Factory do-nut won't work w/KVR fronts.

[David Morton]

The tire talk thread got me to thinking so I went out and tried to put mine on the front. Fidn't dit.

Well, I guess I'm gonna keep it anyways. Can always use it on the back and stick one of them on the front in an emergency.

Anybody got a remedy, chime on in. I guess I might be in the market for a full size spare rim now, but if anybody knows of a do-nut spare that fould wit I'd rather do that.

[SergntMac]

Not to sound like a smart azz here, David, but I first announced this shortly after the doughnut, (mini-spare, what ever) came on the scene. I've tested many brake upgrade kits for fitment, but all of what is available today, was not available back then. Thanks for adding the KVR kit to the list.

BTW, I believe the KVR kit and the BaerClaw kit use the same Alcon caliper, is this true?

[Eric91Z]

Not to sound like a smart azz here, David, but I first announced this shortly after the doughnut, (mini-spare, what ever) came on the scene. I've tested many brake upgrade kits for fitment, but all of what is available today, was not available back then. Thanks for adding the KVR kit to the list.

BTW, I believe the KVR kit and the BaerClaw kit use the same Alcon caliper, is this true?


Mac,

Do you have that list compiled somewhere? Better yet, is there an upgrade kit out there that will work with the donut spare?

[RoyLPita]

I would convert to having a full size spare with your choice of a front or rear sized tire.

[SergntMac]

Mac, Do you have that list compiled somewhere? Better yet, is there an upgrade kit out there that will work with the donut spare? No list per say, just notes I've collected. It would be a short list anyway, due to the variety of choices for the Marauder.

No, I've not found a an upgrade kit that will work with the mini-spare, a kit that's worth the money anyway. Let me explain?

If you wish to keep the mini-spare for what ever reason, it's safe to say that all you can do to improve the Marauder's front brakes, is change out the rotors for an exact size replacement, and improve brake pad compounds with something more aggressive. Now, let's look at that path?

Same size rotors do not increase the "swept area", i.e. brake pad to rotor contact. You're actually reducing it, because while a "vented" rotor (slots and cross drilled) look impressive, you're reducing swept area by removing contact surface. These rotors will heat up sooner and to higher temps (due to more aggressive pad compound), which leads to premature warping and cracking around the slots and cross-drilled vents. Personally and IMHO, this is a waste of time and money.

The factory rotors are more than capable of good brake performance, and an aggressive pad compound can improve brake torque. There is a large variety of compounds to pick from, but keep in mind that more aggressive means more wear and tear. As your brake performance increases, your maintence/replacement costs likewise rise. This is why I cannot call this path any improvement, and why I favor an upgrade to a big brake kit as the only path to follow.

A larger rotor, vented or not, increases swept area. Larger calipers with more pistons, or, larger pistons, improve brake torque. By improving brake efficiency, you need less pedal, and over the long run, your maintenence/repair costs should decline. The only way to really improve brake efficience, is to buy more brake territory. Increase your swept area and support that with larger pads, and you don't need to get as aggressive with the compound. The car stops better and consumables last longer.

In the end, the OEM brakes are more than sufficient for the average Marauder. However, if you have invested in more horsepower, i.e. supercharging, turbocharging, NOS, or even a power tune, give some consideration to your stopping power. The faster you move a 4400 pound missle forward, the sooner you need to stop it. My advice is to go with a big brake kit of choice, and get a full size spare, or, don't mess with it at all.

Just my .02c...Carry on, gents.

[David Morton]

Yup Roy, looks like that's what I'm gonna wind up doing.

Never thought to look at the caliper Mac. It looks like it can use a stock pad to me though.

Thanks guys.

[FordNut]

BTW, I believe the KVR kit and the BaerClaw kit use the same Alcon caliper, is this true?
Same caliper. Different mounting hardware. PBR, is that the same as Alcon?

[David Morton]

Good post Mac! I agree and would like to add some figures to the discussion to give some factual weight to the recommendation to get "the bigguns" up front.

"This is a hijack!"

