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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 11-18-09, 01:51 PM   #1
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How do I figure out bottom bracket size?

I did a search, but so many threads came up I don't know where to look. I have a couple of bikes, and I want to service the BB and headset, but don't know the sizes and/or what tool to get to remove them.

I have an an '84 Peugeot PH501, an '86 Nishiki Prestige, and an '87 Trek 560EX.

I know I can just ask what to use for BB and headsets, but I want to learn how to figure it out for myself. Help appreciated!

Alex
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Old 11-18-09, 01:54 PM   #2
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you'll need a tool called a crank puller to remove the cranks, and a BB tool to remove the BB. I reckon the BB's are shimano, so you will need a shimano BB tool which looks like this.



the crank puller looks like this

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Old 11-18-09, 02:01 PM   #3
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To find out what threading you need, look at teh edge of your bb's on both the fixed and adjustable sides. There should be something somewhere like 1.375 x 24, 35 x 1, or 36 x 24 (I think it's 24). Those are respectively English, French (the Peugeot MIGHT have this, but it's probably too new), and Italian. There could also be The next thing you need to know is the necessary spindle length. If you are not going to change teh crankset, then pull off the crank arms left and right, and measure the spindle from end to end. You need to measure this to 1 mm accuracy, preferably with a metric ruler, and if you have a metric dial or digital caliper, that is the best.

With these numbers and the spindle style (square, Octalink, ISIS, whatever) you can buy new ones, at least with the help of the LBS, and possibly on-line. I usually find the LBS price is less than on-line, once shipping is factored in.

As far as brands, the conservative and simplest approach would be to just buy what you already have.

Last edited by Road Fan; 11-18-09 at 02:08 PM.
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Old 11-18-09, 03:10 PM   #4
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Originally Posted by alexw View Post

I have an an '84 Peugeot PH501, an '86 Nishiki Prestige, and an '87 Trek 560EX.

Alex
These most likely will have a cup and cone bearings and will need the old "C" spanner and square spanner or large adjustable wrench. A pin spanner is also nice for adjusting the BB.

http://www.parktool.com/products/det...=25&item=HCW-5
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Old 11-18-09, 10:56 PM   #5
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If you just want to service them look here. You'd need the crank removal tool and the corrrect spanner to do it.

http://www.parktool.com/repair/readhowto.asp?id=93

Given the age of these bikes most likely these are cup and spindle bottom brackets as stated. Actually not too big of job to replace bearings and regrease
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Old 11-19-09, 04:38 AM   #6
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Ive heard that cup and cone axles have a 2 letter code on them, that signifies there length. But thats on the centre of the axle, so it has to come out to measure it.
If you do change the axle to a modern cartridge unit. Be aware that old axles were longer on drive side. And cartridges are same length on both sides. Its probably ok to use a slightly shorter axle though. As long as theres a gap between the rings and the chainstay
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Old 11-19-09, 10:51 AM   #7
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Originally Posted by mas-az View Post
These most likely will have a cup and cone bearings and will need the old "C" spanner and square spanner or large adjustable wrench. A pin spanner is also nice for adjusting the BB.

http://www.parktool.com/products/det...=25&item=HCW-5
That's what I was thinking. You'll also need a fixed cup tool if you want to remove that too. If just regreasing, you can leave it in and reach inside to clean & regrease.
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