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Old 08-10-10, 05:35 PM   #1
austingoodson
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Bottom Bracket Question..Please Help!

Hi,
I'm trying to replace my old BB with a new one...My back dropouts measure 130mm. I know the width of my BB is 68mm. I've read since my dropouts are 130mm, I need a 68 x 110mm BB...is this correct? Please help! I'm dying to get back on my bike! Thanks for the help!
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Old 08-10-10, 05:41 PM   #2
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It's a bit trickier than that. the spindle length works with the offset built into the cranks to establish the correct chain line. You therefore have to refer to the crank's specs to see what spindle length you need.
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Old 08-10-10, 07:14 PM   #3
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Is your old BB square, Octalink, or? If you have it, just measure the spindle length (if you are using the same crank).
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Old 08-10-10, 08:54 PM   #4
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yep, what those guys said. What kind of bike, there are generally some certain stds for example a road triple is 118mm A MTB triple I believe is usually 113. A compact road is 110 and I think a regular road is whatever the other std size usually is. Generally, your crank will tell you in the instructions. try googling it, most brands have their specs available via pdf on their websites.

Of course, we could always ask you what the hell yo udid with the old one? if it's a modern bike with a cartridge type bottom bracket it should be printed right on it.
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Old 08-10-10, 09:34 PM   #5
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The length of the BB is determined by the crankset and has nothing to do with the frame. You already know the shell width which is half the battle.
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Old 08-10-10, 10:44 PM   #6
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w/o knowing the cranks you are talking about there is no way to guess??????????????
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Old 08-11-10, 06:57 AM   #7
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Quote:
Originally Posted by austingoodson View Post
Hi,
I'm trying to replace my old BB with a new one...My back dropouts measure 130mm. I know the width of my BB is 68mm. I've read since my dropouts are 130mm, I need a 68 x 110mm BB...is this correct? Please help! I'm dying to get back on my bike! Thanks for the help!
Measure your old one, if you are just replacing it, you need one that's the same length in mm, so when you get that number, just make sure to order the same size, and shape (most likely square taper or isis, or octalink, so you may want to post what type of cranks you're using). if your old bb just has square ends, then it's a square taper, and you should be fine ordering that.

Joe
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Old 08-11-10, 08:05 AM   #8
austingoodson
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Thanks for trying to help guys...Sorry I left out the details before. I'm converting a 1978 Raleigh Rampar R-1 into a fixed gear. I replaced the old 3 ring crankset with a new single ring Eighthinch crankset. I tried replacing the old spindle with a new one with the same size. Its too big! The cog and crankset do not align accordingly...therefore, my crank needs to be closer to the frame, ie, i need a shorter BB spindle.

I've read online to measure the back dropouts which will tell the correct BB spindle width, so the cog and crank will be aligned. I know I need a 68mm wide BB. The back dropouts measure 130mm and I've read this means I need a 68 x 110mm BB...IS THIS RIGHT???

This has become a pain because every bike has different lengths, threads, etc....I just wanna ride! If you can help, please inform! Thanks a lot!

This is my bike model:
http://www.jaysmarine.com/TH_Raleigh_Cat_78_12.html
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