Disc brakes : new pads = brake rub??

Discuss light weight issues concerning road bikes & parts.
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Delorre
Posts: 867
Joined: Sat May 24, 2014 12:09 pm

by Delorre

Yesterday I changed the front pads. I suspect Canyon had not mounted the calipers very very straight in the factory, so the pads were worn, but not even, and thought it wwas time for some new ones, and time for caliper alignement job. What I did

*after removing the old pads, I very gently tried to push back the pistons. I even put in the yellow piston blocker to be sure the pistons where all the way back;
*Installed the new pads
*Put in the red pad spacer, and squezed the lever a couple of times
*Put the wheel back in. As I have TA's, wheel can only be in the same exact place as before
*Loosened the caliper bolt, squeeze the lever, rebolt the caliper and loose the lever after it.

Result : lots of pads drag, and very little brake lever stroke before the brakes actually begin to brake. Compared to the rear, the difference is huge! When I look at the calipers, I notice there is almost 0 clearance between pads and disc, and this on both sides. After more than a hour of micro shimming, I managed to get the wheel turning 99% rub free, but I do not feel confortable the way it is.

What have I done wrong? Thepads are the same reference aas the old ones, so, that's not the cause.

by Weenie


traveller78
Posts: 4
Joined: Fri Apr 20, 2012 12:55 pm

by traveller78

Are these hydraulic calipers? My sram red 22 hydraulic calipers had air lock, I need to bleed the hydraulic before it could brake properly. After bleeding it, it was smooth.

Sent from my SM-G930F using Tapatalk

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Curious George
Posts: 255
Joined: Fri Sep 08, 2006 11:48 am

by Curious George

Bleed the brakes...
If you are running discs purchase a kit to DIY

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wheelbuilder
Posts: 331
Joined: Wed Feb 08, 2017 2:10 am

by wheelbuilder

Short of doing a complete system bleed, you can do this in a pinch if you don't have a bleed kit or the know-how. I'm assuming you are running Shimano road brakes by the mention of the red pad spacer. It will work for MTB as well. Your road caliper will have either one of two bleed nipple arrangements....... A hidden nipple that is covered by a small flush mounted rubber plug. Above that plug will be a 3mm allen head screw. OR a protruding nipple with a rubber cap and leash attached to it, actuated by a 7mm wrench. Either very slightly open the nipple by either turning the wrench flat about an eighth of a turn, or open the 3mm hex screw an eighth of a turn. A very small amount of mineral oil may come out. Have the pads removed before hand to avoid contamination. With the bleed port still slightly open, retract the pistons again with a tire lever or something plastic. This will create the space and stroke you are looking for.

wowamj
Posts: 6
Joined: Thu Oct 19, 2017 9:13 am

by wowamj

I guese you should go repair shop

Squashednuts
Posts: 250
Joined: Tue Apr 25, 2017 11:12 am
Location: Christchurch New Zealand

by Squashednuts

Delorre wrote:Yesterday I changed the front pads. I suspect Canyon had not mounted the calipers very very straight in the factory, so the pads were worn, but not even, and thought it wwas time for some new ones, and time for caliper alignement job. What I did

*after removing the old pads, I very gently tried to push back the pistons. I even put in the yellow piston blocker to be sure the pistons where all the way back;
*Installed the new pads
*Put in the red pad spacer, and squezed the lever a couple of times
*Put the wheel back in. As I have TA's, wheel can only be in the same exact place as before
*Loosened the caliper bolt, squeeze the lever, rebolt the caliper and loose the lever after it.

Result : lots of pads drag, and very little brake lever stroke before the brakes actually begin to brake. Compared to the rear, the difference is huge! When I look at the calipers, I notice there is almost 0 clearance between pads and disc, and this on both sides. After more than a hour of micro shimming, I managed to get the wheel turning 99% rub free, but I do not feel confortable the way it is.

What have I done wrong? Thepads are the same reference aas the old ones, so, that's not the cause.

