Outer chain ring rub - HELP!
I have just purchased an FSA Gossamer Mega Exo Compact (34/50) chainset and fitted it according to the instructions to a 68mm shell. It did not come with any spacers for the BB and is not designed to be used with any according to the instructions.
I am running 9 speed on an Ultegra 12-27. The chainset is supposed to be 9 speed compatible.
The fitting instructions warn that there will be some rub on the inside of the outer chainring whilst using the inner chainring and the smaller sprockets on the cassette due to chain crossover. However, I get this on the bottom 4 sprockets and not just the smallest 2, which is a pain. We all like to be able to use most of our gears and have a quiet bike!
I cant see any way that I can remedy it other than to put a spacer between the drive side BB cup and the frame but then I am not sure that there would be enough spindle coming through the non drive side for me to attached the other crank arm.
Is this to be expected and I just have to live with it and spend more time in the 50T/larger sprocket combos? Is it more prominent as it is a 9sp chain and slightly wider than a 10sp?
I am running 9 speed on an Ultegra 12-27. The chainset is supposed to be 9 speed compatible.
The fitting instructions warn that there will be some rub on the inside of the outer chainring whilst using the inner chainring and the smaller sprockets on the cassette due to chain crossover. However, I get this on the bottom 4 sprockets and not just the smallest 2, which is a pain. We all like to be able to use most of our gears and have a quiet bike!
I cant see any way that I can remedy it other than to put a spacer between the drive side BB cup and the frame but then I am not sure that there would be enough spindle coming through the non drive side for me to attached the other crank arm.
Is this to be expected and I just have to live with it and spend more time in the 50T/larger sprocket combos? Is it more prominent as it is a 9sp chain and slightly wider than a 10sp?
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Comments
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I find it happens on the bottom three cogs on my bike. I was told that it's worse because I have a teeny tiny frame and I don't think there's a solution except riding on the big ring more. Sorry0
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Try twisting the front derailleur a bit... undo the fixing bolt and when looking down on it from the top of the seat tube, turn it clockwise a little. :idea:0
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I am running the same setup on my Ribble winter bike and can use all gears other than small/small with no rub. I had to fit a washer behind the drive side cup. I used the washer used on single speed hubs to adjust chain line. It fits perfectly and there is still plenty of axle to spare. Any good LBS should have these.
I also have a Gossamer mega exo on a Trek 5200 with Ultegra 10sp and can use all gears with no rub. The 9sp chain may be part of the problem. You could use a 10sp chain I believe as they measure the same internally.
If it is rubbing on the inside of the ring then moving the mech will make no difference at all. Just maybe muck up the change if it is working fine at the moment.0 -
Bottom brackets come in different spindle lengths.Try fitting a longer one.When I fitted my Stronglight compact I went from 110mm to 113mm.This eliminated chain rub except for 34t-11t,which I don't use anyway.0
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It's an external bearing BB so the spindle is part of the crank rather than part of the BB, which means you can't just fit a longer one.0
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I have the solution, which worked for me and doesn't need another bottom bracket and bottom bracket spacer. Two weeks ago I fitted small spacers (five in all) between the inner ring and crank spider of about .75mm thickness each. This moved the inner ring .75mms closer to the bottom bracket and FURTHER FROM THE OUTER RING. It had no detrimental effect on any gear changing and I can get all 10 sprockets without any chain rub. You will have to find spacers and adapt them to fit over the bolts, but that was easy.0
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fortyone - where did you get your 0.75mm spacers from? I can only find 0.6mm or 1.2mm. Also, did you need longer chainring bolts after fitting the spacers?
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Poulsy - tried what was available at local DIY, but 0.6 might work anyway. No need to change any chainring bolts as they fitted as normal. Thing is, it should still iincrease how many gears you can get without chain rub.0