Turning off ABS

[David Morton]

(deleted by David Morton) Reason: MM03MOK doesn't like what I have to offer to this site. So long guys.

[metroplex]

My Vic also pulls to the right. I think it is a stuck piston. It happens whenever you go through a wet spot and the piston just gets slightly "seized". All the force ends up going to one piston instead of spreading out the load with 2 pistons.

[Marauderjack]

Our 1998 CV pulled hard to the right and when we got a new set of tires about 3 months ago....VOILA...no more pull??:confused:

I really don't understand it since the old tires weren't worn strangely and all were inflated properly!! Weird!!:argue:

Try switching your fronts from side to side and see what happens.....May be worth a try??;)

Marauderjack:D

[RoyLPita]

Is this pulling happening during braking? If it is, have the fron brakes checked out.

[David Morton]

(deleted by David Morton) Reason: MM03MOK doesn't like what I have to offer to this site. So long guys.

[CRUZTAKER]

I really don't understand it since the old tires weren't worn strangely and all were inflated properly!! Weird!!

An internal fault, IE. bad steel belt, will cause hidden drivability issues, shakes, wobbles, and pulls.

[metroplex]

On my Vic, you can definitely feel that its the brakes causing the pull.

[SergntMac]

Rut steer...Groves worn into the pavement over time tend to grab the tires funny, and pull either left or right, depending on your angle of attack to the road. With 245s on the front and 285s on the back, I get it all the time.

My worst experience ever, was just last month on a trip back from Auburn Indiana. I-80 feeds I-69, and this is a stretch of road with heavy truck traffic between Auburn and I-80. It looks like it hasn't been touched up in 20 years.

Moving about 80 MPH, all of a sudden, the whole car is floating around, like I'm losing tire pressure at all 4 corners and fast. Rubbery, very loose, and the more I tried to control it, the worse it got. I knew not to hit the brakes at all, so, I just coasted to the shoulder, and checked all four tires. Nothing...Just fine with 40 PSI...WTF?

Then I took a hard look at the pavement, and found my answer. When I put my foot over the lane I could see, I could feel the dip across the lane, and my tires are wider than my foot is long. Whew, back on the road, a little slower, and I was happy to see I-80 signs again.

[David Morton]

(deleted by David Morton) Reason: MM03MOK doesn't like what I have to offer to this site. So long guys.

[TripleTransAm]

I think the high negative camber the factory calls for is partly to alleviate the very condition you describe, rut steer. Can you supply us with the figures for your front-end alignment?

If the car is lowered, this will also induce bump steer because the toe angles will change differently as the wheel travels along its up/down arc. Either that or a slightly bent suspension arm (which essentially results in the same situation).

[SergntMac]

Hey SergntMac, are you running the lower negative camber specs some of us are running? I think the high negative camber the factory calls for is partly to alleviate the very condition you describe, rut steer. Can you supply us with the figures for your front-end alignment? I'll try, hope I don't loose something in translation. These are Kenny Brown specs from November, 2002, for daily drivers.

Legend: * = degrees
Left Front: Camber = -0.6*, Caster = 6.6*, Toe = 0.04*
Right Front: Camber = -0.6*, Caster = 6.9*, Toe = 0.05*
Left Rear: Camber = 0.0*, Toe = -0.05*
Right Rear: Camber = 0.3*, Toe = -0.11*

Did I get this right?

BTW, Kenny Brown has a more aggressive alignment for competition road course driving, but these number wear the snit out of your tires, and result in severe cupping in under 10K miles. Not for use on a daily driver.

Legend: * = degrees
Left Front: Camber = -0.8*, Caster = 6.7*, Toe = 0.11*
Right Front: Camber = -0.9*, Caster = 6.5*, Toe = 0.12*
Left Rear: Camber = 0.0*, Toe = -0.00*
Right Rear: Camber = -0.1*, Toe = -0.17*

I've also observed that my Marauder does not sit level to the deck. On the flatest of surfaces I could find, the center of the fender lip to deck measures:

Left Front = 28.00"
Right Front = 28.25"
Left Rear = 27.75"
Right Rear = 28.00"

Weird...

[merc6]

psi good all the way around and the airbag sensor are aligned right?

[Petrograde]

I've also observed that my Marauder does not sit level to the deck. On the flatest of surfaces I could find, the center of the fender lip to deck measures:

Left Front = 28.00"
Right Front = 28.25"
Left Rear = 27.75"
Right Rear = 28.00"

Weird...

