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Old 05-08-06, 05:49 PM   #1
mx_599
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ISIS vs square taper question

it is my understanding that the taper fit of square taper cranks "wear" out with with repeated cycles of assembly/disassembly...or any taper fit assembly for that matter.

are ISIS a form of taper as well but with the addition of splines? are they just as susceptible to "wear" as the square taper?

thanks
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Old 05-08-06, 06:47 PM   #2
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Uh. what.
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Old 05-08-06, 07:02 PM   #3
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I don't think the spindle is going to be the wearing component. The aluminum crank arm is the part that will eventually suffer from improper installation and repeated removal.
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Old 05-08-06, 07:36 PM   #4
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Well with my old racing bike of 25 years ago I certainly DID cause the square taper interface to wear from repeated removal/assembly because I used the same frame and cranks for road and track so I was reguarly removing/refiting items.

I currently use an ISIS bottom bracket/cranks and I am happy with its performance and yes it is also a form of taper. I've removed/fitted them a few times now for various reasons and haven't noticed any wear or movement yet so they seem to be better but I haven't had them for as long as the square taper cranks.

Regards, Anthony
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Old 05-08-06, 08:07 PM   #5
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ISIS ain't tapered.
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Old 05-08-06, 08:25 PM   #6
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Quote:
Originally Posted by capwater
ISIS ain't tapered.
It has 1 degree taper

http://www.isisdrive.com
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Old 05-08-06, 08:30 PM   #7
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The spindle is a constant outer diameter shaft with 10 evenly spaced flutes
machined or forged into each end. The flute cuts themselves are 6mm in
diameter and inclined at a 1° angle to the spindle axis. In addition to the
tapered flutes, a hard stop is positioned 16mm from the end of the spindle on
both sides of the bottom bracket.

From:
http://www.chrisking.com/pdfs/ISIS%2...%20Rev%20D.pdf

Isis has some taper to it.
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Old 05-08-06, 08:41 PM   #8
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thanks guys for those links...it kind of confirms what i thought. so i am guessing that because of the "positive" stops on the ISIS, even though there is a slight taper, they are probably not subjected to the same amount of wear as a square taper can be.

right?
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Old 05-08-06, 10:09 PM   #9
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Square-taper BB's function as a taper - it's the taper that stops the crank from going further onto the spindle. And they have a 2-degree taper.
ISIS Bb's have a stop, and therefore the main thing that keeps the crank from sliding further onto the spindle is the stop, not the taper, I think.

If installation is done properly, I think it's the aluminum crank that deforms (and then only slightly) when installed repeatedly on a square-taper. On a micro-level, the deformation of the aluminum is part of what keeps the crank firmly on the square taper.

But I don't think that a properly-installed square-taper crank has any real downside in the department that you seem to think. The issue comes if you're installing it and removing it a lot, but even then I don't think much long-term deformation is likely.
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Old 05-09-06, 05:37 AM   #10
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Quote:
Originally Posted by Soil_Sampler
It has 1 degree taper

http://www.isisdrive.com
OK, 1 degree, close enough for gubmint work. Octalink probably has a slight taper as well, but you don't call them "tapered cranks". The slight taper is used to ease installation. Cheers.......
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Old 05-09-06, 06:27 AM   #11
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A taper is a taper even if its a slow one. Even the old cotter-pins worked on the taper principle. Thinking about it the long, slow taper in the ISIS cranks is what makes them better as well as there being more contact but the problem of long slow tapers is that they keep on going so they put in a stop in the design.

Regards, Anthony
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Old 05-09-06, 09:34 AM   #12
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cool....thanks guys
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Old 05-09-06, 09:54 AM   #13
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For what it's worth, I have never had a square-taper crank wear out from installation/removal. When I was in college, I used to rebuild the bb of my mountain bike about once a week b/c we rode in mud all the time (at the time, we thought it was "cool"). As long as you install it properly, you'll have a hard time wearing out a set of square-taper cranks.

I don't have any personal experience with ISIS, but I do know that most of the mountain bikers I know (including several experienced shop mechanics) refuse to use ISIS on their own bikes. It's either old-skool square-taper or the new hollow spindle stuff. The comments I remember basically sounded like it just creaked all the time. They got tired of having to pull the cranks off all the time to clean it out, so they quit using it. I also seem to remember some issues with the bb's too (wearing out/breaking).

Like I said, I don't have any personal experience with ISIS. Everything I have is either the new XT or old square-taper stuff. The square taper is really bulletproof, and it's easy to get replacements for.
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Old 05-09-06, 10:29 AM   #14
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With the advent of the cartridge BB, crank arms rarely need to be removed. Wear on the taper should be negligable unless the cranks are improperly torqued.
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Old 05-09-06, 10:57 AM   #15
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The bb spindle should never wear as it is hardened tool steel.
The Al cranks can expand or crack if overtouqued.
Since there should be no relative motion between the two there is no "wear".
Octalink and ISIS are solutions in search of a problem.

Enjoy
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Old 05-09-06, 11:07 AM   #16
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If the bolt on a sq taper crank comes undone and the crank comes loose, riding the bike in that condition can destroy the crank fast. Repeated removal and reinstallation doesnt wear the interface. If the crank stretches so the mounting bolt cant tighten it onto the taper, before the bolt bottoms on the end of the spindle, the crank has to be replaced.
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Old 05-09-06, 11:16 AM   #17
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Quote:
Originally Posted by AndrewP
If the bolt on a sq taper crank comes undone and the crank comes loose, riding the bike in that condition can destroy the crank fast. Repeated removal and reinstallation doesnt wear the interface. If the crank stretches so the mounting bolt cant tighten it onto the taper, before the bolt bottoms on the end of the spindle, the crank has to be replaced.
Right. And the exact same problem happens to ISIS and Octalink BB/crank interface systems.
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Old 05-09-06, 12:28 PM   #18
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Quote:
Originally Posted by AndrewP
If the bolt on a sq taper crank comes undone and the crank comes loose, riding the bike in that condition can destroy the crank fast. Repeated removal and reinstallation doesnt wear the interface. If the crank stretches so the mounting bolt cant tighten it onto the taper, before the bolt bottoms on the end of the spindle, the crank has to be replaced.
I have had success filing a chamfer on the inside face of square taper cranks that have been over torqued. You just want to remove enough Al to assure that the crank does not bottom out when tightened onto the spindle.
It’s a ghetto fix but it works great.
My winter FG has been going strong for two seasons.

Enjoy
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Old 05-09-06, 02:48 PM   #19
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You'll wear out the multiple crank arms before wearing the BB spindle out. Most of them are hardened cro-moly steel.
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