I did the same thing recently

Changed pads...the new pads rubbed against the discs

Like you I realigned the calliper then bled brake...problem solved

https://www.youtube.com/watch?v=gQ_oIAPuQR8

This may help

Delorre
Posts: 867
Joined: Sat May 24, 2014 12:09 pm

by Delorre

Squashednuts wrote:
Delorre wrote:Yesterday I changed the front pads. I suspect Canyon had not mounted the calipers very very straight in the factory, so the pads were worn, but not even, and thought it wwas time for some new ones, and time for caliper alignement job. What I did

*after removing the old pads, I very gently tried to push back the pistons. I even put in the yellow piston blocker to be sure the pistons where all the way back;
*Installed the new pads
*Put in the red pad spacer, and squezed the lever a couple of times
*Put the wheel back in. As I have TA's, wheel can only be in the same exact place as before
*Loosened the caliper bolt, squeeze the lever, rebolt the caliper and loose the lever after it.

Result : lots of pads drag, and very little brake lever stroke before the brakes actually begin to brake. Compared to the rear, the difference is huge! When I look at the calipers, I notice there is almost 0 clearance between pads and disc, and this on both sides. After more than a hour of micro shimming, I managed to get the wheel turning 99% rub free, but I do not feel confortable the way it is.

What have I done wrong? Thepads are the same reference aas the old ones, so, that's not the cause.

I did the same thing recently

Changed pads...the new pads rubbed against the discs

Like you I realigned the calliper then bled brake...problem solved

https://www.youtube.com/watch?v=gQ_oIAPuQR8

This may help


Thx, I'll keep this in mind the next time I have to change pads. FYI : after a couple of rides, everything was fine : no rub, normal lever stroke etc. But next time, it will take me 10' to be back on the road instead of 1 hour 8)

Squashednuts
Posts: 250
Joined: Tue Apr 25, 2017 11:12 am
Location: Christchurch New Zealand

by Squashednuts

Delorre wrote:
Thx, I'll keep this in mind the next time I have to change pads. FYI : after a couple of rides, everything was fine : no rub, normal lever stroke etc. But next time, it will take me 10' to be back on the road instead of 1 hour 8)

1 hour's not bad
I changed front pads...no problem
Wee while later changed rear pads...cyclinder was stuck & I broke the calliper...brute force and ignorance :oops:
Then checked the net for what to do...maybe next time I'll reverse the order...net first :)

Lewn777
Posts: 150
Joined: Thu Mar 09, 2017 5:35 am

by Lewn777

Remove the wheel get a plastic tire lever and push the pistons back in because as the pad has worn the piston will be working further out, that's why they're rubbing.

If you removed the caliper or you think it wasn't aligned properly in the factory it's much better to get a dedicated caliper alignment tool than use a business card. http://www.jensonusa.com/Hayes-Brake-Pad-and-Rotor-Alignment-Tool

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CBJ
Posts: 1057
Joined: Tue Feb 02, 2010 4:22 pm
Location: Brooklyn

by CBJ

I totally disagree on suggesting a bleed as the first line of action. If you do not have experience aligning brakes my experience is this is the problem especially on something this new.

I agree with Lewn777 that a good caliber alignment tool is worth it and I also bought the black burn caliber push too.

I would never do the step you mentioned with the wheel off and squeezing. I do all adjustments after pad change with the wheel on the bike. Also sometimes you get it right on the first shot but not always so take your time and see what happens when you tighten the caliber. If the rotor is not straight this can also make it more difficult to align so check that too.

brackc
Posts: 1
Joined: Wed Feb 07, 2018 3:07 am

by brackc

Delorre, firstly the red "pad spacer" is more generally used to prevent the pistons falling out of the calliper during transport with the wheel removed than as part of the alignment and spacing procedure - just use the rotor!
Trying to align the rotor with the lever depressed is simply a first step before fiddling with it to get it fully straight, use your eyes and ears to refine the alignment further.
another thing to check is if the rotor is bent, then no amount of fiddling will get it back to perfect rub-free riding.

by Weenie


AJS914
Posts: 1753
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

I've had good luck centering using a folded business card.

Question: I have Sram road hydro levers. Is it possible to dial in more lever free play? I mean I want to pull the levers farther before the pads engage the rotor.

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