Register now to get rid of these ads!

Bigger rear drum brakes ??

Discussion in 'The Hokey Ass Message Board' started by Rustytoolss, Mar 28, 2013.

  1. Rustytoolss
    Joined: Jul 27, 2009
    Posts: 248

    Rustytoolss
    Member

    Since the front brakes do most of the braking ( up to 70%). How much better stopping performance would you get by swaping the GM 9 1/2" X2" rear drum brakes, and replacing them with 11" X 2". ? Don't want to do a rear disc setup. Truck weighs about 3700/ quite a bit of the weight is over the rear axle.
     
  2. HEATHEN
    Joined: Nov 22, 2005
    Posts: 7,591

    HEATHEN
    Member
    from SIDNEY, NY

    Well, it sure as hell wouldn't hurt. I've never heard of having too MUCH braking area on a truck that does any sort of hauling.
     
  3. goose-em
    Joined: Aug 23, 2008
    Posts: 349

    goose-em
    Member
    from Louisiana

    Will not change your braking power unless you increase the force.

    P=F/A

    P=Pressure
    F=Force
    A=Contact area

    You would be increasing the contact area by ~ 3sq inches (not accounting for the curvature)

    Having more contact area between the drum and the brake pad will create a larger source of frictional forces. However it also reduces the pressure between the brake drum and pad for a given force.

    The above equation shows that although you increased the frictional contact area the increases in the frictional generating area are exactly offset by the reduction in pressure.

    To get a benefit would require that your braking system be able to apply more force to the surfaces in order to keep the surface pressure the same.
     
  4. Bigger brakes never hurt. HRP
     
    Register now to get rid of these ads!

  5. Rustytoolss
    Joined: Jul 27, 2009
    Posts: 248

    Rustytoolss
    Member

    OK..my smaller 9 1/2 X2 system has a 15/16" wheel cylinder. And the 11 X 2 system have a 1.00" wheel cylinder (and a possible 1 1/16" wheel cylinder) . Bigger WC=more pressure.
     
  6. In general you can't have too much brakes. BUt you can have too much rear brakes that will lock up prematurely. If you look at some trucks, they have a load sensing proportioning valve that adjusts the rear braking to account for loaded vs unloaded.

    The best fix is to upgrade *both* front and rear brakes to be bigger and more capacity.
     
  7. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,519

    seb fontana
    Member
    from ct

    About 28% more with 11x2 and 1.00 cyl, about 37% more with the 1-1/16 cyl..Put an adj proportioning valve in [if you don't already have one] and you will be fine.
     
  8. Rustytoolss
    Joined: Jul 27, 2009
    Posts: 248

    Rustytoolss
    Member

    Yeah I do have an adjustable proportioning valve. Looks like I might be swapping out rear drum systems. Thanks.
     
  9. goose-em
    Joined: Aug 23, 2008
    Posts: 349

    goose-em
    Member
    from Louisiana

    Larger wheel cylinder will make the 11 inch drums add stopping power.

    I had assumed the same wheel cylinder.
     
  10. larger brakes wont heat up as fast and use to be the option on most wagons and trucks for towing.
     
  11. Rustytoolss
    Joined: Jul 27, 2009
    Posts: 248

    Rustytoolss
    Member

    I have found that some chevy trucks had 11 5/32 X 2 3/4 rear brakes, and some had 1" wheel cylinders. Any thoughts ? over the 11 X 2's..or would that be to much ? my truck weighs about 3700lbs with 11" disc / 2 15/16" GM calipers/ and a manual non booster master cylinder.
     
    Last edited: Mar 29, 2013

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2020 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.