If you retap it, don't you have to increase the bore as well?
2010-05-12 12:07:17
12
retapping a BB
So I've made another cheapskate bike purchase, an old Raleigh Record frame. Forgetting, unfortunately, that Raleigh threaded their bottom brackets to 26 threads/inch instead of the standard 24 tpi.
There are BB options, Phil Wood, Grand Cru. But I'm trying to get out of this without spending more on the BB than the frame itself. I think retapping is the way to go.
Does anyone know if Free Ride has a BB tap? Or care to recommend a shop?
2010-05-12 11:53:13
call Chris over at Thick. full machine shop...
2010-05-12 16:17:08
Free Ride has a tap, as does Kraynick.
2010-05-12 16:36:19
Free Ride it will be then. I just don't get to the South Side much & haven't been to Thick in ages. Tapping will, in this case, destroy a lot of the existing threads. But I can thread the 24TPI cup into the 26TPI shell 3-4 turns already, and I'll bet that those 3-4 plus whatever isn't wrecked will be enough to hold the BB.
If not, then c'est la vie, I'll have to buy a solution.
2010-05-12 18:01:04
yeah if you totally kill it you can probably machine out all the threads and use an old school press fit bb if you don't want to drop much money on that velo orange one too.
2010-05-12 18:36:08
Cheap option if you do roach the threads:
2010-05-12 21:53:52
I was trying to work on a Raleigh Grand Prix this past year. It had a cottered crank, and a friend told me that those are terrible for holding up under the stress of pedaling - that they're known to break. So the first thing we tried to do was to put a new (well, new to me) bottom bracket with a square taper spindle in. We went through the drawer of spindles, trying to make things work with the old cups, and something went wrong with every attempt. The square taper spindles were too short to meet the adjustable cup - you'd tighten it as far as it would go and the whole thing was still swimming, so we tried grabbing a different cup (this was at FreeRide) but you couldn't thread it very far in. We found (this was after retapping the threads -just to clean them up though) that the chain stay actually sticks into the bottom bracket shell and keeps you from screwing the cup in very far. We tried lots of configurations, but that seemed like the main roadblock we were up against.
Someone told me since that you're kind of stuck with the cottered crank, that the square tapers are just the wrong size. Then I heard that it just depends, sometimes you can convert, sometimes you can't. I really need to head over to Kraynick's and let the master look at it.
2010-05-12 22:25:27
A couple years ago I went through a similar process with a Raleigh 20 (which is why it kills me that I was suprised by it this time -- I KNEW that!) I don't think the cottered cranks are particularly bad or likely to break. Actually, being steel I bet they're stronger than most modern aluminum cranks. If mounted correctly. Instead, if you want something lighter or a different toothed chainring or a single instead of a double, then you have to switch.
With the R20, I kept the original 26tpi cups and searched through Kraynick's drawers (he wasn't optimistic) for a spindle that might work. I did find one after a while. Spindles come in many different sizes, and getting one where the races are set far enough apart is a challenge (if the races are too close, then you have to tighten the cups in way too far, and ... that doesn't work)
Interesting tip on the Sunlite BB. That's the right price, though a little long at 110 for what I want.
I've had serious modifications in mind for the R20, which ought to involve Chris@Thick rebuilding much of it. Maybe someday.
2010-05-13 17:43:20
Just remember the other source for these BB:
I've fixed a lot of cottered cranks on Schwinn Arydynes. They aren't stronger. They are heavy, prone to lessening and hard to remove without destroying the cotter. Not really any redeeming qualities I can see.
2010-05-13 20:07:07
Not really any redeeming qualities I can see.
No argument. I was just questioning the likelihood of them breaking. And maybe with the right tools (the correct cotter pin press) the loosening and maintenance problems go away. And the redeeming quality of "I have it already" could outweigh ... no never mind, very little will outweigh those cranks
2010-05-13 21:11:13
I've really grown to like the thin-ness of steel crank arms, on the right (old) frame. They look like straws compared to aluminum. And I find getting the cotters just right satisfying, more craft-y, really 19th century, but then again, I enjoy that kind of thing.
My newest bike has an FSA Octalink or something, strong and efficient, I'm sure, but really pretty ugly.
2010-05-13 21:44:52