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Old 02-06-09, 06:43 PM   #1
Farleybob
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Bottom Bracket Question

Ok, I currently have a TruVativ Elita triple with ISIS bottom bracket. The left crankarm keeps coming loose so I want to replace the crank. I have a 9 speed with Shimano 105 front deraileur and ultegra rear. I can pick up an inexpensive 105 triple crank, (5505) for less than $100. What bottom bracket do I need for this? I was thinking of going with an Ultegra crank but I didn't want to change anything else. I just want a decent 9 speed crank that won't fail me.

I see a 5500 bottom bracket online for around $35 but it doesn't look like it has the outboard bearing cups like my current setup??

Thanks for your help.
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Old 02-06-09, 07:07 PM   #2
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An ISIS bottom bracket does not use outboard/external bearing cups. It is a cartridge bottom bracket just like square taper.

The 5500 series crankset would use an Octalink bottom bracket which is the cartridge type. The 5600 series cranksets use the external bearing cups.
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Old 02-06-09, 07:07 PM   #3
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FYI - I have the Giga X pipe bottom bracket. Maybe I should just find another TruVativ crank so I don't need to change anything?
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Old 02-06-09, 07:09 PM   #4
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Ok, that makes more sense now.

How many miles are on the current bearings? Are they still smooth? If they are worn at all, I would not let them influence your crankset decision.
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Old 02-06-09, 07:32 PM   #5
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Only about 1500 miles.
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Old 02-06-09, 07:32 PM   #6
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The bearing seem smooth, no troubles there.
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Old 02-06-09, 07:38 PM   #7
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It's your call then. You'll save some money likely by sticking with Truvativ. Lots of people swear by Shimano's cranks though.
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Old 02-06-09, 07:43 PM   #8
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Are the octalink BB's bad or just old school.
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Old 02-06-09, 08:32 PM   #9
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I don't have any experience with Octalink BB's but ISIS (of the same era) has served me well.
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Old 02-06-09, 08:42 PM   #10
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Originally Posted by Farleybob View Post
Are the octalink BB's bad or just old school.
I wouldn't say Octalink is old school. Crank systems went to integrated spindles (spindles that are part of the crankset rather than part of the BB) a few years ago but cartridge BBs like octalink and ISIS are still very common and readily available. Octalink and ISIS basically work on the same principle, they use a splined spindle; Octalink has 8 splines (hence the Octa) and ISIS has 10.

As for your problem, before changing cranksets, have you considered that the problem might be a loose or insufficiently torqued crank bolt? Try changing the crank bolt, then get yourself a torque wrernch and make sure you torque the bolt to specs to ensure the crank on is fully seated onto the spindle.

Last edited by DOS; 02-06-09 at 09:01 PM.
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Old 02-06-09, 08:59 PM   #11
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I have been torque wrenching that bolt for the last part of a year. I checked it everytime after a ride and it was good. I went on a 500 mile week long tour and left the torque wrench at home, the bolt came loose on day four and left me stranded along the road.
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Old 02-06-09, 09:09 PM   #12
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I have been torque wrenching that bolt for the last part of a year. I checked it everytime after a ride and it was good. I went on a 500 mile week long tour and left the torque wrench at home, the bolt came loose on day four and left me stranded along the road.
If you are torqueing to specs -- and for Truvativ crank bolt, thats like 400 inch pounds -- and it appears the crank arm is seating properly onto the spindle splines (shouldn't be any spindle visible bewteen inside of crank and the face of the BBshell) then I would think the problem is either the bolt itself (cheap to replace), or the threads inside the BB spindle (need a new BB), rather than the crank arm.
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Old 02-06-09, 09:24 PM   #13
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Well, once the arm has come loose, the internal splines on the arm are likely ruined. Once that precise fit is gone, there's little hope that the crank arm will stay tight (just like a loose arm on a square taper spindle).
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Old 02-06-09, 10:00 PM   #14
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Well, once the arm has come loose, the internal splines on the arm are likely ruined. Once that precise fit is gone, there's little hope that the crank arm will stay tight (just like a loose arm on a square taper spindle).
Yeah, thats a good point.
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Old 02-07-09, 02:04 AM   #15
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Having just installed a Shimano Hollowtech outboard bottom-bracket, I'm sure they will replace ISIS and Octalink. They are simpler, and the light-weight of the two small sealed-bearings that rotate make them much more efficient - as well as smoother. Two small sealed-bearing disks v. a much heavier metal shaft that revolves? No brainer. Installation was all of 5 minutes.

They are certain to replace the heavier, clunkier ISIS/Octalink sealed-bearing BB's that were all the rage a few years back.
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Old 02-07-09, 03:13 AM   #16
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I have been torque wrenching that bolt for the last part of a year. I checked it everytime after a ride and it was good.
Don't retorque the crank bolt unless you are completely removing and reinstalling the crank. When you ride after installing, the crank squirms up the splines a bit which results in a slight and normal loss of tension in the bolt--but the bolt has not backed out--mark its position with nail polish if you're unsure. You tighten it back to installation torque and next ride it squirms up a little more. Keep going and you damage the splines.

I had (past tense, it's in the junk box now) an Elita GXP triple like yours, they are notorious for loosening. Giga X pipe relies on the same bolt to mate the splines and preload the bearings. So if your BB is just a little wider than 68 you won't get good spline mating. Newer versions do the preload with a spring washer, but I think it's still inferior to the Shimano outboard system which preloads the bearings with one bolt and clamps the splines with another.
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Old 02-07-09, 06:53 AM   #17
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Having just installed a Shimano Hollowtech outboard bottom-bracket, I'm sure they will replace ISIS and Octalink. They are simpler, and the light-weight of the two small sealed-bearings that rotate make them much more efficient - as well as smoother. Two small sealed-bearing disks v. a much heavier metal shaft that revolves? No brainer. Installation was all of 5 minutes.

They are certain to replace the heavier, clunkier ISIS/Octalink sealed-bearing BB's that were all the rage a few years back.
Oh, I think there's no doubt about that; they are coming standard on most new bikes nowadays from mid-level on up. They are becoming standard less because they are superior to cartridge BB, although they may be, but because integrated spindle cranks are lighter and stiffer than the combo of standard crank with cartridge BB.
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