Stock 12" rotors have 138.23 sq/in of swept area. 14" rotors have 163.36 sq/in, an 18% increase, but this isn't the whole story.

Pad center is 5.5" from the spindle center on the stock setup while it's 6.5" on the 14" rotors, a leverage increase of, you guessed it, 18%. But THAT still isn't the whole story.

The bigger rotors have a lot more mass to absorb heat. Maybe someday when I have it apart I'll weigh the difference between the two but I guess we're looking at another similar figure, 18-20%. But there's STILL MORE.

There's the bigger caliper pistons which would cause a greater pedal travel, but the stainless steel braided neoprene core hoses have almost no "swell" under pressure so it turns out pedal travel doesn't suffer and that means we put a lot more force down on the pads.

All told, I'd guess a good 70% increase in braking power came to my car when I installed my KVRs. If I buy another performance car that has 4 wheel ABS it's the first mod I will make, without a doubt.

[SergntMac]

Thank you, David, I'm going to add your data to my big brake file.

Anyone looking for more 411, do a search by member name, ToddTCE. He's a vendor here, and a brake specialist in the biz. He's posted many fine notes on brakes, and always responds to questions. When in doubt, check it out.

[Eric91Z]

Thanks for the input, guys. I have absolutely no real reason to want to keep the mini-spare. But very interested in upgraded performance, but keeping a "spare" option since the car is a daily driver and don't want to be stranded (Allstate Motor Club is not the speediest service in the boonies).

You guys seem happy with the KVR setup. Does it work well as a daily driver setup? The TCE setup does not come with dust boots on the pistons for the Wilwood calipers and I am not planning on road racing the car, so not worried about melting the boots. More worried about getting the best, most reliable daily driver stopping power increase for the money. (Sorry, don't want to start a brake comparison thread or argument here).

[SergntMac]

More worried about getting the best, most reliable daily driver stopping power increase for the money. (Sorry, don't want to start a brake comparison thread or argument here). Comparing notes is good, it's how we all learn. Matching products against each other is healthy too. Every mod has it plus and minus, nothing wrong with outlining them.

It goes sour usually after someone states that there is only one supreme product, and only one way to do things. I think (hope) we're all smarter than that.

When you're ready, ask for the good and bad on each product, but make your own decision. Don't buy something (anything) because you want to fit in with a larger crowd. The only decision that will hurt you, is one not made.

[Agent M79]

However, if you have invested in more horsepower, i.e. supercharging, turbocharging, NOS, or even a power tune, give some consideration to your stopping power.

Upper management has place an edict in effect that states that there will be no more go-fast until there is some stop-fast. Makes sense to me.

[Todd TCE]

Rotor torque is rotor torque here. Let me explain.

You don't pick up 18%, 30% or 70% more 'braking power' with any of these. You only change the method in which you achieve the ultimate torque. What's that? The point of tire lock up.

Larger rotors, changes on piston size or qty, and pads all contribute to this. But in the end they all net you the same result. A stopped tire.

What changes are which aspect of the brake equation you use to 'enhance' the final mathmatics of the torque. Larger rotor means more leverage- less pressure required. More piston means more clamping- less pressure required. Mondo race pad mean more 'bite'- requires less pressure.

Note it all comes back to pressure. On the other hand if you put the rear caliper on the front it might work too. But it will take MORE pressure as it has less piston area. Without opening a spread sheet I'd guess that 70# of leg pressure to lock the stock fronts might take 120# of leg to stop the smaller part. Line pressure would be through the roof however....

The key is a good mix of the right parts, sizes, and compounds to match the intended use. There's good rule of thumb here: Increase rotor diameter, decrease piston area and tune with pad. It's what makes well designed brake kits tick. *one mfg likens it to black magic of sorts but when broken down this is what it amounts too.

Too much of any one element of the mix leads to other problems. Combine two or more of the elements and you'll have a poorly balanced braking system.


And btw; yes the spare tire issue is common on many BBKs.

[merc6]

what about 17's or is 18 the deemed "Safest" size?

[SergntMac]

Thank you, Todd TCE. More insider lingo, but I'm catching up.

