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Slowtwitch Forums: Triathlon Forum:
Is this crank on properly.....space between arm and bb?

slowerthanslow

Nov 6, 09 12:52

Post #1 of 7 (442 views)

Is this crank on properly.....space between arm and bb?	Can't Post

Had the LBS put this on, but it looks odd from my other crank. Same GXP bb bracket, went from Bontrager to SRAM Force. Did they maybe forget a spacer? I just don't remember seeing that gap before between the arm and the bottom bracket. Thanks guys

(This post was edited by slowerthanslow on Nov 6, 09 12:52)

IRONwolf

Nov 6, 09 12:57

Post #2 of 7 (436 views)

Re: Is this crank on properly.....space between arm and bb? [slowerthanslow] [In reply to]	Can't Post

you had an LBS put a crank on for you????? just joking.

As it turns out, what you have is less important than what you do with it...
-Bernd Heinrich, why we run

FatandSlow

Nov 6, 09 12:59

Post #3 of 7 (426 views)

Re: Is this crank on properly.....space between arm and bb? [slowerthanslow] [In reply to]	Can't Post

Hard to tell from the picture, but it looks very much like mine. But my GXP BB is silver and not black. I didn't realize that Bontrager cranks used a GXP BB. I thought those were SRAM only.

Darrell

Nov 6, 09 13:04

Post #4 of 7 (412 views)

Re: Is this crank on properly.....space between arm and bb? [slowerthanslow] [In reply to]	Can't Post

The bigger question is whether there is any play in the crankset. If you push on the crank where the spindle is from either side there shouldn't be any movement. In the event there is a spacer is missing. You could always take it to another shop to get a second opinion if you're worried.

.
-Darrell
Front of the Pack - Silicon Valley's triathlon store

FIST certified retailer of Cervelo, Argon18, Quarq, SRM, De Soto and other fine equipment.
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slowerthanslow

Nov 6, 09 13:20

Post #5 of 7 (397 views)

Re: Is this crank on properly.....space between arm and bb? [Darrell] [In reply to]	Can't Post

No play, but there was definitely not a gap on the non-drive side of my last crankset.

I know this is the right bottom bracket b/c I called SRAM and they said it was good to go. Many of the cranksets from Bontrager, Truvative and SRAM take the GXP....according to the tech services guy I talked to.

I don't know however if the mechanic paid attention to the fact that there might be a spacer required though.....

Darrell

Nov 6, 09 13:43

Post #6 of 7 (348 views)

Re: Is this crank on properly.....space between arm and bb? [slowerthanslow] [In reply to]	Can't Post

I would suggest taking both bikes to the mechanic so that you can ask him directly and show him what you're talking about. It is hard to figure these details out over the internet and grainy pictures. The service manual/installation guide should be available from the from the manufacturer's website too.

Each crankset is different so even though they use the same BB it might or might not need a spacer. Some cranksets are just designed differently than others. Unless you're using the exact same crankset you can't tell just by looking at it. Remember that the same BB is used for both a double and triple crankset. A triple would require a spacer due to teh additional width needed for teh extra chainring.

It should be fine if there isn't any play.

.
-Darrell
Front of the Pack - Silicon Valley's triathlon store

FIST certified retailer of Cervelo, Argon18, Quarq, SRM, De Soto and other fine equipment.
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altocinco

Nov 10, 09 14:41

Post #7 of 7 (237 views)

Re: Is this crank on properly.....space between arm and bb? [Darrell] [In reply to]	Can't Post

No GXP cranks (SRAM, Truvativ, or otherwise) ever require a spacer between the crankarm and the non-drive side bearing seal. If you take the crankset apart, you can see that the spindle is narrower where it slides through the non-drive side BB cup. There is a lip at that point that needs to contact the non-drive side bearing inner race (from the inside). Push the right crankarm/spindle assembly through until it stops.

Look at the left arm. For a Force (or Red) crank, there should be some aluminum sticking out from the carbon around the spindle interface. That's on purpose. The flat aluminum surface must contact the outer bearing seal in the NDS cup. Install the crankarm, apply full torque, and everything should be bottomed-out and you're good to go. Try to move the crankset back and forth in the frame. If it moves, uninstall the left arm and try again, making sure you're torquing the bolt correctly. You should use a torque wrench; If you don't have one, however, I can say that the torque requirement is HIGH, and will seem like it's "too" high, especially if you're using a short-ish hex wrench.

If anything feels "too draggy", do not back off the crankbolt. The crankset will not function properly, and you risk failure of the crankset interface (not to mention you'll have side play, which would be annoying) The bottom bracket seals will break in over time, and drag will decrease significantly.