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Old 11-10-08, 04:00 PM   #1
cman
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First Time installing external BB and crank

I have no problem installing cartridge style BB and square taper cranks. I just purchased some Truativ Firex cranks with a GXP BB. I read the Park tool site and just wanted any pointers. It seems simple enough....I am wrong.
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Old 11-10-08, 04:40 PM   #2
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I'd face the bottom bracket tube before I'd install them.
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Old 11-10-08, 06:47 PM   #3
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I'd face the bottom bracket tube before I'd install them.
This
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Old 11-10-08, 08:45 PM   #4
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I'd face the bottom bracket tube before I'd install them.
Why? I would just torque and go.
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Old 11-10-08, 08:51 PM   #5
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Why? I would just torque and go.
If the bottom bracket tube is not perfectly straight, there is potential for the bearings to become worn much quicker than they would otherwise. If I remember correctly, RaceFace had this problem with their external bb's.
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Old 11-10-08, 09:00 PM   #6
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If the bottom bracket tube is not perfectly straight, there is potential for the bearings to become worn much quicker than they would otherwise. If I remember correctly, RaceFace had this problem with their external bb's.
I would measure for perpendicularity before I started to cut metal. I would be more concerned about shell concentricity than parallelism.
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Old 11-10-08, 09:01 PM   #7
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yeah, I meant the edges being straight. Sorry, it's been a long day... Perpendicularity is key.
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Old 11-10-08, 10:02 PM   #8
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I will let the LBS do this the first time. Maybe I will buy the wrench so I can do it in the future.
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Old 11-11-08, 07:22 AM   #9
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According to my lbs mechanic friend, it's particularly important to face the BB (as mentioned) before installing external bearing cranks if your frame hasn't had that done before. The external bearing are aligned by those surfaces. I had it done on my 5 year old Stump Jumper, but the Santa Cruz Superlight frame I bought for the wife's bike, the BB was surfaced at the factory apparently in anticipation of using the new "style".

You need a small tool to preload the bearings before tightening the crank-arm bolts. I didn't notice it on the Park web site which I used to learn how to do mine. Luckily, I also did a Google search and discovered the need for the tool and was able to order it in time.

I ran into a strange problem on mine. The new LX ext. bearing crank set messed up my chain line. I corrected it to the original chain line (and perfect centering of the pedals) by moving a spacer to the "wrong" side. The result of that was that the chain would bind on the large ring when attempting to shift down to the middle ring.

That didn't matter all that much as I don't like Shimano rings anyhow and put on my old Blackspire rings. Things worked as before with the original crank set. On my wife's bike all went well with the same LX crank set and the spacers installed per directions.

Al


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