Size of brake master cylinder?

[spetz]

Can someone tell me the size of the brake master cylinder on FTO's? All models, and if they are the same as Magna or Lancer items.

Thanks

[Shane001]

FTO GPX Manual is 15/16"
FTO GPX Auto is 1"
Not sure about other models

[spetz]

And which one has the best "feel"?

[Bennoz]

And GR is 7/8"

I've used them all & the difference is minimal. The best master cylinder mod you can do is the bracket that stops the master cylinder & booster assembly flexing the firewall under heavy braking.

[Shane001]

I'll be testing the 1" at the track soon, but as Ben said I doubt there will be a huge difference.

Also just to add to this, the boosters are also different sizes. The GPX auto is smaller than the GPX manual. So if you swap the booster & master cylinder together you'll probably notice no difference as they may balance each other out.

[spetz]

I am a noob to this.
What is a booster?

[Bennoz]

Big black thing that sits behind your master cylinder

Uses manfold pressure to assist brake pressure.

[spetz]

So, bigger booster = better braking?

[spetz]

Shane, did you end up testing the 1" master cylinder?

[Shane001]

not yet, hopefully this month.

[Dras]

Please correct me if I am wrong but as I understand it, a bigger bored on the brake master cylinder will pump more fluid to each caliper with the same amount of pedal movement. As more fluid is moving with the same amount of pedal travel, the pedal will be harder to press, in comes a bigger brake booster to make the pedal feel lighter.

This is all well and good but all you are achieving is having less brake pedal travel between not braking at all and locking up the brakes. Unless you are matching these 'upgrades' with bigger callipers, all I can see being achieved is that the brake pedal will give less feedback and the car becomes less drivable.

Am I wrong?

[Bennoz]

From an engineering perspective, you actually increase the fluid quantity but at a cost of pressure at the caliper.

Realistically, the only reason for changing up a master cylinder size is if you find too much pedal travel with larger calipers fitted.

http://www.grc.nasa.gov/WWW/K-12/WindTu ... ciple.html

[Miv3c]

what if someone like me is running factory brakes on my gpx and have heaps of travel before anything happens???

[Dras]

It may be time for you replace the brake fluid.

[spetz]

In my case though I have a Lancer and did an FTO brake upgrade but with a standard master cylinder which was for single pot calipers front and drums rear.
So I don't know what it would be best to upgrade to