Hi

Went riding in Wales over the weekend with a new set of XT brakes. Set them all up before I went (gave them a bleed, adjusted pad contact etc). and they were great to begin with. But as the weekend went on I found I was having to pull the level further and further towards the bar before they began to bite.

Now there seems to be quite a bit of dead stroke before the pads actually make contact with the rotor. Is this a common issue in these brakes, and if so are there any remedies?

From having a quick look last night in the garage it seems the springs holding the pads in are doing a good job of pushing the pistons back in. But could I get away with less springiness to try to eliminate the dead stroke? Or is there a better way of bleeding the brakes so its more effort to return the pistons – therefore leading to the pads being moved not such a great distance from the rotor?

Any help appreciated. Cheers.

They should adjust for pad wear so as the pull is always the same.

Sounds more like there is air in the system.

How low are your pads? Mine go back to the bar when the pads are really low (though mine are SLX so don’t have the contact point adjustment).

Maybe try giving them a bleed again if they were right to start with, could be a sign of air in the system.

Were you using the proper Shimano funnel?

Check for leaks and blown seals, if nothing re bleed, sounds like you have air in the system.

Had this issue from new with my XT brakes.
I ended up taking the wheel out, squeezing the pistons out then pitting the wheel back in.

I also put red rubber ring grease on the pistons to help them move.

Thanks guys. I’ll try a rebleed. They were bled using all the proper funnel kit, and done from bottom up.

@fozzybear – You squeezed the pistons all the way out with the wheel removed? Did you keep pads in there?

As per fozzybears suggestion, I have never found any of my brakes self adjust properly for wear, take the wheels out, keep the bike upright and just pull the levers in fully 2 or 3 times, refit the wheels, try the brakes, if they still come in too far then repeat the process and just pull in once, test again etc. No need to bleed unless they are really spongy after they have actually bit/started braking

Have you used shimano brakes before? The servo wave action could be interpreted as a bit of dead stroke before pad contact, admittedly that wouldn’t explain why you were having to pull further to the bar as the day went on

@fozzybear – You squeezed the pistons all the way out with the wheel removed? Did you keep pads in there?

No, he means squeeze the lever 3-4 times without a wheel in, so that the pistons/pads come out further and stay further out.

The same thing happens with mine as the pads wear. I just use the reach adjuster on the lever and it seems to deal with it. I could probably improve things with a perfect bleed but I don’t get any sponginess so it’s fine.

P.S. The pad springs don’t push the pistons back – they just hold the pads against the piston.

No, he means squeeze the lever 3-4 times without a wheel in, so that the pistons/pads come out further and stay further out.

I did this at my initial setup. So as the day went on either the pistons got pushed back a bit, or didn’t extend out to account for pad wear. It was a very wet, muddy day and the pads do seem to be about 1/3 eaten. Is this something that I need to be doing on a regular basis?

The pad springs don’t push the pistons back – they just hold the pads against the piston.

Hmm, from looking at the caliper last night, when I press the lever the pads are moved against the rotor as expected. But then releasing the lever the piston definitely moves back ever so slightly ~.5-1mm – that’s without the wheel going around so I can only assume it’s the pad springs putting that pressure back onto the piston.

Nope, its just the lever sucking the fluid back up the hose and pulling pistons back in when you release it.

Nope, its just the lever sucking the fluid back up the hose and pulling pistons back in when you release it.

Would it make any difference if I bled the brakes with the pistons a bit further out. Effectively overfilling the reservoir?

It’s definately NOT the pad spring strength.
The pistons retract when the fluid pressure is released. It’s not so much a case of sucking fluid back into the system but more the effect of the seals on the piston returning to their original unflexed shape (due to the elasticity in the seal). This is a good thing. It’s designed to work like that.

Yes, you will probably find that you need to tweek the reach adjust a little as pads bed in and later again as they start to get low.

Something I have to do every now & again.

Pop the wheels out & pump the lever a few times or however many it takes until the pistons sit a little more proud of the calipers, should bring the bite point back right back without any dead point.

Would it make any difference if I bled the brakes with the pistons a bit further out. Effectively overfilling the reservoir?

Not 100% sure but I do tend to do this anyway.
I assume you’ve checked they’re centring/retracting evenly and you’ve not got a lazy piston.

(Happy owner of three sets of XT brakes)

+1 rsl. I have M770s and there is a lot of lever movement before pad engagement, even with the free stroke screw all the way in.

They all do that, mister.

Would it make any difference if I bled the brakes with the pistons a bit further out. Effectively overfilling the reservoir?

Definitely, and this is what I did with my XTs and they have been the best they’ve ever been since.

Remove caliper, pump the pistons out with the pads in(I did mine until they touched)
Then bleed the system(I do it with a syringe upwards to the funnel/syringe without plunger.
Once done, push pistons back in(You may get a little overflow out of the lever from the breather) and your brakes SHOULD be better. Mine were.

Great, cheers @kayak23 – that’s what I’m doing tonight then! 🙂

Have you used shimano brakes before? The servo wave action could be interpreted as a bit of dead stroke before pad contact

Having just fitted a pair of XT’s to a friends bike this was my first thought.

They came ready bled and work brilliantly, even after shortening the hose with no need to bleed.

I have the same issue, pretty sure there is a bubble of air lurking in the system somewhere, seems from doing some searching the caliper can hold bubble and needs a good hit to release them. Will try again, need to buy more oil first!

crashtestmonkey – Member

+1 rsl. I have M770s and there is a lot of lever movement before pad engagement, even with the free stroke screw all the way in.

They all do that, mister.
Erm, they dont actually. Both F+R on my M770s have very little lever travel before they bite and they are nice and firm too.

I’m not sure about XT but on the Deore 596 I have to adjust reach adjustment on the leaver as wear pads down. Once they are gone and put new ones in I have to adjust the leavers back to where they were when I first put the previous pads in. There is quite a lot of natural movement before pad contact and if the pad wears down my Deores seem very sensitive to this.

I’d agree with ^^^ about the Deore 595s, they seem a lot more sensitive to pad wear and dont seem to automatically compensate.

Saw this on Pinkbike today. Maybe it will help you:

http://www.pinkbike.com/news/tech-spotlight-5-minute-bubble-bleed-2014.html

silly question, how far in is your reach adjustment? if you have it quite far in then the lever will travel a long way back before biting, a small amount out might make a WORLD of difference…try it.

Thank you @curiousyellow – I’ll give that a go!