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#1
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Issue with Shimano 10 Speed chain dropping
I've been a bike mechanic for about 7 years and this one has me
completely baffled. Worse, it's my own bike! I own a Litespeed Palmares (all 6/4 Ti), 61cm frame. It has all Shimano 10 Speed Dura Ace components. I run a 53/39 in front on 175mm cranks and a 12/23 in the back. On a particular work out called a stomp and Jump I roll the chain off the front big ring on the first or second pedal stroke. A stomp/jump is a 53/12 gear setting and you accelerate as hard as you can from a track stand start. Stomps are seated, jumps are standing. I have done this work out for years on 9 speed Shimano and then for much of this year on 10 speed shimano with out any issues. In late March I went to AZ and my frame may have been hit hard in it's bike case. The drop out spacer in the rear was broken when I unpacked the bike. Still, it worked fine and I only noticed some rear shifting issues. I got those mostly worked out by using a DAG and bending the drop out back to place. It's pretty hard to bend the 6/4 Ti drop outs but I got the shifting pretty good. The Stomp/jump issue started some time after that. I can put out 1500 or more watts in a work out like that, so I am really putting tremendous force on the drive chain. I watched the chain during several work outs and as I begin the pedal stroke (either side) the chain flops to the outside and then rolls off the big ring. It is almost like it is being shifted off the big ring. However, the derailleur isn't even toughing the chain. I thought the chain was worn out so I replaced it. Same problem. I replaced the big and little rings the next week, same problem. I triple checked the chain length with two different methods and it is spot on. So, I asked around and I found out a friend with similar power ability has the same problem on his Shimano D/A 10 speed set up. He is on a Kestrel AL bike, probably a 56 cm frame. And his wasn't ever banged up in shipping. So, on two different bikes the only common thing is D/A 10 Speed and the problem is the same. What I can't figure out is why this didn't happen to me at first. The only thing I can remember is that the chain I used to have on was Ultegra 10 speed. Any ideas? Thanks. |
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Issue with Shimano 10 Speed chain dropping
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#3
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Issue with Shimano 10 Speed chain dropping
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#4
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Issue with Shimano 10 Speed chain dropping
This wasn't an issue only 2 months ago. I've stronger, but not THAT
much stronger. Plus, the BB area of the 6/4 Ti Palmares is SUPER stiff. I can also drop the chain stomping fron either left or right foot start. Some ideas on the rings sound interesting... My guess is that you are stronger now than when this was not an issue. Maybe try a bigger chainring? Or a bike with a bike with a monstrously stiff bottom bracket like a Pinarello Dogma FP. Sounds like stomping on the pedals is flexing things outward such that the chain is being led off the side by the angle of the chainrings due to bb flex. Which side are you stomping on when it falls off? Joseph PS: Can I borrow about 50 Watts? |
#5
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Issue with Shimano 10 Speed chain dropping
Thanks. I may just try this!
Switch to a 9s big ring....as did a bunch of pros did with 10s DA...the big ring is flexy...probably causing the chain to shuck. |
#6
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Issue with Shimano 10 Speed chain dropping
I thought of this. I am trying to figure out how the chain line
changed from 2 months ago to now, but maybe teh frame alignment is off a tinge from teh shipping incident and it's just enough (with power, flex, etc) to cause the issue. I like the idea of a different ring so I will try that. Thanks! Any chance the chain-line on the bottom sprocket combined with the power is causing the chain to catch on the little short teath and ramp up them? I'd go with a plain ring (without shimano's little dips and notches) and see if it helps. |
#7
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Issue with Shimano 10 Speed chain dropping
wrote: I thought of this. I am trying to figure out how the chain line changed from 2 months ago to now, but maybe teh frame alignment is off a tinge from teh shipping incident and it's just enough (with power, flex, etc) to cause the issue. I like the idea of a different ring so I will try that. Thanks! Any chance the chain-line on the bottom sprocket combined with the power is causing the chain to catch on the little short teath and ramp up them? I'd go with a plain ring (without shimano's little dips and notches) and see if it helps. You mentioned that the drop out spacer in the rear was broken when you unpacked your bike. Was that a plastic spacer? I always use a hollow axel and the wheel QRs to keep the fork & rear triangle well braced. |
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