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I recently converted a 9 speed bike to 10 speed (to make swapping the powertap wheel less of a hassle). I did not change the front cranks/chainrings. I understand that the spacing between the front cogs is slightly different between 9 and 10 speed cranks. Every once in a while, when shifting from big to small ring, the chain will drop down between the two chainrings without engaging the teeth, and I'll have to give the front shifter a little nudge and then we are back in business.
My first thought was to get a 10 speed crankset, but, my tri bike, which was 10 speed from the day I bought it, does the exact same thing. So my question - is that normal, to have the chain not engage the small chainring on rare occasion with 10 speed shifting? Or do I need two new cranksets??? Thanks.
It definitekly shouldn't drop between the rings, that can be pretty dangerous if it jams. It may drop on top of the teeth of the little ring, which isn't a big deal.
A lot of times a new chain or a different brand of chain will help.
Styrrell
Styrrell
If you're using a 9spd crankset with a 10spd chain, this will happen sometimes. As you mentioned, spacing is slightly different.
Does your tribike have an FSA crankset? I found this happened a lot with bikes around 2005-2007 with assorted FSA 10 spd cranks. I think they eventually trimmed the chainrings to make the spacing narrower to fix the issue.
Greg.
After reading your post I just had a play with my bike on the workshop stand. I have a full 10 speed setup but it is a bit of a mongrel, Shimano small ring, FSA large ring and KMC chain. I was unable to get it to fall between the rings even when gently nudging it off the large ring and turning the pedals slowly. It always dropped onto the small ring so I'm guessing that spacing on the crank spider is the issue.
Perhaps one of the professional bike shop guys can confirm for you. Alternatively, how much scope do you have for adjusting a little more throw on the front mech without continually dropping into the BB? If you can live with the occasional slow shift, a couple of chain catchers to save you from overthrowing into the middle would certainly be cheaper than a couple of cranksets! :o)
You are correct, the tri bike has an FSA crankset. So perhaps that is the issue. Thanks.
I 'think' the difference is mostly in the small chainring. I believe if you pick up a current small chainring for your crank, it will sit ever so slightly closer to the big ring. It should prevent the chain from riding on top of the teeth and not dropping down properly.
Greg.
Some small rings are relief cut on one side to get them closer to the big ring; one side for 7/8/9 use and the other side for 10. Alternatively you could get out a flat file and take 2mm off of your spiders on the small ring side.
That being said I'm riding a 6400 crank (6/7 speed from 1990-ish) with an FSA 10sp 50t big ring and an unknown 38t small ring. Sometimes I have some slow shifting going to the big ring but I have never had the chain drop between the rings going to the smaller ring.
Just wanted to follow up and say thank you. I bought a used Shimano crankset from eBay, took off the Shimano chainrings and put them on the FSA crankset and the shifting is now perfect! So apparently the FSA rings were the problem. I will now go after the converted 9 speed bike and fix it as well. And my new Franken-crank with Shimano rings and the FSA cranks actually looks pretty good as well.
The added benefit is that Shimano rings shift dramatically better than FSA rings. Predominantly I find FSA stuff to be rubbish...
Glad you got it worked out. I'm certainly not a lover of everything Shimano, but I will say their chainrings shift very well. The new FSA rings are better than the older ones but they still don't shift as well as the Shimano.
Greg.