Problems With 406 Master Cylinder

[Jamal 2]

Hi everyone!

 

I have got 206 GTi(266mm) front brakes and standard rear calipers on 1.6 GTi brake lines(with original big compensator) and a MC from a 406(23.8 mm diameter).

 

The system is air free, the MC is new from PUG.

 

The problem is: I have to push harder than the normal 1.9 to get enough brake force.

Could it be that I oversized the brakes with the MC? Just thinking about the fluid physics.

 

Have anyone meet this problem?

 

What is the size of the MC using GTi6(283) brakes?

 

Thanks for the help!!!

[Anthony 1,002]

Is the servo working correctly and sealed properly against the new 406 MC? I've not noticed any significant extra force needed with a larger MC whenever I've fitted them for people.

[Jamal 2]

I will test the servo today.

But it was ok with the old standard MC.

 

If I can't figure out the problem, will swap it for a smaller(22.2 from 605) or a standard GTi one.

[Cloverleaf 1]

What size are the pistons on the 206 brakes? What size are standard pistons? What size is the standard m/c? Then you should be able to decide if it's related to m/cyl size.

[Jamal 2]

206 GTi Piston 56 mm

Standard piston 48mm

406 MC 23,8

Standard MC 19.8 I think

Edited December 14, 2009 by Jamal

[pug_ham 244 3 Cars]

Standard GTI mc should be 20.9mm iirc.

 

Is on UK cars & would've thought it'd be the same on all GTI's.

 

Graham.

[B1ack_Mi16 67]

The whole point in fitting a larger diameter MC is to change the gearing ratio between pedal force and braking force.

 

The pedal is supposed to be harder to push with this setup unless you increase the total brake caliper piston area the same amount.

[Cloverleaf 1]

Your hydraulilc ratio is actually slightly better with this setup, 1:11.1, compared to your previous setup of 1:10.5 (using Graham's figure for std m/cyl size). Therefore, with the additional disc size and hence effective radius, you should have to apply less pedal force for the same braking torque (assuming the pads have the same coefficient of friction, caliper has the same stiffness etc).

[Jamal 2]

Standard GTI mc should be 20.9mm iirc.

 

Is on UK cars & would've thought it'd be the same on all GTI's.

 

Graham.

 

 

I wrote bad infos.

 

Std setup

48mm piston 20,6mm MC 248 mm disc

My setup

54mm 206 GTi piston 23,8mm MC 266 mm disc

 

So it has to be pushed a little harder. I think I will swap it for a 22.2 MC from a 605.

But I have to say after a few hard breakings it's good now.