[David Morton]

This is what I learned in many factory brake schools, as well as extensive literature on brakes NOT coming from the manufacturers of brake components, but from engineering sources.

We aren't just rubbing pads against rotors to stop or slow the car. We are converting the kinetic energy of the moving car into heat. Heat is made on the pads and the rotors, but the pads have a limited ability to absorb this heat since their mass is small so most of the heat is absorbed into the rotors. Brake systems are designed to put the heat into the rotors and have pads designed to be resistant to heat build-up. Old style pad materials were asbestos with some types having metal particles added to enhance friction and create more heat on the rotor. Metallic pads wore out rotors pretty fast, but the main concern with manufacturers was the tendency to squeal, so they came up with something that works just as well, and gives us better rotor life to boot. Modern pads have a polymer infused into the pads that liquefies and deposits on the surface of the rotor at the microscopic level. This give more heat transfer to the rotor without wearing it out since it effectively increased the surface area of the rotor at the microscopic level. It's "smoother'.

Old brake drums had fins on the outside to try to blow off this heat since fade was a predominant and persistant problem. As the drum got hotter it got bigger, the pistons had to push the shoes farther out until the pedal hit the floor and you lost all friction. But disc brakes solved most of this problem since the design is such that things get tighter when the rotor gets hotter and a little bit thicker. But brake fade can still occur when the rotor gets so hot that it can't absorb more heat, and we can only do so much with internal vanes to blow off some of the heat. BTW, cross-drilled holes and slots don't help with this problem at all, they don't help cooling, they're there to let steam and other gases that build up between the pad and the rotor get out faster so they don't push the pad away from the rotor. Technically the rotor could absorb more heat but the materials won't allow continued friction at such high temperatures and besides other things start to happen like bearings burning up, grease catching on fire, seals melting, so to solve fade there's really only one other option, increase the mass of the rotors so they can absorb more heat. This is one of, if not the biggest advantage of bigger diameter rotors. Increased resistance to fade because they have a lot more mass to absorb heat. Also, more swept area and leverage advantage actually make this larger rotor absorb more heat, faster than smaller ones, and that's why the car stops faster. They convert more kinetic energy into heat faster.

About lockup. With ABS, and especially on a car like ours that doesn't sit low like Corvettes, balance between the fronts and rears is problematic. On our car, increasing front braking power makes the front dip lower and causes the rear-end to actually lose traction when it rises up from the weight transfer. On my car, under a full effort stop, the azz-end rises up like crazy and the ABS goes nuts turning the rears off and on, which is good in so far as it keeps the rears from locking up and putting the car into a spin, but power is lost because of this off-on-off-on ABS action.

So I plan to lower the rear suspension as a stop-gap until I can find a workable modification to the rear suspension, and this is what I have in mind.

Since the air-ride rear bags are the main culprit here I want to put springs back there with air bag inserts or air shocks then hook the air bags or shocks up to the air-ride. With some heavy springs of the right size, I should be able to get a suspension that has a lot less air pressure in it, and that might lessen the tendency to shoot up the back of the car and give me better traction on the rear tires.

Then I can still have air-ride leveling, without the drawback of high air pressure causing so much havoc under hard braking.

At least I hope so.

[DEFYANT]

Since I just got my Baer brakes in, this info is great, thanks for the posts here. I have researched here and other sites and am happy with my choice. But these "new" threads are very informative regardless.

David, do you think a beefy sway bar help with the weight transfer under the hard braking you spoke of?

I completely agree with the statements above stating more HP requires bigger brakes. When I first began this project, I let the brake mods go since our cars share the CVPI brakes. I have had lots of seat time in many CVPI's and only made the brakes fade out once. I've seen them smoke on ocassion after a hot run to a call and not warp after parking. So I had confidence in the stock brakes.

Well after attaining 425 HP (more to come in the future), making several trips down the 1/4 mile tracks and a mild interest in road racing, I decided the stock brakes were at their limit. They have not quit yet, but at this rate they will not last under this stress.

On spare wheels;
What size tire comes on the full size spare tire?

Thanks again.

