Wilwood Brake Peddle - Proper Adjustment

[landmass]

I have a Wilwood brake pedal in my car. Although it stops OK, it just doesn't feel right. When I come back from a ride, the rear brakes are warm and the front brakes are cold. Went onto Wilwoods site to find info and discovered that my peddle bias adjustment is WAY wrong. In the instruction/information PDF, it mentions using a brake line pressure gauge to set up the pedal, which I have. Does anybody have any info on starting points for the front -vs- rear pressures or pressure ratios. Or any suggestions on how to set the brakes for proper operation with these Wilwood setups? When do you know it's right?

[Snake2998]

Others on here might well have a direct answer for you but if you get no help then google for Mike Polan's Brake Calculator that will help in your decision making process. Otherwise a riskier process is to measure the pressures as they are at the moment then you at least have a starting point to start moving the bias towards the front.
I would move the bias 10% - 20% more to the front - find a safe place with lots of room for a spin - take her up to 30mph and stomp on the brakes - if she spins move the bias another 10 - 20% to the front - keep this up until she stops straight and true. Then the fine tuning starts moving the bias back until she starts getting unstable then moving it forward again until it feels safe.

Be warned - this whole process is risky - be ultra careful and make sure there is nothing or no one near you that can be injured or damaged or can injure or damage you or your car if things go wrong.

[mdross1]

When setting up my car knowing the front does most of the stopping chores went to a local dirt road made panic stops till both ends of the car locked together. Even went so far and did the same thing on asphalt. Sounds prehistoric but now have the Wilwoods dialed in. I used a pressure gauge when setting up pedal feel. Of course I was careful that's common sense for the politically correct.

[Tommy]

landmass,
There is more to getting the front/rear brake balance correct than just the pedal bias adjustment. It will vary from car to car depending on the size of the front and rear master cylinders and the calipers and the rotors. Pressure alone will not tell the entire story. .... It sounds like you didn't choose and install your brake components, so I suggest you go over the entire setup as if you were installing it yourself for the first time. For example, you'll want the front brakes to do most of the work, so in most cases the pedal bias should push harder on the front master cylinder AND the pushrod to the front master cylinder should be adjusted longer than the rear to allow for full throw under hard braking. The Wilwood website info should cover this type of information.

The rule of thumb is that you want the front brakes to lock up before the rear. Since the front tires carry more down force during heavy braking, they will do most of the stopping when you need it most. By having the front brakes lock up first, you know you're getting all you can from the most effective tires, and you reduce the likelihood that the rear tires will skid you into a spin. For these reason, I'd start with settings that strongly favor the front brakes doing most of the work. Then, as was described above, find a safe place to test the brakes and find out which ones are locking up first. Make adjustments and repeat the tests until you're getting as much from the rear as you can, but the fronts still lock up first.

If you're not comfortable doing this sort of work yourself, try to find a race shop or hot rod shop to do the work. Normal mechanics don't typically do this kind of thing.

[landmass]

Thank you guys for the good info. I looked up Mike Polan's Brake Calculator and I'm sure it will put me in the ballpark. From there I can do the fine tuning you all suggested. I wish I would have taken the pressures, but I made adjustments before thinking about it. Car is up on jacks now for clutch work and maybe trading the T5 out for an auto trans, so I'll have time to really look at this issue. I've tried to lock it up in the past with my GoPro watching one of the front or rear tires and was unable to do so. But, I did notice that under very hard braking, right at the end, just before the car stopped, the front tires tried to turn to the left. It didn't do this each time, but it was not a good thing, and I'm concerned that Wilwood tech may have steered me wrong. I have the .81" rotors on the front, and have the calipers for the 1.01" rotors, which they said would work. I questioned them about it, and they assured me there would be no problem. Do you guys have any idea what may have caused this to happen - the wheels turning to the left, abruptly, right when the car stopped??? I also installed the Wilwood suggested MC's, front is 3/4" and rear is 7/8". I do not have Wilwood calipers on the rear, just the stock Ford Explorer calipers, which seem to be working better than the new Wilwood calipers on the front - but that is probably due to a misadjusted pedal.

[strictlypersonl]

Originally Posted by landmass

... But, I did notice that under very hard braking, right at the end, just before the car stopped, the front tires tried to turn to the left.

