Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

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.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 06-23-06, 07:13 PM   #1
edmcnierney
Senior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 77
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Hard to trim down on STI/105 front der

I'm having a very hard time with the downshift trim on my 105 front derailleur (double) on a 2005 Trek 2100 with STI shifters. Trimming up seems just fine - I can move from the small chainring to the large chainring in four distinct steps. But going back doesn't work properly. When I press the small lever to downshift, I have to press pretty hard before anything happens, and then it makes a big click and drops all the way down to the lowest (closest to the frame) position.

The upper and lower limit screws seem properly set, given the overall chain behavior - i.e. if I can get the front derailleur in the right trim position, the chain runs properly without rubbing in all normal positions, and I neither shift the chain off the big or small ring.

The Shimano documentation (at the end, under Troubleshooting) seems to address this symptom, but the "fix" is to "loosen the upper screw 1/8th turn" - that is, to move the upper cage limit away from the bike. This doesn't make sense to me, as I don't see how that's related to my problem, and it indeed doesn't fix anything. It just makes the cage rub against the inside of the chain at the large chainring/small cog position with the cage trimmed all the way out.

On the stand I can maybe carefully get a down-trim click once out of three or four tries, but that's not nearly good enough for real-world usage.

Tips on how to adjust this setting - it seems like some kind of spring tension or something - would be greatly appreciated. Thanks!
edmcnierney is offline   Reply With Quote
Old 06-24-06, 09:06 PM   #2
eidem123
Newbie
 
Join Date: Apr 2006
Bikes:
Posts: 4
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Check your cable for dirt or grime it may be hanging up.
eidem123 is offline   Reply With Quote
Old 06-25-06, 06:40 AM   #3
edmcnierney
Senior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 77
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks for the reply - I was surprised no one commented!

I disassembled the entire cable mechanism. I found a small burr on one end of the cable housing, which was causing slight resistance to the movement of the cable. I cleaned it off and replaced the cable with a newly-lubed one that slides very smoothly now.

It made no difference at all. The downshift lever still has to be pressed quite hard, and downshifts with a solid "click" all the way down to the bottom.
edmcnierney is offline   Reply With Quote
Old 06-25-06, 09:27 AM   #4
pityr
Senior Member
 
Join Date: May 2006
Location: PDX
Bikes: Trek 1200, Kona Honky Inc, PX Stealth
Posts: 641
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
My tiagra shifter does that also...

I was thinking of upgrading to the 105 just to get around it.
pityr is offline   Reply With Quote
Old 06-25-06, 10:35 AM   #5
edmcnierney
Senior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 77
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Well, this IS the 105 shifter, so I wouldn't bet on an upgrade being a fix
edmcnierney is offline   Reply With Quote
Old 06-25-06, 11:00 AM   #6
Ray Dockrey
Senior Member
 
Ray Dockrey's Avatar
 
Join Date: Nov 2005
Location: Mustang, OK
Bikes:
Posts: 728
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
There was a thread on this the other day. Something about doing a two finger shift. You use one finger to lightly push the brake lever over then release and follow with the other finger to hit the inner shift lever. You might do some searches on it.
Ray Dockrey is offline   Reply With Quote
Old 06-25-06, 11:24 AM   #7
Landgolier
THIS SPACE FOR RENT
 
Join Date: Jan 2006
Bikes:
Posts: 2,849
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Try backing off your cable tension just a little using the barrel adjusters. My 105 triple will do this if the tension is too high when in the outermost position, such that it's like a bowstring being let go when you release it. How much tension is in the cable at the innermost position? It should be pretty much none, but with no slack.
Landgolier is offline   Reply With Quote
Old 06-25-06, 11:26 AM   #8
girlyman
Member
 
Join Date: Jan 2006
Bikes:
Posts: 41
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
"Well, this IS the 105 shifter, so I wouldn't bet on an upgrade being a fix"

I would have to agree. My 105 shifters do the same thing. However the Dura Ace shifters on my other bike work perfectly
girlyman is offline   Reply With Quote
Old 06-25-06, 01:46 PM   #9
BlastRadius
Direct Hit Not Required
 