[Todd TCE]

From the techno standpoint David you'll enjoy playing with the bias estimator I hope to have up and running on the web page soon. Getting it web friendly has taken some time as I had to remove some of the variable in the formula that would only go to confuse folks. Because it's a single MC we won't concern ourselves too much with pedal ratio (locked at 7:1), bias bar offset and center distances etc of twin MC design.

You'll be able to work the basics; Rotor OD, Pad Cf, and Piston Area. It will aslo retain the pressure values allowing you to put in both Leg and MC bore to see what and how these changes effect the system as a whole.

Give me a few more days as the web guy's backed up on things but look for it soon.

[David Morton]

Thanks Todd. I just remembered another thing I've been thinking about.

Anybody run out of booster assist? I wondered if the vacuum check valve went bad (it's not) but there's been a couple of times I was like, hard on the accelerator and then immediately to the brakes and the pedal was pretty hard, like the booster had run out of vacuum. So here was my thought.

Remember the days when Detroit put coffee cans under the hood for a vacuum reservoir to operate the air conditioning doors? Why not put a bank of them on top of the ABS valve and hook them up with the booster? We could run a longer hose to the booster but tee off along the hose and put cans in to create a larger reserve of vacuum for the booster to use. All we need to do is put another check valve in the hose before its run to the booster, and we could put two or three cans in between there.

[David Morton]

... David, do you think a beefy sway bar help with the weight transfer under the hard braking you spoke of?

What size tire comes on the full size spare tire?

Thanks again.I don't see how that would keep her from rising up in the butt but you got me thinking about the QA1 shocks and the rates for extension and compression being adjustable.

Anybody know if this helps? Say put the extension resistance at a high value?

The factory puts a front tire on the full size rim.

[Eric91Z]

Anyone know what the stock front/rear brake bias is on these cars? I know like the Chevy B-Body cars (Impala SS, Caprice, etc) were set from teh factory at like 90% F/10% Rear. Even with rear discs. And there was a kit you could get to change that factory bias to like 75%F/25% R and completely changing the braking of the car and lessen nose dive. And we are talking $25 in parts (which I have sitting in a closet right now). Just wondering if changing brake bias with the proper setup front and rear rotors and calipers could do even more for the car.

[Todd TCE]

Of course I do. The notes I have reflect my compiling the data of rotor OD, and piston area on both vehicles.

*Note that pad Cf has an impact on this so we'll use .40 as a spec on both ends.

The SS had about 64/36 at rest. It was noted somehow that it went to a much as 90/10 for hard braking due to the prop valve cut. Rear line pressure was reduced quite a lot.

The Marauder is at 69/31 at rest. Without knowing the knee point of the stock prop valve I cannot say to what the bias shift is under hard braking.

All vehicles reduce rear line pressure under hard braking. Thus preventing rear wheel lock. When sizing the parts for an aftermarket kit it's nice to know the specs being installed and what this does to both bias and rotor torque. Going too far one way or the other can have negative effect on things.

[Eric91Z]

Of course I do. The notes I have reflect my compiling the data of rotor OD, and piston area on both vehicles.

*Note that pad Cf has an impact on this so we'll use .40 as a spec on both ends.

The SS had about 64/36 at rest. It was noted somehow that it went to a much as 90/10 for hard braking due to the prop valve cut. Rear line pressure was reduced quite a lot.

The Marauder is at 69/31 at rest. Without knowing the knee point of the stock prop valve I cannot say to what the bias shift is under hard braking.

All vehicles reduce rear line pressure under hard braking. Thus preventing rear wheel lock. When sizing the parts for an aftermarket kit it's nice to know the specs being installed and what this does to both bias and rotor torque. Going too far one way or the other can have negative effect on things.

What would it take to figure out the "knee point" of the stock setup and whether or not it can be adjusted - if need be. Just wondering if braking can be helped some by changing that bias if it goes as bad as the 90/10 of the SS. And I do understand too much rear bias can cause the rears to lockup, especially when unloaded some by the forward motion of braking.

