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Old 09-07-09, 07:16 AM   #1
yellowcanoe1
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Campy compact crank conversion?

I have Chorus 8-speed on my ~1998 steel bike, with front sprockets 52 and 39 teeth and a brazed-on front derailer, and a 26-tooth gear in back I'm trying to figure out how to change to a compact crankset for lower gearing. My questions are:
1. Are compatible compact cranksets available for this bike?
2. Would I need to change the front derailer? If so can I use the same braze, or would I need to go to a ring mount?
Thanks for any advice.
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Old 09-07-09, 07:26 AM   #2
Chris_W
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You should be able to get a compact for this bike, but as well as the crankset, you will probably also need to change the bottom bracket. Hopefully your current BB will come out without a struggle, but there can occasionally be problems with getting ones out of 10-year old bikes that have never been removed before.
There shouldn't be any need to change your front derailleur. At least, try it with your current one and only consider changing it if you are not happy with how it performs.
One more thing to consider, modern cranksets are made for 9, 10, or 11 speed chains, so the chainrings are slightly closer together. You'll still be able to use your 8-speed chain, but it may rub on the large ring when on the small ring and you use the smaller cogs in the back. You could avoid this by using a 10-speed chain (while still using the 8-speed cassette and derailleurs).
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Old 09-07-09, 07:30 AM   #3
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Quote:
Originally Posted by yellowcanoe1 View Post
I have Chorus 8-speed on my ~1998 steel bike, with front sprockets 52 and 39 teeth and a brazed-on front derailer, and a 26-tooth gear in back I'm trying to figure out how to change to a compact crankset for lower gearing. My questions are:
1. Are compatible compact cranksets available for this bike?
2. Would I need to change the front derailer? If so can I use the same braze, or would I need to go to a ring mount?
Thanks for any advice.

1. You can use any compact crank(as well as any other crank) on your bike.(Though you wouldn't want a mtb triple! )

2. You can use your current FD with a compact crank.
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Old 09-08-09, 07:00 AM   #4
yellowcanoe1
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Thank you both! I'm thinking of changing out the Chorus 52/39 crankset to a 1 or 2 year old Centaur 50/34 so that I can stay with alloy - should I expect any deterioration in the shifting? Do you anticipate any need to change the RD to a longer cage (this would probably kill the plan). Thanks again!
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Old 09-08-09, 07:51 AM   #5
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You'll have to swap the BB from your 102mm to a 111mm (Centaur or AC-H)

Total Chain wrap currently 13-26 + 52-39 = 13+13 = 26 (I'm assuming 13 small cog)
proposed 13-26 + 50-34 = 13+16 = 29

29 is probably doable, but at the limit. I'm running 27 and it would appear to have some room.

Velobase.com lists the max chain wrap on some earlier Chorus at 25. I ran an early one at the same 27 w/o issue.

Last edited by Ex Pres; 09-08-09 at 07:55 AM.
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Old 09-08-09, 03:45 PM   #6
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A 1-2 year old crank would be the new UT outboard bearing type, made for 10 speed. An old 8 speed chain might be too wide. A 9 speed might work better.

Chain wrap should not be a problem. Campy listed the wrap to correspond to the chainring and cassettes they sold, not the true maximum wrap. The short cage length has not changed in a long time, but my 11 speed short cage and wrap a 50/34 with an 11-27 (11 speed).

The way to tell is to set the chain length using the big/big plus one inch method first, then double check for the chain hanging loose in the little/little (through the RD in the normal fashion). I use the little/little method exclusively, since I know I'm no exceeding the max. wrap capacity.
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Old 09-08-09, 08:33 PM   #7
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Thanks Dave - Branford agrees with you that a 9 speed chain should work well, along with 0.6 mm spacers between the rings. Thanks also for the chain length info. Am getting the 2008 Centaur UT 50/34. Any advice out there on facing and tapping in BB that formerly held the internal BB, now changing to the outboard bearings - is this necessary? - if so I suppose I should have it done by the LBS as I have no experience with this?
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