Chain or shift guides for RFX- Mtbr.com
Results 1 to 14 of 14
  1. #1
    mtbr member
    Reputation: jgusta's Avatar
    Join Date
    Oct 2004
    Posts
    2,966

    Chain or shift guides for RFX

    So what is the preference for a chain guide on an RFX for primarily all-mt. purposes. Would like to have something that will work without being too bulky since my new RFX trail bike wt. is already at 37lbs.

    I just recently switched from years of using Shimano to 07 Sram X.9 and so far pretty well pleased with the shifting, but the shifting is still a little off in the last two lower cogs, even after adjusting the RD to the best position. So, will a chain guide help with shifting on a
    2 x 9 (22-32t) set-up with 11-34 cogs, or should I consider a shift guide (Truvativ)? I don't have any problems with chain drop or suck, just need better alignment of the chain to the rear cogs. Also would just switching to 11-32 cassette help with this?

    Thanks.

    J.

  2. #2
    Amphibious Technologies
    Reputation: SCUBAPRO's Avatar
    Join Date
    Jun 2004
    Posts
    3,472
    I guess you didn't read this thread:


    http://forums.mtbr.com/showthread.php?t=228095
    "The best you've ridden is the best you know" - Paul Thede, Race Tech

  3. #3
    mtbr member
    Reputation:
    Join Date
    Mar 2005
    Posts
    2,029
    I absolutely love my E - 13 DRS. It is a little over built for this purpose/bike, but you will not be buying replacements..

    As far as your shifting goes, running 2 rings, changes your chainline. The ideal (centered on the cogs) chainline on a 13 5mm rear hub is 47.5mm. So 47.5mm from the centerline of the bike to the middle of the front rings. On a three ring system, this is measured at the middle ring. On a two ring system, the middle is no longer the middle ring, but 2.5mm further inward. So IF you bike was set up propperly with three rings, the cranks should be bumped out 2.5mm to the drive side to maintain the correct chainline.

    A hesitation to drop into the smallest cogs could very well be agrivated by this chainline change. Many other things however could be at fault. From cable friction, to a weak return spring, to incorrect b -tension, to a chain that is too long, to a bent cog tooth, to a bent hanger..etc etc. Best bet is to systematically eliminate possible causes one by one, and you will eventually find the cause.

  4. #4
    Lay off the Levers
    Reputation: Bikezilla's Avatar
    Join Date
    Dec 2003
    Posts
    10,128
    Also included in the FAQ is : Tscheezy's Excellent Chainguide Thread.

    I'm confused (nothing new there).
    Why would the chainline change when you stop using the big ring?
    I just set my Fder limit to stop after the middle ring. Is this wrong?
    The rings have not changed position with three or two rings so why alter the chainline?
    Faster is better, even when it's not.

  5. #5
    3 "fiddy" for short
    Reputation: be350ka's Avatar
    Join Date
    Dec 2004
    Posts
    2,739
    Quote Originally Posted by Bikezilla
    I'm confused (nothing new there)

    Me too!!

  6. #6
    mtbr member
    Reputation:
    Join Date
    Oct 2004
    Posts
    6,689
    Quote Originally Posted by Bikezilla
    Also included in the FAQ is : Tscheezy's Excellent Chainguide Thread

    I'm confused (nothing new there)
    why would the chainline change when you stop using the big ring?
    I just set my Fder limit to stop after the middle ring. Is this wrong?
    The rings have not changed position with three or two rings so why change the chainline?
    You don't NEED to change the chainline, you just CAN, for somewhat better shifting performance in little and middle, since big has left the building.

    I've never seen the need for this, and to the original poster, it's almost impossible to believe that this is the problem. Youse gots other stuff goin on, and whether or not you go the guide/tensioner route, it would be best to solve this issue before installation.

    Otherwise you're treating the symptom, not the illness.
    Whining is not a strategy.

  7. #7
    long standing member
    Reputation: PCinSC's Avatar
    Join Date
    Oct 2005
    Posts
    3,091
    Quote Originally Posted by Bikezilla
    I'm confused (nothing new there)
    Quote Originally Posted by be350ka
    Me too!!
    You noobs, get with the program.

    You gotta do like I do. If your chain drops off, just Fred Flinstone yourself down the mountain, no chainguide needed.

  8. #8
    mtbr member
    Reputation: jgusta's Avatar
    Join Date
    Oct 2004
    Posts
    2,966
    Quote Originally Posted by davep
    I absolutely love my E - 13 DRS. It is a little over built for this purpose/bike, but you will not be buying replacements..

    As far as your shifting goes, running 2 rings, changes your chainline. The ideal (centered on the cogs) chainline on a 13 5mm rear hub is 47.5mm. So 47.5mm from the centerline of the bike to the middle of the front rings. On a three ring system, this is measured at the middle ring. On a two ring system, the middle is no longer the middle ring, but 2.5mm further inward. So IF you bike was set up propperly with three rings, the cranks should be bumped out 2.5mm to the drive side to maintain the correct chainline.

