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10 inch front, 9 inch rear brakes?

Discussion in 'Flat Fender Tech' started by sammy, Jan 13, 2010.

  1. Jan 13, 2010
    sammy

    sammy Coca-Cola?

    Albuquerque, NM
    Joined:
    Jul 1, 2007
    Messages:
    1,577
    Is this possible to do/do safely? I'm thinking here....
     
  2. Jan 13, 2010
    garage gnome

    garage gnome ECJ5 welder

    Western MA
    Joined:
    Jun 19, 2009
    Messages:
    3,083
    I have 10" fronts and rears and they work just fine. I had to modify the brakeline kits due the angle of the brake cylinders. Thats all.

    Those 10" really stop all 1500 lbs of jeep nicely. :)
     
  3. Jan 13, 2010
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    Possible. Why not put 10s on the rear as well?

    Most of the braking comes from the fronts (weight transfers forward when stopping), so you aren't losing much by not adding 10" brakes to the rear too. The main problem will be balancing the fronts and rear with different sized brakes, so that you don't lock up the fronts or rears while the other axle does nothing.

    If I wanted to do this, assuming there's no proportioning valve, I would look at the factory brakes surface area and wheel cylinder area. The force applied to each wheel is proportional to the area of the wheel cylinder. Multiply that by the friction surface and you have force-area, which should be proportional to stopping power. The number for the front will be larger than for the rear, because the front does most of the work.

    Once you have the two numbers for front and rear, see if you can get close to the ratio between them by swapping around the wheel cylinders. The new 10" brakes will have a higher stopping power than the original 9" fronts, so you need to boost the power of the rears till you get roughly the same ratio between front and rear. For example, you may be able to run front cylinders on your rear 9" brakes and get close to the factory numbers.

    The other possibility is to add a proportioning valve and adjust the setting till the fronts and rears lock up at the same time.

    Some of the 10s are self-adjusters. In that case, you'd be ok only if you religiously adjust the rears to keep up with the self-adjusting fronts.

    hth!

    <edit> Also, I expect the rears will wear out fast, since they will be supplying braking to match the 10" fronts.
     
    Last edited: Jan 13, 2010
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