Master Cylinder - 19.0 vs 20.6mm

[ArthurH 5]

We are about to replace to master cylinder on the race 205 GTI.  I see that most brands offer a choice of two diameters (nominally 19.0 and 20.6mm).  Is it just down to preference and feel - i.e., a softer, longer travel pedal vs a shorter but harder travel?  Or are there other considerations?

 

TiA

[Richard309Sri XU5JA 205GTi 7]

I was thinking the 20.6mm is for the 1.9gti for extra braking due to increased engine power but now I am not so sure reading around - isn't the 20.6mm also meant to give more braking power/force? 

 

what brakes do you have front and rear? 

front ventilated discs? rear discs unventilated or rear drums? 

 

 

[ArthurH 5]

The championship rules allow a change of brake pad material, but have to retain the standard type of brakes, so for our 1.6GTI, vented fronts and drums on the rear.

 

The larger the bore of the master cylinder, the less hydraulic 'leverage' there will be at the brakes, so for any given amount of foot pressure the pressure at the pads will be less - but it will give a very 'solid' feel to the pedal.

 

We haven't yet taken ours off, so not sure which we have - I'm guessing the 19mm

 

[pug_ham 240 3 Cars]

All GTi's should have the 20.6mm bore master cylinder, the 19mm is for the base models.

 

I wouldn't be surprised to find a GTI with the 19mm one fitted though now, I've seen it before.

 

g

[ArthurH 5]

Thanks Grahm, based on your advice, I looked for a 20.5mm version.  I have found many suppliers suggest the 19mm fits all 205s and also many suppliers say the 20.6 fits all 205s   I guess the difference is between 'fits' and 'was originally fitted'

 

[pug_ham 240 3 Cars]

Yes, either master cylinder will fit as the servo bolt hole pattern is the same but whether it's the right size as the factory intended is a different matter.

 

Just had a quick look on autodoc and selected the 1.6 GTI as the model and on the first page of the results, the majority of them are 20.6mm but if you select the diameter to 21mm, all 20 are the correct size, just the price varies from £30.41 for a Bosch to £268.88 for a Ferodo!

 

g