Disc brake caliper centering
#1
Full Member
Thread Starter
Join Date: Mar 2021
Location: San Diego, CA
Posts: 283
Bikes: 1986 Schwinn High Sierra, 1989 Supergo Access Comp, 1989 Nishiki Pinnacle,1990 Trek 750, 1990 Trek 970, 1991 Miyata Quickcross, 1992 Bridgestone RB-2, 2002 Stumpjumper M4 Pro
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 157 Post(s)
Liked 266 Times
in
116 Posts
Disc brake caliper centering
Hi, newbie to disc brakes. Just got a 2003 bike with Shimano XTR discs (BR-M965). The front wheel calipers are not centered and rub very slightly on the inside caliper. It's consistently off-center through the entire rotation. The rotor seems straight and tight and the wheel is true. These brakes have the "post" mounting thing, where the mounting bolts are perpendicular to the rotor (see pictures). So it doesn't seem possible to adjust in/out with those bolts? I found a manual online here, but it's way over my head:
https://hollandbikeshop.com/images/SI-8CM0G-000-ENG.pdf
Any advice would be much appreciated, thanks.
https://hollandbikeshop.com/images/SI-8CM0G-000-ENG.pdf
Any advice would be much appreciated, thanks.
#2
LR÷P=HR
Join Date: Sep 2019
Location: SF Bay Area
Posts: 2,180
Bikes: 1981 Holdsworth Special, 1993 C-dale MT3000 & 1996 F700CAD3, 2018 Cervelo R3 & 2022 R5, JustGo Runt, Ridley Oval, Kickr Bike 8-)
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 867 Post(s)
Liked 1,205 Times
in
694 Posts
Maybe retract the pistons, slip a business card in the side that rubs, squeeze brakes several times, remove business card.
It's cheap to try.
Barry
It's cheap to try.
Barry
#3
aged to perfection
Join Date: Jun 2009
Location: PacNW
Posts: 1,817
Bikes: Dinucci Allez 2.0, Richard Sachs, Alex Singer, Serotta, Masi GC, Raleigh Pro Mk.1, Hetchins, etc
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 839 Post(s)
Liked 1,258 Times
in
663 Posts
that mounting will be hard(er) to center
best I can suggest is take the pads out and either replace them or re-use the old pads but
RE-ARC the retraction springs !
I have found that the Swiss Stop retraction springs are wimpy and so use the Shimanos which are better but I still "re-arc" them to get a bit more spring action
you might also try bleeding the line. if there's a bubble inside the caliper that could account for the behavior noted.
/markp
best I can suggest is take the pads out and either replace them or re-use the old pads but
RE-ARC the retraction springs !
I have found that the Swiss Stop retraction springs are wimpy and so use the Shimanos which are better but I still "re-arc" them to get a bit more spring action
you might also try bleeding the line. if there's a bubble inside the caliper that could account for the behavior noted.
/markp
#4
Senior Member
Join Date: Oct 2013
Location: Mich
Posts: 7,395
Bikes: RSO E-tire dropper fixie brifter
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked 2,979 Times
in
1,920 Posts
you might be able to adjust the axle to shift it over, or if that is not an option, add an axle spacer in between the hub & fork leg.
__________________
-Oh Hey!
-Oh Hey!
#5
Senior Member
Join Date: Feb 2017
Location: Northern Shenandoah Valley
Posts: 4,141
Bikes: More bikes than riders
Mentioned: 36 Post(s)
Tagged: 0 Thread(s)
Quoted: 1446 Post(s)
Liked 762 Times
in
570 Posts
Is there a model number on the caliper itself (a Shimano model number)? Perhaps with that, you could find some service info from Shimano that might offer a tip or trick on where to start.
#6
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,725
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 140 Post(s)
Tagged: 1 Thread(s)
Quoted: 5793 Post(s)
Liked 2,585 Times
in
1,433 Posts
On that mount, it's possible to shim the caliper inward, but not outward. Before doing so, try the steps suggested above, especially bleeding, since any air will limit pad retraction.
Then if the action is good, and you still have issues, you can make shims of paper, cloth or plastic. My personal favorite is paper soaked in oil because it's easy and durable. Also the hole punch reinforcements sold for ring binders are spot on perfect if the thickness is right. A caveat is thickness. I prefer to limit paper or cardboard shims to under 1mm. For thicker shims, I prefer plastic shim stock, or stock metal washers.
If you opt to shim, regardless of thickness or material, make sure that the shim fits on the flat mounting area ONLY, any contact outside that area will cause the brake to be tilted.
Then if the action is good, and you still have issues, you can make shims of paper, cloth or plastic. My personal favorite is paper soaked in oil because it's easy and durable. Also the hole punch reinforcements sold for ring binders are spot on perfect if the thickness is right. A caveat is thickness. I prefer to limit paper or cardboard shims to under 1mm. For thicker shims, I prefer plastic shim stock, or stock metal washers.
If you opt to shim, regardless of thickness or material, make sure that the shim fits on the flat mounting area ONLY, any contact outside that area will cause the brake to be tilted.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
Likes For FBinNY:
#7
LR÷P=HR
Join Date: Sep 2019
Location: SF Bay Area
Posts: 2,180
Bikes: 1981 Holdsworth Special, 1993 C-dale MT3000 & 1996 F700CAD3, 2018 Cervelo R3 & 2022 R5, JustGo Runt, Ridley Oval, Kickr Bike 8-)
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 867 Post(s)
Liked 1,205 Times
in
694 Posts
Soda Can makes great & durable shims.
Barry
Barry
Likes For Barry2:
#8
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,725
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 140 Post(s)
Tagged: 1 Thread(s)
Quoted: 5793 Post(s)
Liked 2,585 Times
in
1,433 Posts
Most definitely. But IME people have problems working with them when things like holes are needed. Since they're thin enough to be in my paper range, I opt for the convenience of going with paper in these applications.
FWIW soda can cuts are easy to get, and tend to be worse than paper cuts. That said, if you have a decent hole punch, soda cans are a great option for this.
FWIW soda can cuts are easy to get, and tend to be worse than paper cuts. That said, if you have a decent hole punch, soda cans are a great option for this.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
Likes For FBinNY:
#9
Senior Member
Join Date: Oct 2013
Location: Mich
Posts: 7,395
Bikes: RSO E-tire dropper fixie brifter
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked 2,979 Times
in
1,920 Posts
there are no pictures showing the description of the issue imo. cannot understand which way the tolerance issue is in question. ymmv
__________________
-Oh Hey!
-Oh Hey!
#10
Senior Member
Join Date: Apr 2011
Posts: 7,068
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 4410 Post(s)
Liked 1,566 Times
in
1,028 Posts
Hi, newbie to disc brakes. Just got a 2003 bike with Shimano XTR discs (BR-M965). The front wheel calipers are not centered and rub very slightly on the inside caliper. It's consistently off-center through the entire rotation. The rotor seems straight and tight and the wheel is true. These brakes have the "post" mounting thing, where the mounting bolts are perpendicular to the rotor (see pictures). So it doesn't seem possible to adjust in/out with those bolts? I found a manual online here, but it's way over my head:
https://hollandbikeshop.com/images/SI-8CM0G-000-ENG.pdf
Any advice would be much appreciated, thanks.
https://hollandbikeshop.com/images/SI-8CM0G-000-ENG.pdf
Any advice would be much appreciated, thanks.
However, this is not a new set up, so it is more likely you are having a problem of the pistons no longer moving symmetrically. Grab the lever and watch the pistons - do they move at the same time? Do they move the same distance?
If not, the pistons should be cleaned and lubed. If that isn't sufficient, I have had great success getting the slow piston to move by holding the more active piston while I pull the lever. A couple of those in and out gets the late moving piston freed up.
Don't just shim the pads. You'll find that the off center condition just gets worse as the one side gets stickier.
Likes For Canker:
#12
I'm good to go!
Join Date: Jul 2017
Location: Mississippi
Posts: 14,992
Bikes: Tarmac Disc Comp Di2 - 2020
Mentioned: 51 Post(s)
Tagged: 0 Thread(s)
Quoted: 6196 Post(s)
Liked 4,811 Times
in
3,319 Posts
I tend to agree with Kontact for the most part. You should check to make sure the gunk is cleaned off around the piston seals. Though it's not really necessary for both to move the same amount. All that is needed is for both to move some but not necessarily equal amount. And even if the pad doesn't visually move a perceptible amount, then it still isn't going to be causing you to pedal harder. Any warpage or out of true on your rotor will move the piston far enough to be out of the way. And even if there doesn't appear to be a gap, it's still okay, It doesn't need a perceptible gap if the rotors are true enough.
Likes For Iride01:
#13
Full Member
Thread Starter
Join Date: Mar 2021
Location: San Diego, CA
Posts: 283
Bikes: 1986 Schwinn High Sierra, 1989 Supergo Access Comp, 1989 Nishiki Pinnacle,1990 Trek 750, 1990 Trek 970, 1991 Miyata Quickcross, 1992 Bridgestone RB-2, 2002 Stumpjumper M4 Pro
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 157 Post(s)
Liked 266 Times
in
116 Posts
Thanks very much for the advice. I ended up using a thin metal washer on the inside of each fork mount. They are pretty crappy washers, but I suppose they're as good as soda cans. It centered the rotor anyway, now it spins clean w no rubbing.
Likes For SDHawk:
#14
Senior Member
Join Date: Oct 2013
Location: Mich
Posts: 7,395
Bikes: RSO E-tire dropper fixie brifter
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked 2,979 Times
in
1,920 Posts
Pics by chance?
__________________
-Oh Hey!
-Oh Hey!