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PostPosted: Mon Mar 07, 2011 11:29 pm 
Newbie

Joined: Fri Jan 15, 2010 3:24 pm
Posts: 3
Hello,
I'm trying to find out the BCD (bolt circle diameter) for the following crankset.

Shimano 600, model 6100 - 3 arm

Please see the attached description,
Any information would be helpful.

www.velobase.com/ViewComponent.aspx?ID= ... 5&AbsPos=9

Thanks,


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PostPosted: Tue Mar 08, 2011 12:14 am 
Old School Grand Master
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Joined: Wed Feb 20, 2008 12:21 pm
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Location: Lost in Translation
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PostPosted: Tue Mar 08, 2011 10:01 am 
Devout Dirtbag

Joined: Fri Nov 13, 2009 11:38 am
Posts: 131
Location: Porthtowan, Cornwall
i've got a set of those at home. I'll have a go at measuring tonight.


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PostPosted: Wed Mar 09, 2011 9:50 am 
Devout Dirtbag

Joined: Fri Nov 13, 2009 11:38 am
Posts: 131
Location: Porthtowan, Cornwall
sorry, I knew there was something I was going to do last night. Will try and remember tonight., ben


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PostPosted: Wed Mar 09, 2011 2:50 pm 
Retro Guru
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Joined: Thu May 29, 2008 11:11 pm
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Location: Letchworth Garden City
distance between adjacent bolts multiplied by 1.155 = BCD for 3 bolt chainrings
HTH 8) :D


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PostPosted: Wed Mar 09, 2011 3:31 pm 
Old School Grand Master
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tonyf39 wrote:
distance between adjacent bolts multiplied by 1.155

... or two upon root 3.

Surds are so much more retro eh? :wink:

I found (and then lost) an old Shimano catalogue in which replacement rings were listed from 30 teeth up. That suggests a bcd of about 95mm. The more common 3-bolt cranks of the period used 116mm.


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PostPosted: Wed Mar 09, 2011 3:48 pm 
Retro Guru
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you can divide by 0.866 which is the more accurate method I believe..lol


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PostPosted: Thu Mar 10, 2011 11:53 pm 
Devout Dirtbag

Joined: Fri Nov 13, 2009 11:38 am
Posts: 131
Location: Porthtowan, Cornwall
measured distance between adjacent bolts = 82mm (as far as my failing eyes van tell)

using the calcs suggested above gives bcd 95mm (ish)

my best guess measurement was 94mm so if 95mm is a 'standard' then that is probably right.

hope that helps

ben


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