Can't remember how much it cost, but it was worth it at the time, because 3/4" models couldn't be found at reasonable cost: the MGA unit was nearly £300.Ĭan someone explain the issues concerned with the two m/c cylinder sizes. Just start, and go on thinking of ways to clean it until it's clean.Īlan, I remember getting an old unit from you a dozen years ago, for the yellow Sprite, and sending it off to be sleeved. But by the time a full revolution has been done the brakes should be fully released. The initial resistance is quite high but as soon as it begins to turn the pads are nudged back, but still drag. This is easily seen if, with the wheel jacked off the ground, you firmly apply and release the brakes. This should be very slight but that is all that is needed to ease the friction between pads and disc. What does release the piston is very slight run out in the discs. The beauty of disc brakes is that there is virtually no movement needed to bring the pads into contact with the disc, so pedal travel is minimised. The seals themselves are very soft and flexible and I very much doubt that there is sufficient energy stored when they "lozenge" to have any effect at all on the pistons.Īgreed, there is no spring to release the pistons (or pads). Having just replaced the pistons and seals on my Golf, and having done the same on my Sprite I don't believe the idea that the seals act to pull the pistons back. Apparently with drums all round, it works ok, though I wouldn't recommend that master cylinder to anyone having read so much bad press, and based on my own experience. I don't understand the detail but I'm sure youre right. It may be in the case of the TRW master cylinder that the residual pressure is maintained at too high a level so preventing that action. During operation the piston seal is lozenged and when the pressure is released to seal relaxes and due to its grip it pulls the piston back a small distance to release the grip. With disc brakes the main piston seal acts to retract the piston back into the cylinder when the pressure is released. I certainly would not buy another TRW one. Solved by adjusting the rod until they just released. The first one leaked straight out of the box so was returned and the second one arrived and I had that problem. Graham, thats exactly the problem I had with the second TRW one I had. I have bought a new Caparo master cylinder which I hope will work straight from he box. The rear drums release as they should, apparently because the springs are able to return the shoes, but obviously there are no springs on the discs.Īpparently there is a fix that involves drilling the tiniest of holes on the relief valve but I don't know the full details as thats not for me. When I press the brake pedal and then release it, the front discs remain locked for over five minutes. I bought it in 2010 and it has been sitting in a draw, so cannot say whether current production run is better.įor those that are interested, the problem is with the relief valve. Yesterday, I fitted a TRW master cylinder on my MGA and had a problem. Your old master cylinder bodies, even if the cylinders are pitted, are probably suitable for sleeving by a Co such as Past Parts although the service is not cheap. Some three years back I had a complaint from a Frogeye owner who tried three TRW master cylinders before settling on one that worked O.K. If you consider buying new then do first look at MGA Guru website regarding problems with TRW brand master cylinders. Probably works out cheaper anyway - under 50 quid on EBbay. Unless you enjoy the challenge of messing about just buy a new one. Doesn't harm rubber parts and doesn't remove any good metal, only rust. 1" dia! So that wouldn't go the length of a master cylinder, would it? (it does now)Įvaporust is what I use. but the cone which seats the back ends of the hone legs is approx. How would you go about cleaning it up? The bores are the easy bit.īTW, my new Sealey multi-purpose hone set goes down to 3/4" dia. One of them is very good, but it's also the rustiest throughout. MG Midget and Sprite Technical - Refurbishing Twin Master Cylinder I've got three 7/8" twin master cylinders, and I've been cleaning them up and test-honing them to find which is the least pitted.
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