Thread: How bad is it to run 12" rotors, Front & Back?

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  1. #1 How bad is it to run 12" rotors, Front & Back? 
    SE Level Member Incomudrox's Avatar
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    So a while back I read somewhere that someone said it was bad to run 12" rotors front and back. Because it messes with the ABS system. Is it because they are all the same size or just anything bigger in the back will mess with the ABS? I was considering running the fbodies with the GXP rears. Anyone doing this and is it worth it?
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  2. #2 Re: How bad is it? 
    Bastard Reptile's Avatar
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    First I've heard of this problem.

    If all the wheels are reading the same speed, then there shouldn't be a problem.
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  3. #3 Re: How bad is it? 
    GTP Level Member Toasty's Avatar
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    i cant see why there would be an issue, but rather at least until the GXP, there wasnt a viable alternative for bigger rear brakes. -- that being said, the rear brakes dont do much of the braking to stop the car, so you may not feel much benifit.
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  4. #4 Re: How bad is it? 
    SE Level Member Incomudrox's Avatar
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    Toasty - True but I think that comes from people who upgrade the rear rotors and pads to better pads of the same size. I think that with a larger calipers and larger pad surface with good rotors there are nominal gains to be had. Especially if you can get the upgrade parts for the right price. Also with 18's it looks a little beefier which is cool.
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  5. #5 Re: How bad is it to run 12" rotors, Front & Back? 
    GTP Level Member TyroElite's Avatar
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    I've heard of the issue but to my recollection, it was because the proportioning was set for the rotors of different sizes so when you slam on the brakes, the bigger rear brakes, getting fluid ment for smaller brakes, could mess with the ABS. I'm not sure I'm saying that clearly but I'm sure someone can correct me.
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  6. #6 Re: How bad is it to run 12" rotors, Front & Back? 
    GTP Level Member s1795so2's Avatar
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    I think I know what you are saying, well since I got 04 comp-g I might just do the gxp upgrade myself.
    Steven Oliver
    2004 GTP comp-g WS6. Gator and suede all around interior.
    Advanced MECP certified installer, custom upholsterer.
    <img src=http://i86.photobucket.com/albums/k87/s1795so2/random%20pics/manbike.jpg border=0 alt= />
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  7. #7 Re: How bad is it to run 12" rotors, Front & Back? 
    GTP Level Member VinnieGTP's Avatar
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    97-03 had the same size rotor front and rear. The difference is the rears are not vented like the front. The GXP rears are though which is why it will mess with the ABS, by design, they will stop better than a non-vented rotor.
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  8. #8 Re: How bad is it to run 12" rotors, Front & Back? 
    SE Level Member Incomudrox's Avatar
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    Okay thanks Vinnie makes good sense. Has anyone ever tried running a different master cylinder?
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  9. #9 Re: How bad is it to run 12" rotors, Front & Back? 
    GTX Level Member Ridin ON Chrome's Avatar
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    I will be running 12" front and rear soon..

    F-body front and GXP rear.
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  10. #10 Re: How bad is it to run 12" rotors, Front & Back? 
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    Why not gxp brakes all around
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  11. #11 Re: How bad is it to run 12" rotors, Front & Back? 
    GTP Level Member VinnieGTP's Avatar
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    Because they are almost impossible to find used.
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  12. #12 Re: How bad is it to run 12" rotors, Front & Back? 
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    Right ed's got some give him a call and see what he has or baer has a 12 front and rear kit for the gen 2
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  13. #13 Re: How bad is it to run 12" rotors, Front & Back? 
    GTP Level Member Toasty's Avatar
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    Quote Originally Posted by 19SE92 View Post
    Right ed's got some give him a call and see what he has or baer has a 12 front and rear kit for the gen 2

    downside is, baer's are $$$$$$$$$$$$$$$$$
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  14. #14 Re: How bad is it to run 12" rotors, Front & Back? 
    GTX Level Member Ridin ON Chrome's Avatar
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    Quote Originally Posted by 19SE92 View Post
    Why not gxp brakes all around

    Couple reasons

    1. I like my F-body brakes. They have done well for me so far.
    2. I run 16" Slicks
    3. Dont need to spend $400+ on brakes.
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  15. #15 Re: How bad is it to run 12" rotors, Front & Back? 
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    The rears are pretty much useless to upgrade. They only account for 20% of your stopping power at most. The front is where it is at.

