Rear wheel cylinder size

[mgmad]

Hi all,
I've recently purchased a Maestro Turbo, which has been sat for a few years. Naturally, it needs some work to the brakes, especially rear cylinders.

I've got one out and measured bore at 11/16", but have found listings primarily for 5/8" (and some larger 13/16" ones). Which is correct?
I'm pretty sure these have been changed in it's past, so it's easily feasibly the wrong size has been fitted in the past.

Cheers
Andrew

[Jeff Turbo]

Hi all,
I've recently purchased a Maestro Turbo, which has been sat for a few years. Naturally, it needs some work to the brakes, especially rear cylinders.

I've got one out and measured bore at 11/16", but have found listings primarily for 5/8" (and some larger 13/16" ones). Which is correct?
I'm pretty sure these have been changed in it's past, so it's easily feasibly the wrong size has been fitted in the past.

Cheers
Andrew

There's not really a size as I've seem many different ones over the years that fit. The part numbers for all Montego's are GWC132 RH and GWC133 LH and these didn't change from start to finish of the models. For Maestros GWC1148 LH/GWC1147 RH. My Unipart parts list doesn't cover Maestro Turbos. There are many after market brake cylinders and I've not yet known one that doesn't fit

[Doctordiesel77]

I think the 13/16" ones will be for the Montego estate. As Jeff says, it doesn't really matter as long as you have the same size on both sides, if you want increased braking on the back, then use the bigger ones. I seem to remember going mad with a vernier & parts list & working out what size they all were, but can't remember whether I posted it on here or not.

[Nigel Fox]

The size you have measured is 17.46 mm (source Austin Rover repair manual 1983) this is probably a metric equivalent from an old imperial size. These are often listed as 17 mm on EBAY and similar sites, but I believe that these are correct for the Maestro. The Haynes manual for the Montego lists 17.46mm diameter as well, this may be an error, the supplement in this manual then lists 17.8mm diameter for the Montego saloon and 19.05 for the estate. I've come across 19 mm but never "18 mm". There is a further size which is shown in the Haynes manual for the Maestro van as 20.57 mm. The 19 mm diameter may be too much for the Maestro and could give rear wheel locking under extremal braking - but manufacturers are very conservative on rear wheel braking force (some people insist on braking hard on corners!) and 19 mm would probably be OK. The cylinders are not handed except for the position of the bleed nipple and this can be swapped over. For production the would have come with the bleed nipple fitted - hence 2 different part numbers for left and right but that doesn't cause any problem for us.

[Doctordiesel77]

The van ones are the same as Freelander and various Ford cars, they are different to the car ones, which don't fit any other vehicles as far as I know. The Maestro is 5/8" diameter, Montego saloon is 11/16" and Montego estate is 3/4". They are all imperial sizes, so probably best measured using imperial units to avoid the sort of confusion GM caused when they switched to metric threads on their oil filters The Maestro turbo parts list doesn't list a difference between Efi and turbo, which implies that Rover didn't upgrade the back brakes, so maybe a previous owner has upgraded to Montego sized cylinders? The Unipart catalogue has the Efi Montego using the estate cylinders but, as Jeff has already pointed out, the Rover catalogue says that the saloons are all the same. In theory the 'twin G.P.' valve should stop the back wheels from locking up under heavy braking.