That is weird... your left side is 1/4" lower,.. my right side is a 1/4" lower. :confused:

I just measured mine:

Left Front = 28.25
Right Front = 28.00
Left Rear = 29.75
Right Rear = 29.50

I'm running 35 psi all the way around.

Yup,.. Weird...

[SergntMac]

psi good all the way around and the airbag sensor are aligned right? Yep...You bet.

[merc6]

Wow thats odd. Now I wanna measure mine for "nascar settins" but my parkinglot is already on a slant.

[SergntMac]

Wow thats odd. No, it's weird. Tom and I already agreed on that. I have no problem being weird, I rather like it. But, I'm not odd, neither is Tom.

[jimlam56]

I pulled the fuse numbered 14 from the inside fuse panel with the engine running today just to see what would happen. As I expected the ABS light and Brake warning lamps came on. I then did a hard stop and the rears locked up good (with no ABS, duh) and the azz end tried to come around on me. The car is currently pulling to the right, (I'm having some trouble with the local dealerships' rookie alignment tech.) so I figure that's the cause of the lack of control, but I wanted to see what she was capable of without ABS interference. Unable to get a good test on the capability I was able to answer a question I've had that nobody at the dealership could give a good answer to.

Without shutting the engine down, I then replaced the fuse and both lights went out. This was the answer to my question. My question had been "Will this set a hard code that will leave the ABS light on until a scan tool clears the code or will the ABS warning lamp go back off as soon as the "fault" disappears. Apparently it will go out as soon as power is restored.

What I'm probably going to do now is pull the wire coming from that fuse and run it to the inside of the console and install a switch there, then run it back to the fuse panel to complete the circuit. Switch on, ABS. Switch off, no ABS. Being able to shut off ABS will enable me to do some things I couldn't do before, like stop faster on gravel and dirt roads and also get some practice in and see if I can get a better stop on dry pavement, maybe by tuning some rear brake power down some or lowering the rear suspension a little bit to get the weight transfer a bit less drastic. Right now I'm sure there's just too much rear brake power for non-ABS mode. What I want to find out is if this is limiting the front brake effectiveness.
David, would this mod allow us to put the same size tires all around, if we wanted to? (No ABS) Not sure that I would want to, but rotating tires adds lots of miles...
Thanks, Jim

[David Morton]

David, would this mod allow us to put the same size tires all around, if we wanted to? (No ABS) Not sure that I would want to, but rotating tires adds lots of miles...
Thanks, JimI'm not sure Jim. Ask Carfixer or look at a service manual and see if front wheel speed sensors are an input to the PCM. On first blush I'd guess it would, you'd have to get used to running with two red lights staring you in the face all the time, but this begs a question.

Q: Why do you think rotating tires will save you money? It adds some miles, but not that many.

I don't want to seem argumentative but I know from experience with tires like ours, that a good front alignment is really the only thing we can do that saves our tires enough to defray the extra cost. Rotation is problematic on high-end tires like ours. Most don't like to have the direction of roll changed, it can cause belt separation, so we have to dismount from the rims in order to put them on the other side of the car, (BTW, you cannot do this with the KDWS tire. It says "this side out") anyways a huge cost. I suppose same side changing would help some, but the front braking suffers from a larger tire there. It isn't worth it in my opinion, and paying to have them rotated is a cost you have to figure into your wear savings.

Rotation is good on narrower tires that can be easily rotated. But on our car, you lose too much performance wise making a change in order to do something that won't give you 5000 miles more life on the tires, and paying $ to do it.

It's like spending a dollar in gas to go cross-town and save a dollar on a bag of potato chips.

Tires are our lowest "consumables" expense anyways, if you don't count fluid services. Break the cost per mile down and see. Spend $1000 on good tires, and even if you drive like Mario and only get 10,000 miles on them it's 10c a mile. My round town gas expense is 20c/mile.

But hey, my butt squeaks when I walk. But that's so I'll have money to spend on my baby.

[Warpath]

...are you running the lower negative camber specs some of us are running? I think the high negative camber the factory calls for is partly to alleviate the very condition you describe, rut steer. Can you supply us with the figures for your front-end alignment?

The higher caster is, the more sensitive the vehicle is to road crown, ruts, etc. I'm not stating that camber may be the issue in this particular instance since I'm not sure. But, caster has some play in it for sure.

