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

Chain rubbing on chain ring

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.

Chain rubbing on chain ring

Old 09-19-23, 09:56 AM
  #26  
choddo
Senior Member
 
Join Date: Apr 2019
Location: UK
Posts: 582
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 267 Post(s)
Liked 155 Times in 120 Posts
Yeah that sounds like you're hitting trim first (which is designed to half-move the FD to allow large / large without scraping the cage) but if you push on through that first ratchet release, it should allow a full change without having to release & move the shifter again (I've never used Apex, but assume it's like Shimano in this regard)
choddo is offline  
Likes For choddo:
Old 09-20-23, 05:40 AM
  #27  
alcjphil
Senior Member
 
alcjphil's Avatar
 
Join Date: Jun 2002
Location: Montreal, Quebec
Posts: 5,792
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1747 Post(s)
Liked 1,609 Times in 921 Posts
OP has a SRAM drivetrain. Doesn't work the same as Shimano
alcjphil is offline  
Old 09-20-23, 06:38 AM
  #28  
XxHaimBondxX
Full Member
Thread Starter
 
Join Date: Mar 2013
Location: Albany, NY
Posts: 339

Bikes: Trek FX 7.3, Specialized Roubaix & Allez, Huffy RedRock, Aostimotor S17 ebike

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 153 Post(s)
Liked 198 Times in 97 Posts
I've read somewhere that SRAM Apex requires a very tight cabling for FD, which would explain why it hesitates or takes two taps to downshift.
XxHaimBondxX is offline  
Old 09-20-23, 06:55 AM
  #29  
smd4
Senior Member
 
Join Date: Dec 2020
Location: Wake Forest, NC
Posts: 4,857

Bikes: 1989 Cinelli Supercorsa

Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 2893 Post(s)
Liked 2,448 Times in 1,475 Posts
Cross-chaining simply doesn't make sense on its face.
smd4 is online now  
Old 09-20-23, 07:33 AM
  #30  
choddo
Senior Member
 
Join Date: Apr 2019
Location: UK
Posts: 582
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 267 Post(s)
Liked 155 Times in 120 Posts
Originally Posted by alcjphil
OP has a SRAM drivetrain. Doesn't work the same as Shimano
Ah of course. The old double tap on mechanical. And no trim?
choddo is offline  
Old 09-20-23, 07:40 PM
  #31  
oldbobcat
Senior Member
 
oldbobcat's Avatar
 
Join Date: Jul 2005
Location: Boulder County, CO
Posts: 4,234

Bikes: '80 Masi Gran Criterium, '12 Trek Madone, early '60s Frejus track

Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 453 Post(s)
Liked 377 Times in 295 Posts
Originally Posted by choddo
Ah of course. The old double tap on mechanical. And no trim?
Trim won't prevent the chain from rubbing on the inside of the big ring. Unless you want to trim it to rub on the outer plate of the derailleur instead. This something you will regret after the chain wears a hole in it.

Little-little is the sacrificial gear. Short chainstays and wide gear spreads between the (50-34?) chainrings make this inevitable. Don't use it. You can find a similar ratio using your big ring.
oldbobcat is offline  
Old 09-20-23, 10:38 PM
  #32  
choddo
Senior Member
 
Join Date: Apr 2019
Location: UK
Posts: 582
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 267 Post(s)
Liked 155 Times in 120 Posts
Originally Posted by oldbobcat
Trim won't prevent the chain from rubbing on the inside of the big ring. Unless you want to trim it to rub on the outer plate of the derailleur instead. This something you will regret after the chain wears a hole in it.

Little-little is the sacrificial gear. Short chainstays and wide gear spreads between the (50-34?) chainrings make this inevitable. Don't use it. You can find a similar ratio using your big ring.
For sure. I was just referring to him saying he had to shift twice to get into the small cog and whether that was just the double tap design or also because sram have a trim feature too so another step involved?
choddo is offline  
Old 09-22-23, 09:05 AM
  #33  
XxHaimBondxX
Full Member
Thread Starter
 
Join Date: Mar 2013
Location: Albany, NY
Posts: 339

Bikes: Trek FX 7.3, Specialized Roubaix & Allez, Huffy RedRock, Aostimotor S17 ebike

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 153 Post(s)
Liked 198 Times in 97 Posts
Originally Posted by AndreyT
Mine does the same thing. Also 2x10 SRAM drivetrain on a Specialized bicycle. This is normal for small-small combination.