BlastRadius's Avatar
 
Join Date: Nov 2003
Location: San Bruno, CA
Bikes: Leopard DC1, Ridley X-Fire, GT Zaskar 9r
Posts: 6,190
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Try pressing the small lever near the very bottom of the paddle. Pressing there gives you more leverage and therefore more control over amount of travel your lever moves.
BlastRadius is offline   Reply With Quote
Old 06-25-06, 02:19 PM   #10
edmcnierney
Senior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 77
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks, but it's not a matter of leverage - it's a matter of applied force. If I push on the bottom there's more horizontal travel but the force is the same; if I push higher up I have to press harder with less displacement of the lever, but the force is the same.

I get the same result no matter where I push on the lever. A considerable amount of force must be applied (i.e. I have to push pretty hard) and I get a loud, firm click and the derailleur shifts all the way to the bottom / low / closest to the frame position.
edmcnierney is offline   Reply With Quote
Old 06-26-06, 07:52 AM   #11
BlastRadius
Direct Hit Not Required
 
BlastRadius's Avatar
 
Join Date: Nov 2003
Location: San Bruno, CA
Bikes: Leopard DC1, Ridley X-Fire, GT Zaskar 9r
Posts: 6,190
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
In that case, the Shimano documentation makes sense. If when shifted to the big ring and the limit is set too tightly, the cable will have a lot of tension. Loosen the H limit a bit and the cable will have less tension when in the big ring index position.
BlastRadius is offline   Reply With Quote
Old 06-26-06, 08:56 AM   #12
edmcnierney
Senior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 77
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
OK - thanks. I'm trying to think this through, and want to make sure I know what you mean by "loose" and "tight" when referring to the high limit adjustment. It sounds like "tight" means "the cage is further from the frame" which means "the limit screw is unscrewed too far", so "loosen the H limit" sounds like it should mean "tighten the H limit screw clockwise to keep the cage from moving as far, so the cable isn't as tight". Am I reading that correctly?

If so, it sounds like a counter-proposal might be to loosen the cable. I don't want to change the limit screws - the cage is in the right place, and changing the limit screw is just going to mess that up. But if you think the problem is due to too much tension in the cable when the chain is on the big ring, then I could also just loosen the cable. It's hard to judge from the documentation what the "right" tension for the cable is when it's being attached (and the shifter and chain are set to the smaller chanring).

So if you think the problem is excess cable tension, then I'll try loosening the cable when I get home tonight. Thanks!
edmcnierney is offline   Reply With Quote
Old 06-26-06, 09:14 AM   #13
Al1943
Senior Member
 
Join Date: Feb 2005
Location: Oklahoma
Bikes: Trek 5500, Colnago C-50
Posts: 9,433
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by edmcnierney
So if you think the problem is excess cable tension, then I'll try loosening the cable when I get home tonight. Thanks!
Generally there should be no slack in the cable but very little if any tension when the shifter is in the small chainring position.
Shimano 105 shifters are double/triple so there are extra clickstop positions that really are not needed on a double setup.
It sounds to me as if you have too much tension in the cable. Hosing out the shifters with WD40 may also help with smoother shifting.

Al
Al1943 is offline   Reply With Quote
Old 06-26-06, 09:46 AM   #14
BlastRadius
Direct Hit Not Required
 
BlastRadius's Avatar
 
Join Date: Nov 2003
Location: San Bruno, CA
Bikes: Leopard DC1, Ridley X-Fire, GT Zaskar 9r
Posts: 6,190
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by edmcnierney
OK - thanks. I'm trying to think this through, and want to make sure I know what you mean by "loose" and "tight" when referring to the high limit adjustment. It sounds like "tight" means "the cage is further from the frame" which means "the limit screw is unscrewed too far", so "loosen the H limit" sounds like it should mean "tighten the H limit screw clockwise to keep the cage from moving as far, so the cable isn't as tight". Am I reading that correctly?

