Advertise on Bikeforums.net



User Tag List

Results 1 to 8 of 8
  1. #1
    Senior Member
    Join Date
    Aug 2009
    Location
    Toronto, Canada
    Posts
    658
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Not able to shift to the biggest cog at the back

    Some background of the bike that I am working on, it has SRAM Apex RD, FD, and shifters.

    I can't get it shift to the largest cog at the back. I tried to adjust the L low limit screw but it will shift to every single cogs but not the last one. Cable tension 'seems' fine to me but I am not 100% sure. Please advise

  2. #2
    Senior Member
    Join Date
    Feb 2005
    Location
    Oklahoma
    My Bikes
    Trek 5500, Colnago C-50
    Posts
    9,201
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Sounds like either the shifter wasn't in the smallest cog position when the cable was attached to the derailleur or the cable needs more tension. Try shifting to the smallest cog then see if it will shift one more time. If so, loosen the fixing screw and remove all slack in the cable. Then add tension as needed to shift through all cogs.

    It is important to have the chain on the smallest chainring and largest cog when adjusting the low limit screw.

  3. #3
    Senior Member mulveyr's Avatar
    Join Date
    Feb 2010
    Location
    In the wilds of NY
    My Bikes
    Box Dog Pelican, Raleigh Sojourn, Specialized Secteur, 1991 Cannondale tandem
    Posts
    1,305
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by ahson View Post
    Some background of the bike that I am working on, it has SRAM Apex RD, FD, and shifters.

    I can't get it shift to the largest cog at the back. I tried to adjust the L low limit screw but it will shift to every single cogs but not the last one. Cable tension 'seems' fine to me but I am not 100% sure. Please advise
    If you pull on the cable by hand, can you get it to shift to the largest cog?

    If so, then your limit screw is not the problem, it's a tension issue.
    Knows the weight of my bike to the nearest 10 pounds.

  4. #4
    Senior Member
    Join Date
    Aug 2009
    Location
    Toronto, Canada
    Posts
    658
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by mulveyr View Post
    If you pull on the cable by hand, can you get it to shift to the largest cog?

    If so, then your limit screw is not the problem, it's a tension issue.
    I pulled the cable by my hand and tighten it down, but it still wouldn't shift to the largest cog. Time to use the 3rd hand tool to pull it harder?

  5. #5
    Low car diet JiveTurkey's Avatar
    Join Date
    Aug 2007
    Location
    Corvallis, OR, USA
    My Bikes
    2006 Windsor Dover w/105, 2007 GT Avalanche w/XT, 1995 Trek 820 setup for touring, 201? Yeah single-speed folder, 199? Huffy tandem.
    Posts
    2,401
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Loosen the L limit screw quite a bit and then pull the cable by hand. Be sure you're unscrewing the correct screw.
    Quote Originally Posted by slopvehicle View Post
    Not wearing a helmet makes me more aware of my surroundings. I find myself anticipating the hardness of concrete 50 or 100 feet in front of me, it's almost a zen-like connection between my face and the pavement.

  6. #6
    Senior Member mulveyr's Avatar
    Join Date
    Feb 2010
    Location
    In the wilds of NY
    My Bikes
    Box Dog Pelican, Raleigh Sojourn, Specialized Secteur, 1991 Cannondale tandem
    Posts
    1,305
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by ahson View Post
    I pulled the cable by my hand and tighten it down, but it still wouldn't shift to the largest cog. Time to use the 3rd hand tool to pull it harder?
    No, only a very small amount of tension is required to pull the cable across the entire range. So it's either your limit screw setting, or you have another issue like bent parts.
    Knows the weight of my bike to the nearest 10 pounds.

  7. #7
    DRF aka Thrifty Bill wrk101's Avatar
    Join Date
    Jan 2008
    Location
    The NC Mountains
    My Bikes
    Too many to list, all vintage
    Posts
    18,869
    Mentioned
    71 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by ahson View Post
    I pulled the cable by my hand and tighten it down, but it still wouldn't shift to the largest cog. Time to use the 3rd hand tool to pull it harder?
    I think you misunderstood the advice. Leave the cable attached to your derailleur. Then pull the cable manually, find a spot where it is exposed, like on the downtube. From the highest gear (smallest cog), you should be able to manually pull the cable enough to reach all of the gears while moving the pedals (a bike stand works best for this, or have a friend raise the rear wheel into the air for you). If it doesn't reach the biggest cog, then either something is bent or your low limit is stopping you. Loosen the low limit a lot, and see if you can reach it. Remember to readjust the low limit before you ride the bike, so you do not risk throwing the chain and derailleur into the wheel and either crashing, or doing serious damage to the bike, or both.

    Take close up pics and post if you want someone to guess whether something is bent.

  8. #8
    Senior Member mulveyr's Avatar
    Join Date
    Feb 2010
    Location
    In the wilds of NY
    My Bikes
    Box Dog Pelican, Raleigh Sojourn, Specialized Secteur, 1991 Cannondale tandem
    Posts
    1,305
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by wrk101 View Post
    I think you misunderstood the advice. Leave the cable attached to your derailleur. Then pull the cable manually, find a spot where it is exposed, like on the downtube. From the highest gear (smallest cog), you should be able to manually pull the cable enough to reach all of the gears while moving the pedals (a bike stand works best for this, or have a friend raise the rear wheel into the air for you). If it doesn't reach the biggest cog, then either something is bent or your low limit is stopping you. Loosen the low limit a lot, and see if you can reach it. Remember to readjust the low limit before you ride the bike, so you do not risk throwing the chain and derailleur into the wheel and either crashing, or doing serious damage to the bike, or both.

    Take close up pics and post if you want someone to guess whether something is bent.

    Ah, I had misinterpreteted the OP's response and hadn't caught that he was simply retensioning the cable. Good catch.

    OP: Once you check for full movement across the cogs by pulling by hand, as other posters said, loosen up the low limit screw and try again.

    Additionally, on Apex RD's, if you stand behind the bike and look directly at the largest cog, try ( somewhat gently ) to move the RD so that the it is directly under the large cog. Check to ensure that the large cog, and the two pulleys ( gears ) on the RD are *exactly* lined up. That should give you perfect shifting into the large cog.

    As a further sanity check - I presume you're not hearing any grinding when you try to move to the largest gear? If so, check and make sure that the upper pulley is not striking the large cog. If it is, you need to back off the 'B' adjustment screw so that there is a 6MM gap between the pulley and the cog.

    And that makes me think - are you absolutely positive that you're using the low limit screw ( i.e, the upper one on the side of the derailler ) and not the B screw ( the one that comes out of the back of the RD )?
    Last edited by mulveyr; 08-01-11 at 09:20 AM.
    Knows the weight of my bike to the nearest 10 pounds.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •