How to Improve Performance of Wilwood Manual Brakes

[karlos]

Looking for suggestions on what to do to improve the performance of my Wilwood manual brake setup. Kit is a 2015 Mk4 with the old style IRS. 12.88" 6-piston front brakes and 12.19" single piston rears. Wilwood pedal box with two individual master cylinders, 3/4" front and 5/8" rear. Brake pads are Wilwood BP-10 front and back. Brakes were properly bedded per the Wilwood instructions. Balance bar is roughly centered. No signs of air in the system, as it's been bled multiple times and the pedal is high and firm.

Issue is that the braking performance isn't what I expected given the size of the brakes and the weight of the car. Fully expected that this thing would stop on a dime, but braking is mediocre at best. Pedal effort is fairly high, which I did expect, but the stopping distance is longer than I think it should be, particularly with cold brake pads. Improves a bit with some heat in the pads, but still not great. Not sure that it would be possible to lock the brakes, as the rate of deceleration just isn't that high.

I initially thought I may have had too much rear brake bias, so I've been slowly increasing the bias to the front a little bit before each drive. Can't say that's helped all that much. Maybe I haven't gone far enough or maybe that's not the issue. I've read that the performance will improve over time, so maybe I'm just being impatient (only a couple hundred miles on the car so far). Thinking of replacing the BP-10 pads with something with a bit more initial bite. Hawks HPS 5.0 compound looks good, or maybe one of the other Wilwood offerings. But don't want to sheetcan a set of new pads if I don't have to.

My plan is to find a deserted parking lot and set the balance bar progressively toward the rear until the rears lock first. Then go the other way a couple turns to safeguard against that happening in actual usage. At that point I'll have the front/rear bias optimized and maybe I'll be good to go. Or maybe the performance just isn't ever gonna be great until I go ahead and swap out the pads. Curious what the feedback is like from other owners running the Wilwood manual brake setup. Would very much like to hear comments and/or suggestions for things I could set up differently.

Thanks.

-Karl

[2bking]

I have the same brakes and IRS except original masters were both 3/4" front and rear. The car would stop but the pedal effort was very high. As I adjusted the balance bar putting more force to the rears the pedal effort got worse but it improved the stopping distance by making the rears do more work before the fronts locked. I changed both masters to .70" and rebalanced the bar. It reduced the pedal effort by 10% (mathematically) with no noticeable change in pedal stroke.


I think you could change your 3/4" master to 5/8" (rebalancing would be a must) and have about 15% mathematical reduction in pedal effort. The .70" master is also a possibility but the improvement would be less. My masters were about $50 each. The more aggressive pads are also a possibility.

[Dave Howard]

It’s important to have the brakes balanced properly. Most of the stopping effort being done by the front brakes. There is a procedure for this. In short, take the car to a safe place. From a straight line run at 30-40 mph, apply the breaks hard until you lock them up. Fronts need to lock up before rears. If not, adjust the push rods on the Master cylinders and adjust the balance bar.
Another method is to measure the pressure at the calipers when applying the brakes. The fitting and gauge can be bought through Wilson’s. This can be done in your garage - stationary. I think the pressure for the front is 1,800 psi.

[CraigS]

"My plan is to find a deserted parking lot and set the balance bar progressively toward the rear until the rears lock first. Then go the other way a couple turns to safeguard against that happening in actual usage. At that point I'll have the front/rear bias optimized and maybe I'll be good to go."
This is a good plan except that I wouldn't go 'a couple turns' back toward the front. I have an in cockpit adjuster on my CNC dual MC and it has clicks every 1/4 turn of the knob. I adjust 1-2 clicks at a time. Once you get the rears to lock, I'd go a max of 1 turn toward the front. Be sure to do this on a grippy surface. That way any reduction in traction later, in different circumstances, would have your fronts locking first. Of course different pads could help also but, unfortunately, I don't have experience w/ Wilwood compounds. Here is some info
http://www.hrpworld.com/store/media/...ies/1051_1.pdf
Reading through the above I have to wonder why the best friction on a street pad is medium and you have to go to a race compound to get high cold temp friction. And why are they so adamant about not using a race compound on the street. Your BP10 has a friction coefficient of .42 at 100 deg while the J is .53 at 100 deg. and has a flat curve.

[Erik W. Treves]

if you are running stock pads from FFR>.. then you need to change them. I just went to yellow stuff pads... my rears locked like crazy... so I had to add front bias back in... WAY better! I would adjust the bar so that you can get on end to lock up... then go from there.

[Bob Cowan]

I think the first thing you should do is change the pads. I also thought the BP-10's didn't work all that well. The BP-20's are a big improvement.

"stepping up" to a race pad is not recommended for a variety of reasons. They are usually noisy, dusty, and will eat the rotors much quicker. Try the BP-20's before doing anything else. It's a quick and relatively inexpensive change.

Whenever you change pad type on any vehicle, you need to resurface the brake rotors. You don't need to cut them, just remove the layer of previous material that's been deposited with normal break in and use. A brake disc hone is hard to come by. They're out there if you search for it, but few places sell them. I used a 120 grip sanding disc in a drill motor.

[FMJ]

I have the same issue and called Wilwood a few weeks ago. After we worked through various questions they recommended the following pad. My plan is to switch them out this weekend after which I'll report back how they worked.

https://www.wilwood.com/brakepads/Br...mno=15E-12605K

-Fred

[karlos]

Thanks for the comments so far. Sounds like there may be a pad change in my future. Fred: Please report back on the PolyMatrix E compound. Also considering the BP-20's as Bob suggests.

With regard to the balance bar adjustment...

Put together a spreadsheet to help understand the relationship between the number of turns on the bar versus what effect that has on the braking force. Graphic is shown below. I've been making adjustments 1 turn at a time, and can now see that I need to get more aggressive with it. As shown by the table at the bottom of the graphic, 1 turn produces less than a 3% change in the front/back bias. To effect a change of about 10%, need 4 turns on the balance bar. I'm currently sitting at 2-1/2 turns from center, which is probably not enough to produce a noticeable difference (only 6 or 7%).

[Bob Cowan]

Thanks for the comments so far. Sounds like there may be a pad change in my future. Fred: Please report back on the PolyMatrix E compound. Also considering the BP-20's as Bob suggests.

I used the PolyMatrix E pad, but only on the track. It works extremely well hot and cold. But it makes a LOT of dust. And when they're hot, they make a tremendous amount of noise. They will also chew up the rotors much quicker than most anything else. I would not recommend them for a street car.

[scottiec]

I’m having great success with G-loc pads

[Derald Rice]

I have had the. E pads on since 2010. Still have the original set of pads , and I have not noticed any apprepciable wear on either the pads or rotors. Brake dust is minimal, and yes they will talk back when they are hot.

I wanted a pad that would work well on the street when cold, and would also work at an autocross or occasional track day.

I will buy them again.