[Todd TCE]

A factory supplied data sheet would be nice. Other than that the only way I know is a pressure gauge on both ends of the car and a way to increase pedal effort in precise amounts.

Other than that, the only thing is to gut the stock valve body and plumb in a true adjustable unit. That tends to be a pain with four circuits as you either need to Tee them in/out of the valve or run two adjusters. Both have their pros and cons.

Pull apart the stock valve body and see if you can alter it perhaps.

[David Morton]

Nose dive is caused by the car stopping faster, not because 'proportioning' is out of whack. If you rob front brake power in order to achieve better 'proportioning' you cut down on nose dive simply because the car isn't stopping as fast. With modern active 4-wheel ABS, hydraulic proportioning is outdated and unnecessary. The only reason they still have proportioning valves is because the "service" brakes have to meet old DOT standards when the ABS is malfunctioning and out of service. Proportioning valves are a DOT requirement. If it weren't for that the manufacturers would have done away with them. Now if I could turn off the ABS and use the "service" brakes, proportioning would be important, but why would I? I would not be stopping as well, since it would be robbing front power to keep the rears from locking up. Going 70/30 or 75/25 sounds great when you don't have ABS, and you're worried about the rears locking up. I have ABS. I'm not worried.

What we need to do to make maximum use of the big front rotors and get more from the rear brakes is to limit rear end travel, stiffen the front springs and tune the compresion and extension ratios of the shocks. I'm at 90/10 lots of times, and 90% of the weight of the car is up front too, but the ABS is keeping the rear-end in line. What I am saying is that if we proportion away front brake pressure to try to 'balance' more power to the rears, we'll just lose front brake power, and the car won't stop as fast. Without a better suspension on this car, less nose dive is just gonna mean we aren't stopping as fast. Again, modern 4-wheel active ABS has made all those "good old days" brake school lessons about 'proportioning' and 'balance' obsolete. Put as much power up front as you can, tweak the suspension as best you can live with, and hold on! BTW, it's called ANTI-LOCK brake system. Duh!

I know we'd do better if we had all four tires giving it all they got, we'd stop even faster. But the solution here is not in the non-sequitur discussion about proportioning. The real enemy is the suspension combined with the design of the car. We're pretty high up in the air and inertia is gonna make the car stand on it's nose, the faster we stop, the more weight transfer to the front. Talk about proportioning on the vintage car boards where it's useful. Here it's not. The best solution we can do here is to modify the suspension. The way this baby is stopping, I have way too much power in the back as it is. The last thing I need to do is give the rear brakes more power at the expense of front brake power.

And BTW, I'm out-stopping Corvettes all day long now. I got toasted at the light by a C6 once, but as we came to the next light and he was slowing down, I came sailing past him doing 50 and waited till the last 70 feet or so and stood on it. She stopped so fast the guy rolled his window down and said, "Damn! Where the hell you get those brakes! Man I wish this thing could stop that fast!"

:cool:

[Todd TCE]

If you want te believe the dive is due to stopping better that's up to you. In the end your total braking effort is simply the max rotor torque the whole car can generate prior to wheel lock up. If you prefer the fronts to do all of that work that's up to you. Reality is that four wheels out brake two.

Seeing they do not produce a kit for the Marauder, I'll pass you off to the rather extensive testing done by Stoptech to show this in more high zoot format.

http://www.stoptech.com/tech_info/wp_brakebiasandperformance.sht ml

I don't agree with everything they post but they've done a fine job of showing this in detail. So yes; it has everything to do with bias.

*Your suspension comments are valid too. Keeping things in check here WILL go to improve braking.

[SergntMac]

Seeing they do not produce a kit for the Marauder, I'll pass you off to the rather extensive testing done by Stoptech to show this in more high zoot format.

http://www.stoptech.com/tech_info/wp_brakebiasandperformance.sht ml

I don't agree with everything they post but they've done a fine job of showing this in detail. So yes; it has everything to do with bias. Enjoyed this article very much, Todd, thanks!

I learned a long time ago that effective braking includes the right tire compound and PSI. Without that, no big brake kit can improve anything.