That has nothing to do with the master cylinders. One of the front calipers is working differently than the other, either because of geometry or contaminated pads.

[Tommy]

Keep in mind that if one front tire locks before the other, the one that locked is likely working correctly. It's the other side that has the problem. ... Next time take a friend who can stand safely to the side and watch as you apply the brakes. Or just let it slide to a stop and check the skid marks.

[LMH]

This might be a dumb question but are the calipers the same left to right?
I saw that one time where both front calipers were Wilwood but were different piston size left/right.
Larry

[landmass]

stricklypersonl - I'll re-bleed the brakes and clean/sand the pads(new Wilwoods that came with the calipers).
Tommy - that is a good point, and once I get everything cleaned up and adjusted I'll take a friend who can observe.
LMH - well, to be honest, I assumed they were the same, new out of the box, but I can mic them when they are removed.
Do any of you see any problem regarding the use of calipers made for 1.01" rotors on a .81" rotor - maybe the pistons sticking out too far and binding??? Twice, the brakes on my car locked up when I came to a stop, the mechanic suspected the front line lock, and once he relieved the pressure from it, the front brakes released and I was able to get back to the house. The second time it happened, he said the line lock had probably failed, so I removed it from the vehicle. I'm just suspicious of the "gap" the rotors have with the calipers.......

[427sharpe]

2/10ths of an inch (about 5.08 mm), should make no difference unless your calipers are pulling back too far, or you go metal to metal on the brakes really badly. If you are really concerned about it, you could make 4 2.5mm shims to attach securely behind the pads to clear up any apprehension. I use a brake pad pressure tool from Innovative to set my brakes up.

[ame="http://www.amazon.com/Innovative-Products-America-7884-Pressure/dp/B000850MZK"]Amazon.com: Innovative Products of America 7884 Brake Pad Pressure Tester: Automotive@@AMEPARAM@@http://ecx.images-amazon.com/images/I/31xMhQgv5RL.@@AMEPARAM@@31xMhQgv5RL[/ame]

[Tommy]

As for the line lock, are you referring to a line lock or a residual pressure valve? Residual pressure valves are used to maintain a small pressure in the line to keep the piston/pad from backing too far from the rotor. It's commonly used when the master cylinder is lower than the caliper. If you removed a residual pressure valve, you will have a larger than desired gap between the pad and rotor. This can result in the master cylinder running out of fluid before the pad is fully engaged with the rotor and, subsequently, reduced braking action.

Edited because I misread the earlier post.

[LMH]

On the calipers I was referring to in my previous post, we found different piston sizes than the other side, in spite of the part numbers being the same on the box. Both were Dynalites. I'm sure however that it wasn't something that happens often. Just something to check for.
Larry

[landmass]

427sharp - I forget how the pads are affixed to the calipers, but when I remove them, I will definitely check out that option.
Tommy - a line lock for locking the front brakes during a burn out prior to drag racing.
Well, it looks like I'm going to have to read up on this and study some of the calculators to ensure I have the proper equipment. I think my main problem was having the pedal adjustment all wrong. I got a bias figure from another site that suggested a 54% bias to the front brakes and a 46% bias to the rear. Using my pressure gauge and doing the math, I may be able to achieve the proper bias and get my brakes working. I'll test them on my dirt road with an observer to ensure they are locking front first, then rear. To be honest, I don't think my front brakes were even engaging because when I felt them after a trip - they were cold. The rear brakes were warm. I'll also check out the shim option for the front brakes, the gap makes me nervous, and I can't help but to feel that it's a little excessive and narrowing it would improve the performance. For some reason, that gap is bothering me. The pistons are very shallow in the calipers, not designed for a whole lot of movement, and I noticed it when I was installing them. Always in a hurry - I went ahead and installed them. Now I wish I would have held off and, somehow, worked it out prior to installation. You guys have given me a lot of good advice and I appreciate it very much. Thank you.

[Snake2998]

If you are that worried about the gap maybe get thicker discs - I know that's an expensive option but you gain better cooling and worsen unsprung weight but not by much..

Another option is splitting the calipers and having them milled to the right size - check with Willwood first before doing this.

[427sharpe]

Speedway has a neat setup that could help, maybe permanently mount if you want to adjust bias occasionally:
Speedway Dual Brake Pressure Gauge