Just can’t seem to get my front XTR brake working correctly. XTR Dual control lever and XTR caliper (975). It really lacks power and I can even get the wheel to move through with the lever pressed.

Tried different rotors (Alligator rotors), new pads and still pretty much the same. Swapped back to old XT rotors yesterday, sprayed disc brake cleaner on rotors/pads. Then watered down the area with watering can. Suddenly worked fine around the garden. Went back to get bike out the next day and its back to having no power and not grabbing.

Can’t see a leak, but it does seem like the rotors/pads keep getting contaminated. Any ideas as to what the problem is? If the caliper is leaking how do i fix this?

Thanks
Amit

Not sure what it could be, but if you’re after an IS mount front XTR caliper then I have a brand new one for sale. Looking for around £60 if possible, as I want to get a post mount caliper to replace it.

damitamit i have the same problem with my slx’s plus an ear peircing squeal.

Yep, they squeal too!

If I were to buy a new caliper (last resort), will a XT one work with the XTR levers?

daft question but have you tried bleeding it?

Yep, bled it. Lever has good feel.

I had exactly this with an XT M760 caliper. Bled it fine and it was nice and firm, but lacked any real power.
Swapped the lever, then the hose until I got to the caliper. Further fiddling, bleeding etc eventually led to the pistons which were making a slight squelching noise when the lever was applied. Turns out it was letting a bit of air in and just buggered up the power. Got an M595 caliper and all was well once more.
First thing would be a bleed though.

I had the exact problem with SLX calipers, got through a few pairs of pads as I was convinced I had contaminated them somehow. When the front brake started to lose power and squeal just like the back when all it had done was hang up in the garage, I realised the calipers were knacked. Swapped them with deore ones and the problem went away immediately. I have since upgraded to brakes that allow replacement caliper parts as the SLX brakes were 18mths old before they died.

18 months from an SLX caliper is rubbish. Wonder what caused them to go off so quickly?
My S/H XTs hve been going strong for over 2 years and the Deore M555s they replaced I’d had for 5 years and were still fine when they were packed away.

Put on my old XT caliper yesterday. Seemed to work. Went back the next evening and its the same again.

Now I’m not sure what is it!

Tempted to ditch the dual control and get a cheap set of SLX discs from merlin. (in time for mayhem)

If it’s not the caliper end it has to be the lever end. Can’t you try a different lever with the XTR caliper just to confirm?

Have you replaced the bladder under the top cap in the lever, you might have caught it whilst re-assembling it after bleeding. I damaged mine without realizing it and oil used to seep out under breaking, you might be able to just re position it.
Worth a try

I have similar problems with my front XTR. Squirt a bit of water on the pads and rotor and it could almost flip you over the bars, but try it the next day and all I get is a horrible squeal and huge stopping distance.

I don’t think the pads are contaminated or the caliper is leaking, and they are bled correctly I think. I’ve tried both Superstar sintered and kevlar pads, to no avail.

Back XTR is actually OK, and pretty reliable.

When I worked in the trade, I saw more a couple of sets of XTR DC’s with the same issue.

if you fully drain the system, take a look inside the master cylinder, there was a small number of early units where the master cylinder had been machined to such an extent that in one corner there was a tiny pin-prick hole or certainly machined too thinly. This could also have developed over time if it has been milled in this way.

I will stress I think this problem was very limited but it might be relevant and could even still be a warranty claim.

I had saints for a while and although there wasnt any major consistent leaking they did ‘weep’ a little sometimes 😕 causing horrible squealing and cutting down braking performance
I was told shimano brakes do this time to time and it can be helped by pumping out the pistons[minus the pads] not too far they pop but far enough to be able to clean around the piston sides,a wipe of silicon grease then push them back in place.I did this and it solved the problem.
Shimano brakes dont like cold conditions and do weep in that kind of weather.
If they are consistently leaking then im afraid its the bin for them as shimano decided in their infinite wisdom to make the seals within their systems NON REPLACEABLE.
🙄

whyter, that’s exactly the same problem I have.

resisted, what would this lead to? I cant see any leaking oil

Gonna try the XTR calipers with old XT levers tonight.

would lead to gradual loss of power over a few rides. The nature of the problem was that small amounts of fluid were forced inside the main lever body assembly so it was hard to detect.