I am in the process of overhauling the brakes on my 90 including fitting new pistons and seals to the callipers all round.

The pistons are Allamakes and the seals genuine Land Rover. The front callipers cleaned up nicely and the new parts fitted fine, however when I come to the rears the pistons are a very tight fit in the calliper, they have gone in but don't slide as easy as they should. Thinking this a bit odd I measured the new pistons and they measure 0.05mm larger than the originals, this seems a lot for hydraulic components.

So am I being picky or are these pistons just not made to close enough tolerances? I had hoped by buying parts that didn't come in a blue box I could avoid this sort of problem.

So the question remains are Allmakes parts as crap as Britparts? Or should I have known better and bought OEM/genuine?

Yes, Allmakes is a bit cheap and cheerful. however, five hundredths of a millimetre probably won't make that much difference. After all, there isn't (or there shouldn't be!) any metal to metal contact and the pistons are typically quite a bit smaller than the bores in the callipers, so differences of that magnitude are unlikely to be critical. They sit on the rubber seals. When I renewed my seals and pistons the new ones were a bit 'sticky' which I thought was a good thing as it meant they were nice and tight. They've been OK of over a year now. So if I were you I'd carry on and try them out on the car and see if they're OK. The brake pedal and servo can push them out a lot harder than you can with your fingers.

Pushing out is not the problem, they have to return easy buy the seal else you will get bind

yes I know but unless they're very bad they find their way back in sooner or later.

When I did the pistons on my Disco, Allmakes piston and seal kit, I found that the rear caliper needed a helluva lot more cleaning than the fronts. Dunno why, I suspect 'cos they get more srud caught in them. I'd remove them, make sure the piston bores are properly clean and try again. I used a wire brush mounted in a battery drill.

Cleaning the cylinder bores is probably the answer, the pistons are probably chromed so you can't do much with them, or may be fine-turned stainless.

Much of this stuff comes from the same place, regardless of the label on the box.

Peter

The main thing is the grooves in the cylinder that the seals go in. You want them to be in good condition and nice and sharp looking with no erosion or pitting, looking like they did wen they were freshly machined, so the rubber can make a good seal against them. Whilst you wouldn't want to use a particularly dirty or rusty cylinder, the rest of it is less critical as it shouldn't be making contact with the metal of the piston.

ive cant think that ive ever needed to clean piston bores apart from a wipe clean ,dirt seal groove and surface usually need wire brushing,piston should be very difficult to fit unless absolutely square