[David Morton]

The higher caster is, the more sensitive the vehicle is to road crown, ruts, etc. I'm not stating that camber may be the issue in this particular instance since I'm not sure. But, caster has some play in it for sure.Actually the steering axis inclination (SAI) is an angle that determines directional stability much more than caster. Three dimensional thought on this topic is hard to describe but I'll give it a shot.

Imagine a line drawn through the two ball joints of the upper and lower control arms on a front suspension. When viewed from the side, it appears to lean backwards towards the rear of the car as it rises up from the lower joint. This angle is what we call caster, and the leaning backwards is positive caster. If the caster were negative (I know of no manufacturer that uses negative caster) the line would rise towards the front of the car. But this angle only describes a two dimensional aspect of the line.

When viewed from the front of the car, it rises up from the lower joint and leans inward towards the center of the car. This is called the SAI. Most RWD cars have this angle in the 9-10 degree range, and it is not adjustable per se. It's this angle that determines 75-80% of how stable the tires ride on the road because the weight of the car tends to push the spindles upwards and together with equal amounts of caster, to a centering tendency, that is straight ahead. The greater either of these angles is, the stronger the push. Positive caster makes the spindle push inward, negative caster pushes it outward. If caster is zero, both wheels will want to point straight ahead. There will be no tendency except straight ahead from both wheels and any slop or loosness in the tie rods would make the steering very unstable, we need the struggle toward opposing sides from the wheels to take out all the slop and make the car track well.

The tie rod structures cancel out (on positive caster) a leftward push from the right side and a rightward push from the left side to give a return-to-center tendency that makes the car want to go straight. This is why less caster is used on the left side to give a little bit more left tendency and cancel out road crown.

But both of these angles are almost identical to the ones on GMs and CVs, and they don't have near as much "road input" as we do. It's our wide a$$ tires that give us hell in this respect, and that's mainly because the "camber reality", the totality of the contact patch with the road, where the rubber hits hard and soft from inside to outside, that causes this steering input effect. Higher negative camber will wear the $h!t out of the insides, but it will reduce this effect somewhat. This is why I believe the specs for our camber is so negative. They are trying to protect the customer from the inherent instability of wide tires on uneven roads.

[Warpath]

I'm familiar with SAI. I'm starting to learn more about vehicle dynamics (handling) for my new job. So, I'm familiar with this type of stuff. But, I'm no expert. Caster and camber are easier for most people to understand. So, I just stick with that. SAI is adjustable directly. Since the included angle between the wheel and SAI is fixed, SAI changes with alignment changes.

[Bruce Wayne]

How did you make out with the switch for the ABS, any luck in getting info on the front to back braking arrangement. This sounds like an interesting mod. I would be interested in doing.

[David Morton]

Hey Batman! Good to hear from you. I'm taking her in for an alignment tomorrow morning and I'll get on it soon. I'll let you guys know when I do it.

You're right about SAI Warpath. The included angle is designed into the steering knuckle, so SAI changes with camber. Add .2 camber and you subtract .2 SAI. Looking at the included angle is the best way to determine if a spindle has been bent.

*sigh* (here goes nothing)

My attempt to describe SAI was intended to help you see why it plays a much more significant role in stability and how more caster, not less, makes a car track better. Spend a few years setting alignments, stop thinking somebody is trying to make you look bad, (I'm not. I'm just trying to set the record straight with my experience) and then come back and tell us less caster is better for stability. It's not man, and that's not a matter of my opinion, it's an accepted industry standard and a geometric fact. On this issue more caster helps a little, but it doesn't address the problem adequately. Camber has a much greater effect on rut-steer. I'll try to explain why later.

Now for road racing less caster is better for cornering. Go back to my description of the angles and imagine the spindle travel, in a semi-circle because of the SAI. With no caster, a wheel pointed straight ahead has the end of the spindle at the top of this semi-circle. With positive caster, the top is after the wheel has a few degrees of inward turn. So, positive caster causes the outside of the car in a turn to dip lower for the first 10 degrees or so while the inside of the car rises, making the roll over worse, until more turn recovers from the arc. Go outside, get somebody to turn the wheels, and watch your car roll over just as I described. Conversely, negative caster makes the inside dip lower. Some race cars use negative caster, circle track racers use a lot of negative on the left only and none on the right, while some road racers use 1-2 degrees negative on both sides. Negative caster would not be good for our cars though because it makes them want to turn, driving our car with negative caster would be like walking a tightrope. Some racers don't like it for that very reason, and don't use it.

