The Triumph Dolomite Club - Discussion Forum

The Official Triumph Dolomite Range 1976 onwards parts catalogue indicates that the part number for a 1500 Clutch Master cylinder is part 158695 and that part number 138928 is used on both the 1300 and 1850s.

Looking in a Rimmers parts and accessories catalogue, edition 2.2, this gives part number 158695 for the 1500 Master cylinder but it lists a part number GMC1023 for the 1300 and 1850. My assumption is that this GMC part number has superseded the earlier number. Rimmers is the only supplier that I have found that actually indicates it can still supply a clutch master cylinder part 158695 (but at a cost of £142 and with a one week delay in sourcing the item). All the other suppliers I have looked at either do not list a 1500 master cylinder or where they do, they do not quote a part number or indicate it is the same 1300/1850 a GMC 1023 and all only cost about £45. MEV do include a comment that the units they supply has the correct 7/16 thread so there is no need to source an adaptor.

I did telephone Rimmers and asked if they knew what the difference was between a 1500cc master cylinder part 158695 which they are able to supply and the GMC1023. The response was that it has a larger reservoir which may be the case but I do not understand why this would be needed. The master cylinder that I took out of my green 1500hl dolomite had only covered about 38,000 miles when I purchased it so I am assuming that it still had its original master cylinder fitted and this had a longer push rod fitted so I am now wonder if this might be the difference.

In Dolly Mixture issue 212 I stated that I had removed that Master cylinder from my green 1500cc dolomite because with the engine removed I could see that the clutch pedal returned to a higher position than the brake and accelerator pedals and when I checked my other dolomites all the pedals were at the same height. I had not been aware of this when I had driven the car and it was not a problem. The reason it was returning to a higher position was because its push rod was slightly longer, by about 1/8 inch. However when I fitted a normal length push rod I could not select gears when the engine was running. The outcome was I managed to overcome the problem by fitting a 0.7 inch bore master cylinder with the normal shorter length push rod but it does make the clutch operation heavier.

I still have 5 in number old Master cylinders which I have removed from various 1500cc dolomites or have been given them having been told they have come from 1500cc dolomites which have a 5/8in = 0.625 bore, one 3/4in = 0.75 bore which I was told came from a 1500 dolomite. So it seems the normal size of the Master cylinder bore is 5/8in

Can you advise what the difference is between a Clutch Master cylinder part 158695 and a GMC1023

Just to complete the details of clutch hydraulics and to correct an error that I made in another post I have now checked on the various slave cylinders part number RTC7215, which has been superseded by GSY 105, that I have and they all have a 7/8in bore. When I looked at a spitfire clutch slave cylinder in MossEurope part GSY 103 a few months ago I think it was an aftermarket item that had a different pipe connection size and that this is why I decided not to purchase it and to file another notch in it. I now believe the bore size was the same as a GSY105.