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  1. #1
    Enthusiast FlashFyre's Avatar
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    Gen II Brake Upgrade

    I recently heard about an owner who did the 40mm rear and Gen 3/4 front calipers on a non-ABS car. No proportioning valve.


    I'm very interested in this combo as it doesnt involve chopping the rear knuckle and can go back to stock very easily. Ive already got the 40mm rears installed.

    Im guessing it would make the braking front heavy again as to compared to just having the 40mm installed?

    Anyone do this combo and can comment?

  2. #2
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    uvbnbit's Avatar
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    we have it on our 98 RT10 (that's listed for sale recently)
    One of the best upgrades you can do. We didn't track the car, only the usual, occasional club driving schools. But right away, on the street could tell the difference, confidence in stopping power, distribution. Search "brake bias" on either here or the VCA forum. Someone had done and extensive study on it.
    Comparing different pads on different set up even
    2017 GTS Competition Blue
    1998 RT/10 Silver 6.5 Roe S/C, 1.7 HS RR's, Roe Hi-Flow Cats, B & B Headers/3" exhaust, 3.33, Eibachs, SRT front brake upgrade, Toms 40mm rear upgrade .....

  3. #3
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    No brake modification requires chopping of anything. Unless your mechanic is a moron and can't do quality work like a craftsman would. I have Gen 4 brakes on my GTS and like anyone doing that mod had to cut the old caliper ears off. At no point was anything on the car chopped.
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  4. #4
    Enthusiast FlashFyre's Avatar
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    Quote Originally Posted by dave6666 View Post
    No brake modification requires chopping of anything. Unless your mechanic is a moron and can't do quality work like a craftsman would. I have Gen 4 brakes on my GTS and like anyone doing that mod had to cut the old caliper ears off. At no point was anything on the car chopped.
    Chop, cut, lop off, saw off, hack off, remove, sever, separate. Whatever you want to call it.

    I am my own mechanic for the most part and far from a moron. But until they make a glue strong enough to put the mounting ears back on, I'll refrain from destroying the ability to go back to stock without replacing the knuckle.
    Last edited by FlashFyre; 11-08-2021 at 07:59 AM.

  5. #5
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    No cutting if you retain the 40mm rear design. Fronts use relocation brackets that do not require any modifications. If you want to put the big BREMBO calipers on the rear, then "chopping, hacking, sawing, grinding, cut, lop off, and all around mayhem" is required.

  6. #6
    I’m missing a few pieces to complete this mod and don’t ever see going back to stock. I think this is one of those mods that won’t depreciate the value of the car if I would consider selling. Unless there’s another reason you would want to go back to stock that I’m missing.

  7. #7
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    The stock Gen II has a pretty crappy brake bias.

    70.5 - Stock Gen II
    62.7 - Stock Gen II ABS cars
    66.0 - Stock Front / 40mm rear calipers - GOOD

    74.2 - SRT front / Stock Rear
    70.0 - SRT front / 40mm rear - barely better than stock.
    66.9 - SRT front / Gen II ABS rear - Pretty decent.
    65.9 - Brembo F40 Front / Gen II ABS rear
    65.6 - Stoptech Front / 40mm rear


    You can also put a more aggressive rear pad in to help improve the bias.
    Last edited by stuntman; 11-09-2021 at 06:56 PM.

  8. #8
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    Hummm...good data. What about SRT front (14") and GENII rear (13") with GENII fronts/rotors moved to rear....
    From my standpoint, pad selection is where I see the biggest change.

  9. #9
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    daveg's Avatar
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    Quote Originally Posted by ellowviper View Post
    From my standpoint, pad selection is where I see the biggest change.
    What do you suggest for Pads on Gen II for the best braking (non tracking)
    96 GTS (# 33, Bone Stock), 66 Mustang Convertible, 66 Mustang Hardtop, 69 Corvette Roadster

  10. #10
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    Quote Originally Posted by ellowviper View Post
    Hummm...good data. What about SRT front (14") and GENII rear (13") with GENII fronts/rotors moved to rear....
    From my standpoint, pad selection is where I see the biggest change.
    54.6 - SRT Front with Gen II front caliper on a 13" rear rotor - way too much rear bias
    52.4 - SRT Front with Gen II front caliper on a 14" rear rotor - WAY WAY too much rear bias.

