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I have had SRAM rival brakes on my road bike for a year and I am not impressed. They aren't very powerful, they eat pads and they require constant recentering to make them work. At the moment I can't get them to stop rubbing because one piston works much better than the other. If they were Shimano I would have sorted it by clamping the good piston and repeatedly pulling the lever while using min oil on the lazy piston
So what do I do with Stam brakes using normal dot fluid?
Wot! Has nobody had a problem with Sram road brakes?
I don't know these specific brakes but its the same procedure for any. calliper off, pads out, hold the piston that moves easily in, pump lever to get the sticky piston to move out ( but don't pop it right out) soak in correct fluid or smear with red rubber grease, work it in and out a few times. You can also centre the pads the hope way - see vid on their website. Its much better method than the loosen bolts, pull lever, tighten bolts method
Rubber grease will be the better method, strictly no brake fluid is a seal lubricant. It's common practice however.
Dont grease the pistons. The way a sram brake works is through the friction of a square o-ring seal that deforms as the piston extends, and then pulls the piston back in as it tries to reset itself. One of the common issues for lazy pistons is oil/grease getting on these seals and meaning they no longer bite the piston hard enough to pull it back in.
Best bet is to 'massage' the pistons. This should be done by the shop before sending it out, but I guess it doesn't always happen. I have a piece of old disc to do this, but I think you can use the pad spacer on the tapered end, hence the taper. Basically you need to push the pistons out, and force them back in a few times, depending on how sticky it is, that can be quite a few times. Obviously if the pistons have been running out a while, cleaning them up before resetting is a good idea.
Ben - yes thats how all disc brakes work but a sticky piston needs to be lubed. Its sticky because its dry
Yes, but if you use grease, the grease will get on the oring and it will no longer engage, and not pull the piston back, so it might be free moving, but it still wont retract. The oil is enough of a lubricant, grease is not a good idea IMHO.
Nope - red rubber grease is the correct thing to use with dot fluid brakes as the dot fluid is a poor lubricant. Its not the seals relying on friction on the pistons - its the way the seals ( not o rings) deform at the lip that provides the retraction.
All my brakes work perfectly, all are lubed with red rubber grease on assembly
OK after an hour fiddling, I tried Ben's method first as I don't have any rubber grease. After quite a few repetitions of the in-out with bad piston while clamping good piston, there is little if any improvement.
So, down to motor spares shop for some rubber grease and we will give that a shot!
I have never had such problems with Shimano brakes, it took very little manipulation to get their pistons reasonably equal again, accepting you will never get them exactly simultaneous .
mineral oil is a better lubricant than dot fluid
You can grease it for sure, it will move better! But as per the manual
" Grease will prevent the pistons from fully retracting into the caliper bores which will reduce braking performance."
I did spend some time with the guy who writes the manuals and he was pretty convincing on this from his own experience and playing about. They don't assemble them with grease, it's more likely not set up right from day one as the OP mentions. Otherwise you'd have to assume that every brake ever made by SRAM needed to be stripped down and rebuilt on day one.
That means stock grease which will damage the seals I assume - not the dot compatible red rubber grease which is designed and sold for this very purpose amongst others
You use grease on all other o-rings etc. but you run the piston 'dry' (well with a bit of dot fluid but you know what I mean). If you want to do it by the book that is.