MTB disk brakes rubbing. Tried everything

[Matuka]

Hi all

I have just replaced my promax decipher brake pads on the back wheel to try fix a poor braking issue. I have bled the brakes as well. But now i have two issues, the first is that the brakes are still not 100% effective, they are better than they were but they are not locking the wheel when I am at speeds over 20km/h. But I am assuming that it will take a while for the brakes to seat properly (I only changed them last night? )

The second issue is that the brakes are rubbing on the disk and I cant seem to fix it. I have checked the disk is not warped. If I loosen the calipers the wheel runs freely but as soon as I tighten them it stops the wheel. I have done this multiple times and am at a loss. I realise the promax are old entry level brakes but I am not quite in a position to get new ones so have to try sort these out. Thanks for any advice!

[Fred_MTB]

Hi all

I have just replaced my promax decipher brake pads on the back wheel to try fix a poor braking issue. I have bled the brakes as well. But now i have two issues, the first is that the brakes are still not 100% effective, they are better than they were but they are not locking the wheel when I am at speeds over 20km/h. But I am assuming that it will take a while for the brakes to seat properly (I only changed them last night? )

The second issue is that the brakes are rubbing on the disk and I cant seem to fix it. I have checked the disk is not warped. If I loosen the calipers the wheel runs freely but as soon as I tighten them it stops the wheel. I have done this multiple times and am at a loss. I realise the promax are old entry level brakes but I am not quite in a position to get new ones so have to try sort these out. Thanks for any advice!

Have you tried to loosen caliper , pull brakes and tighten while holding brakes . I changed mine last week . Was still rubbing a bit as if disc was warped but was sorted after a good ride

 

 

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[Schnavel]

Something else you may want to check:

 

Overtime, dirt builds up around the pistons in the caliper. As you pull the brake lever, the pistons push out, but they don't always fully retract. Try taking the brake pads out and checking the position of your pistons - are they fully retracted? If not, then use a tyre lever or similar tool to press them back into the calipers and then rebleed. 

 

If this fails, check that the disk isn't bent - sometimes very difficult to see. Have you perhaps got a different rotor that you can try to see if the problem persists?

[Matuka]

Have you tried to loosen caliper , pull brakes and tighten while holding brakes . I changed mine last week . Was still rubbing a bit as if disc was warped but was sorted after a good ride

 

 

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Hi Yes thanks I have tried tightening while holding brakes in. What I havent done yet is had a proper long ride which I will do when I have a chance

 

Something else you may want to check:

 

Overtime, dirt builds up around the pistons in the caliper. As you pull the brake lever, the pistons push out, but they don't always fully retract. Try taking the brake pads out and checking the position of your pistons - are they fully retracted? If not, then use a tyre lever or similar tool to press them back into the calipers and then rebleed. 

 

If this fails, check that the disk isn't bent - sometimes very difficult to see. Have you perhaps got a different rotor that you can try to see if the problem persists?

Thanks for this. When I initially installed the new pads the pistons where too close so I levered them all the way out. I lubricated them a bit with dot 4 as well hoping to free up the movement. I havent tried again though since then but was worried that this might be the problem. I will have a try this again tonight.

.

[V12man]

Hi all

I have just replaced my promax decipher brake pads on the back wheel to try fix a poor braking issue. I have bled the brakes as well. But now i have two issues, the first is that the brakes are still not 100% effective, they are better than they were but they are not locking the wheel when I am at speeds over 20km/h. But I am assuming that it will take a while for the brakes to seat properly (I only changed them last night? )

The second issue is that the brakes are rubbing on the disk and I cant seem to fix it. I have checked the disk is not warped. If I loosen the calipers the wheel runs freely but as soon as I tighten them it stops the wheel. I have done this multiple times and am at a loss. I realise the promax are old entry level brakes but I am not quite in a position to get new ones so have to try sort these out. Thanks for any advice!

Did you bleed with bleed blocks in the brake, or did you use the pads and rotor when bleeding?

[dirtypot]

If you loosen the caliper and spin the wheel and there's no noise/biting/stopping the wheel but there is when you tighten up the caliper, then it's an issue with the bolts.  I'm guessing you have no washers or spacers between the bolts and the caliper?  Often this can be an issue with caliper alignment.  