    Either of these will likely result in rear lockup under heavy braking. I know a lot of cars run this setup, but i'm not sure how many run this and track their cars regularly. On the other hand, I've tracked many cars with messed up brake bias that also lock the rears at the limit. The owners of these cars are many seconds off pace and when they do finally brake hard and spin, they either dont know what happened or blame it on a non-existent failure.

    Brake bias is very important....

  11. #11
    Enthusiast FlashFyre's Avatar
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    Quote Originally Posted by stuntman View Post
    The stock Gen II has a pretty crappy brake bias.

    70.5 - Stock Gen II
    62.7 - Stock Gen II ABS cars
    66.0 - Stock Front / 40mm rear calipers - GOOD

    74.2 - SRT front / Stock Rear
    70.0 - SRT front / 40mm rear - barely better than stock.
    66.9 - SRT front / Gen II ABS rear - Pretty decent.
    65.9 - Brembo F40 Front / Gen II ABS rear
    65.6 - Stoptech Front / 40mm rear


    You can also put a more aggressive rear pad in to help improve the bias.
    Great data.

    So if I Went with the SRT fronts with my 40mm rears it would have a similar setup to stock brakes albeit with better stopping action for the same bias.

  12. #12
    Enthusiast GTS Dean's Avatar
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    I've been tracking my Gen 2 for 25 years. 22 of those have been on stock front/40mm rear calipers with 13" discs and no proportioning valve spring. I have run a number of different pad combinations. My next big move is better 13" front rotors.
    96 GTS. Viper Days Modified Class. Fresh motor 10-2020!

  13. #13
    Enthusiast My98RT10's Avatar
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    Quote Originally Posted by stuntman View Post
    The stock Gen II has a pretty crappy brake bias.

    70.5 - Stock Gen II
    62.7 - Stock Gen II ABS cars
    66.0 - Stock Front / 40mm rear calipers - GOOD

    74.2 - SRT front / Stock Rear
    70.0 - SRT front / 40mm rear - barely better than stock.
    66.9 - SRT front / Gen II ABS rear - Pretty decent.
    65.9 - Brembo F40 Front / Gen II ABS rear
    65.6 - Stoptech Front / 40mm rear


    You can also put a more aggressive rear pad in to help improve the bias.
    I assume that 66.0 - Stock Front / 40mm rear calipers - GOOD is WITHOUT the proportioning valve spring? What would it be in this case but WITH the spring still installed (that's my current setup. I don't track the car, just looking for a better braking performance overall...)?

    Thanks for the very comprehensive information!!

  14. #14
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    Quote Originally Posted by My98RT10 View Post
    I assume that 66.0 - Stock Front / 40mm rear calipers - GOOD is WITHOUT the proportioning valve spring? What would it be in this case but WITH the spring still installed (that's my current setup. I don't track the car, just looking for a better braking performance overall...)?

    Thanks for the very comprehensive information!!
    Yes, it is without the proportioning valve spring and the same pressure at the front and rear caliper. With the spring, I would need to know the front and rear pressure differential. Someone would need to put pressure gauges on their front and rear caliper, have someone press the brake pedal and record what the front and rear readings are. Then I can edit the chart.

  15. #15
    Can you even get the 40mm rear calipers now? I looked and the site that sold them is 504 now.