No, our problem is solely related to the wide tires, and how uneven road surfaces introduce an effect where the "dynamic SAI" angle changes radically depending on where the lions share of the weight is on the tire contact patch. One microsecond most of the weight is on the inside of the tire, the next it's moved 7" to the outside. This effect is present on all tires but when the contact patch is only 4" wide the changes in this "dynamic SAI" are small and given a high caster angle, easily controllable and much less noticeable.

The factory has it right (duh) on how to address this steering problem. High negative camber. Then the lions share of weight is on the inside of the tire most of the time. When I bought mine last year I took her in for the "new" specs I found on this site and the tech told me there was a bulletin with revised specs, as I recall it called for -.7 degrees camber on both sides!

Now that I think about it, I'm gonna tell the guy tomorrow to set it at -.7 and we'll see if it's better. I've got plenty of money for tires, hell I spend ten times more money per mile on gas and I'm not granny-ing all over town because of that. I'll let you guys know how it feels.

[Warpath]

As part of my ongoing education, the vehicle dynamics experts in my area explained to me that increasing caster increases the vehicles tendency to follow ruts/grooves and road crown. They explained the physics behind it. But, as with most of my education, I remember the principle thought and not the details. I wasn't trying to disagree with you. I'm just sharing what I learned.

[BlueThunderPerf]

On my CVPI, I rebuilt the front calipers, replaced the balljoints and bushings, and gave her a good alignment with a slight camber adjustment and she went from pulling hard right to stoping straight as an arrow.

[David Morton]

OK. I got her back yesterday, put 40 psi in all the tires and the "rut steer" is almost gone!

I'm not kidding. The car goes over those 1/2" raised lines on SR41 like they weren't there! You can feel the car raise up over them but the steering wheel input is almost non-existent!

I'm in the process of getting a feel for the handling outside that specific topic, how she glides through a turn, how she makes a WOT left turn across a six lane road from a stop, how she reacts to an emergency stop, straight line and on an exit ramp. All these maneuvers, of course, under conditions when nobody is close enough should I push too hard and lose control. So far she seems to handle just as well, maybe better.

I didn't get a printout from the tech even though I asked for one. Monday I'm going back to voice my appreciation for a job well done and ask him if he can remember the exact figures. But I told him to use the factory specs and to keep the caster as low as possible for handling reasons, so I assume camber is -0.7 (It sure looks like -0.7) and caster 5.5 - 6, and toe in the negative, probably -0.13.

With the KDW2 tires I can swap the fronts by remounting when the insides get about 2/3rds worn out and even if I only get 10,000 miles out of them I think it's worth it. Now the car is a pleasure to drive and much more predictable. If the specs aren't what I think they are, I'll let you guys know what they really are Monday.

:o

Men, I've been here on this board many times bytchin' 'bout the factory specs wearin' out tires, and have been one of the big promoters of 0.0 degrees camber and 0.0 toe. Had mine changed to those specs before I had it a week! Maybe those specs give good wear, but I've been fighting those ruts for over a year and a half and am here to eat crow and say I'm sorry I ever thought tire wear was more important than well rounded and predictable handling. Not every road is like the Daytona International Speedway and for my money, I'll be glad to buy more tires to have my Marauder handling like it is now.

[Warpath]

Welcome to suspension compromise. You rarely can get everything you want. To me, nothing is more important than handling. I love to drive. Why make it boring. Handling should be given top priority IMO anyway since a better handling vehicle can be safer.

[Bruce Wayne]

How did you make out with this ABS switch. I would be interested in this mod. Thanks

[Drock96Marquis]

What I'm probably going to do now is pull the wire coming from that fuse and run it to the inside of the console and install a switch there, then run it back to the fuse panel to complete the circuit. Switch on, ABS. Switch off, no ABS. i am doing basically the same exact thing in my Merc to eliminate the d@mn Traction Assist buzzing when traction is lost. Just one note if/when you do yours, make sure you use a relay if the switch you use is rated for less amps than the fuse rating.

[Mike Poore]

Y'know, David, there's an up side to this, and you get all the credit, although we can put it down to an unintended consequence benefit.

What I'm talking about is "Line Lock" type installation where you want to smoke the rear tires at the line with the front brakes locked. With your interrupter switch thrown, and defeating the ABS, this will become much easier to accomplish, and a hell of a lot cheaper.
:burn: