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Post by fredjdukes on Sept 29, 2008 12:19:01 GMT -8
For two rides in a row I attempted to climb Greenwood Road on my Kona Jake, which has a triple ring. Earlier this Spring the chain was replaced with a new SRAM, is well lubricated, and well within industry tolerances. The teeth on the rings also are in good condition. I never use the granny ring except under extreme grades.
On these two rides when the grade gets steep and I have a lot of torque on the cranks the chain either skips or is thrown off the ring to the inside. Three LBS have looked at it and so far visually they agree (separately) that the chain alignment looks acceptable and that the drive train is is good working order. I have even ensured that I stay on the first four large rings on the cassette when I am on the small front ring at still had the skip occur.
Do you have any ideas?
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Post by richbelson on Sept 29, 2008 12:58:39 GMT -8
It is possible that your chain shifting off the granny and the skipping you are experiencing are completely unrelated.
It sounds like your front derailleur could use a little tweaking (which we'd be happy to take care of for you here at the shop for a nominal fee).
As for the skipping under heavy torque, without actually seeing the bike to evaluate the problem, it's hard to say. But I'll try.
On the assumption that the other shops looking at the drivetrain know what they're doing/saying, it is possible that your freehub mechanism is starting to wear out and skips under a load. It's hard to say without knowing how old the bike is, nor the mileage you have on the wheel.
Also, even if a ring "looks" like it's not worn, it still might be.
I would also suggest bringing it into the shop for evaluation of this issue, as there are some quick tests we can do to determine the root of a problem like this.
Also, it is certainly possible to imagine that you have received some advice from mechanics that may not know some of the finer details to look at/measure to determine the cause of your problem.
Maybe a new granny ring can be tested, as there is no real way to "measure for industry tolerances" on a chainring. Either it sjkips under a load or it doesn't. This is especially obvious when a newer chain is introduced to a worn drivetrain.
Perhaps bring the bike up to NDBS and we can help you get to the bottom of this once and for all! We've got over 60 collective years here at the shop troubleshooting this kind of thing. If anyone in town can fix it, we can!
-Richard
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Post by fredjdukes on Sept 29, 2008 14:31:15 GMT -8
You are correct I neglected to leave many details:
2006 Jake 59cm
Triple Ring 30/42/52
Rear Hub Shimano FH-M3300 (since "upgraded' to a Tiagra Rear Hub, see below)
BB TruVativeElita GXP (never verified)
Cassette CS-HG50 12-25 8 Speed
Chain CN-HG53 (is now SRAM mid range chain, I forget the model)
Less than 1% usage of the small ring in my ownership
Lastly, I am a larger man weighing in at 270 lbs +-. I used to train as a strength athlete and can deliver good leg torque due to current and previous training methods (lots of squats and deadlifting).
I use the bike to commute daily to work and then use it on the weekend for other stuff. It has some miles but not excessive and it has had the upgrades that I usually end up making to a bicycle because of the demands I seem to put on the hubs and wheels of any entry level equipment.
I realize that real analysis cannot be performed without the bike and if the problem persists it may end up in your shop if I am ever on your side of town.
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