Bicycle Mechanics - Shifting issues
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09-13-10, 07:04 PM
Please help me with this issue. I have a relative new BMC roadracer that I have put on about 600 miles. It's a bit difficult to upshift on the front cog sometime when I ride. The real cogs make some clicking sound when I put it's in the smaller ring upfront. I have taken it in 3 times now to get it adjusted. Every single time in the shop, shifting is perfect on the repair stand. However, every time I take it on the road and put weight on the bike the shifting sucks again. Clicking sound is worse when I mash it up a hill. What can I do the make shifting better? Is it just cable stretching? Thanks for the help
09-13-10, 07:17 PM
Possibly cable stretching but one or two adjustments should have been enough.
Is there a tight link in the chain?
Check that the high limit screw is properly set.
09-13-10, 07:18 PM
Which drive train are u talking about to start with? The repair shop put the bike in a repair stand? Are u talking about a 2009/2010 model?
09-13-10, 07:58 PM
Trying to diagnose here when we can't hear or feel it will be very difficult. The mechanic (pref head mechanic as you've had to take it back repeatedly) should take it for a test ride. It's nonsense to avoid that after the 2nd time in, as it saves more shop time and customer grief in the long run. They should also tighten cranks, pedals, chainwheel bolts, etc to spec. Finally have them explain to you the gear combinations to avoid (primarily cross chain and esp small front to small rear).
You could in addition also have a knowledgeable cyclist ride with you to point out the finer points of using and shifting gears.
09-13-10, 10:02 PM
Thanks for the suggestions so far guys. This bike is a 09 with full rival components and compact crank. Shifting is smooth as silk when ever the bike is on the repair stand but whenever I take it out on the road, shifting becomes an issue. The sound is present especially when I start mashing the pedals in the small front cog. I really don't think I'm cross chaining. I'm going to take it back to the shop tomorrow and make them ride it to see what the issue is. It's just kind of frustrating that it only happens when I ride it. Otherwise the bike has been awesome.
09-14-10, 12:24 AM
I hate mystery noises that are intermittent.
Hopefully the bike will mis-behave for the mechanic when he rides it and your shifting will be properly adjusted.
09-14-10, 04:09 PM
Update: I took it to another shop to let them look at it. I make them ride the bike and the tech felt what I was dealing with. After he got back, he was still stumped. Call another tech over to check out the problem. They started to inspect the cables. They told me that the cable to the rear derailleur was routed wrong and was causing all the shifting issues. Replaced the cables and shifting is much better. Will take it out for a 40 mi ride tomorrow. We'll see if this will finally fix the problem.
09-14-10, 06:44 PM
WOnder if the cable or the cable tubing thing has a bent somewhere and that's what is causing you the problems, Just in case, wonder how the guys at the original LBS put the bike in the repair stand, with the road racer unless u have a rpair stand that grabs the bike from the fork or the rear end, there is no way to get the bike actually well seated in a common repair stand.
09-15-10, 07:17 PM
Just completed the 35 mi ride. What a night and day difference!!! Bike is super smooth now and shifting is awesome now. Question for those with a compact front rival and 10 ring cog. When you are in the small ring upfront, is it normal to have rub (cross chaining) when the it's in the two smallest cogs in the back? When I'm in the big ring upfront, I can use all the rings in the back.
09-15-10, 08:06 PM
Question for those with a compact front rival and 10 ring cog. When you are in the small ring upfront, is it normal to have rub (cross chaining) when the it's in the two smallest cogs in the back? That's the very definition of cross-chaining; with rare exception, any bike built in the last 40 years with multiple cogs and multiple chainrings shouldn't be shifted to the smallest cog on the small(est) chainring, or the largest cog on the large(st) chainring. Even if the chain isn't rubbing on the front derailleur plates, the chainline angle is hard on the driveline. With more recent bikes, with 7 to 10 speed cassettes, it's the largest (or smallest) two (and even sometimes three) cogs you should avoid. Those combinations typically overlap with other chainring/cog combinations anyway.
09-15-10, 08:39 PM
That's the very definition of cross-chaining; with rare exception, any bike built in the last 40 years with multiple cogs and multiple chainrings shouldn't be shifted to the smallest cog on the small(est) chainring, or the largest cog on the large(st) chainring. Even if the chain isn't rubbing on the front derailleur plates, the chainline angle is hard on the driveline. With more recent bikes, with 7 to 10 speed cassettes, it's the largest (or smallest) two (and even sometimes three) cogs you should avoid. Those combinations typically overlap with other chainring/cog combinations anyway.
Gotcha. I'll avoid the two smallest cog when I'm in the small chainring. The large chainring has no rub whatsoever no matter what cogs it's in. I'm so relieve that the bike is better. Have a couple of long rides next week before the charity ride. I'll take it in for a cable stretch adjustment next week before the charity ride.
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