well this i hope will help some of us out on here. haveing experienced this myself it is pretty scary. when i upgraded my 71 dart from small bolt pattern to large i went from a 4 wheel manual drum setup to a manual front disc and drum rear. the rear drums went from the 10x 2' to 10x 2 1/2 '. everything went on perferctly. i didn't change the portion valve and brakes worked fine or so i thought. i quickly realised that the car stopped better at 20 mph or less. above that it would pull to the right. i looked into that thinking air in the line or a bad caliper. i then realised it would try to swap ends at higher speeds. at higher speeds it also would lock up pretty easy! well i wanted to pass this along to let everyone know what the possible cause and cure is. these are to articles i found realted to this common problem. http://68cuda.com/disk.html and this http://www.moparaction.com/tech/archive/disc-main.html
here are the excerpts from both articles pertaining to this problem.......
Having fat front rotors is a treat. I can now almost out brake most cars on the road. However there is a common problem with this setup that is easily remedied. The back brakes tend to lock up before the front brakes which is not good (fishtail in the rain). Solutions below:
1) My 8 3/4 from a Fury cop car with 11" drums uses a 15/16" rear wheel brake cylinder. Look closely at your rear end as you may have the same size, if you are unsure change it anyway as cylinders are $9.00 or so and why not put new ones in your car. If you swap out to a 7/8" or 13/16" version (old mopar P.N.# 2530136) the rear brake action will be lessened. These wheel cylinders were supposedly used on vans and trucks in the 80's."
"There are other ways to alter front/rear balance. One way, which reduces rear lockup, is to use a 7/8-inch rear wheel cylinder in place of the standard 15/16-inch unit. Try Raybestos part number WC37236 for this. (Original application: late 70-early 80s light-duty Dodge trucks w/10-in. rear drums).
i hope this helps!!!!!
here are the excerpts from both articles pertaining to this problem.......
Having fat front rotors is a treat. I can now almost out brake most cars on the road. However there is a common problem with this setup that is easily remedied. The back brakes tend to lock up before the front brakes which is not good (fishtail in the rain). Solutions below:
1) My 8 3/4 from a Fury cop car with 11" drums uses a 15/16" rear wheel brake cylinder. Look closely at your rear end as you may have the same size, if you are unsure change it anyway as cylinders are $9.00 or so and why not put new ones in your car. If you swap out to a 7/8" or 13/16" version (old mopar P.N.# 2530136) the rear brake action will be lessened. These wheel cylinders were supposedly used on vans and trucks in the 80's."
"There are other ways to alter front/rear balance. One way, which reduces rear lockup, is to use a 7/8-inch rear wheel cylinder in place of the standard 15/16-inch unit. Try Raybestos part number WC37236 for this. (Original application: late 70-early 80s light-duty Dodge trucks w/10-in. rear drums).
i hope this helps!!!!!
