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I have a 2004 Giant Cypress I use for commuting, and the entire drivetrain is very worn out (shark teeth and chipped teeth, front and back). I need to replace the Shimano MF-TZ20 7-speed (14-34t) freewheel, chain (I know to enough to always replace the chain when replacing the freewheel!), and Shimano M131 (48/38/28t) crankset (not just the chain rings, unfortunately, because they're riveted on this cheap crankset)-:

I have a very flat commute and would like a taller top gear, so I'm thinking of using an MF-HG37 (13-28t) freewheel in back (since I never need the 34 rear gear on my ride anyway), and that seems like a straightforward substitution.

What I'm really wondering about is whether I can increase my top gear further by using a crankset such as the FC-2303 (52/40/30). Shimano says it is "8 speed compatible", and I know 8 speed chains are the same width as 7 speed chains, so it seems like it should be OK. Can anybody set me straight for sure?

Thanks.

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2 Answers

Should work fine. Look up your front derailer model number on Google and see if you can find the max teeth spec, generally the curvature of the front derailer cage will limit it to use with a max number of teeth on the largest ring of the crankset. Even if the front derailer says max 48T you could probably get it to work well enough with some tinkering. Front derailers are relatively cheap, so replacing that is always an option.

@zenbike is correct. I overlooked the fact that a front mountain shift/der with a road crank may cause issues for the exact reasons he listed.

JTek does make a product called ShiftMate which is an inline pulley that changes cable ratio/travel. The #7S model allows the use of a mountain front shifter with a road derailer/crankset. Albeit you might be able to find a front road flat bar shifter cheaper than the JTek ShiftMate. In either case a road front derailer is a necessity.

According to Sutherlands, 7/8 speed chain is 7.1 - 7.3mm wide with 7.1 often associated with Shimano IG and 7.3 with Shimano HG.

EDIT: DNP Epoch makes an 11-28 freewheel if you wanted to get even taller.

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Front derailer is a Shimano FD-C102. Found something on the Shimano website saying the max teeth for this derailer is 48, so looks like I need a new front derailer if I go this way. Not a big deal, as you mentioned. Thanks for the help. :-) –  Dave Apr 11 '12 at 23:28
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If you're on a budget, I would try making your existing front derailer work. You would need to move it upwards slightly on the seat tube and get it to clear the max chainring by about 1mm. Then simply test ride and see if works to your liking, if not, get a new one. –  802bikeguy.com Apr 11 '12 at 23:38
    
Saw the DNPs, heard very bad things about them. Wish Shimano or SRAM still made an 11-28 freewheel. :-( –  Dave Apr 12 '12 at 16:45
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The FC-2303 is a non series road crank set. It will work, with some shifting degradation, but it is not an ideal match.

8 speed road shifters, and 8 speed mountain shifters pull a different amount of cable, because the spacing of the chain rings on a road crank is different than that on a mountain crank set.

If you want it to work well, you need to also change your front derailleur, and front shifter. Depending on your bike and the direction of cable pull, you may or may not be able to put a road dérailleur on it, but you can get a touring dérailleur. And you'll need an 8 speed flat bar road shifter which will pull the correct amount of cable for for an 8 speed road crank set.

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OK, FD-2303 is the front derailer that goes with this crank, I can get that reasonably enough. Not sure what shifter to get, currently have twist shifters, kinda like them (weird, I know). Suggestions? Thanks. –  Dave Apr 12 '12 at 16:44
    
For Shimano, no, no suggestions for a twist shift. Are your shifters indexed on the front? That is, one click, one gear, or 5-8 clicks, and turn until it shifts? –  zenbike Apr 12 '12 at 17:12
    
My current shifters are SRAM, and I'm fine with any manufacturer as long as they're compatible with the FD-2303 front derailer.On the front it currenty takes about 4 clicks to shift. (On the rear it only takes 1, obviously.) –  Dave Apr 12 '12 at 17:24
    
4 clicks total, or 4 clicks per gear? –  zenbike Apr 12 '12 at 17:30
    
Sorry wasn't clear; 4 clicks per gear. They say "SRAM MAX" on them (just looked). –  Dave Apr 12 '12 at 17:44
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