XTR pads touching rotor

[Titanium Rocket]

Can any of you technical wizards help please: <?: prefix = o ns = "urn:schemas-microsoft-com:office:office" />

 

I have a dual control <?: prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />XTR setup. No matter what I do, the pads are always touching the rotors to some extent. Very rarely do the wheels rotate without touching.

 

At least once a month, I remove the pads, squeeze out the pistons, clean the piston surfaces and lube. I have brand new (un-bent) rotors. I have replaced the hydraulic fluid and re-bled them?..but nothing seems to make the pistons retreat enough. Are the clearances are just so fine that it?s a permanenet problem? I reckon they need another 0.25 mm clearance either side to avoid touching the rotor entirely. I

 

Is this normal? Anyone got any bright ideas?  Do other brands have this problem?

[Mojoman]

Are they new pads? Has it always been acting up or has it just started recently? Do the brakes drag excessively?

[Titanium Rocket]

1.  No, the state of the pads doesn't seem to be an issue.

2.  Not really excessive drag, really just touches the rotors as certain points during the revolution. But it should never touch, that's my point.

3.  Can't really remember if it was like this from new. Only know it's really pissing me off big time right now! 

4.  The kit is now 3 years old. Do hydraulic brake systems "wear out"? Can they lose their ability to effectively retract the pistons? Some sort of "wear" in that complex mechanism at the exit inside the reservoir?

 

[Reghard111]

When last did you replace the springsteel clips that pushes the pads back? They do get old, I tweaked mine for a bit more pressure on the XTR and it did the job fine!

[Giant]

Check your wheel/rotor alignment with the caliper.

is the rubbing evenly on both sides?

I find that before clamping the quick release, I very slightly move my wheel then clamp.

Should probably re-align the caliper, but I'm lazy

[Mario2]

I have to go to XT rotors for mine touch so much on Juicy/XTR rotors.

[Weight Weenie]

OPC never thought of that, does it really push back the pads ? Might solve allot of issues

[Titanium Rocket]

OPC - can't believe that pissy little spring really forces the pads apart....??

It takes considerable effort with a strong plastic goodie like a tyre lever to do this. Those little springs are really just to position the pad firmly aginst the piston surface. Anyway thanks, but I have already tried new springs. Alas, no difference.

 

[AndreZA]

You will have to play with the caliper position. I place a small torch below the caliper shining up so that I can see what's going on between the discs and pads. Then spin the wheel and see where it touches. Then move it that way. If it touches the other side then move it back a bit. You will find a place where nothing is touching anymore. Just take your time.

[Johan Bornman]

This is the nature of disc brakes.

There is no mechanism in the system to retract the pads and the only reason they do seem to retract a bit is thanks to some stiction and elasticity in the piston seal and fluid.

 

On cars, motorbikes and aeroplanes they constantly touch and there is no reason why people should expect them to behave differently on bicycles.

 

Further, the distance the pad travels from resting to engaged is in the order of 0.1mm - the "clearance" between pad and disc. Should the disc have the slightest run-out, it will touch as you describe.

 

You are right about the little springs on the pads. They cannot retract the piston, they're too weak. Their job is to stop the pads from rattling.

 

Also, it is no use constantly adjusting the system to avoid today's problem. Tomorrow you apply the brakes, ride through water and they're warped at a different place.

 

Upgrade to V-brakes or live with that one drawback of discs.

 

 

[Reghard111]

Yup, I was very frustrated with this before, also the more the pads wear the more the contact angle from the plate changes.

[Weight Weenie]

'Upgrade to V-brakes' ? Nee regtig Johan kom nou dis al 2010 man

[parabola]

OPC - can't believe that pissy little spring really?forces the pads apart....??

 

It takes considerable effort with a strong plastic goodie like a tyre lever to do this. Those little springs are really just to position the pad?firmly aginst the piston surface. Anyway thanks' date=' but I have already tried new springs. Alas, no difference.

 

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Spring is there really just to keep the pads on the pistons, the retracting power comes from the hydraulic fluid.

[BrendonMyb]

precisly ( spelling ) the reason why i dont like hydraulic system brakes

 

It eventually starts squeeking driving everyone & myself absolutely dilly.

 

Ive since "downgraded" to mech discs. The pads retract when i let go of the lever, they stop me just as well as hydraulic discs.

 

Best of all is they are low or rather almost no maintenance

 

This is just my opinion, hydraulic works really well on cars, motorbikes etc. due to wheels turning at higher speeds than bicycles hence very little squeeling

 

MTB on the other hand is slower than that & inveriably the inevitable squeeling comes about after a while unless your diligent enough to sand the pad down every so often to take glazing off

 

I wont go back to hydraulic but thats just me, other will probably nail me for this but a great set of mech disc brakes = very low - no maintenance except pad changes

[Johan Bornman]

 

Spring is there really just to keep the pads on the pistons' date=' the retracting power comes from the hydraulic fluid.[/quote']

 

 

Please explain.

[rawoke]

Try this I don't know how or why it works but it works for me every time

Loosen the bolts of the caliper where they are fasten to your fork/frame. Not the bolts/screw that holds the pads  !

 

Then pull a few times the brake lever, then pull and HOLD brake-lever WHILE fastening   the bolts you loosen.

 

I had it a few times, and every time this works.

This assume of course that your rim is not bent.