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Old 08-08-14, 12:24 AM   #1
gate28
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Raleigh Bottom Bracket

My question is with regard to retapping from the Raleigh 26 to 24. Are the tools sold to retap bottom bracket thread designed to retap or just to rethread? The reason I ask is that whne you take a cup out of a Raleigh, the existing thread is 50% of the thread required for a Cartridge cup. That means that once the existing 26 has been tapped to 24, the tool then has to cut thread into fresh pipe to get the needed width.

Are the bike tapping tools suitable for this. Does it have a destructive effect on the retapped thread the tap has to pass over. All the vids I've seen show the tapper spinning the tool like a crank - not heaving with it as it carves out fresh steel?

Anyone done it and left a nice bit of even and undamaged thread?
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Old 08-08-14, 12:52 AM   #2
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From Sheldon Brown; Threading/interchangeability Issues for Older Raleigh Bicycles

Re-tapping to B.S.C./ISO


This option is the most versatile, but also the most drastic. Only the top bike shops will have the necessary guided tap set required for this. The threads will not be as strong as they would be if the shell was made for standard threading, but this approach generally works well. You will still need to deal with the overall shell width. A shop that has the correct taps will also have the correct tool to face the ends of the shell, and this tool can be used to bring the width down to a more standard size (though it takes a lot of elbow grease! Beware, though, the welds to the bottom bracket shell of a Raleigh Twenty can be very hard, maybe harder than the taps.

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Old 08-08-14, 03:03 AM   #3
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Originally Posted by onespeedbiker View Post
From Sheldon Brown; Threading/interchangeability Issues for Older Raleigh Bicycles

Re-tapping to B.S.C./ISO


This option is the most versatile, but also the most drastic. Only the top bike shops will have the necessary guided tap set required for this. The threads will not be as strong as they would be if the shell was made for standard threading, but this approach generally works well. You will still need to deal with the overall shell width. A shop that has the correct taps will also have the correct tool to face the ends of the shell, and this tool can be used to bring the width down to a more standard size (though it takes a lot of elbow grease! Beware, though, the welds to the bottom bracket shell of a Raleigh Twenty can be very hard, maybe harder than the taps.
Yeah I have read this. What I am trying to say is that the thread on a Raleigh 20 cup is half that of a cup from a moden cart BB. If you screwed a modern cup in half of it would be sticking out because it will have run out of available thread. You need to actually cut fresh thread further into the BB than the original thread reaches. Does that destroy the rethreaded thread that the tap has already passed over to reach the unthreaded steel. I might try and find a picture.
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Old 08-08-14, 03:18 AM   #4
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Is the final goal to have a modern bb?
Grand Cru Threadless Bottom Bracket - Bottom Brackets - Components
This might be a solution. I am using one in a Gary Fisher right now. No problems.
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Old 08-08-14, 05:45 AM   #5
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Quote:
Originally Posted by gate28 View Post
My question is with regard to retapping from the Raleigh 26 to 24. Are the tools sold to retap bottom bracket thread designed to retap or just to rethread? The reason I ask is that whne you take a cup out of a Raleigh, the existing thread is 50% of the thread required for a Cartridge cup. That means that once the existing 26 has been tapped to 24, the tool then has to cut thread into fresh pipe to get the needed width.

Are the bike tapping tools suitable for this. Does it have a destructive effect on the retapped thread the tap has to pass over. All the vids I've seen show the tapper spinning the tool like a crank - not heaving with it as it carves out fresh steel? If you buy the correct tools they would be, however you are looking at several hundred dollars worth of taps and handles. The videos your seeing where the tap is spinning quickly are likely just 'chasing' the threads, running the tap through a new frame just to clean paint and other contaminants out. A tap, even just chasing the threads should never spin like a cranks it should be moved slowly and backed up a bit every turn or so. Recutting original threads to a different size and adding new threads in a BB shell will be tough going for a bike shop let alone a home mechanic.

Anyone done it and left a nice bit of even and undamaged thread? I have chased dozens of BBs, but never done this. I would not attempt it myself unless there simply no other option.
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Is the final goal to have a modern bb?
Grand Cru Threadless Bottom Bracket - Bottom Brackets - Components
This might be a solution. I am using one in a Gary Fisher right now. No problems.

That's what I started thinking about 1/2 way threw the post.

@gate28 what kind of bike is this and what is your ultimate goal?
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Old 08-08-14, 06:08 AM   #6
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Another option might be Phil mounting rings, which are available in 1-3/8" x 26tpi and fit other cartridges.
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Old 08-08-14, 06:53 AM   #7
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The Velo Orange Grand Cru threadless BB is cheaper than any of the other "solutions" and is way easier. I have done it with my older Raleigh.
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Old 08-08-14, 09:47 AM   #8
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The very cheapest solution is to grind off all the threads but the outer 3 rows from a 24 TPI bottom bracket cartridge. $20 for a UN54 BB and a little work with a file, and you haven't done any modification to the frame. It will screw right in, and hold just fine without creaking or loosening.

When you re-thread a 26 TPI shell to 24 TPI, you only end up with about 3 rows of good threads anyway. Might as well take the material from the replaceable unit (the cartridge BB) rather than the irreplaceable part (the frame).
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Old 08-08-14, 11:19 AM   #9
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Originally Posted by JohnDThompson View Post
Another option might be Phil mounting rings, which are available in 1-3/8" x 26tpi and fit other cartridges.
Which cartridges will they fit? I know there used to be a Shimano, but it's been out of production for years. If there is one currently being made it would be good news for those with Swiss-threaded bottom brackets. I know that Miche Primato won't fit the Phil cups. I tried it.
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Old 08-08-14, 11:21 AM   #10
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Originally Posted by cycle_maven View Post
The very cheapest solution is to grind off all the threads but the outer 3 rows from a 24 TPI bottom bracket cartridge. $20 for a UN54 BB and a little work with a file, and you haven't done any modification to the frame. It will screw right in, and hold just fine without creaking or loosening.

When you re-thread a 26 TPI shell to 24 TPI, you only end up with about 3 rows of good threads anyway. Might as well take the material from the replaceable unit (the cartridge BB) rather than the irreplaceable part (the frame).
That info is not useless.
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Old 08-08-14, 08:48 PM   #11
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Which cartridges will they fit?
SunTour, for one.
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Old 08-09-14, 02:42 AM   #12
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Whoah. What is my Ultimate Goal!.
Honestly...re: the R20. It's about living in the seventies but being able to trick it out then and blow people in the High Street away....you dig?
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Old 08-09-14, 02:42 AM   #13
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Originally Posted by Bianchigirll View Post
That's what I started thinking about 1/2 way threw the post.

@gate28 what kind of bike is this and what is your ultimate goal?

Whoah. What is my Ultimate Goal!.
Honestly...re: the R20. It's about living in the seventies but being able to trick it out then and blow people in the High Street away....you dig?
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Old 08-09-14, 04:53 AM   #14
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Whoah. What is my Ultimate Goal!.
Honestly...re: the R20. It's about living in the seventies but being able to trick it out then and blow people in the High Street away....you dig?
Perhaps I should have narrowed the scope of my question. I had thought you were working on a Sportster or some other 3spd, I don't recall seeing a model mentioned. I was curious if it was a keeper or a flip. I don't think the average buyer of a three spd would care how tricked out the crank it so I would have suggested just reusing the existing BB with new balls.

Another thing to consider if the softness of the metal. I don't imaging those 20s had a nice firm ChroMoly frame and BB shell? You could end up with real mess when you start grinding away at the HiTen steel.

Since you goal is to pimp out your 20 I would go the easy route and use the VO threadless and their cool retro single speed crank.

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Old 08-11-14, 05:04 AM   #15
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I had a R20 tapped out and it was a bit of a mess. I then saw a youtube video and wondered about retapping vs new thread.
The replacement axle looks like the easiest way actually. Thanks.
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Old 07-05-15, 09:33 AM   #16
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Originally Posted by cycle_maven View Post
The very cheapest solution is to grind off all the threads but the outer 3 rows from a 24 TPI bottom bracket cartridge. $20 for a UN54 BB and a little work with a file, and you haven't done any modification to the frame. It will screw right in, and hold just fine without creaking or loosening.

When you re-thread a 26 TPI shell to 24 TPI, you only end up with about 3 rows of good threads anyway. Might as well take the material from the replaceable unit (the cartridge BB) rather than the irreplaceable part (the frame).
Now this is a solution I have never heard of before - and actually it's pretty good. With an old free bottom bracket and a file - the R20 thread is left unharmed. A lot of the solutions cost a lot of money. This is nice and budget.
Interesting.
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Old 07-05-15, 09:46 AM   #17
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Um...The bottom bracket shell of a R20 is 76. Most cartridge bottom brackets are either 68 or 73. So you can have the bb shell filed down 3mm to fit the 73 mm bottom bracket or I've seen where the "lip" is removed from the adjustable side of a cartridge bb (73mm), so that cup can be turned inside the bottom bracket shell to take up slack.

Anyway, if you're talking about a Raleigh Twenty then this applies. I don't know about the bb width of a standard Raleigh bike. I suspect it's 68.

Also, the threadless bb, like the VO are not wide enough for 76mm shell.
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Old 07-05-15, 10:20 AM   #18
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Quote:
Originally Posted by Velocivixen View Post
Um...The bottom bracket shell of a R20 is 76. Most cartridge bottom brackets are either 68 or 73. So you can have the bb shell filed down 3mm to fit the 73 mm bottom bracket or I've seen where the "lip" is removed from the adjustable side of a cartridge bb (73mm), so that cup can be turned inside the bottom bracket shell to take up slack.

Anyway, if you're talking about a Raleigh Twenty then this applies. I don't know about the bb width of a standard Raleigh bike. I suspect it's 68.

Also, the threadless bb, like the VO are not wide enough for 76mm shell.
+1

was just about to post this information until i got to vv's message.

this is good information to keep in mind for other raleigh models with 26tpi threading as well since their shells will be 71mm.
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