Wheel Cylinders For 9" Brakes

I'm installing 11" drum brakes on the front wheels of my M38A1. The rear wheels for now anyway are going to stay 9". I've read in the service manual that for 9" brakes the front wheel cylinders are 1" and the rear 3/4". I assume this is for balancing, to make sure the rear wheels don't lock up before the front.
If I'm putting larger diameter brakes on the front, would it make sense to install 1" wheel cylinders on the rear? Would they even fit?
Any thoughts are appreciated.
Thanks,
Ken

 

A guess. No matter what you do to the rear brakes, the rear 9s will never lock up before the front 11s. There's just too much difference. I've asked about lockup with the 9s, and apparently any lockup is difficult even with the original skinny tires. You could put the 1" cylinders in the rear and I'd guess it would be an improvement over the 3/4" cylinders.

Yes, almost all of the braking is done by the front wheels. The harder the braking, the more the weight transfers and the more the fronts dominate. In the later Jeeps, the proportioning valve intentionally reduces force on the rear cylinders in hard braking so they don't lock when they are lightened so much. If the rears lock up before the fronts, you could go into a spin. If the fronts lock up first, you'll lose steering and plow in whatever direction you're going ... likely a better outcome than a spin.

 

That line brought back so many memories... of both experiences....

 

I am putting 11" brakes on the front of my Jeep too, Ken. I have 66 axels with 10" X 2" brakes on it now, and bought a set of 71 front brakes from a member to upgrade mine. I think I would put it together with what you already have and try it out, it may be just fine, I don't think either way you will lock up one set of wheels. All the weight is on the front wheels anyway. If you don't like it you can put 10" X 2" brakes on the rear later. Just a suggestion, I have read here that the 11" and 10" work well together, so that is what I am doing, for the fact that you can still get the parts for both 11's and 10's at a reasonable price. Ken I have some be-build kits for 9" cylinders if you want them, I got them with the Jeep, and won't ever use them. Rick

 

I have 11's all around. Great upgrade. I had to have a shop do it years ago but they've worked well all this time.