    The rears are different since they are set up to use the parking brake as well. I forget how it is set up, but it will be tricky to upgrade unless you dont care about parking brakes.
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  16. #16 Re: How bad is it to run 12" rotors, Front & Back? 
    Donating Users GR8racingfool's Avatar
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    F-Body front, stock rear for me.

    Cross drilled, and slotted rotors all four wheels.

    It stops better than stock, and they work flawless, I'm happy, and don't plan to evolve them any further.

    I do run 16" front rims with slicks on them at the track.

    ~F~
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  17. #17 Re: How bad is it to run 12" rotors, Front & Back? 
    GTX Level Member Ridin ON Chrome's Avatar
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    Quote Originally Posted by Fish View Post
    The rears are pretty much useless to upgrade. They only account for 20% of your stopping power at most. The front is where it is at.

    The rears are different since they are set up to use the parking brake as well. I forget how it is set up, but it will be tricky to upgrade unless you dont care about parking brakes.

    If the rears doing nothing, then tell me why the ZR1, porsches, Viper, ferraris etc all have the same size or a 1/2" smaller rotors in the rear?

    and the rear GXPs fit without any modification. Read the write up on clubGP

    I dont care much if they doing nothing at all. I just hate seeing my puny ass rotors through my 18s...
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  18. #18 Re: How bad is it to run 12" rotors, Front & Back? 
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    ZR1, porches, vipers, ferraris are in a totally different class then daily driver 4 doors. Hell, they have vents to cool the rear brakes. Why dont we??

    That doesnt change the fact that the rear brakes are for more stability while stopping then anything. The fronts do 80% of stopping. That is why you change your front pads 3Xs as much before doing a set of rears.
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  19. #19 Re: How bad is it to run 12" rotors, Front & Back? 
    Donating Users GR8racingfool's Avatar
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    Quote Originally Posted by Fish View Post

    That doesnt change the fact that the rear brakes are for more stability while stopping then anything. The fronts do 80% of stopping. That is why you change your front pads 3Xs as much before doing a set of rears.
    Yup...same reason why you will see disk brake front only set ups on some mid-level mountain bikes, then full disk front and rear on high-level models. When I built mine I had disk front and rear, both 6.5" and on some down hills I was running OUT of brake, so I upgraded the front only to a larger 8" rotor, and made all the difference in the world.
    Before:


    After:

    The fork change was because I broke the "before" one on a jump, and when I bought new, I upgraded to a thru-axle design.

    Real men don't need full suspension on a mountain bike.


    80% of your braking power is upfront, when I grab a hand full of brake on my bike, I can actually compress the front fork sometimes as much as 2-3", the for I have is a 5" travel. Same thing with my GTP...put the foot to the floor, I swear I could almost hear plastic dragging. LOL Not really, but the car does nose dive pretty damn good.

    ~F~
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  20. #20 Re: How bad is it to run 12" rotors, Front & Back? 
    GTX Level Member Ridin ON Chrome's Avatar
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    Quote Originally Posted by Fish View Post
    ZR1, porches, vipers, ferraris are in a totally different class then daily driver 4 doors. Hell, they have vents to cool the rear brakes. Why dont we??

    That doesnt change the fact that the rear brakes are for more stability while stopping then anything. The fronts do 80% of stopping. That is why you change your front pads 3Xs as much before doing a set of rears.
    I know the front brakes do most of the stopping.
    Doesnt take a genius to figure that out..You think is my first post about brakes.

    But there sno reason not to upgrade the rears. Its not going to hurt anything, except your cheap ass pockets I guess
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