mc510

I've read all of Sheldon Brown's stuff on this conversion; if I understand correctly the route for my 71mm bottom bracket is to keep the original bearing cups and swap in a 5-series or 7-series JIS spindle with 6mm bearings (unless some new cartridge options have appeared since Sheldon wrote those pages?). Lots of old bikes pass through out local bike free swap bin, so maybe I can find one there, or at one of the local bike repair clubs. But I don't quite understand what JIS spindle I'm looking for ... it appears that 5-series JIS spindles ran from 116mm long up to 134mm ... seems like they all have the same distance between the two bearing surfaces, but different lengths for left and right. Are there some particular spindles that are known to work well/not well? And what's a good clue that bike might have a JIS spindle in the bottom bracket? Probably a Japanese made 10 speed from, what, the 1980s? Or is it any Japanese made road bike that doesn't have a cartridge?

Narhay

The 5 and 7 series are identified for the bottom bracket shell width but the overall length will depend on which crank you select. Some need longer spindles than others.

juvela

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your post does not say if you wish to stay with the stock planetary gearing or convert to derailleur gearing

for derailleur gearing you would need to decide if you wanted to go with single plateau or multi plateau drive

the most common nutted spindle ("Type II") for the single plateau conversion you describe would be the 5N

for a two plateau arrangement the most common woud be the 5S

readers would be able to assist you a bit better if you could give some additional information

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branko_76 

mc510 , what's wrong with the original crank?

jackbombay

I've done this on several Raleigh/Hercules 3 speeds, the BB shell is 71mm, my buddy turned one down to 68mm for me with the proper park facing tools. For another I had a Ti cartridge BB that didn't have flanges on the threaded portions of the BB so I could just screw them in far enough to clamp the Cartridge BB and they are a bit inset, I did also use a JIS MTB spindle on my ex wife's conversion, and did not face that BB shell to get it to 68mm, I have no idea what spindle it is though :-/ BUT with every Raleigh I have converted to a square taper crank I have always had to have the cog as far outboard as possible to get good chain line, so I am confident when I say that you want the shortest overall length spindle you can get.

As for the threads, the BB shell is 26TPI and anything square taper is 24 TPI, I have some old steel cups that I cut notches into the threads of and I screw them in and out of the BB shell repeatedly and it works quite well, I actually use a large drill to run my "taps" in and out repeatedly.

jackbombay

Resto mod Raleigh are just so sweet!

650b, centerpull brakes, Campy crank, aluminum bar and stem, this bike is such a sweet townie!

branko_76 

It's a nice frame jackbombay , the alloy components no doubt make the bike lighter but it's hard to beat those old chrome heron head cranks for looks...

mc510

Mainly the impossibility of finding decent cotters and the difficulty of adequately fitting the shoddy ones that I'm able to get. Makes me reluctant to properly maintain the bottom bracket.
I'm intending to stick with the existing Sturmey Archer AW3 hub; I love that thing!

jackbombay that's a beauty! Mine is a disaster of a beater; I've given up on the idea of restoring it but it's still my favorite bike that I've ever had and want to get it in better running shape for my kid to use. Basically just this crank switcheroo and better brakes.)

3alarmer 

.
...the only people I know of who make a BB unit in proprietary Raleigh 26 tpi threading are the ones at Phil Wood, which is pretty expensive for a three speed conversion.
I have heard from multiple sources that people re-tap these to standard 24 tpi all the time without any problems down the road, but I try not to do stuff like that myself.

If you decide to go that route, the Shimano units marked for 68 mm shells will work, you just have to tighten the lipless, non drive side cup in a little farther, to lock the cartridge in place. Not hard to do.

You might have to fiddle around a little bit figuring out what spindle length you need, depending on you crank you pick. the problem with the method you read about using a replacement spindle with your present cups is that those spindles can be hard to find these days. It used to be an easy swap when there were more of them around in the parts stream.

jackbombay

I love chrome cottered cranks too!

I have a super course with them, not a Heron head chainring of course, but, I like/appreciate most anything bicycle related and I do take my resto modded 3 speeds on 50-100 mile rides which makes for a nice day, but to put down a century on a stock Raleigh sports is somewhat less appealing to me, primarily due to the steel rims, but the overall weight is also unappealing.

cudak888 

This one has been tapped to 24tpi right over the 26tpi threads. I've installed a Shimano UN55 in it with no issues. Unfortunately, I can't say anything about longevity, as I'm still hemming and hawing about getting "just the right" crankset onto this thing.



I'm really tempted just to use Raleigh's current square-taper Heron crankset, but I can't find anyone selling 'em.

-Kurt

jackbombay

The outer 4-5 threads don't even get touched by the tap, I have zero qualms about retapping Raleigh BB shells!

branko_76 

Bikesmith Design & Fabrication is a great resource for cottered crank parts and tools...

BikeSmith Design and Fabrication

mc510

Oh yeah, I remember seeing these last time I went searching for cotters. If I can't find an easy and affordable way to switch to cotterless, I'll go with the BikeSmith fallback.

mc510

jackbombay I missed what you were saying here the first time I read it. So you use an old 24tpi cup as a die to recut the threads? I'd have assumed that would just result in destroying the threads on both the cup and the BB, but interesting to hear that it's worked reliably for you. Could you post a picture of your thread cutting cup?

jackbombay

The Raleigh BB shell steel is not very hard, the BB Cups cut the threads just fine. I made 6 groves in the cups, paying particular attention to keeping the cutting edge perpendicular to the threads like a proper tap.

Fixed cup side, I ground off the flange so it can screw in and out further,



And a bolt that I welded to it so I can spin it in and out with a drill repeatedly,



Adjustable cup,



Adjustable cup already had a big hex on it so no need to weld a bolt to it,



I rarely use these, I'll gladly tune up the "cutting edges" and mail them to you to use if you like, but you have to return them!!!!

thumpism 

I have also tapped a 26TPI Raleigh frame to 24TPI, but not on my own Sportses. I just figure I'll use the Raleigh cups unless something suggests otherwise but those projects are down the road. The cotters work fine for now but if I ever decide to lighten the bike that crank will have to go.

mc510

jackbombay , that's incredibly generous; thank you. I'll try not to inconvenience you, though; first effort will be to find an appropriate JIS spindle, if not then I'll need to decide which direction to go.

jackbombay

Not an inconvenience at all, I ship products from the post office 3-4 days a week anyway :-)

If your cups are in good shape getting a spindle of the correct length is a great way to go too!