your understanding of why this is, and of how a LSD works is flawed, unless we're talking about a Locker, Viscous, or Gerotor design. You can not lump these all together, as they are all very different approaches to the problem, and operate very differently. My post was an effort to explain the differences, and in doing so, reduce some confusion about the LSD used in the MM...Again, I don't disagree that the tires wear at different rates, it's the lack of understanding of how clutch-type LSDs work that prompted me to post.
That's the rub here. One can be techincally correct in the main, and end up being of no help whatsoever because the explanation was technically over-explained, and over the top.

I disagree...IMHO yes, this type of 411 can be lumped together, and it's probably wise to make sure that it does get lumped together when the hardware is identical from car to car/owner to owner, and your goal is to direct someone's attention towards a possible problem, or, suggest a reasonable explanation in reply to their querry, rather than explain how stuff works.

We're not taking an exam here, there are no grades at the end of a semester. It's more about the people who own these endearing automobiles than the MM specifically. The car is the same among us, but the owners asking about them, ask from a wide variety of backgrounds, experience, and communication skills. IMHO...Scale/tailor your reply to the level of the inquiry and you'll be helpful, and earn the respect your personal experience deserves. Being "specifically vague" in reply can deliver your message better than a post that explains precisely how something is so, and how you know that it is so. OTOH, if "precisely" is the question, fire away?

Please go back and read from the first post here? The question was simple, and several simple explanations followed. The fact that the right rear tire slips more than the other three (in it's friction relationship to the ground under normal circumstances) is a fact. It's also one of many possible legit answers to the original query.

Whether you, or, I agree/disagree on exactly how/why the MM's differential functions only distracts from that query here, and we can hammer out agreement over that while we hammer down beers at MV-III, eh?

BTW...Thanks for sharing your experience and knowledge, I'm sure you earned it the hard way too.

[MSR7878]

So I was totally incorrect in thinking that difference in wheel speed caused the LSD to 'engage'?! I apoligize to anyone I may have mislead. The explanation provided here on our diffs really dissappoints me, I thought that the diff was basically open until a difference in speed, lef to right, occured and then the clutches/pawls/whatever actually mechanically stopped the difference by preventing the planetary (I think) gears from spinning

Thanks for clearing this up, however I can't help but be dissappointed, I liked the way I thought it worked better :D

[Marauderjack]

Next we will engineer and build a "Marauder Space Shuttle"?? :confused: :rolleyes: Hmmmm.....Will it have limited slip or a locker??

Thanks for all the replys and good 411...... :banana:

Marauderjack :beer:

[warren]

I've got a new set of the BFGoodrich KDW NEW tread on the way. Going with OEM size on the fronts and 255/55/18 on the rears. I like the looks of these MUCH better and I'm hoping to get much more wear out of these over the OEM - KDWS. These will go on after I burn through my current rears next Saturday @ SSHS4...and I'll be glad to report/take pics on what I and others think of them. (Why do you think the OEMs are only going for $80 on TireRack??!! These are $130)

Click HERE to learn more about the NEW BFG's (http://www.tirerack.com/tires/tires.jsp?tireMake=BFGoodrich&tireModel=g-Force+T%2FA+KDW+2&vehicleSearch=false&partnum=555VR8GFTAKDW2RF&fromCompare1=yes)

http://www.tirerack.com/images/tires/bfg/bfg_gforce_ta_kdw2_ci2_l.jpght tp://www.tirerack.com/images/tires/bfg/bfg_gforce_ta_kdw2_ci1_l.jpght tp://www.tirerack.com/images/tires/bfg/bfg_gforce_ta_kdw2_ci3_l.jpg
Taf is right these are much better. The correct No. is KDW2
They are in the Ultra Hi Perf. Summer group.


KDW2--Rank-2nd, Dry Trac.-9.5, Wet Trac.-8.8, Hydro Resis.-8.7, Croner-9.2, Steering-9.3

KDW--RANK-12th, Dry Trac.-9.0, Wet Trac.-8.1, Hydro Resis.-7.9
Corner-8.8, Steering-8.8

Below is the Ultra Hi Perf. All-Season Group
KDWS--Rank 8, Dry Trac-8.7, Wet Trac.-8.2, Hydro Resis.-8.1
Snow Trac.-6.2, Corner-8.4, Steering-8.3
These are the OEM tires that came with our MM's.

As you can see ( got facts from TireRack ) the KDW2's are the tops.
BFG did some real good re-design work on the G-Force tires.
The Firehawk SZ50 EP was Rank 1, however was lower in
Dry Trac, Corner, and Steering Response and these are things we
find more important.
Just for your info.

WarrenB

[JACook]

So I was totally incorrect in thinking that difference in wheel speed caused the LSD to 'engage'?! I apoligize to anyone I may have mislead. The explanation provided here on our diffs really dissappoints me, I thought that the diff was basically open until a difference in speed, lef to right, occured and then the clutches/pawls/whatever actually mechanically stopped the difference by preventing the planetary (I think) gears from spinning

Thanks for clearing this up, however I can't help but be dissappointed, I liked the way I thought it worked better :DWell, if you REALLY want it to work the way you thought, you could swap out the factory TractionLok unit for a Detroit Locker.
But be prepared to hear things out back you don't hear today... :-)

[AndyB]

IMO Under normal acceleration the power is applied to one rear tire and that is causing the additional wear. The posi only kicks in when one wheel starts to spin.

Can RR and LR be rotated to compensate for this, or are these uni-directional?

[Bradley G]

This can be done all tires are unidirectional. front to front only + rear to rear.
Bradley G
Can RR and LR be rotated to compensate for this, or are these uni-directional?

[Marauderjack]

My LR tire (formerly my RR tire) is wearing at about twice the rate of the RR (formerly my LR tire)....Confused?? :confused:

BTW....Tire Rack has our OEM rears on sale for $79.00 each.....must be because they are nowhere near as durable as the fronts!!!! :mad2:

Marauderjack :(

[TripleTransAm]

You guys must read my mind or something, with the timeliness of these threads.

With 2 days under my belt with these low mileage snow tires on the car, I'm seeing my fuel mileage increase by what seems like 10%. The mileage on my trip odometer is pretty much beyond where I'd expect to be sitting in the ditch with a totally empty tank, and I still have the needle sitting at just under 1/4. And with our snowfall of the past 24 hours, I've had to idle the car much longer in the driveway as I loaded up wife and kid and cleaned off the car, and was stuck in 30 minutes of stop/go traffic which usually doesn't happen on my other tankfuls.

Will report the results once I've had a few more tankfuls through the car. Hopefully the new BFGs in the spring will restore my mileage to what I was getting when the car was newer.