Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Stacking caliper adapters

Notices
Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

Stacking caliper adapters

Old 08-11-21, 11:32 PM
  #1  
sjanzeir
Keeling over.
Thread Starter
 
sjanzeir's Avatar
 
Join Date: Apr 2016
Location: Jeddah, Saudi Arabia
Posts: 1,354

Bikes: 1990 Raleigh Flyer (size 21"); 2014 Trek 7.6 FX (size 15"); 2014 Trek 7.6 FX (size 17.5"); 2019 Dahon Mu D9; 2020 Dahon Hemingway D9

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 668 Post(s)
Liked 1,299 Times in 418 Posts
Stacking caliper adapters



I came across this while looking at 203mm rotors and wondered just how safe and reliable this kind of setup could be. I'm not a formally trained engineer, but I see a few too many possible fault points here. Wouldn't you agree?

Last edited by sjanzeir; 08-12-21 at 07:19 PM.
sjanzeir is offline  
Old 08-12-21, 02:40 AM
  #2  
CliffordK
Senior Member
 
CliffordK's Avatar
 
Join Date: Nov 2014
Location: Eugene, Oregon, USA
Posts: 27,273
Mentioned: 216 Post(s)
Tagged: 0 Thread(s)
Quoted: 17015 Post(s)
Liked 3,853 Times in 2,856 Posts
Fault points like missing the upper mounting bolt?

Likely it only has moderate side to side force, but does experience a significant sheer force in tangent with the disc.
CliffordK is offline  
Likes For CliffordK:
Old 08-12-21, 02:45 AM
  #3  
sjanzeir
Keeling over.
Thread Starter
 
sjanzeir's Avatar
 
Join Date: Apr 2016
Location: Jeddah, Saudi Arabia
Posts: 1,354

Bikes: 1990 Raleigh Flyer (size 21"); 2014 Trek 7.6 FX (size 15"); 2014 Trek 7.6 FX (size 17.5"); 2019 Dahon Mu D9; 2020 Dahon Hemingway D9

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 668 Post(s)
Liked 1,299 Times in 418 Posts
Originally Posted by CliffordK View Post
Fault points like missing the upper mounting bolt?

Likely it only has moderate side to side force, but does experience a significant sheer force in tangent with the disc.
I actually missed that. But still, as you said, that's putting a lot of faith in an extra pair of 6mm bolts.
sjanzeir is offline  
Old 08-12-21, 04:45 AM
  #4  
Barry2 
LRP=HR
 
Join Date: Sep 2019
Location: SF Bay Area
Posts: 1,649

Bikes: Holdsworth 1979 Special, C-dale 1993 MT3000 Tandem & 1996 F700CAD3, Cervelo 2022 R5 & 2018 R3, JustGo Runt, Ridley Oval, Kickr Bike 8-)

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 640 Post(s)
Liked 819 Times in 477 Posts
JENGA !

Barry
Barry2 is offline  
Old 08-12-21, 05:46 AM
  #5  
cobba
Senior Member
 
Join Date: Aug 2006
Posts: 1,871
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 170 Post(s)
Likes: 0
Liked 53 Times in 42 Posts
Spend a few $ and buy the correct adapter.

https://www.jensonusa.com/Shimano-F2...-Brake-Adapter
cobba is offline  
Likes For cobba:
Old 08-12-21, 05:52 AM
  #6  
hokiefyd 
Senior Member
 
hokiefyd's Avatar
 
Join Date: Feb 2017
Location: Northern Shenandoah Valley
Posts: 3,991

Bikes: '18 Redline Zander, '14 Surly Pugsley, '97 GT Vantara, '97 Trek MultiTrack 750, '70 Peugeot UO-18 Mixte

Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 1383 Post(s)
Liked 670 Times in 505 Posts
Additionally, for what it's worth, those calipers should not have the ball-and-cup washers as shown in the image -- they're designed to sit square with the mounting surface, with only a flat washer under the M6 bolt head. It appears that the bolt head is not square with the caliper, indicating some sort of misalignment somewhere. It's not clear whether that really is a long bolt that does thread into the posts on the fork or if it's just set in the hole for the photo.
hokiefyd is offline  
Likes For hokiefyd:
Old 08-12-21, 06:20 AM
  #7  
andrewclaus
Senior Member
 
Join Date: Feb 2012
Location: Golden, CO and Tucson, AZ
Posts: 2,595

Bikes: 2016 Fuji Tread, 1983 Trek 520

Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 599 Post(s)
Liked 478 Times in 315 Posts
Originally Posted by hokiefyd View Post
Additionally, for what it's worth, those calipers should not have the ball-and-cup washers as shown in the image -- they're designed to sit square with the mounting surface, with only a flat washer under the M6 bolt head. It appears that the bolt head is not square with the caliper, indicating some sort of misalignment somewhere. It's not clear whether that really is a long bolt that does thread into the posts on the fork or if it's just set in the hole for the photo.
That's a good catch. In addition, it looks like there's no way to thread a longer bolt through the upper holes in the adapters, they're so misaligned.

Yeah, that's a bad installation. I've seen a few (maybe 5 mm) stacks of conical washers between the frame and the caliper, and that didn't bother me much, but this one does.

The guy who mentored me on all sorts of mechanical work stressed to me the importance of brakes. If you mess up on a drive train, the vehicle stops working. If you mess up on the brakes, the vehicle doesn't stop. He insisted on checking my first couple of solo brake jobs. That was for cars, but I use it for bikes, too.
andrewclaus is offline  
Likes For andrewclaus:
Old 08-12-21, 06:48 AM
  #8  
base2 
Doesn't brain good.
 
base2's Avatar
 
Join Date: Jun 2015
Location: Pacific Northwest
Posts: 2,374

Bikes: 5 good ones, and the occasional project.

Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 1308 Post(s)
Liked 1,015 Times in 591 Posts
Originally Posted by hokiefyd View Post
Additionally, for what it's worth, those calipers should not have the ball-and-cup washers as shown in the image -- they're designed to sit square with the mounting surface, with only a flat washer under the M6 bolt head. It appears that the bolt head is not square with the caliper, indicating some sort of misalignment somewhere. It's not clear whether that really is a long bolt that does thread into the posts on the fork or if it's just set in the hole for the photo.
The ball & cup washer set up there is actually pretty common. I've built hundreds of bikes with the ball/cup on top of the caliper (as shown) The reason is to account for an off-square drilled hole evenly loading the bolt/hole threads & bolt head; Or both above & below the caliper for the same reason, but to also allow caliper rotation to better square the frame mounting face to be perpindicular with the plane of the rotor. Townie Go! OEM single piston mechanical disc brakes for example, spring immediatly to mind.

The rear caliper mount of Giant branded frames are the worst offenders, IME. I think they heat treat the frames after facing the mounting surface & invariably there is some movement in mount surface perpindicularity. The mounting surface becomes not perpindicular to the rotor, & indeed some times not even in the same plane as itself as the frame stresses equalize during treatment.

This appears to be Rockshox fork. Older Avid/Sram post mount adaptors come with the ball/cup washers & instructions to install the cup/ball washers on both sides of the caliper (2 each per bolt.) For obvious reasons, the instructions instruct the ball/cup not be installed at the post interface to the frame. The lever action there would be insane.

https://www.worldwidecyclery.com/pro...mm-rear-rotors

Installed per instructions by Richard Mozzarella, on Flickr
Note the ball washer under the caliper nested in the mating cup of the post.

Last edited by base2; 08-12-21 at 07:09 AM. Reason: Numerous grammer & typographical errors
base2 is offline  
Likes For base2:
Old 08-12-21, 07:09 AM
  #9  
cobba
Senior Member
 
Join Date: Aug 2006
Posts: 1,871
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 170 Post(s)
Likes: 0
Liked 53 Times in 42 Posts
Originally Posted by hokiefyd View Post
Additionally, for what it's worth, those calipers should not have the ball-and-cup washers as shown in the image -- they're designed to sit square with the mounting surface, with only a flat washer under the M6 bolt head. It appears that the bolt head is not square with the caliper, indicating some sort of misalignment somewhere. It's not clear whether that really is a long bolt that does thread into the posts on the fork or if it's just set in the hole for the photo.
With some adapters you're supposed to use those spherical washers above the caliper.

+20mm adapter
https://si.shimano.com/pdfs/si/SI-8170A-001-ENG.pdf

+23mm adapter
https://si.shimano.com/pdfs/si/SI-0146A-000-00-ENG.pdf



cobba is offline  
Likes For cobba:
Old 08-12-21, 07:15 PM
  #10  
cobba
Senior Member
 
Join Date: Aug 2006
Posts: 1,871
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 170 Post(s)
Likes: 0
Liked 53 Times in 42 Posts
When you double stack those types of adapters, you won't have a straight hole going through both adapters.


cobba is offline  
Likes For cobba:
Old 08-16-21, 06:05 AM
  #11  
hokiefyd 
Senior Member
 
hokiefyd's Avatar
 
Join Date: Feb 2017
Location: Northern Shenandoah Valley
Posts: 3,991

Bikes: '18 Redline Zander, '14 Surly Pugsley, '97 GT Vantara, '97 Trek MultiTrack 750, '70 Peugeot UO-18 Mixte

Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 1383 Post(s)
Liked 670 Times in 505 Posts
Originally Posted by base2 View Post
The ball & cup washer set up there is actually pretty common.
Thanks! I learned something. I've only ever seen them used above and below the caliper ears (as in the Avid BB7). I've not seen them used only above the caliper ears before. But I can understand from your description how they'd be useful.
hokiefyd is offline  
Likes For hokiefyd:
Old 08-16-21, 07:32 AM
  #12  
base2 
Doesn't brain good.
 
base2's Avatar
 
Join Date: Jun 2015
Location: Pacific Northwest
Posts: 2,374

Bikes: 5 good ones, and the occasional project.

Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 1308 Post(s)
Liked 1,015 Times in 591 Posts
Originally Posted by hokiefyd View Post
Thanks! I learned something. I've only ever seen them used above and below the caliper ears (as in the Avid BB7). I've not seen them used only above the caliper ears before. But I can understand from your description how they'd be useful.
No worries. Learning is one of the reasons I this forum.
__________________
I shouldn't have to "make myself more visible;" Drivers should just stop running people over.

Car dependency is a tax.
base2 is offline  
Likes For base2:
Old 08-16-21, 08:45 AM
  #13  
cobba
Senior Member
 
Join Date: Aug 2006
Posts: 1,871
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 170 Post(s)
Likes: 0
Liked 53 Times in 42 Posts
Originally Posted by base2 View Post
This appears to be Rockshox fork. Older Avid/Sram post mount adaptors come with the ball/cup washers & instructions to install the cup/ball washers on both sides of the caliper (2 each per bolt.) For obvious reasons, the instructions instruct the ball/cup not be installed at the post interface to the frame. The lever action there would be insane.

https://www.worldwidecyclery.com/pro...mm-rear-rotors

Installed per instructions by Richard Mozzarella, on Flickr
Note the ball washer under the caliper nested in the mating cup of the post.
That setup looks like it might be wrong for that caliper, the pads aren't connecting with the inner part of the brake track on that rotor and they're probably overhanging the rotor.

The top CPS washer stack is about 5mm thick, that will give you an idea of how thick the lower spacers are.

With the SRAM/Avid spacers, there is spacer setups for CPS type calipers (BB7's and older Avid/SRAM hydraulics) and there is spacer setups for standard type caliper (anything that isn't a CPS caliper).

SRAM adapters: https://www.servicearchive.sram.com/..._mtb_rev_e.pdf


* 20mm (160-180mm & 180-200mm) spacer stack for a CPS caliper


* 20mm (160-180mm & 180-200mm) spacer stack for a standard caliper.



If you use a CPS spacer stack with a standard caliper, the pads will overhang the rotor by about 5mm, this is something that shouldn't happen.
Overhanging pads will get a step worn in them, this could lead to brake failure.




cobba is offline  
Old 08-16-21, 10:43 AM
  #14  
base2 
Doesn't brain good.
 
base2's Avatar
 
Join Date: Jun 2015
Location: Pacific Northwest
Posts: 2,374

Bikes: 5 good ones, and the occasional project.

Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 1308 Post(s)
Liked 1,015 Times in 591 Posts
Originally Posted by cobba View Post
That setup looks like it might be wrong for that caliper, the pads aren't connecting with the inner part of the brake track on that rotor and they're probably overhanging the rotor.

The top CPS washer stack is about 5mm thick, that will give you an idea of how thick the lower spacers are.

With the SRAM/Avid spacers, there is spacer setups for CPS type calipers (BB7's and older Avid/SRAM hydraulics) and there is spacer setups for standard type caliper (anything that isn't a CPS caliper).

SRAM adapters: https://www.servicearchive.sram.com/..._mtb_rev_e.pdf


* 20mm (160-180mm & 180-200mm) spacer stack for a CPS caliper


* 20mm (160-180mm & 180-200mm) spacer stack for a standard caliper.



If you use a CPS spacer stack with a standard caliper, the pads will overhang the rotor by about 5mm, this is something that shouldn't happen.
Overhanging pads will get a step worn in them, this could lead to brake failure.




Indeed. That is why it is a 185mm rotor. I had the issue you describe with a 180mm rotor.

I could find a mm or so facing the powdercoat off fork post mounting face. But it seems to work well enough & has full pad contact.

I'm not worried.
__________________
I shouldn't have to "make myself more visible;" Drivers should just stop running people over.

Car dependency is a tax.
base2 is offline  
Old 08-16-21, 07:52 PM
  #15  
cobba
Senior Member
 
Join Date: Aug 2006
Posts: 1,871
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 170 Post(s)
Likes: 0
Liked 53 Times in 42 Posts
Originally Posted by base2 View Post
Indeed. That is why it is a 185mm rotor. I had the issue you describe with a 180mm rotor.

Why didn't you just buy an adapter for the 180mm rotor?

If you ever want to replace the rotor, there won't be much of a choice in what you can get.


I could find a mm or so facing the powdercoat off fork post mounting face. But it seems to work well enough & has full pad contact.

Do the pads overhang the rotor by a couple of mm or do they have full contact?
cobba is offline  
Old 08-16-21, 09:20 PM
  #16  
base2 
Doesn't brain good.
 
base2's Avatar
 
Join Date: Jun 2015
Location: Pacific Northwest
Posts: 2,374

Bikes: 5 good ones, and the occasional project.

Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 1308 Post(s)
Liked 1,015 Times in 591 Posts
Originally Posted by cobba View Post
Why didn't you just buy an adapter for the 180mm rotor?
Because I was at the mercy of what the bike shops had in stock. I went to 4 bike shops and this was the best that the 4th bike shop could come up with. They assured me it was the correct one. It turns out it was the correct one for a 185mm rotor, but I didn't realize that for a few years. A the 2.5 mm larger radius of a 185mm rotor was just the easier fix, since I needed a rotor anyway. So that's what I did. I do see what you are saying. A 17.5 upper/10 lower should be proper for a SRAM/Avid caliper on a 180mm rotor. But this caliper is a TRP caliper and a 185 rotor, hence the 12.5 lower post to compensate for difference in my installation. If the proper 10 mm post was included in the package the bike shop handed me, I surely would have used that & saved all the trouble. Page 8 illustration 25S of the pdf you linked to is the closest illustration the installation I have. I got here by way of experimentation & empirical evidence to derive the best fit. I believe I have succeeded.

If you ever want to replace the rotor, there won't be much of a choice in what you can get.
I'll cross that bridge when I get there. There is hardly anything more common than a post mount adapter & now that I have access to QBP, JBI and the other usual suppliers, none if this is likely to be an issue.

Do the pads overhang the rotor by a couple of mm or do they have full contact?
Nope. the peak of the shark fin edge is about 1/4 to 1/2 mm taller than the top of the pad. Full contact. It's not unusual to have a few mm of unworn area stabilizing rotor edge in the area you seem concerned about. I set up 6 bikes this way today. It is done so that if the rotor wears too thin it doesn't shred to Chantilly lace & self destruct leaving the bike operator with no brakes at all. Something has to connect the rotor spokes to each other to share the braking load.

Last edited by base2; 08-16-21 at 10:04 PM. Reason: Hitting enter before thinking.
base2 is offline  
Likes For base2:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell or Share My Personal Information -

Copyright © 2023 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.