|   Sugar3 shifting driving me nutts!!! | Toad
Oct 17, 2001 8:00 AM | | 00' Sugar-3 has been driving me nutts with front shifting gremlins! It has LX front deraileur and Bontrager Race cranks. It doesn't seem to want to drop down to the granny gear when under load (works fine in stand). Plus has chainsuck like mad out on the trail. After numerous attempts to ajust the front deraileur I decided to try a different crankset. So I bought a new LX mega-9 (square taper) and put it on the bike. It became apparent immediatly that something wasn't right. With the chain on the large cog and middle chainring the chain gets pulled back down to the granny as soon as the crank is turned. Regaurdless of the front deraileur ajustment, this kept happening. This led me to ask these two questions. Could the LX crank have a different "offset" than the Bontrager? Could the BB be too long (even though the chainline appears straight)? The BB is stock and measured at ~114mm. I thought I saw another post on here that recommended a BB size but can't remember the size. Anyone out there have any suggestions? |
| try a 110mm BB nm | scrappy-doo
Oct 17, 2001 9:08 AM | | nm |
| Typically you'd find a 113 x 73mm BB on that frame... | næstep
Oct 17, 2001 12:50 PM | | ...for a square taper setup (118mm for splined). But I can't imagine 1mm is causing all that frustration. I'm curious to know if you've measured your actual front chainline distance (center of tubing to middle chainring).
næstep |
| c/l of middle ring to c/l of tube=51mm | toad
Oct 17, 2001 7:05 PM | | does this sound normal? |
| Looks normal. Anyone else: 1mm makes a difference? | næstep
Oct 18, 2001 10:47 AM | | A 50mm chainline is considered normal. I can't imagine an extra millimeter is going to cause all those problems. Does this middle ring absolutely line up with the middle cog of your cassette, or can you stand to move the crank in another 3 or 4mm?
næstep |
| it could move in another 3mm but... | toad
Oct 18, 2001 3:44 PM | | I'm not sure which cog to put chain on. On 8spd it's usualy the forth cog down. But on nine speed the middle cog is the 5th down. Do I use the 4th or 5th cog to check the chainline on 9spd. |
| 5th (center) cog (nm) | næstep
Oct 18, 2001 4:31 PM | | |
| starting to think it could be front delaileur... | toad
Oct 18, 2001 6:49 PM | | The chain looked pretty straight (eyeballing) on the 5th cog. So I decided to play around with the front deraileur. After about an hour and a half of F'n with it (rotating it on the seat tube and set screw ajustments) It finaly started to act almost normal (BTW the Bontrager Race crank is back on). It now shifts into all three chainrings but inconsistantly. While ajusting the deraileur(LX)I did notice an unusual amount of play. I compared it to two different bikes in my basement including a 98' XT and a 95' XTR. Both were "tighter". So I think I might try an XT frt deraileur. If the Bontrager cranks shift a lot better, then I will put the LX cranks back on to see if they work better then last time. |
| re: Sugar3 shifting driving me nutts!!! | scott
Oct 18, 2001 11:10 AM | | Good, you've taken the first step to good shifting by getting rid of
the Bontrager crank. You should be able to get a clockwork drivetrain
without messing with a new bottom bracket. (I know 3 people that have had the same problem). LX and XT cranks work just fine with the stock
BB.
Check to see if the bottom bracket is tight. On my sugar3 it was not, and loosened backing out about 1-2 mm (drive side) before I noticed it (when does a bottom bracket ever unscrew itself? ans: when the guy in the factory doesn't tighten it up) - could happen to you too. |
| Good point. My BB couldn't have been much more than hand tight. | næstep
Oct 18, 2001 4:34 PM | | ...when I parted out a brand-new, never riden Giant bike. I put the adapter on the bottom bracket and was able to unscrew it by hand.
næstep |
| did you notice anything before... | toad
Oct 18, 2001 6:52 PM | | you put the tool to it. Any loosness in the crank arms? creaks ro noises. I haven't noticed anything unusual... |
| I didn't notice, but I didn't really check... | næstep
Oct 19, 2001 8:20 AM | | ...I had the intention all along of stripping it down as soon as I got it home, so I really didn't "preflight" the bike. And the loose BB actually made the job alot easier, but I still cussed anyway.
næstep |
| re: Sugar3 shifting driving me nutts!!! | Bob
Oct 19, 2001 1:27 PM | | My wife got a new (2000) Sugar 3 last spring and had a lot of shifting problems. The bike shop finally ended up replacing the Bontrager cranks with some Icon Onyx cranks, which I guess are under the Trek umbrella also. The shifting has been great since then. The shop was a pain to work with, so I emailed Gary Fisher (the company, not the man)and within minutes (literally) the bike shop called me back saying the problem was resolved. |
| |