While holding the brakes in with a loose caliper, tighten up the two caliper bolts separately and slowly (a quarter of a turn per bolt at a time, then the other one).  If you tighten up one bolt tight, it can twist the caliper causing the brakes to rub.  Doing it incrementally and alternating which bolt you're tightening allows the caliper to be tightened without twisting.  Also, the caliper will often stay straight until the very last tightening turn - be sure to watch for this. 

 

As for the brake power - if you've bled the brakes correctly, then give the pads time to bed in.  Do a few heat cycles if you need to.   

[cfcjim]

This vid gives a few ideas which are explained well. Including those which Mr.DP mentioned above.

 

[Matuka]

Did you bleed with bleed blocks in the brake, or did you use the pads and rotor when bleeding?

I used the pads and rotor. 

 

 

If you loosen the caliper and spin the wheel and there's no noise/biting/stopping the wheel but there is when you tighten up the caliper, then it's an issue with the bolts.  I'm guessing you have no washers or spacers between the bolts and the caliper?  Often this can be an issue with caliper alignment.  

While holding the brakes in with a loose caliper, tighten up the two caliper bolts separately and slowly (a quarter of a turn per bolt at a time, then the other one).  If you tighten up one bolt tight, it can twist the caliper causing the brakes to rub.  Doing it incrementally and alternating which bolt you're tightening allows the caliper to be tightened without twisting.  Also, the caliper will often stay straight until the very last tightening turn - be sure to watch for this. 

 

As for the brake power - if you've bled the brakes correctly, then give the pads time to bed in.  Do a few heat cycles if you need to.   

Thanks! I will try this next. I didnt  tighten the bolts incrementally which in hind sight is quite stupid. The fact that tightening one could cause twisting makes sense. I will definitely try this. 

 

 

This vid gives a few ideas which are explained well. Including those which Mr.DP mentioned above.

 

Thanks I'm watching it now. 

[V12man]

I used the pads and rotor. 

 

That's the problem - they are too close - use a bleed block and you will be sorted.

[SwissVan]

*#[Redirect request to all road bike owners wanting disc brakes]#*

[stefmeister]

If you loosen the caliper and spin the wheel and there's no noise/biting/stopping the wheel but there is when you tighten up the caliper, then it's an issue with the bolts.  I'm guessing you have no washers or spacers between the bolts and the caliper?  Often this can be an issue with caliper alignment.  

While holding the brakes in with a loose caliper, tighten up the two caliper bolts separately and slowly (a quarter of a turn per bolt at a time, then the other one).  If you tighten up one bolt tight, it can twist the caliper causing the brakes to rub.  Doing it incrementally and alternating which bolt you're tightening allows the caliper to be tightened without twisting.  Also, the caliper will often stay straight until the very last tightening turn - be sure to watch for this. 

 

As for the brake power - if you've bled the brakes correctly, then give the pads time to bed in.  Do a few heat cycles if you need to.   

Most likely this.

Shine a flash light from the other side of the caliper while you carefully and incrementally tighten each bolt. This will give you a better view of what's happening when setting the caliper, and you should be able to gauge parallelism between the pads and rotor.

[dev null]

I always check clearance with light. Will show if you have an alignment issue also, mostly caused by bolts twisting the caliper out of alignment when you tighten and don't have those special dome/cove shaped washers to prevent that.

 

And as others said, always, always bleed with spacer. Besides ensuring clearances, it also prevents contamination of your pads by oil spills and your dirty, oily fingers.

[Eugene]

*#[Redirect request to all road bike owners wanting disc brakes]#*

None of the guys wanting disc brakes on their road bikes want to believe me on this.

[Eugene]

I struggled the first time I built a bike with disc's. A problem I experienced was the wheel would spin freely on the stand, but the moment I sat on the bike, it rubbed.

 

With my non engineering accountant brain, I assumed the stays were flexing somewhat.

 

I went to pains to see which side was rubbing, then I shifted the caliper in the opposite direction, using a credit card to create the gap and tightened it.

 

It worked perfectly.

 

Not sure if my method is mechanic approved, but it worked.

[lechatnoir]

And as others said, always, always bleed with spacer. Besides ensuring clearances, it also prevents contamination of your pads by oil spills and your dirty, oily fingers.

^^^THIS!!!

 

 

It worked perfectly.

 

Not sure if my method is mechanic approved, but it worked.

 

If it looks stupid, but it works, it's not stupid. thanks for the tip

[Matuka]

Thanks for the advice guys. I will use a spacer next time. You live and learn!  I will have another bash at it tonight using the advice.