[fast Ed]

David, wouldn't your statements about the need for proportioning only apply when the ABS is engaging during a stop?

Not trying to be argumentative, just not following your logic on this one. :)


cheers
Ed N.

[Todd TCE]

Your'e spot on Ed. ABS has no impact on braking unless the wheel senses a lock up. It does not help nor hinder overall braking performance. EBD and other brake enhancements can and do effect things- by monitoring rotation as well as pitch and yaw. Even so the max decel is still that at which a wheel no longer can keep weight and contact to the road.

Stiff rear shocks, stiffer front springs, tire diameter changes will effect braking performance and the newer EBD systems try to work with those designs to maximize the dynamics of the car.

[David Morton]

I give up. If guys want to believe the car is dipping in the front because it's actually not stopping as fast as a car that isn't and that the ABS computer is going nuts turning off the rear brakes because there's not enough power back there(?), that's their reality. No amount of logic can sway sombody from their beliefs if they're not open minded. This is all too obvious to me now.

I know the front is dipping hard because the weight is going there faster than the suspension can handle it. I know this is because I'm stopping faster. I know it wasn't dipping this hard before I got the big rotors. I know this because I understand inertia. I know this is because of the design of our car, sitting up high as it is. It's a law of physics. None of these things have I taken on faith.

You guys go ahead and put big rotors up front and then take the power away from them with proportioning valves so your "bias" will be OK. Don't listen to me. Maybe I'll see you at the test track someday.

I quit.

[fast Ed]

So David, ignoring the large brake swap, are you implying that a vehicle with non-functioning ABS has unsafe brake proportioning without it? That doesn't make sense ...


cheers
Ed N.

[SergntMac]

David, If you have that much body "language" under severe braking, something is broken, or, worn out. I get none of that language, because I have very tight suspension, and very sticky tires backing my braking events. I feel no need to disrupt the ABS system, it's usually very helpful in controlling the car in the twisties. When Car and Driver did their skid pad testing back in '03, my MM ran 70 to 0 MPH in 171 feet. IMHO, that's impressive braking power for a 4400 pound car.

[David Morton]

Fast ed, I implied nothing. I took the ABS fuse out one day and did a normal stop w/no problem but under hard, perhaps 3/4 effort the rears locked up fast, but I got big front rotors now. In my opinion there's too much power back there with the front mod. What's needed is suspension modifications. The air-ride load leveling rear suspension is the culprit.

Wait a minute, I said I quit and now I do. If you guys can't see the answers to your questions in what I've already posted, good luck. And good riddance to this dead horse. Go buy the wrong stuff for your brakes. Forget about suspension, all you guys know our car brakes and handles just like a Formula 1 Indy car. Has a 60R/40F weight ratio too, just like the Indy cars.

Right.

[Todd TCE]

Davids points about suspension and weight transfer are all very valid ones. His only down fall is not understanding how that combined with the proper brake balance can yet improve his total braking package. If I had the data on the kit in hand I could spit it out in a spreadsheet side by side with the stock data. But since he's chosen to not contribute further then we'll simply have to leave it to guess work.

The link supplied (while it pains me to refer to a competitor!) explains well the importance of a well designed package. And also covers weight transfer or dynamic bias as well. The bias page on the web site should be up and running as early as tomorrow. Anyone is welcome to use it and I hope they do.

[fast Ed]

As Todd said, David's point about weight transfer is valid, we're not disputing that.

On the 87 Mustang 5.0 I had from new, which evolved into a track-only car, I ended up in a situation where the car could not be slowed down as quickly, with larger brakes installed. Before this, the car had larger piston calipers on stock sized front rotors, and a 10" rear disc conversion (originally drums). I went to a Baer 13" front / 12" rear kit, this was before the 13" Cobra brakes were available. Anyway, with the larger brakes on the car, there was so much weight transfer to the front (with 1000 lb. springs even), that no matter where I set the adjustable proportioning valve, the rears wanted to lock up. This was out on the track at Mosport.

In this case, the solution was revised geometry (relocated control arm mounting points) for the suspension, for less dive on the front, and less jacking on the rear.


cheers
Ed N.