    A hesitation to drop into the smallest cogs could very well be agrivated by this chainline change. Many other things however could be at fault. From cable friction, to a weak return spring, to incorrect b -tension, to a chain that is too long, to a bent cog tooth, to a bent hanger..etc etc. Best bet is to systematically eliminate possible causes one by one, and you will eventually find the cause.
    Thanks for the handy advice. Yeah I just recently put on new cables/housing (Nokon), RD/shifters (07 Sram X.9), new chain (Sram 971) on a new RFX frame w/straight der. hanger. My cassette is only 4mths old (Shimano XT 760 11-34) and does not appear to be worned out or bent and everything on my new ride was installed and tensioned by my good ol' trusty local mechanic.

    We both confirmed that my chainline is off a bit due to the configuration of the 2 ring set-up and confirmed by a chain guide measuring tool. Will a chain or shift guide correct this mal-alignment or do I have to go back to a 3 ring set-up to eliminate this? Or, going to a 11-32 cassette vs. a 11-34 cassette change the chainline at all on a 22/32 two ring set-up?

    Thanks again.

    J.

  9. #9
    mtbr member
    Reputation:
    Join Date
    Mar 2005
    Posts
    2,029
    Quote Originally Posted by Bikezilla
    Also included in the FAQ is : Tscheezy's Excellent Chainguide Thread.

    I'm confused (nothing new there).
    Why would the chainline change when you stop using the big ring?
    I just set my Fder limit to stop after the middle ring. Is this wrong?
    The rings have not changed position with three or two rings so why alter the chainline?
    'Chain line' is defined as the distance from the centerline of the bike to the center of the front rings. On a 3 ring system, thiis ends up being center to the middle ring, as the middle ring is the middle of your rings. When you ditch your big ring, you only have two rings left and thus the center of these two rings IS NOT the middle ring any more (it is the middle of what is left). On current 9 speed, the middle of the two rings is now 2.5mm inboard of the larger (what was the middle) ring.
    Your cranks and or rings obiously do not move relative to the frame, but you no longer have a 'big' ring, nor the same 'chain ring width' to center with respect to the rear cogs.


    As I said before, this could agrivate things, but like others have said, this should not be causing the shifting problem. Measure your chain line and adjust accordingly. If your bottom bracket has a lip on the drive side cup, you can adjust chain line by adding spacers between the cup and frame until it is correct. Depending on what guide you get and how it is mounted, it may act like a spacer itself, and push your chainline out.

  10. #10
    mtbr member
    Reputation: jgusta's Avatar
    Join Date
    Oct 2004
    Posts
    2,966
    Quote Originally Posted by davep
    'Chain line' is defined as the distance from the centerline of the bike to the center of the front rings. On a 3 ring system, thiis ends up being center to the middle ring, as the middle ring is the middle of your rings. When you ditch your big ring, you only have two rings left and thus the center of these two rings IS NOT the middle ring any more (it is the middle of what is left). On current 9 speed, the middle of the two rings is now 2.5mm inboard of the larger (what was the middle) ring.
    Your cranks and or rings obiously do not move relative to the frame, but you no longer have a 'big' ring, nor the same 'chain ring width' to center with respect to the rear cogs.


    As I said before, this could agrivate things, but like others have said, this should not be causing the shifting problem. Measure your chain line and adjust accordingly. If your bottom bracket has a lip on the drive side cup, you can adjust chain line by adding spacers between the cup and frame until it is correct. Depending on what guide you get and how it is mounted, it may act like a spacer itself, and push your chainline out.
    So is the primary purpose of a chain guide is just to prevent chain drop or suck when hauling balls in rough terrain? It is not used for getting a better chain line alignment? Just use spacers at BB cup to accomplish this?

  11. #11
    mtbr member
    Reputation:
    Join Date
    Mar 2005
    Posts
    2,029
    Quote Originally Posted by jgusta
    So is the primary purpose of a chain guide is just to prevent chain drop or suck when hauling balls in rough terrain? It is not used for getting a better chain line alignment? Just use spacers at BB cup to accomplish this?
    correct.
    Last edited by davep; 09-20-2006 at 06:31 PM.

  12. #12
    mtbr member
    Reputation: jgusta's Avatar
    Join Date
    Oct 2004
    Posts
    2,966
    Quote Originally Posted by davep
    correct.
    Can I use spacers on their own or are the supposed to be used with a chain guide?

  13. #13
    mtbr member
    Reputation:
    Join Date
    Mar 2005
    Posts
    2,029
    You should read the set-up instructions that came with your cranks/bb.Should be on the mfg seb site. What type of cranks/bb are you running?

    Have you read the other threads about guides..and other peoples results?

  14. #14
    mtbr member
    Reputation: jgusta's Avatar
    Join Date
    Oct 2004
    Posts
    2,966
    Quote Originally Posted by davep
    You should read the set-up instructions that came with your cranks/bb.Should be on the mfg seb site. What type of cranks/bb are you running?

    Have you read the other threads about guides..and other peoples results?
    I have, a little confusing to me since I am not the most mechanically inclined dude out there.

    I have the RF Evolve DH cranks w/ X-type BB.

Members who have read this thread: 0

Posting Permissions

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

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2019 VerticalScope Inc. All rights reserved.