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Unable to Identify Bottom Bracket
#1
Hello,
I just want to make the point that I am only 16 and a beginner. My situation is that I have bought a frame and fork from ebay to make into a single speed bike.
I have got into some trouble with identifying the bottom bracket but think that I may have chosen a suitable bottom bracket.
I don't know the model bike, only that it is a Raleigh that I think may be from the 80's. But I have little to go on.
The Bottom Bracket shell is 70mm. But this is the confusing part. I think the internal diameter is 34.5 mm (or around there). I have a bottom bracket cup - SM-BB70 - which fits the threading so I think the thread is 24tpi. However, I am a complete newbie and am open to any criticism. Please ask questions, and I will find any measurements you need.
Thanks

BTW, can anyone recommend a specific bottom bracket?
I thought that it may be a proprietary Raleigh bb but it doesn't fit the thread on Sheldon Brown .com?
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#2
Pictures required.
Nigel
  Reply
#3
Measure the BB shell again and check the threads on both sides carefully. Common widths are 68 and 73. There is a 70mm size but this is usually only for "italian threaded" BBs which would be very odd on a Raleigh. The other check is to see if the left side threads are reversed (so turning counter clockwise tightens the cup into the frame.) If reverse, and the 24tpi fits, you should have a normal "english" thread BB which is good. There was also a Raleigh specific size that's different, but I think that is only on much older bikes. There's a good chart here: http://sheldonbrown.com/gloss_bo-z.html under the "Bottom Brakcet" section.

Once you know what BB you have, you need to figure out how long a spindle you need. This depends on the crank and rear wheel. It doesn't need to be exact and there's a few ways to adjust things if you end up slightly off, but better to be as close as possible when you buy things.

Building up a bike from scratch can get a little complicated and frustrating, but don't get stuck. You'll figure it out and learn a lot along the way. It's just going to take more than a day or two.
  Reply
#4
(09-26-2014, 07:24 PM)DaveM Wrote:  Measure the BB shell again and check the threads on both sides carefully. Common widths are 68 and 73. There is a 70mm size but this is usually only for "italian threaded" BBs which would be very odd on a Raleigh. The other check is to see if the left side threads are reversed (so turning counter clockwise tightens the cup into the frame.) If reverse, and the 24tpi fits, you should have a normal "english" thread BB which is good. There was also a Raleigh specific size that's different, but I think that is only on much older bikes. There's a good chart here: http://sheldonbrown.com/gloss_bo-z.html under the "Bottom Brakcet" section.

Once you know what BB you have, you need to figure out how long a spindle you need. This depends on the crank and rear wheel. It doesn't need to be exact and there's a few ways to adjust things if you end up slightly off, but better to be as close as possible when you buy things.

Building up a bike from scratch can get a little complicated and frustrating, but don't get stuck. You'll figure it out and learn a lot along the way. It's just going to take more than a day or two.
OK, thank you.
I have tested the cups. The left side tightens clockwise while the right side tightens counter-clockwise (like English style or raleigh style). The diameter could also be either one but the width and threading just doesn't make sense. It appears that I have a Raleigh shell width (71mm) and an english thread (24tpi).
I suppose I will buy and test an english threaded one if that is more likely?
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#5
Yeah, I'd guess English. I think there can be some variation on the shell width so I'd go by the threads.
  Reply
#6
A Raleigh is most likely a british bottom bracket. You can tell by right side tightened anti clockwise. The type of bottom bracket to get depends on the cranks you are going to use.
Get more info on this topic at :www.doityourselfbicyclerepair.com

Please respond with any new ideas !

Thanks,

Jimmy
  Reply


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