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Old 11-20-05, 08:24 PM   #1
SSRI
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Compact Crank Conversion ?

I am considering converting my 53/39 shimano ultegra cranks( 6400 seris) to compact gearing (ie 50/34).
what is the smallest chaining I can get? or is 39 the smallest I can go.

thanks for any input.
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Old 11-20-05, 09:04 PM   #2
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Generally a 38 but, there use to be an obscure source for a 37.
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Old 11-20-05, 09:40 PM   #3
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"Compact" cranks have a 110 mm bolt circle diameter (BCD) that permits using a 34T chainring. You have a 130 MM BCD crank that, as Sydney said, takes a 38T ring as the smallest (I've never seen a 37 offered). Don't pay for a 38T for your current crank as the improvement over your 39 will be minimal.
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Old 11-21-05, 06:10 AM   #4
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Just curious...

But why do you want to change to a compact crank. Weight savings, or better gear ratios or are there another reason?
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Old 11-21-05, 07:13 PM   #5
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I want to swap it out mainly for better gear ratios, since I hardly find myself pushing the 53 (for city riding anyway). The main factor was the compact crank I install on my bro's bike a 50/34.
I find the 34 kinda wimpy but I can accelerate with the 50 with out too much effort.
after that I am pretty much sold.
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Old 11-21-05, 09:57 PM   #6
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Quote:
Originally Posted by SSRI
I want to swap it out mainly for better gear ratios, since I hardly find myself pushing the 53 (for city riding anyway). The main factor was the compact crank I install on my bro's bike a 50/34.
I find the 34 kinda wimpy but I can accelerate with the 50 with out too much effort.
after that I am pretty much sold.
You might consider a 50/36 compact. If I were looking to buy a compact that's what I'd want. It really depends on your needs, get what you need.

Al
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Old 11-23-05, 04:59 PM   #7
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You might consider a 50/36 compact. If I were looking to buy a compact that's what I'd want. It really depends on your needs, get what you need.

Al
I've yet to find a 50/36 being sold anywhere. They are normally, it seems, being sold as 50/34 but you can buy a 36 ring to replace the 34. You may be able to get it done at point of purchase if you buy at LBS as opposed to Internet purchase.
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Old 11-23-05, 05:09 PM   #8
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We have lots of guys liking the compact road setup. Some of them are running the outboard bearing two-piece crank setup and switch back and forth, quickly, depending on the type of riding or race. Lots of guys using it for cyclocross as well.
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