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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 04-20-09, 09:54 PM   #1
renton20
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crank and chainline question

So I was just able to pick up a used dura ace 7600 crank and a dura ace 47t chainring off ebay for way less than I should have paid. (yay) I am now wondering what bottom bracket I'm gonna need to get my chainline prefect on my mark v. Right now I'm using some stock hubs with a 42 mm chainline but within the next month or so I'm building up some paul hubs which have a 44 mm chanline. I'm wondering if I can get an adjustable bb or if I should just swap out bbs when I change wheelsets. I plan to use my stock wheelset in the winter is why this is an issue. I'm still pretty new to all this and I suppose 2mm might not even make a difference at all in functionality. Any help would be appreciated, thanks in advance.
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Old 04-20-09, 10:43 PM   #2
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Do NOT buy an adjustable BB.
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Old 04-20-09, 11:05 PM   #3
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Some good reading.

http://www.businesscycles.com/tr-refspec.htm
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Old 04-21-09, 03:55 AM   #4
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Do NOT buy an adjustable BB.
What? Why not? To deal with those Paul hubs appropriately it seems like he's gonna have to.
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Old 04-21-09, 04:51 AM   #5
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What? Why not? To deal with those Paul hubs appropriately it seems like he's gonna have to.
Incorrect. 2mm is inconsequential, even when it comes to chainline. You don't need to do anything special to "deal" with the hubs.

Alternatively, the OP can get a symmetrical spindle that's 4mm longer than whatever is paired with the crank in question.
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Old 04-21-09, 08:35 AM   #6
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What? Why not? To deal with those Paul hubs appropriately it seems like he's gonna have to.
There are very few situations a chainline cannot be remedied without resorting to "adjustable chainline" bb's. 3 piece bottom brackets went to two piece for a reason. They are more tolerant of bb shell errors and above all, they can be secured with torque. Adjustable bb's are secured with lines of loctite. Phil wood/Miche. If you don't have problems with these bb's then great, but if you do you're in for a world of headache. think what happens when you start getting a creak in the bb area. Now is is the left cup? Right cup? Is it backing out? Is it where the cups meet the bb? Left or right side? Have fun removing loctited bottom brackets.

Bottom line is, don't buy it unless you *really*, *really* need to.
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Old 04-21-09, 09:00 AM   #7
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yea if the chainline is 42 now, and you'll be moving on to 44, it's no big deal.
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Old 04-21-09, 10:01 PM   #8
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So if I go with a 109mm bb it looks like I'll have a 43mm chainline. So either way I go I won't have a perfect chainline, but will always being 1mm off make any real difference in performance or chain noise?
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Old 04-21-09, 10:41 PM   #9
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No
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Old 04-22-09, 12:24 AM   #10
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anyone have a picture of a bad chainline?
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Old 04-22-09, 07:19 PM   #11
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Picture of bad chainline:
is there specific in this picture you linked that says this is a bad chainline?
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Old 04-22-09, 08:21 PM   #12
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is there specific in this picture you linked that says this is a bad chainline?
most trackhubs plus standard cogs put the rear at 42.5 or 43mm. so with the chainring's center being at about 47mm (i'm assuming, since it looks like the caliper stays inside it), yeah, you can assume it's a bad chainline.
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Old 04-23-09, 05:30 AM   #13
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What kind of crank is that, and what kind of bottom bracket? BBs come in all sorts of spindle widths. All you'd need to do would be to get the same BB with a shorter spindle.
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Old 04-23-09, 05:40 PM   #14
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What kind of crank is that, and what kind of bottom bracket? BBs come in all sorts of spindle widths. All you'd need to do would be to get the same BB with a shorter spindle.
Not in this case unfortunately with the infromation provided in the above post. The OP will probably need a LONGER bb, and move the chainring on the inside for a 42. Gauging from the picture idiots setup the bike from the factory with that stock bb/chainring position.

But then again the rear wheel might be 47mm...
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