As always, the intensity of this effect will depend on chainline parameters and chainstay length. But even longer chainstay bicycles often show this effect.
Hey, wondering if this normal operation for left shifter. To shift to small chainring, I tap the lever once lightly, it clicks, but nothing happens to FD, I tap it a little harder and it clicks again and finally downshifts, literally double tap. If I shift with one single lever moment, it still click twice to downshift. RD shifts with single light tap.
XxHaimBondxX is offline  
Old 09-22-23, 10:16 AM
  #34  
choddo
Senior Member
 
Join Date: Apr 2019
Location: UK
Posts: 582
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 267 Post(s)
Liked 155 Times in 120 Posts
Originally Posted by XxHaimBondxX
Hey, wondering if this normal operation for left shifter. To shift to small chainring, I tap the lever once lightly, it clicks, but nothing happens to FD, I tap it a little harder and it clicks again and finally downshifts, literally double tap. If I shift with one single lever moment, it still click twice to downshift. RD shifts with single light tap.
So I think this is SRAMís trim feature. The FD should move just a little bit to reduce cage rub when in the biggest couple of cogs.

Bizarrely, I read that in earlier SRAM groups, they had trim work the other way, for small / small which is what you orignally asked about. But they changed it because almost no one uses that combo for all the reasons mentioned above and the pros wanted trim in the big ring.
choddo is offline  
Old 09-22-23, 10:27 AM
  #35  
XxHaimBondxX
Full Member
Thread Starter
 
Join Date: Mar 2013
Location: Albany, NY
Posts: 339

Bikes: Trek FX 7.3, Specialized Roubaix & Allez, Huffy RedRock, Aostimotor S17 ebike

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 153 Post(s)
Liked 198 Times in 97 Posts
I thought so too, but like I said fd did not move, I even tried to move it manually by hand in case it was sticking.
XxHaimBondxX is offline  
Old 09-22-23, 10:43 AM
  #36  
choddo
Senior Member
 
Join Date: Apr 2019
Location: UK
Posts: 582
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 267 Post(s)
Liked 155 Times in 120 Posts
Originally Posted by XxHaimBondxX
I thought so too, but like I said fd did not move, I even tried to move it manually by hand in case it was sticking.
apparently cable tension can inhibit it. I know bugger all about SRAM so Iím going to shut up now.
choddo is offline  
Likes For choddo:
Old 09-22-23, 10:50 AM
  #37  
AndreyT
Full Member
 
AndreyT's Avatar
 
Join Date: Nov 2011
Location: CA
Posts: 495
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 244 Post(s)
Liked 55 Times in 30 Posts
Originally Posted by XxHaimBondxX
Hey, wondering if this normal operation for left shifter. To shift to small chainring, I tap the lever once lightly, it clicks, but nothing happens to FD, I tap it a little harder and it clicks again and finally downshifts, literally double tap. If I shift with one single lever moment, it still click twice to downshift. RD shifts with single light tap.
As it has already been explained previously, this is how it should be. The first (fainter) click is not a shifting click. It is "trim" - a feature intended to eliminate chain rub in big-big combination. The second click is actually a shifting click. So, yes, in order to shift to the small ring you have to push the lever through two clicks.

Originally Posted by XxHaimBondxX
I thought so too, but like I said fd did not move, I even tried to move it manually by hand in case it was sticking.
It should move a little. If it doesn't, your shifter cable might be too short.

Last edited by AndreyT; 09-22-23 at 10:53 AM.
AndreyT is offline  
Likes For AndreyT:
Old 09-22-23, 10:58 AM
  #38  
XxHaimBondxX
Full Member
Thread Starter
 
Join Date: Mar 2013
Location: Albany, NY
Posts: 339

Bikes: Trek FX 7.3, Specialized Roubaix & Allez, Huffy RedRock, Aostimotor S17 ebike

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 153 Post(s)
Liked 198 Times in 97 Posts
Originally Posted by choddo
apparently cable tension can inhibit it. I know bugger all about SRAM so Iím going to shut up now.
no you were right, I got it figured out. Thanks.
XxHaimBondxX is offline  
Likes For XxHaimBondxX:

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.