My GTD Brake upgrade

[Simon]

Well, thanks to the excellent advice and help given on this board, I'm now getting a better picture of my future brake upgrade. I've decided on four pot calipers all round, with a separate spot caliper for the handbrake. I'm keeping (but fully rebuilding) my servos, and am installing a balance bar system to give me full adjustment front and rear.
I've got a couple of questions though and I was wondering if anyone could shed some light on them.
Firstly, piston size. whats the difference between calipers with, say, 1.38 pistons and the same pistons with 1.75 pistons. More surface area? why?
Also whats the difference between radial and lug mount calipers?
Sorry if these seem like daft questions, but I'd like to have a fuller understanding before I go messing with things.
Thanks guys.
Simon
Oh by the way, the car will be mainly for road use with maybe the occaisional track day.

 

[Simon]

Oh, and before I forget, when it's all fitted and up and running, how will I know when I've got the balance between front and rear just right? is it a feel thing? I DON'T want a repeat of my recent "trouble" /ubbthreads/images/graemlins/confused.gif

 

[Julian West]

Simon,

As a guess I'm starting with a .625" MC front and .7" rear. I'll start off by setting the balance bar as Carrol Smith describes in his book...

Jack the car with all four wheels off the ground. Get an assistant to alowly increase pedal pressure while you keep turning the front & rear wheels. keep increasing pedal pressure until either the front or the rear wheel is too tough to turn by hand. This will give you an indication of which 'end' will lock first, & you can adjust the balance bar accordingly.

The front should lock before the rear. If it doesn't you'll be doing 360's down the road everytime you brake hard!

If there isn't enough adjustment in the balance bar, you'll have to swap the MC's for a different size.

Thinking about it, I'm not sure how the servos will afect the operation.. might be worth trying it with the engine running??

 

[Simon]

[ QUOTE ]
The front should lock before the rear. If it doesn't you'll be doing 360's down the road everytime you brake hard!

[/ QUOTE ]


Hmmmm.....done that already...... /ubbthreads/images/graemlins/mad.gif

Thanks Julian.

 

[Malcolm]

Simon

You want as big a piston size as your budget allows. This will give you bigger brake pads so giving better braking control. Some of the cheaper systems give you 4 pot brakes but tiny pads. A big single or dual piston caliper could then give a better drive.

I guess you will be at teh track day so have a good look at all teh cars and ask around. You will see more there and gain more knowledge than any other way I know of.

For info only, I still use a single pot rear caliper with 4 pot Alcon front brakes, no balance bar with a single standard GTD dual line master cylinder. It works for me!

 

[Tony Hunt]

[ QUOTE ]
Oh, and before I forget, when it's all fitted and up and running, how will I know when I've got the balance between front and rear just right?

[/ QUOTE ]
A fun way to set up your brake balance is to find a clear grassed area, and with the aid of an assistant outside the car, brake firmly in a straight line from a reasonable(!) speed. The assistant checks which wheels lock up.
Adjust brake balance until the fronts just lock up first.

 

[Hershal Byrd]

Simon,
Here is a site that may have some helpful insight on setting up a brake system.
http://www.stockcarproducts.com/tech1k.htm

Hersh /ubbthreads/images/graemlins/smile.gif

 

[Julian West]

Check out the 'Braking capacity' thread on this Forum. Goram makes some wise comments, well worth taking on board!

Cheers!