Is It Possible To Reduce Brake Pedal Effort?

[bronsin]

I have severe polyneuropathy in my feet. When I bought this car (09 hatch basic with auto) three years ago I was not happy with the effort required on the brake pedal to stop the car.

Now my condition is worse and the effort is getting to be more than I think is safe. I drove a rental Cavalier recently and the effort was less than the Yaris.

Is there a way to make the brake pedal effort less?

Thanks!

[CTScott]

There are a few options, none of which would be trivial:

1. Increase the mechanical advantage of the brake pedal arm.

2. Use a more efficient brake booster (perhaps off a larger Toyota vehicle).

3. Increase the existing brake booster's assist by increasing the vacuum on it.

[bronsin]

No brake pad change? :confused:

[CTScott]

No brake pad change? :confused:

No. They can make your stop more aggressive, but changing them won't reduce the leg force.

[CoryM]

Brake pads can actually change the pedal effort, but it would be difficult to find which one. Different friction materials grip more initially, but then overheat sooner (and wear faster). If you bought your car used, try a set of OE pads. A lot of aftermarket pads require more effort to stop. That being said, I don't think that is your best option. The other thing that changes pedal effort is the size of the master cylinder. Smaller the bore, the less effort but more distance it requires. You could probably find a M/C that bolts up to the Yaris.
Your easiest solution will be to bump up the vacuum with a vacuum pump though. Search Summit racing etc for them. Problem is, they are meant to help cars that have very little vacuum. The Yaris probably already has 24" or more and those pumps may not do better. Some 90s ford diesel trucks had vacuum pumps which pulled bloody close to 30" though so they can be found. Just make sure to get a strong enough one.

After that maybe left foot brake if it's any better, or start thinking about hand controls.

PS: Sorry to hear about the feet.

[CoryM]

http://www.summitracing.com/parts/HLA-009428087/

29.5" vacuum according to that. Electric are noisy buggers, but easiest to install.

[CTScott]

http://www.summitracing.com/parts/HLA-009428087/

29.5" vacuum according to that. Electric are noisy buggers, but easiest to install.

That's a potentially fairly simple solution. It would be interesting to connect a vacuum pump to the booster and compare the difference from stock. I have a vacuum pump for AC repair that pulls about 27"-28" that I can test with.

[Yar Is Word]

Found this summary, part of a much longer article:

"If the braking system is only marginal, upgrading the pads and brake fluid and/or getting more air to the system will probably cure the problem at minimal cost. Replacing the stock rubber flexible hoses with stainless braid armored Teflon hoses will improve the ability to effectively modulate the braking force at moderate cost. When a decision is made to upgrade the braking system, make sure that the replacement components and system have been properly engineered and designed for your specific application ask technical questions and expect valid technical answers.

1) Discs should have curved vans and both greater thermal storage capacity and better airflow characteristics than OEM - otherwise you will not have achieved anything worthwhile. Depend on actual test results, not advertising claims. Discs should be mill balanced to less than 0.75 ounce-inch (54 g-cm), run out should be less than 0.002" (0.051 mm) and thickness variation should be less than 0.0007" (0.018 mm). On race applications these tolerance are typically reduced to .25 ounce-inch, 0.0005" and 0.0001" respectively.

2) Calipers should be stiff at elevated temperature. Again, look at laboratory test results, not claims. Calipers must be mounted true to the plane of rotation of the rotor.
3) Multi-piston calipers should have differential bores to reduce taper wear. Piston area should be consistent with master cylinder size.

4) Ideally no modifications to the knuckles or uprights should be required for installation.

5) Front to rear brake torque bias should be consistent with the dynamics of the specific vehicle."

The whole article here:
http://stoptech.com/technical-support/technical-white-papers/brake-system-and-upgrade-selection

[Astroman]

Please try to post your threads in the correct thread section. It's getting old moving all the stuff from the "general discussion" when this was DIY/service related. I've moved it to the proper sections :thumbsup: