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Old 01-14-10, 12:18 PM   #1
ls0725
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crankset question

hello,

i am planning to replace my crankset but am not sure of the specs and some technical aspects. The current one installed is a 'Truvativ Isoflow' triple and it has markings that says 'power spline'. When I look at the end opposite pedals (bottom bracket level) it appears I need an allen wrench (maybe 8 or 9mm) to remove it but am scared I may be doing it wrong.

My questions are:

1. Is it as simple as using an allen wrench to remove the crank arms? What direction should I turn the allen wrench to remove the arms (drive side)?
2. Is this what they call ISIS? I know it is not square for sure.

I do not intend to replace the bottom bracket though.

Thanks for help.
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Old 01-14-10, 12:34 PM   #2
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remove it like a standard square taper crank. power spline is not the same as isis. use a square taper puller.
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Old 01-14-10, 01:16 PM   #3
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If you get new cranks, I would avoid the Powerspline system. It offers no real advantag, it is proprietry and aimed at budget bike builders who fit it as original equipment. The retail support is not that good.
If you want good value for money and you are not into racing then a good quality square taper system will be sufficient. You can get high grade bottom bracket units and cranksets.
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Old 01-14-10, 01:38 PM   #4
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Should I consider replacing the BB too, I know it's 68mm english but how do i measure the length. i have been looking online and it seems there are a lot of choices on length. do i measure with a ruler from one end to the other where the bottom bracket fits?
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Old 01-14-10, 02:02 PM   #5
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Crank makers will usually specify a couple different BB lengths. So, BB spindle length is dependent on the crank. Just about any crank you get will be an upgrade- alloy rings, lighter arms, lighter BB spindle, ec. Don't rule out modern 2 pc crank designs. ISIS and Octalink systems are no longer supported on the OEM side, so I'd avoid those 2 designs entirely. Traditional square taper will never go away. The 2 piece designs with external bearings are very popular as new aftermarket and OEM. That's where crank makers are spending product development and design dollars on.

But why do you want to upgrade? can you replace the chainrings to alloy? what bike are you riding?
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Old 01-14-10, 02:15 PM   #6
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well, you see there are 2 main reasons why I want a change, first I dont use and hate to 'carry' the 30 gear ring (52/42/30) for nothing and I dont like the 175mm crank arms length, it seems 170mm feels better for me, from trying out other bikes.

if you could suggest a cheaper way of getting rid of those 2 problems, I am all ears.
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Old 01-14-10, 02:43 PM   #7
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it is a 5-bolt pattern 130mmBCD outer/middle and 74mmBCD inner.
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Old 01-14-10, 02:44 PM   #8
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You may need to put a washer or something between the spindle and the pad of the crank puller so the crank puller doesn't fall into the hollow spindle. but otherwise it comes off the same as a square taper crank.
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Old 01-14-10, 03:03 PM   #9
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Very cheap method:
1. Remove the 30t inner.

2. there is no cheap way to reduce crankarm length.

52/42/30 sounds like you have a road triple, on a road bike or hybrid, and you want to replace it with a double. There's usually more to converting from triple to double than removing the inner ring or even crankset- the BB needs replacing, the front derailleur usually needs to be replaced. The long cage rear derailleur can work in a pinch but there's a lot of excess chain and that will not be taken up otherwise. And the left side front shifter may or may not need to be changed too.

The weight 'penalty' of an inner chainring is kinda small as to what you are having to deal with in terms of all the other details.

So, what bike are you riding? A trek? a mongoose? a Walmart schwinn? A kona? What model?

For higher end bikes, converting from triple to comnpact double is totally reasonable. For entry level bikes there are diminishing returns cost wise- the Truvaitiv powerspline crank is not a high end piece of hardware at all. Unless it's your mostest favoriteist bike and you are completely satisfied witht he fit, I'd ride it for a little more as is, and look at other bikes that have a component chice you are more satisfied with.
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Old 01-14-10, 03:26 PM   #10
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Quote:
Originally Posted by zzyzx_xyzzy View Post
You may need to put a washer or something between the spindle and the pad of the crank puller so the crank puller doesn't fall into the hollow spindle. but otherwise it comes off the same as a square taper crank.
Nope. Power spline uses the same size fixing bolt as square taper.

Last edited by Dan Burkhart; 01-14-10 at 03:43 PM.
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Old 01-14-10, 03:37 PM   #11
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i have 2 road bikes, one is a trek 5200 oclv that i use for group rides and my 'chores' ride which is in question which is an ironhorse 2005 w/ 105 group except for the crankset which is still stock. i use it when i have to go down and tie it down to a post or something and not feel so bad when it gets stolen, although the seatpost, fork, stem and handlebars are all carbon already.

i am not willing to change the shifter to double which will be practically half the bikes cost. those shifters are expensive really and the current 105 is just serving me fine.

i am now just contemplating removing the inner gear (30) and maybe change the middle and outer gear to upgraded ones and ride that setup to trhe bikes death.

i probably just have to be careful with the left shifter downshifting to a gear that is no longer there.
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Old 01-14-10, 04:02 PM   #12
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if you drop the 30 just reset the stop on the fd and you should be "good to go".
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Old 01-14-10, 04:10 PM   #13
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if the ironhorse is a beater, errand bike, have some fun with it. Maybe a 1x9 or singlespeed setup? make it a basket bike?
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