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Old 05-31-09, 08:25 PM   #1
noobike
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upgrading crankset for my Trek 7.2 fx

Please help this clueless commuter.

My left pedal just fell off because the crank threads were stripped. I want to take this opportunity to upgrade the $23 crankset instead of finding a replacement crank arm.

This is a nyc beater/commuter bike so I'm looking to spend no more than $200.

I'm thinking about this one:

Shimano 105 5600 Crankset
http://www.nashbar.com/bikes/Product...345_-1___11003

The stock rings are 48/38/28. The above is 50/39. Will the larger ring cause any shifting problem using the stock front derailleur?
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Old 06-01-09, 07:39 AM   #2
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Ask Nashbar if there will be any problem running these rings with an 8-speed chain and Alivio derailleur and shifters.

If they give the all clear you will need to get outboard bottom bracket bearings, raise the front derailleur to clear the larger outside chainring, and block off the the #3 position of the front derailleur using the outside ("H") limit screw.
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Old 06-01-09, 08:41 AM   #3
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You could just get a crank such as this Sugino. http://www.velo-orange.com/suxddocr48.html

And the Grand Cru BB http://www.velo-orange.com/grcrubobr.html

I'd take the Sugino over the 105 every day of the week, as a tapered crank allows for custom chainline tweaking and, it uses a 110 BCD. The 105 is a 130BCD.... limiting you to a 38t small ring. (If that matters to you)

These cranks will work fine with your current setup. The rings are a close match to your current . Do you know the difference between the 105 crank from Nashbar you were considering, and the Sugino one I mentioned?

Either one takes some knowledge and skill to install. Just how clueless are you?... it helps for the forum to know!

Don't let the lower price of the 105 crank influence your decision...... you may be clueless, but you don't have to be cheap too!

Last edited by Garthr; 06-01-09 at 08:45 AM.
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Old 06-01-09, 09:31 AM   #4
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Thank you "oldbobcat" and Garthr.

In term of competency I only know how to fix flat and manage to strip crank arm with a cheap wrench. The shop will do this upgrade.

I will read up about 110 vs 130 bcd. I can see the obvious difference in BB - the shimano uses the new external ball bearing cups whereas the one you recommended is internal and has a squared tapered spindle. It seems like the chain rings are riveted to the crank arm?
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Old 06-01-09, 10:00 AM   #5
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No... the rings are removable, attached with recessed bolts. 110 BCD offers the widest choice of rings, and replacements are inexpensive and easy to change.
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Old 06-01-09, 10:41 AM   #6
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No... the rings are removable, attached with recessed bolts. 110 BCD offers the widest choice of rings, and replacements are inexpensive and easy to change.
I was referring to the shimano and wondering about the ability to switch rings.
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Old 06-01-09, 12:02 PM   #7
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Yes, the 105 rings are removable. Every decent crank made these days has replaceable rings.
That crank is a 10 speed model though. As far as I know, it requires a narrower chain, and a new front dérailleur(FD). 38 teeth is the minimum chainring. I believe you need 10 speed chainrings though too if you wanted to replace them. It's always best if you can get the rings you want on the new crank to start with.

That's why I suggested the Sugino. It uses a 7,8 or 9 speed chain. Uses any FD designed for 5,6,7,8 or 9 speeds, including your current one. It's more universal overall.

I'm not a fan of Shimano and the like for constantly making parts obsolete. It really makes it a pain in he arse for average user.... and for a complete novice.... a train wreck because the parts have become too specific and proprietary.

Last edited by Garthr; 06-01-09 at 12:05 PM.
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