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Old 12-01-10, 04:50 PM   #1
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Crank Compatability?

Lets say I want to upgrade the crank on my hybrid how do I find one that would be a direct swap? The current crank is a SR Suntour XCT triple 48/38/28 the spindle is 122.5mm square taper, and the BB is 68mm wide. This is a 2009 model. I'm not impressed with the current crank as it has riveted chainwheels not bolt-ons. So, what would I get that would be a direct swap?
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Old 12-01-10, 04:53 PM   #2
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it's very hard to find a perfect replacement for cheaper cranks. There's usually always a BB axle length change that's involved.

best bet is to find a replacement crankset first, and don't worry about the interface required. BBs are very cheap compared to cranksets.
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Old 12-01-10, 05:06 PM   #3
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Can you suggest a tripple crankset with 48/38/28 chainwheels? I don't mind replacing the BB if I have to. My question is, if I choose a crankset that states it requires a 113mm spindle length, and I install the the new crank with a new BB with a 113mm spindle will this give me the correct chainline?
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Old 12-01-10, 05:20 PM   #4
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Originally Posted by Capecodder View Post
Lets say I want to upgrade the crank on my hybrid how do I find one that would be a direct swap? The current crank is a SR Suntour XCT triple 48/38/28 the spindle is 122.5mm square taper, and the BB is 68mm wide. This is a 2009 model. I'm not impressed with the current crank as it has riveted chainwheels not bolt-ons. So, what would I get that would be a direct swap?
Now's the perfect time to change to an external bottom bracket crank. This one is a great bargain. Dead simple to install.
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Old 12-01-10, 05:35 PM   #5
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I would go with a shimano external too.
no need to worry about BB spindle length. Just follow the manual and install with correct amount of spacers, done.
for some reason, it seems to be hard to find a 28/38/48 triple for newer cranksets.
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Old 12-01-10, 05:36 PM   #6
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Maybe I should have mentioned this is a seven speed setup (7speed freewheel)....
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Old 12-01-10, 05:48 PM   #7
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it would be best if you had a shop that will allow returns or trades if the chainline wasn't great.
manufacturer recommendations are almost always spot on.
I say usually, because there are some special combinations that don't work for whatever reason, but it's pretty rare in my experience.
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Old 12-01-10, 07:20 PM   #8
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Originally Posted by Capecodder View Post
So, what would I get that would be a direct swap?
The cranksets that used a bottom bracket spindle lenghth of 122.5 were quite common in the earlier versions of Shimano’s mountain series of triples, (XT, LX,DX, etc) of the late 1980's utill the early 90's. The XT line was considered the “best” prior to the release the XTR series. The vintages of these series utilize the “Full” size chainrings that are the same size that you have now verses the compact series that were introduced around the mid 90’s and are more common on higher end rides today

If you take a look at Sheldon Brown’s bottom bracket guide, you can see what cranksets use a 122.5 bottom bracket. Link is HERE

Keep in mind, should you decide to change to a different series (configuration wise) of crankset, you may find that you will have to change the bottom bracket and the front derailleur as well. All of these components are meant to play nicely with each other.

You can find NOS (New-Old-Stock) versions of these once great cranksets often on EBay among others. These series are perfect for a current Hybrid application

Last edited by Deaver; 12-01-10 at 07:22 PM. Reason: I spelt stuff rong
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Old 12-02-10, 12:43 AM   #9
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So you want to replace your crank because the chain rings are riveted? Do you plan to mix and match different chainrings?

I think I'd only replace the crank when the tooth are worn out or you need different gear ratios. But to replace because they are riveted together is kinda silly isn't it?

Anyhoo, I think this set is a a buy if all you want are bolt-on chainrings. The Alivio is one step below the Deore however it's half the price. You don't even have to replace the BB.
http://www.amazon.com/Shimano-FC-M41...1271849&sr=8-1

Last edited by wunderkind; 12-02-10 at 12:47 AM.
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Old 12-02-10, 02:33 AM   #10
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Quote:
Originally Posted by AEO View Post
for some reason, it seems to be hard to find a 28/38/48 triple for newer cranksets.
The switch from freewheel to cassette made it possible to use smaller cogs, allowing for smaller chainrings while keeping the same ratios.
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Old 12-02-10, 08:14 AM   #11
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Maybe I should have mentioned this is a seven speed setup (7speed freewheel)....
Not really an issue. 9 speed cranks will work with 7 speed.
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Old 12-02-10, 09:46 AM   #12
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^ Yup. Currently I am running a 7spd chain on a 8 spd cassette with a 9spd compatible crankset on my commuter. Seems to be fine.
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Old 12-02-10, 05:12 PM   #13
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Originally Posted by cyccommute View Post
Now's the perfect time to change to an external bottom bracket crank. This one is a great bargain. Dead simple to install.
Will it matter the this setup is 48/36/26 and my current setup is 48/38/28 or will the 2 tooth difference on the middle and small ring not be a big deal?
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Old 12-02-10, 11:22 PM   #14
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Will it matter the this setup is 48/36/26 and my current setup is 48/38/28 or will the 2 tooth difference on the middle and small ring not be a big deal?
Makes no difference. You could even run a 22 inner with few issues. My touring bike, my wife's bike and my daughter's bike are set up with 22 tooth inners. Actually my touring bike is set up with a 20.
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Old 12-03-10, 03:24 PM   #15
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Originally Posted by cyccommute View Post
Now's the perfect time to change to an external bottom bracket crank. This one is a great bargain. Dead simple to install.
Yes, a link to Shimano Deore M590 crankset. And they don't have a chainguard on it. Forgive me for the rant but why do they do this to people anyway? Looks like I'd be forced to get the Alivio to get a chainguard on it. Blah, whatever...

EDIT: Just found something interesting http://www.singletrackworld.com/foru...aper-chainsets

Some people are saying square taper is better. lol

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