braintree39

This is my first bike build and I'm running into some trouble...


When my front derailleur is on the largest ring, the chain either rubs against the side of the derailleur or (if I adjust the stop) the crank hits it... I suspect the problem might be my crank - it's a Suntour XC LTD. When I measured the distance between the largest ring and the crank arm, there was only 5mm. The crank arms on my other bikes seem to be much more than that - 8mm...


Any input is appreciated. I've tried adjusting the locations of the derailleur, making it between 1mm and 5mm above the largest ring, made sure that it was parallel to the rings (and tried slightly off...). I originally tried a BB with a length of 127mm, but removed the smallest ring and installed a 110mm because it had a better chain line.


I'm stumped... my next step is to buy a new crank set, but looking for other things to try first.


Frame - Surly Cross Check

Derailleur - Deore DX (purchased used)

Crank - Suntour XC LTD - 46T

Chain is a SRAM Powerlink 8 speed


Let me know what you think. Thanks!

Andrew R Stewart 

There are some crank arm/ring size, ft der cage shape combos that just don't work. Ft der cages that has a step to the end of the cage can be extra hard to get all to play nice. Andy

88Tempo

Have you tried a little bit longer spindle length? You might only need 2-3 millimeters. As Andrew R. Stewart said some combinations don't play well together.

88Tempo

The Surly site states that the stock Cross Check uses a Shimano BB-UN55 68 x 118mm bottom bracket in answer to a question

bwilli88 

I would not figure on what the frame needs but the crank arms.

88Tempo

@bwilli88

I tried looking up that crankset on velobase hoping to see recommended spindle length with no luck. I went to the Surly site because I hadn't been there in a while and started reading. Another thing I noticed is the new Cross Check can use either a 130 or 135 mm hub. That will change the chainline won't it?

braintree39

Hmmm... I'm not sure about the chainline, but I don't think it will impact this particular problem. (It might be a separate problem though)

Even if I unhook chain and let it dangle, if I adjust the stop so that the chain doesn't rub the inner side of derailleur, the crankarm will hit it. The problem exists no matter what rear cog it's on and would likely still exist if I bought a different BB.

I think it's what Andy posted. These just aren't playing well together. I ordered a 105 derailleur. I'm ultimately going to be upgrading anyway. If the crank doesn't work with that, I'm probably just going to buy a 105 crank/BB... Upgrade the whole drivetrain.

88Tempo

I'm no expert believe me. The biggest issue I've had with a FD was a RSX FD that didn't want to work with a Sora crankset. I think that particular FD was set up for a max chainring of 46 or 48.