Help - XTR Inconsistent Power - Not Lever Pull

My xtrs have same pull on levers every time but the power is noticably inconsistent -sometimes fantastic sometimes not great. Sometimes front, sometimes back. A friend has same problem. I've done everything imaginable and so has he. My hopes never did this. There is no air in the system and I use metal pads. When they are good they are fantastic then next time its as if they got a little oil on one of them ... then next time I ride brilliant again - wierd anyone else had this?

Believe me I have become an expert at bleeding them and my firend who has the same problem is a bike mechanic, a graduate engineer and used to build racing cars for a hobby (I mean he knows what he's doing).

I use Dual Controls but tried the XT levers for a month - same problem. My friend uses XT levers. Exactly the same problem. I have tried 203mm XT rotor on front and 180mm Hope rotor. Tried changing pads. Pistons dont stick. Lever pull is solid and perfect. Its just as if they decide to get an atmospheric film of moisture or grease on one of the rotors for a day then its gone the next. When it doesnt happen they are brilliant and can lock with one finger, when it does, its difficult to lock at all.

Hopes on same rotors are brilliant every time. I know two other people with same problem. Its not a real problem as one is usually working fine and overall they are light and stop you. Its just a niggle that shouldnt be there on an expensive piece of kit. Friend thinks its weak caliper design or very slight piston centering problem even though they dont actually stick at all (does that sound like a contradiction?).

LBS mechanic said this problem is why he gave up on his own XTR's (!). I would go for hopes but the DC's with rapid rise XTR are so fast at changing and totally noiseless over bumps which the old XTR mech is not even with the rubber bump stop fitted.

Should I give up and get another hobby?

What pads are you using? The stock organic pads are not too good IMO (although I never experienced the issue you are dealing with), I much prefer the metallic pads... More power and they last a lot longer.

I can't see why you are having this problem tough. You have tried different pads, if it's true there is no air in the system and there is no leak, rotors cleaned with alcohol? Why would they do this once in a while? Are they old? Could you get a new set under warranty maybe? Did you get the shop you got them from involved? What do they have to say about it?

If you reach your patience's limit, like Dual Controls and like Magura brakes, check this thread. Interesting...

From your post it sounds like this has nothing to do with air in the system etc. I recently got a set of XTR caliper/XT levers and have found them to work fantastic with the organic pads. I previously used the old XT four pot brakes with sintered pads and noticed that they worked better when warm; i.e. early on in a ride they would produce little power, but once they heated up they would be down right grabby. First, I suggest going to an auto part store and getting some disc brake cleaner to use on your rotors and pads. If that doesn't work, try a new set of pads. Good luck.

tried metallic and tried resin pads and a mix. Tried Fibrax and Shimano pads. Tried cleaning rotor with disc cleaner. Friends have same problem and the engineering guy claims its a weak design on the caliper. Not sure myself but know that if I change for an XT caliper it goes away. It could be a mixture of poor caliper design and the fact that they need sintered pads to get grab but sintered pads work better on a warm day with no moisture in the air (I'm in the Uk so we have a lot of that!). Maybe I'll give up on XTR like many others have.