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Thread: Setting Brake Bias

  1. #1

    Setting Brake Bias

    So, I understand HOW (mechanically) to adjust the Brake bias on the MK4 (Pedal kit and Wilwood brakes from FF). However, what I'm looking for is a little guidance to understand how to know when I've got them set correctly? I'm sure it is a bit of set it, try it and see how it stops, and then adjust. However, I'd like some guidance towards getting it close in the first place. I'm not racing the car, but rather using as a "Summer Driver" but certainly want it set properly. Common sense tells me that you want more bias on the front brakes, so that they would lock up first, but again, not sure how to look at the bias adjustment bar and figure out where it should be set.

    I have manual brakes, 15" wheels. Let me know if there is other info that is required to provide some guidance.

  2. #2
    Senior Member DaleG's Avatar
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    I think a few of us would like to know the answer to this. Although, I'm not sure you want the fronts to lock-up first?
    SOLD 03/2013: MK II #5004: 5.0 EFI: 8.8, 3.55, E303, TW heads, GT40 intake, 24#, 70mm MAF

    Ordered MK IV Coyote Complete Kit.

  3. #3
    I would also like confirmation re brake bias set-up.

    My brakes are functioning very well (manual brakes) with plenty of pedal with the bias set towards the front. The manual brakes take a little getting used to and needed to be worked in. After a few hour +/- drives, the brakes are very solid.

    I have not tested the brakes at lock-up yet but plan to - to confirm handling.

    Confirmation of proper bias set-up would be much appreciated.

    I am amazed at the power of the Coyote and at this point I am glad I went with the manual steering rack as I prefer the full feeling of the road given the power. The car tracks like it is on rails! Nice!

  4. #4
    Not a waxer Jeff Kleiner's Avatar
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    Quote Originally Posted by DaleG View Post
    ... Although, I'm not sure you want the fronts to lock-up first?
    Absolutely you want the front to lock before the rear.

    Jeff

  5. #5
    I replaced my donor MC with a Wilwood set last summer. I had my wife watch as I drove down the street, then locked them up right in front of our driveway. I kept adjusting until the the fronts locked first. Difficult to tell from inside the car, how have to have someone watching. I was glad I got it right after about the 5th run, because I was starting to get some nasty looks from one of my neighbors . An empty parking lot would probably be a better venue...

    Pete

  6. #6
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    I find a country road w/o much traffic and do all my brake bias testing at only 35-40 mph. I keep adjusting for more rear brake til it is obvious the rears are locking first. Then dial slightly back. The low speed keeps the car from doing anything crazy when those rears lock first. Once it is set I think you will be surprised how fast these cars can stop. The good thing about this overall, is that any traction reduction such as rain will then have the fronts locking first which is more stable.
    FFR MkII,400hp/351,Tremec TKO,3 link,DA Koni's,Forte front and VPM rear bars,APE hardtop.

  7. #7
    The way I found to make preliminary adjusts for the brake bias is to use a bending beam type torque wrench and check the torque required to rotate the front and rear wheels with some pressure applied to the brake pedal . In order to check the front wheels I will make up a plate that will bolt onto the hubs with the wheels removed and then weld an old socket to the center of that plate or machine a square hole in the center. For the rear wheels you can use a socket directly on the axle nut. I then get something that I can wedge between some frame part and the brake peddle. My favorite item is a 1x2 piece of wood with one end cut at an angle which makes fine adjustments easier and cut to the proper length. I then wedge the wood between the frame and brake peddle so that it take close to 100 lb/ft of torque to rotate the front hub assembly. It will take more that that to get the assembly to start to rotate because of sticksion so you want a reading when the reading is stabilized. With a 100 lb/ft torque on the front I shoot for about 50 to 55 lb/ft on the rear. If you are running some down force from a wing that my go to 55 to 60lb/ft. The balance will change some after the pads a broken in and also when they are hot but this has always gotten me close to a base setting.

    Bill Lomenick
    Last edited by CHOTIS BILL; 04-29-2013 at 08:40 AM.
    Chotis Bill

  8. #8
    What Jeff said, if the rears lock up before the fronts, you will find that the front quickly becomes the rear and you are facing the wrong way.

    Quote Originally Posted by Jeff Kleiner View Post
    Absolutely you want the front to lock before the rear.

    Jeff
    MKIII #3835 IRS, Anderson Performance 408 Levy T-5 Trans, Team III Wheels
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  9. #9
    Senior Member DaleG's Avatar
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    Quote Originally Posted by Jeff Kleiner View Post
    Absolutely you want the front to lock before the rear.

    Jeff
    Thanks Jeff, that's why I added the (?). For those of us still learning, could you explain why?
    SOLD 03/2013: MK II #5004: 5.0 EFI: 8.8, 3.55, E303, TW heads, GT40 intake, 24#, 70mm MAF

    Ordered MK IV Coyote Complete Kit.

