Wheel Cylinder, upgrade

[Vibraphone]

Hello all, Cold here in NYC, saving up parts like a squirrel for the weather to break, then back to the DIY projects. We work on the street here in NYC.

I'm doing the rear brakes on the '06 Vibe. Most parts look very old & well-worn. Drums are unbelievably bad--189K mi, could be orig?

Wheel cylinders: OEM are 11/16in bore. There's no reason to replace 'em with same bore when so many Toyota models have rear cylinders with larger bores. I'm not a performance nut, but it's easy to see a piston pushing a 3/4in or .92in piston is going to deliver better braking--especially on those peanut sized rear drums. Toyota makes many cylinders that look like same physical wheel cylinder, but with larger bores. I've found select years of: Solera, Avalon, Camry that have what I want.

Anyone found a specific Toyota aftermkt wheel cylinder that fits best? It looks like many have identical config as the Vibe/Matrix? Btw (I'm showing my age) but I've done this on several BMW 2002 cars, and even on a '61 Benz 190 that had 2 wheel cylinders per wheel! on all 4 wheels. What a job. I used Ford Falcon wheel cylinders for that one. Stopped on a dime.

[joatmon]

I've seen threads here about converting rear drums to disks, but don't remember seeing any about upgrading the drums to other drums.

I wonder if you switched to larger cylinders in the back if it would alter the power distribution between front and rear. Seems like most the braking on my 03s were the front disks, a larger cylinder might make the fronts even more dominant. But that's just wagging (Wild A-- guessing)

[jolt]

You will effect the brake balance from front to rear on the car by changing the wheel cylinder size. By going bigger on the rear wheel cylinders, you will have more, or stronger braking, on the rear tires. Since the rear has little weight on it, this could cause the rear tires may lock during braking. Of coarse with anti-lock brakes this will not happen, but you will be using the anti-lock brake system more as a result of the wheel cylinder size change. In the end you will have gained nothing. If your Vibe had more weight in the rear of the car, then you may gain braking by the wheel cylinder change but there is nothing to gain by changing size on a regular car except for more wear and tear on the anti-lock braking system.

[Vibraphone]

C’mon guys & gals. The majority here are armchair mechanics who haven’t done any of the mods or repairs in this forum. I’ve done many--over 60yrs. I spent my career working on Benz-BMW-Volvo-VW. My beloved little 2002 BMW’s (many) all suffered from weak rear (drum) braking—and they weighed average 300lbs LESS than our Vibes.

I expected this braking ratio argument to counter my small upgrade—it’s improved engineering vs performance—but I beg to differ. Based on simple physics. Upgrading a wheel cylinder 1.58mm will not alter the Front Disc-to-Rear Drum ratio. It will only make a very good system (albeit puny) better. Going from 11/16in OEM bore to 3/4in bore, the master cylinder will simply push the rear brake shoes to the drums faster, with less pedal effort.

For me, nothing’s better than better braking response—backed up by oodles of experience with my own rear drum cars, and many others I’ve worked on--especially American behemoths. Boy do slightly bigger drum wheel cylinders improve with those monsters. It’s commonly done in that world.

I’m puttin’ in .750 Raybestos WC370112--Element3 Wheel Cylinders. Ironically, they’re spec’d for the Vibe/Matrix, too. But for you purists out there the OEM ones are .6875. I suspect Raybestos knows what I know and kicked up the bore just a hair to improve on Vibe’s 1990’s technology.

[joatmon]

C’mon guys & gals.

wasn't trying to discourage you, just that I don't remember anyone here doing that before.

Would be cool if you could do some performance measurements, data to compare stopping distance before and after the mod

[andrewclaus]

The dimensions you're changing are probably okay. But a larger rear cylinder will take more fluid to actuate, will take more time to fill, and won't travel as far. But it will provide slightly more force across the lower range of travel. There are always trade-offs.