Well, I'm moving on to the rear brakes on my truck and the wheel cylinders are listed at 1 3/16" bore for stock. Upon inspection of the units pulled, one is a 1 3/8" and the other is 1 1/4".
Obviously not correct. But it had me thinking (from a financial standpoint). Any reason I can't or shouldn't use the 1 1/4" bore wheel cylinders on both sides? Here is the wallet reason.
- RAYBESTOS WC3406 (1 1/4") $22.79 each on RockAuto
- RAYBESTOS WC3396 (1 3/16") $48.79 each on Rockauto
Nearly twice as much?
Now, I've mounted giant twin piston modern calipers on the front and I assume will be placing a new master cylinder soon (Need to figure that out still)
Going to the larger cylinder could affect the brake balance, front to rear but then again the odd mix from before didn't seem to be a problem, or did it.
Are there two different brake sizes on the rear? Most of the time that is why the wheel cylinders are different sizes. Best to match wheel cylinder to brake size. My 2 cents worth.
I've never driven the truck. it was parked in a barn 30+ years ago and who's know what Great-Grandpa did do it in repair terms (Farm use truck)
Yep, have the fun of old trucks, not knowing what was done before to them, especially farm trucks. Should have clarified better, does Rock Auto list different brake sizes? On my old 79 GMC, you had to know what brake system option it had (mine was JB8), cause everything was different for each brake option.
The smaller cylinder will have two effects if you install two new ones.
The pedal travel will be a bit shorter since the volume of fluid the MC moves with each increment of travel will not change if the same size as stock MC is retained. Since the WC are smaller, less pedal travel will result.
Also the amount of pressure the WC will push on the brake shoes will be less as the area of the WC is less then the larger one.
It may not be a problem since most braking is done by the fronts and if you install modern compound brake shoes which should have better grip you shouldn't see any problems braking.
Under full on panic braking these may be an issue but without testing who knows.
Also over time the rear shoes may wear slower than they would due to the lower pressures of the smaller WC but again only time will tell.
jimbbski nailed it, with one small exception: the WC doesn't apply pressure to the shoes, it applies force to the shoes.
As far as changing the system balance, I'd say buy the cheaper wheel cylinders and evaluate their performance once the truck is together. If you want to give me some more details on the brakes you've chosen, I will do some calculations for you.
My two cents-go with the 1-1/4. You will not be driving this thing in anger, and you drastically improved the front brakes. This is my opinion.
+1 to wheelsmithy.
THe 1.25 WC versus the 1.18 WC will generate 12% more force. Probably not detectable with the front upgrades.
Rog
On the xj Cherokee there was one year that had a 3/4" wheel cylinder on the ABS model and the non ABS was 11/16". Subsequent years including mine were all 11/16". After I replaced my third set of front brakes with the original rears still looking good I swapped in the bigger rear cylinders and added shoes with better friction materials.
The difference was amazing, particularly when pulling a trailer. It would be the first upgrade I did if I brought home another xj.
Assuming that the shoes are adjusted properly the volume of fluid shouldn't be much of an issue. The added force that slightly larger cylinders would have over stock would only help if you have upgraded the front brakes. I'd be interested in the price for the 1 3/8" ones myself.
RockAuto fail. Switched my search to Chevrolet VS GMC and was provided another option for the 1 3/16"
- CENTRIC 13466032 Brake Drum - Centric Preferred - Premium Premium Wheel Cylinder-Preferred $13.70.
Guess what I'm ordering...With the 5% discount from the shop thread.
