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Permalink Reply by GabeW (not the other Gabe) on January 6, 2009 at 11:19am

Ha Ha Ha - I was just reading sheldon brown's help page and trying to figure out what size BB I need, when I thought: I'll ask the chainlink! What timing!

My problem is similar, but first here's an answer for J Mills - http://sheldonbrown.com/bbsize.html - scroll down to the photo's; he shows you how to measure the chainline.

My problem: is it 68, 70, or 73? I've got a 1980 Raleigh super record; getting ready to upgrade form stock cranks (running fixed on just the 52 ring) to a Pake 1/8" track crank. Sheldon said Raleighs use either 68 standard, or 73 oversize. Anyone have experience with this? Thread pitch is a mystery to me too, and trial and error seams mildly expensive.

And for the funny stories, this isn't hilarious, but when I was building my bike I stripped it down and lost the little bit of hardware that holds the rear brake cable for centerpull brakes. I searched all over my workspace. At that time I was going to make it a freewheel. After much debate, and a winter of building, I decided to just go fixed so wouldn't need that piece anyway. So the bike's finished as a fixie now, and what turns up? Yup, you guessed it.

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Permalink Reply by J Mills on January 6, 2009 at 11:28am

I guess, I hadn't scrolled down far enough on the Sheldon bb page. Thank you.

Of course, when you don't need the parts they show up! hahaha

Cheers

GabeW said:

Ha Ha Ha - I was just reading sheldon brown's help page and trying to figure out what size BB I need, when I thought: I'll ask the chainlink! What timing!

My problem is similar, but first here's an answer for J Mills - http://sheldonbrown.com/bbsize.html - scroll down to the photo's; he shows you how to measure the chainline.

My problem: is it 68, 70, or 73? I've got a 1980 Raleigh super record; getting ready to upgrade form stock cranks (running fixed on just the 52 ring) to a Pake 1/8" track crank. Sheldon said Raleighs use either 68 standard, or 73 oversize. Anyone have experience with this?

And for the funny stories, this isn't hilarious, but when I was building my bike I stripped it down and lost the little bit of hardware that holds the rear brake cable for centerpull brakes. I searched all over my workspace. At that time I was going to make it a freewheel. After much debate, and a winter of building, I decided to just go fixed so wouldn't need that piece anyway. So the bike's finished as a fixie now, and what turns up? Yup, you guessed it.

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Permalink Reply by Bikefreeek on January 6, 2009 at 11:43am

Road bike bottom bracket shells (the part of the frame you insert the bottom bracket) are 68mm and mountain bike bottom brackets are 73mm, generally. These are the standards that Japanese frame builders adopted in the '80s and have pretty much stuck since.

The problem comes with old French bikes from the '70s into the '80s, old British 'Racer' three speeds, and some other European bikes from the '70s and earlier. Many of these bikes have 70 mm spacing and standard new bottom brackets don't fit so well. French and Italian bikes also had their own threading and cup diameter on top of it. Italian bottom brackets are still somewhat available, but good luck on the French... (reminds me of a bad joke - Q: What's the best thing that the French ever did for bicycling? A: Quit making them!)

I don't think that shell size is the issue with either Gabe or J Mills project (I'm pretty sure your BB shells fit a 68mm road). The issue is with spindle length for correct chainline. How far away from your frame your crank sets is determined by the crank (brand, year and model) and the length of the BB spindle.

When you do a road to single speed conversion, it's often necessary to move the crank closer to the frame for better chainline considering you no longer have derailleurs to guide your chain and keep it from falling.

An easy way to do this is to put the chainring on the inside of the spider, but some people feel it's not very stylish or aestetically pleasing that way. Another way to do it is to put another bottom bracket in with a different length spindle. When building up a conversion from scratch using a crank that wasn't on the bike to begin with sometimes takes troubleshooting like putting in and taking out bottom brackets until you find the right match.

If you're building up from new, go do a little internet searching and find out what bottom bracket will fit the crank that you plan to use.

You can also come by West Town Bikes and try to troubleshoot if you're building from used parts.

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Permalink Reply by GabeW (not the other Gabe) on January 6, 2009 at 12:18pm

Thanks Bikefreeek, I was afraid I'd be stuck with trial and error. I had assumed it was a 68mm, but the BB I got (long story, 103mm so probably won't work anyway) looks a lot smaller in diameter than the BB shell - so unless there's a lot of thickness to the shell, I can't see the 68 working.

One of the main reasons I'm changing cranks, is that mine don't have a "spider", the 52 ring is crimped to the crankarm at the center and can't be removed. Only the smaller ring has chainring bolts holding it to the 52, and that one's been removed.

Is there a difference in BB shell of the raleigh 3 speeds you speak of and the 10(?) speeds from the early 80's? I took off suntour derailleurs, no archer 3 speed hub on this one. Just want to make sure I know what you're talking about..theres so much good stuff.

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Permalink Reply by Bikefreeek on January 6, 2009 at 12:38pm

The bottom bracket you have is the right shell width, I'm not sure about the spindle length (depends on the crank you're putting on) and if it's an English standard bottom bracket it's the right thread pitch and cup diameter.

The 68mm is the distance of the right edge of your bottom bracket shell to the left edge.

I'm pretty sure your bike is English standard (the most common standard still used) if it was equipped with Japanese componets like SunTour. Your frame may very well be Japanese made also. Raliegh, like many bike companies in the '80s, jobbed out to Japanese frame builders such as Panasonic and Bridgestone.

GabeW said:

Thanks Bikefreeek, I was afraid I'd be stuck with trial and error. I had assumed it was a 68mm, but the BB I got (long story, 103mm so probably won't work anyway) looks a lot smaller in diameter than the BB shell - so unless there's a lot of thickness to the shell, I can't see the 68 working.
One of the main reasons I'm changing cranks, is that mine don't have a "spider", the 52 ring is crimped to the crankarm at the center and can't be removed. Only the smaller ring has chainring bolts holding it to the 52, and that one's been removed. Is there a difference in BB shell of the raleigh 3 speeds you speak of and the 10(?) speeds from the early 80's? I took off suntour derailleurs, no archer 3 speed hub on this one. Just want to make sure I know what you're talking about..theres so much good stuff.

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Permalink Reply by GabeW (not the other Gabe) on January 7, 2009 at 6:44am

Ohhhhhh....ok, I had it in my head that the 68, 70, 73 referred to the diameter of the BB, not the width. I can see now that a diameter of any of those sizes is way larger than any BB. duh. And I'm pretty sure your right about it being Japanese steel. Thanks

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