  16. #16
    Enthusiast My98RT10's Avatar
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    Quote Originally Posted by stuntman View Post
    Yes, it is without the proportioning valve spring and the same pressure at the front and rear caliper. With the spring, I would need to know the front and rear pressure differential. Someone would need to put pressure gauges on their front and rear caliper, have someone press the brake pedal and record what the front and rear readings are. Then I can edit the chart.
    Thanks for the quick feedback! Unfortunately, I don't have those gauges... can we assume, that with the spring still installed the bias is less favourable than without it!?

  17. #17
    Enthusiast FlashFyre's Avatar
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    Quote Originally Posted by 98RedGTS View Post
    Can you even get the 40mm rear calipers now? I looked and the site that sold them is 504 now.
    Yes. A fellow named Rick took over making them.

  18. #18
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    Quote Originally Posted by My98RT10 View Post
    Thanks for the quick feedback! Unfortunately, I don't have those gauges... can we assume, that with the spring still installed the bias is less favourable than without it!?
    Yup. I have no idea on how much worse until I or someone measures them. My car is in storage but I probably need to take those measurements.

    I don't know how the prop spring works. It could either be a linear pressure difference that widens as pressure increases, or it could be a 'clipping' valve, where the pressure is the same front and rear until a certain PSI, where the rears are 'clipped' and remain relatively flat while the front pressures continue to rise. If it's the latter, depending on where that point is, removing the valve may not make a difference in most cases... Need to test!

  19. #19
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    Non-ABS cars might experience rear lock-up due to biasing. I was led to believe the ABS cars would not have issues with the larger rear options...since ABS would "magically" compensate for any lock-up scenarios.

  20. #20
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    For ABS to do anything it has to activate. Which I have done many times in every vehicle I've owned. So if the ABS in the Viper is sensing an imbalance it will not be an enhancement or anything magical when it activates. With 14" Gen 4 ACR brakes on all four corners of my Gen 2 I have never activated the ABS and had that be an improvement. Nothing magical. Just ask the guard rail
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  21. #21
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    My 'point' was that with ABS, you will not experience rear lockup because of different calipers from stock...or any lockup for that matter. Like I said, I recall a similar thread years and years and years ago where this issue was put to rest.

  22. #22
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    You are correct Eric. ABS does address caliper changes as well as tire OD changes or stagger. My ABS car has all of those.

    So my point was... yes, ABS does prevent wheel lockup if that is your only measurable goal, but it's not a solution to all situations. I've learned to dislike it under performance driving conditions. But it's a lifesaver when Fluffy darts out from behind a parked car.
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  23. #23
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    Quote Originally Posted by ellowviper View Post
    My 'point' was that with ABS, you will not experience rear lockup because of different calipers from stock...or any lockup for that matter. Like I said, I recall a similar thread years and years and years ago where this issue was put to rest.
    If your ABS-equipped Gen II has aftermarket brakes that have way too much rear bias in it, then you CAN HURT BRAKING PERFORMANCE.

    If the rear bias is too high and causes the rears to lock at a relatively low pressure, then the rears are locking well before the fronts are at the limit. Then the ABS will pulsate the pressure to prevent the rears from locking - pulsating and further reducing brake pressure at the front tires - further reducing the overall braking ability of the car.

    It's important to realize that ABS does not just 'magically' take care of everything and you can easily reduce the braking performance and ability of your ABS-equipped car by messing up the bias. It's a good idea to stick to close to stock brake proportioning because the factory ABS system is programmed for that bias. FWIW Gen-3's probably have the worst brake bias from the factory (the most rear) but the ABS is programmed for that bias; so changing the calipers to improve the brake bias could potentially still hurt braking performance, but that's a better direction than changing the brakes and adding more rear bias.

    0.02

  24. #24
    Enthusiast TTSnake's Avatar
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    Is this proportioning valve spring the one attached to the hex nut on the brake distribution block? I want to take it out but wasn't sure if that was the correct spring.
    '97 GTS
    Twin Turbo 1300RWHP

  25. #25
    Yes. The hex nut with black cap. The spring is strong so watch or the nut will shoot across the stage and hit the striper pole.


 
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