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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 05-21-10, 11:23 AM   #1
jnbrown
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FSA Crankset Issues

I am having some issues with the SLK front crankset.
Initially it was fine and quiet.
Recently is has been noisy.
When pushing hard while seated it makes a knocking sound, like marbles.
When standing it makes a loud creaking noise.
When I installed it I used a torque wrench so I don't think any thing is loose.
It could be the eccentric, I have not taken things apart to investigate yet.
I know FSA isn't known for being super reliable so it could the bearing is already failing.

Another issue is the crank spacing. Since this bike has a 145mm rear wheel vs. 160mm on our Santana I thought the cranks would be closer together. I measured them and compared to my road bike they are 20mm further apart which would be about what the Santana was. I am finding it feels awkward and may be aggravating some knee pain.
For some reason it never was a problem on the Santana. I am thinking about replacing the FSA crankset with a standard Ultegra installed backwards with Helicoils to reverse the pedal threads. This was an idea I had when building the bike but opted to go with FSA so I would have a perfect chain line. But now i think my knee comfort is more important than the chain line. My understanding is that the timing chain can have lots of offset without it being a problem since it is much longer than the rear which of course works with plenty of offset.
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Old 05-21-10, 01:40 PM   #2
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I had a Santana and the crank spacing was about 20 mm wider than my Co-Motion. Like you, my knees notice the wider spacing. Teflon tape on the bottom bracket threads will sometimes stop the creaking of the bottom bracket.
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Old 05-21-10, 02:13 PM   #3
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Originally Posted by tandem rider View Post
I had a Santana and the crank spacing was about 20 mm wider than my Co-Motion. Like you, my knees notice the wider spacing. Teflon tape on the bottom bracket threads will sometimes stop the creaking of the bottom bracket.
Is your Co-Motion standard road crank spacing?
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Old 05-21-10, 04:45 PM   #4
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I run my FSA SLK with Chris King bottom brackets have not had any noise issues
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Old 05-21-10, 06:57 PM   #5
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I just made some measurements and it turns out that the chain line would be perfect by mounting the 40T chainring on the outside of the Ultegra cranks.
The FSA cranks have to 40T ring on the inside.
I think I am going with the Ultegra's.
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Old 05-21-10, 07:58 PM   #6
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Originally Posted by jnbrown View Post
Is your Co-Motion standard road crank spacing?
Yes, the Supremo is the same as my single and both have the older Shimano Ultegra triple crankset. I also have a Mocha with FSA Gossamer which is spaced about a half inch wider than the Supremo.
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Old 05-22-10, 12:21 AM   #7
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Use some loctite on the BB threads when installing, this should prevent it from creaking. However, as you said, it could also be coming from the interface between the eccentric and the frame.
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Old 05-22-10, 12:28 AM   #8
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Quote:
Originally Posted by jnbrown View Post
Another issue is the crank spacing. Since this bike has a 145mm rear wheel vs. 160mm on our Santana I thought the cranks would be closer together. I measured them and compared to my road bike they are 20mm further apart... I am thinking about replacing the FSA crankset with a standard Ultegra installed backwards with Helicoils to reverse the pedal threads....My understanding is that the timing chain can have lots of offset without it being a problem since it is much longer than the rear which of course works with plenty of offset.
By crank spacing you are referring to the Q factor?

Quote:
Originally Posted by Sheldon Brown
Q Factor/Tread: The lateral distance between the pedal attachment points on a crankset. For most cyclists, the narrower the tread the better....
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Old 05-22-10, 10:37 AM   #9
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[QUOTE=Ritterview;10848948]By crank spacing you are referring to the Q factor?

Yes (aka Tread) , It's 164 on the FSA SLK tandem and 147 on the Ultegra.
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Old 05-23-10, 02:19 PM   #10
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I pur an FSA SL-K crankset (spindle attached to spider) on our new tantem and we both noticed the wider Q factor right away. The spindle comes in one length and you make up the difference with the spacers so no matter what your bottom bracket width or rear spacing is you get the wide Q. The wider Q hasn't caused me any problems but my stoker is having knee pain when we ride the tandem. A new crankset will be costly but it's not worth risking knee injury.
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Old 05-24-10, 11:20 PM   #11
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Originally Posted by jnbrown View Post
[Q factor?] Yes (aka Tread) , It's 164 on the FSA SLK tandem and 147 on the Ultegra.
The Lightning, which has worked out great for us so far, has a Q factor of 155 mm.

The Cyfac used by the French racing team has a square taper Stronglight Impact Tandem crankset. These are really inexpensive. I don't know the Q-factor, but sans external bearings it might be favorable. The weight is 1350 grams, figure 400 grams for two bottom brackets, and at 1750 grams your roughly on par with the FSA. A review of sorts on the triple version here. If this solved your crankset and Q-factor issues for less than $200 would be a nice resolution.






_________________________________________________________________edit.

Upon further review, the Stronglight is not the answer to your Q-factor woes. It is 168 mm.

Last edited by Ritterview; 05-24-10 at 11:27 PM.
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Old 05-25-10, 07:45 AM   #12
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Quote:
Originally Posted by Chris_W View Post
Use some loctite on the BB threads when installing, this should prevent it from creaking. However, as you said, it could also be coming from the interface between the eccentric and the frame.

FSA says to use Loctite 641 on the spindle itself. However, I've never been able to find the stuff locally. Here's a web link. http://www.shoplet.com/Loctite-641-R...S44228802/spdv

I have used Loctite blue (242) on the threads of the bolt, and it seems to help.

The inherent problem in the FSA design is that one bolt tightens the crank, as well as setting the preload on the bearings.

The shimano approach of one bolt to set pre load, and another two to hold the crank arm in place is a much better design IMHO.
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Old 05-25-10, 09:17 AM   #13
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I think I can get an Ultegra crankset for around $100 - $150 and then $50 to helicoil both arms, so similar in cost to the Stronglights
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Old 05-25-10, 05:03 PM   #14
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Go for the reversed Ultegra. I have done the same thing with an older DuraAce crank on the front of our tandem. Didn't use helicoils, just (with the help of a mill to keep everything square) put new, reversed threads right over the original. It has served me well for several years -- but I'm only ~150 lbs, so YMMV.
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