  10. #10
    Senior Member DaleG's Avatar
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    Quote Originally Posted by Someday I Suppose View Post
    What Jeff said, if the rears lock up before the fronts, you will find that the front quickly becomes the rear and you are facing the wrong way.
    Well, sure don't want that to happen; now I know. Thanks.
    SOLD 03/2013: MK II #5004: 5.0 EFI: 8.8, 3.55, E303, TW heads, GT40 intake, 24#, 70mm MAF

    Ordered MK IV Coyote Complete Kit.

  11. #11
    Quote Originally Posted by DaleG View Post
    Thanks Jeff, that's why I added the (?). For those of us still learning, could you explain why?
    I'll try to do this without getting techincal.

    What keeps your car pointed straight is the four contact patches on the tires. When tires lock up, the friction that they provide goes WAY down. Now you have front tires with full friction, rear tires that have very low friction, and the weight of the whole car trying to still move forward. It basically makes a pivot point at the front wheels. This is like dropping an anchor off the bow of a moving boat.

    If the fronts lock up first, the rears are acting like rudders and keep the car in a straight line.

  12. #12
    I do it on a wet road, you'll loose traction quicker. If you have more on the rear you'll Kow it, it will go around. Having more rear bias is fun if your expecting it. And if your tracking the car, some tracks you'll be quicker with more rear bias. Get it a little sideways entering the corner, then steer out of the corner with your right foot.

    Are you guys using this? http://www.jegs.com/p/Wilwood/Wilwoo...56330/10002/-1
    It hooks right up to the bias bar. Then you can adjust it while your driving.

  13. #13

    Got one

    Quote Originally Posted by fastthings View Post
    I do it on a wet road, you'll loose traction quicker. If you have more on the rear you'll Kow it, it will go around. Having more rear bias is fun if your expecting it. And if your tracking the car, some tracks you'll be quicker with more rear bias. Get it a little sideways entering the corner, then steer out of the corner with your right foot.

    Are you guys using this? http://www.jegs.com/p/Wilwood/Wilwoo...56330/10002/-1
    It hooks right up to the bias bar. Then you can adjust it while your driving.
    Like this? Bias adjuster with front/rear pressure gauges.
    Attached Images Attached Images

  14. #14
    Senior Member DaleG's Avatar
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    Quote Originally Posted by Avalanche325 View Post
    I'll try to do this without getting techincal.

    What keeps your car pointed straight is the four contact patches on the tires. When tires lock up, the friction that they provide goes WAY down. Now you have front tires with full friction, rear tires that have very low friction, and the weight of the whole car trying to still move forward. It basically makes a pivot point at the front wheels. This is like dropping an anchor off the bow of a moving boat.

    If the fronts lock up first, the rears are acting like rudders and keep the car in a straight line.
    Good description; I understand now. So in the video last week of the guy leaving the auction and careening into the median, he probably locked the back brakes up first trying to panick stop?
    SOLD 03/2013: MK II #5004: 5.0 EFI: 8.8, 3.55, E303, TW heads, GT40 intake, 24#, 70mm MAF

    Ordered MK IV Coyote Complete Kit.

  15. #15
    Quote Originally Posted by DaleG View Post
    Good description; I understand now. So in the video last week of the guy leaving the auction and careening into the median, he probably locked the back brakes up first trying to panick stop?
    Could be. The ends swap pretty quickly when the back loses traction mid turn.

    There are a couple of excess throttle ways to oversteer across the median into the ditch: Too much throttle, lose traction, then slideout or the other more subtle way to do this is with almost too much throttle, mid turn courage loss/throttle dump then slideout when engine braking tears the rearend loose (trailing throttle oversteer). Both can happen pretty quick especially when distracted by an audience.
    Enjoy SoCal: Sun Valley to Newcomb's Ranch to Wrightwood to Crestline to Idylwild to Palm Springs and back
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  16. #16
    Do you guys with the bias adjuster find that you use it after initial setup? I have gone back and forth on it. It has a cool factor, and it would certainly be easier to adjust. I talked to a guy that has one that has never touched it since setup. So I am on the fence.

  17. #17
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    I have to admit I don't use it very often now. But I do use it especially at an autocross where I sometimes crank in a click or two more rear brake and then go back to standard for the trip home. I got mine from Forte and I think it was around $50 so I just did it.
    FFR MkII,400hp/351,Tremec TKO,3 link,DA Koni's,Forte front and VPM rear bars,APE hardtop.

  18. #18
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    I'm presently at go cart stage and had the same question about how to set the brake bias. I talked to the tech support guys at Wilwood and they suggested like the rest of you to take the car for a ride...apply the brakes firmly until wheels start to lock up. Make adjustments to the bias so the fronts lock up just before the rears. That's fine and dandy but the last thing I wanted to do was piss off the neighbours in my less than street legal go cart. Besides, at the time there was still 2' of snow in the front yard. The alternative method suggested by Wilwood was to measure the brake line pressure at the front and rear calipers. They offer a pressure gauge to 1500 psi with adaptor to thread into one of the bleed screws. Should have 800 psi at the front...20% less for the back. With the calipers set we are running from Wiwood this will be pretty close.
    Would really like to get it set for good before riveting the top covers on the foot box

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