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Compact Drive Confusion

Old 08-17-10, 08:18 PM
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mountainwave
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Compact Drive Confusion

Hi Everyone,

I'm in need of help. My chainrings are worn out on my Mountain Bike. According to my measurements and what I've learned on Sheldon Brown's Website. I have a Compact Drive (MTB Triple) chainring combination. Before I go any further, I have a pair of Sugino square taper cranks with a 5 bolt pattern and 42/32/22t chainrings. The BCD is 94mm for the outer and middle ring while the inner chainring is 54 mm.

While reading Sheldon's website about Compact Drives, he says, "The downside of compact drive is significantly reduced chain life, and decreased interchangeability of parts. I consider compact drive to be a very bad idea for mountain bike use, but it seems to have become ubiquitous."

This has thrown me off a bit because I was going to match up my current ratios of 42/32/22, but the comment on the reduced chain life has me wondering if it is best to make a move to a more interchangeable ratio that provides longer chain life. I just bought a 7 speed HG cassette and a HG 6/7/8 speed chain with 116 links.

Is there a better ratio that I can use with my current Sugino Cranks that will work with my 7 speed cassette and chain that would give longer chain life? Or, would it be best to invest in a crankset other than a Compact Drive with different chainring combinations that could work with my current cassette and chain? I would greatly appreciate any help. Thank you in advance!

Confused,
Mountainwave
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Old 08-18-10, 07:39 AM
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Sheldon's writing is way out of date. Nearly every MTB uses smaller chainrings than a road bike - it's the acepted norm. The only fact about smaller chainrings that you can't avoid is more chain tension.

I've owned road bikes with a 28T little ring on the triple crank and spent about one of every three hours riding up mountains in that small ring. I still managed to get up 6,000 miles from a Campy chain. The chain tension may also be harder on the cogs.
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Old 08-18-10, 08:03 AM
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Originally Posted by mountainwave View Post
Hi Everyone,

I'm in need of help. My chainrings are worn out on my Mountain Bike. According to my measurements and what I've learned on Sheldon Brown's Website. I have a Compact Drive (MTB Triple) chainring combination. Before I go any further, I have a pair of Sugino square taper cranks with a 5 bolt pattern and 42/32/22t chainrings. The BCD is 94mm for the outer and middle ring while the inner chainring is 54 mm.

While reading Sheldon's website about Compact Drives, he says, "The downside of compact drive is significantly reduced chain life, and decreased interchangeability of parts. I consider compact drive to be a very bad idea for mountain bike use, but it seems to have become ubiquitous."

This has thrown me off a bit because I was going to match up my current ratios of 42/32/22, but the comment on the reduced chain life has me wondering if it is best to make a move to a more interchangeable ratio that provides longer chain life. I just bought a 7 speed HG cassette and a HG 6/7/8 speed chain with 116 links.

Is there a better ratio that I can use with my current Sugino Cranks that will work with my 7 speed cassette and chain that would give longer chain life? Or, would it be best to invest in a crankset other than a Compact Drive with different chainring combinations that could work with my current cassette and chain? I would greatly appreciate any help. Thank you in advance!

Confused,
Mountainwave
Since you are running a 94mm/54mm BCD crank, I'll assume that this isn't a new bike or crank I bet this bike is from the mid to late 90s so you've been using it for a while. That, on its own, says that the rings last long enough. Just get new rings and ride. You can find rings here for $20 each.
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