rear triangle flex? ghost shifting?
11-20-10, 09:59 PM
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rear triangle flex? ghost shifting?
i have a tre tubi columbus road frame, tight wheelbase, downtube friction shifters, lugs.
ive recently noticed the rear der. shifts unexpectedly while pumping out of saddle up hill (noticed it in 53/16 and 38/13)
im wondering if theres an issue with the chainstays or if this is typical of vintagey steel? any tips?
im about 175lbs+15-20lbs of backpack
thanks
ive recently noticed the rear der. shifts unexpectedly while pumping out of saddle up hill (noticed it in 53/16 and 38/13)
im wondering if theres an issue with the chainstays or if this is typical of vintagey steel? any tips?
im about 175lbs+15-20lbs of backpack
thanks
11-21-10, 06:51 AM
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Are shifters adequately tightened?
11-21-10, 07:09 AM
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uphill in a 53/16? the bike may be crying for mercy LOL
I am with Bob check to ensure your shifters are tight, also clean them but don't lube them. any steel frame, well not a MAX so much, and actually all bike frames flex especailly under a heavy load. clan up your shifters and try again.
I am with Bob check to ensure your shifters are tight, also clean them but don't lube them. any steel frame, well not a MAX so much, and actually all bike frames flex especailly under a heavy load. clan up your shifters and try again.
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11-21-10, 07:32 AM
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Lubricate the rear shifter cable where it passes under the bottom bracket in case the shifting problems comes from the cable binding there. 38/13 isn't a gear I'd use; smaller sprockets such as a 13 wear out quickly. Maybe what feels like shifting slippage in that gear is actually the chain skipping on the teeth of the 13 sprocket. To maximize sprocket life, always avoid small chainring/small sprocket combinations.
11-21-10, 08:13 AM
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+1 to the above comments. If they do not solve the problem, the cable and housing may be slighlty corrored, causing some binding. New cable and housing are cheap. Go with teflon lined, compressionless, index, cable housing. And perish the thought, but I'd also be very carefully inspecting the frame. You don't want to be in the early phase of a catastrophic frame failure, especially with a downhill following those climbs.
11-21-10, 09:12 AM
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I often mash up hills x-chained in a small-small combination too, and in so-doing it's not uncommon for the chain to skip a tooth.
The only way I have been able to address it, is with a new chain and FW (since I won't change my behavior - and even if I did, I would not feel comfortable knowing the problem was lurking back there.)
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11-21-10, 02:31 PM
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What size frame?? Tretubi frames were never known to be too flexy. On the contrary, I would think they should be on the stiff side, unless your frame is so large that your rear stays are on the long side.
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11-21-10, 02:51 PM
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What are your components? I've had this problem with some cranks and long cage derailers. But I've got about 60 pounds on you also,.
11-21-10, 06:41 PM
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All good suggestions so far and want to add one more - if the frame is a large frame and the wheel is set too far back into the rear dropout, there may not be enough chain wrap on the cog. Try adusting the rear wheel to sit closer at dropout entry, enough so the skewer clamp is completely secure in the dropout. This drove me crazy years ago on my 25.5" Trek. I swapped gear clusters, chains, tried different chain lengths, and even a rear derailleur and this simple adjustment fixed it.
11-21-10, 09:46 PM
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hey everyone
thanks for the replies and tips!
ive read a bit more since i posted this and will try cable and housing maintenance as it seems that is the problem. who knew!
additional specs, frame size is 54, full 600 in okay shape. new chain. shifters are tight and no other problems on flats, downhill or slight inclines. ill check the frame out this holiday weekend. thanks!
thanks for the replies and tips!
ive read a bit more since i posted this and will try cable and housing maintenance as it seems that is the problem. who knew!
additional specs, frame size is 54, full 600 in okay shape. new chain. shifters are tight and no other problems on flats, downhill or slight inclines. ill check the frame out this holiday weekend. thanks!
11-21-10, 10:01 PM
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I'll interject my thoughts. I had similar problem with flex from the bottom bracket spindle length, 112mm, changed to 102mm sealed campy bb on my Gios and the problem went away. It sure is annoying when the bike shifts on it's own, not good for the "couilles".
11-22-10, 01:33 AM
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A new chain will skip if your rear cogs are worn, even if the old one didn't. This recently happened to me. Also there's no way you're flexing that Columbus frame enough to make it ghost shift.
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