If so, it sounds like a counter-proposal might be to loosen the cable. I don't want to change the limit screws - the cage is in the right place, and changing the limit screw is just going to mess that up. But if you think the problem is due to too much tension in the cable when the chain is on the big ring, then I could also just loosen the cable. It's hard to judge from the documentation what the "right" tension for the cable is when it's being attached (and the shifter and chain are set to the smaller chanring).

So if you think the problem is excess cable tension, then I'll try loosening the cable when I get home tonight. Thanks!
You should try loosening the H limit, i.e. let the cage move further outboard.

The index positions cause X amount of cage travel. If the H limit is too tight (too inboard) there would be a hard limit to how much the cage can travel. The shifter, if you push hard enough, will make that last click into the big ring position but it'll do it by stretching the cable and putting excess tension on it. If you loosen the H limit, the cage will be allowed to move the intended amount of travel the index position dictates.

Hope that was clear.
BlastRadius is offline   Reply With Quote
Old 06-26-06, 09:49 AM   #15
BlastRadius
Direct Hit Not Required
 
BlastRadius's Avatar
 
Join Date: Nov 2003
Location: San Bruno, CA
Bikes: Leopard DC1, Ridley X-Fire, GT Zaskar 9r
Posts: 6,190
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
PS. Don't let the cage too far out that the crank arm hits it. There's a fine art in getting the L limit and H limits set just right.
BlastRadius is offline   Reply With Quote
Old 06-26-06, 09:58 AM   #16
edmcnierney
Senior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 77
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Great - thanks. That makes sense. I was mainly worried about the risk of the cage going so far as to shift the chain off the ring, which seems like it would happen before it hits the crank arm. But I might be wrong about that and I'll take a look tonight - obviously I don't want EITHER of those things to happen!
edmcnierney is offline   Reply With Quote
Old 06-26-06, 01:50 PM   #17
truckin
road rash/tree burn
 
Join Date: May 2005
Location: Chapel Hill, NC
Bikes:
Posts: 726
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Ed-

Not sure if this has really been answered at this point, but as blastradius said in post #11, the Shimano documentation does make sense to me on this one. The cage might end up just slightly further outboard due to loosening the limit, but it's the detent in the shifter body that determines where the cage really ends up. So to prevent the high limit and the detent's positioning of the der. cage from coinciding so closely, you want to move the high limit out just slightly (by loosening the H limit screw- loosening limit screws widens the range; tightening them narrows it).

When you click to trim down, the shifter has to take up a very small amount of cable, just enough to release tension from the pawl it's sitting on for the high position. If you're already up against the high limit, it's very hard to push the derailleur cage outward against the limit; but if you set the limit outward a shade, you'll have the slight amount of cable travel available and hopefully be able to make your trim shift without popping all the way down to the small ring. I've dealt with this on a couple of bikes, and I've always been able to resolve it with enough fiddling.

Sorry to waste your time if all of that was explained well enough for you to understand it in previous posts!

Last edited by truckin; 06-26-06 at 01:55 PM.
truckin is offline   Reply With Quote
Old 06-26-06, 02:47 PM   #18
masiman
Senior Member
 
Join Date: Oct 2005
Bikes:
Posts: 1,735
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Are you able to click down in steps when you are not in your highest/outermost position on the FD? That is, if you can downshift from position 3 to pos 2 and then to in pos 1 with the single click/short throw feature, then cable tension could be the issue. If you cannot single click down from #3 to #2 then I would think that cable tension will not fix your problem. The cable tension adjustment I believe will only solve an upper or lower limit cable tension shifting problem. If the FD is really out of adjustment and you are only making it to your next to last position it could mask your top position.

Good Luck. Interested to hear if the fix works.
masiman is offline   Reply With Quote
Old 06-26-06, 07:11 PM   #19
edmcnierney
Senior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 77
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Well, I went out for a ride tonight and I find that the derailleur shifts down hard from ALL trim positions, so it is certainly not specific to the highest stop. The upshift lever moves up one position, and the downshift lever clicks hard and moves all the way down to the lowest position regardless of where you are.

