GT6 Master cylinder

[petegardner_901]

Hi all

I am replacing the brake master cylinder on a late GT6 that originally had a servo fitted as standard. I have fitted an aftermarket Powertune replacement servo...BUT

I understand the master cylinders fitted to servo cars were 0.75" diam.

I can only find one place that has one - MEV Spares. It is a lot less expensive than, say Rimmers, who are saying the only option is now to fit the 0.70" diam. as the larger bore is unavailable.

So - couple of questions really - do I trust MEV Spares and do I really need the larger bore?

 

Thanks

Pete

[Clive]

You could fit one of the small reservoir land rover master cylinders, and use an extension to increase fluid capacity. The masters are very cheap, £15?

As to Rimmer's, could be the exact same part as MEV? 

Or search the his suppliers on size, they were used on all sorts of cars, not just triumph.

[dougbgt6]

Pete,

I had a struggle fitting my new servo to my late MK3, I suspected a problem with the master cylinder. Unlike you I couldn't find a supplier so borrowed a spare 0.70" from a friend. This moved the contact point on the pedal half way down! Unacceptable for me, so Clive's solution may be necessary if you stick with the 0.70" 

The rear brake cylinders are bigger on the late mk3 and unobtainable, Rimmers used to offer the smaller bore used on earlier mk3s instead. If you fitted those, would it reduce the volume of fluid required to make the 0.70" master acceptable? I'm not sure, calculations required!

I'm currently running 0.75" master and large bore brake cylinders, but when the rubbers fail, as rubbers do, there are no spares and I may be back to 0.70" and small bore, so VERY interested in your progress.

I also tried making the servo work on all 4 wheels, don't do it!  A frightening experience, I can confirm that front wheels only was best on the late mk3. 

Earlier MK3s with the servo fitted as an option had it on all 4 wheels.

The difference is down to the bigger cylinder sizes and the wider rear brake shoes on the late Mk3. The rear brakes on the late mk3 are much stronger and putting them on the servo is too much.

Doug

[johny]

I think its not just the size of the slave cylinders but also having a servo that makes a 0.75 the better option as both of these require more fluid to be moved so increasing peddle travel. I have a very cheap Land Rover 0.75 MC fitted instead of the standard 0.7 even though I have no servo and its been fine - the only down sides are: less fluid available to make up for leaks and; more risk of overflowing the reservoir in the event of pushing the pistons back in when changing brakes pads etc.

Ive had no problems but may get another 0.75 MC at some stage with a screw in reservoir which are bigger...

[rlubikey]

Pete, I would suggest you have the original reconditioned - it will probably be better than a new part.

Cheers, Richard

(Dual-circuit MCs where also 0.75" but they are longer and would require modification to your bulkhead to fit)

[Nick Jones]

I found a cast iron one intended for a Landrover which is takes a remote reservoir.  Minor mods made it possible to fit the plastic Girling reservoir.  Haven't actually tried it yet.....

Nick

[Pete Lewis]

places like car builder solutions  or merlin motor sport have a wide selection of build you own Cyl and reservoir  combinations and pushrods 

Pete