So truckin, I don't think that's really the issue, and I have tried moving the upper limit screw out before. I've screwed around so much that I'm always willing to try again, but I'm skeptical.

Since there isn't any "stop" in the middle trim positions, I'm beginning to suspect that there's something about the shifter itself that's involved. I don't really understand the anatomy in there - this is my first new road bike in 23 years, and the downtube friction shifters on my 1983 Peugeot P8 are a heck of a lot easier to understand!

The Shimano docs I've found don't really give a good picture of the internals of the shifter. I opened it enough to replace the shift cable and clean the burrs off the housing, but was reluctant to do much more without a picture. If anyone has good pointers to a drawing of what's happening in there, they would be appreciated.
edmcnierney is offline   Reply With Quote
Old 06-26-06, 10:20 PM   #20
oilman_15106
Senior Member
 
Join Date: May 2005
Bikes:
Posts: 6,900
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
If you have or can get Parks Blue book, there is a good step by step for der adjustments. If you can not resolve it with some of the above suggestions, try starting over. This has worked for me. If you keep adjusting and tweaking you are sometimes making things worse. Good luck. The change from downtube friction shifters can be shall we say maddening.
oilman_15106 is offline   Reply With Quote
Old 06-27-06, 01:44 AM   #21
cascade168
Klaatu barada nikto
 
cascade168's Avatar
 
Join Date: Sep 2004
Location: Southern NH
Bikes:
Posts: 1,453
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by oilman_15106
If you have or can get Parks Blue book, there is a good step by step for der adjustments.
There is no need to have the book when it's all on-line here:

http://www.parktool.com/repair/byregion.asp?catid=53

Pretty much everything that is in the BBB can also be found on the Park website.
cascade168 is offline   Reply With Quote
Old 06-27-06, 06:12 AM   #22
edmcnierney
Senior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 77
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Yes, I read all that. Did it several times. Doesn't help. If you read that material you'll see that there's absolutely nothing in there about this problem.
edmcnierney is offline   Reply With Quote
Old 06-27-06, 06:19 AM   #23
truckin
road rash/tree burn
 
Join Date: May 2005
Location: Chapel Hill, NC
Bikes:
Posts: 726
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Try disconnecting the cable from the derailleur and shifting just the shifter alone. See if it still skips over certain shifts.

Could be that the shifter is skipping over a pawl or two on the way down. Try opening it up enough that you can shoot a ton of a light lube in (Finish Line, 3 in 1 oil spray, whatever you have that is light enough to spray into the internals). I've found that Shimano shifters will gum up over time and sometimes miss shifts as a result. The explanation that I've heard for it is that they use a fairly viscous grease that hardens over time and can prevent the weak springs from popping the ratchet into place against a given pawl.

You can try just lubing the heck out of it, or you can go the route I had to go on one of my MTBs wherein I sprayed a bunch of citrus degreaser in, let that get all the crudded-up grease out that it would get, and then relube with a light spray lube.

Let us know if you have any luck!
truckin is offline   Reply With Quote
Old 06-27-06, 01:22 PM   #24
edmcnierney
Senior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 77
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks, truckin! In thinking all this through I am beginning to suspect there's something in the shifter that's the problem - it's the only hypothesis that seems to make sense. I didn't have time for it last night but I'll dive in there tonight and take a look.

The bike's a 2005 Trek 2100 that I just purchased new, so it has been sitting around for a while since it was manufactured. That doesn't prove anything, but it would be consistent with some lube gumming up over time; I have not attempted to re-lube anything inside the shifters (cables - yes, shifter - no).
edmcnierney is offline   Reply With Quote
Old 06-27-06, 02:48 PM   #25
Phantoj
Certifiable Bike "Expert"
 
Join Date: May 2005
Bikes:
Posts: 5,641
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
For what it's worth, the trim in my 2000 105 double works like a champ.

Think - you have two relevant adjustments: H limit and "cable tension". So just fiddle with em until you get it right.

I think you should back out the H limit screw a little bit and ease in the front barrel adjuster.
Phantoj is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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



All times are GMT -6. The time now is 12:44 PM.