Bicycle Mechanics - Tricky one - Ashtabula bottom bracket conversion :-)
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05-11-11, 01:19 PM
Here's a tricky one - I have an a 1970's Swedish crescent bike with an astabula one-piece bottom bracket (http://imgur.com/a/tqJMM). I bought new cranks with which to replace these but was told in the shop they wouldnt fit my new bike. This is due to the bottom bracket shell being larger than most modern ones, similar I believe to the older Schwinn models. If this was the case, I could use a bottom bracket converter (http://harriscyclery.net/product/truvativ-bottom-bracket-conversion-american-to-euro-adapter-1335.htm).
However, life is never that simple and when I returned to the bike shop with this idea they tell me that my bottom bracket shell is threaded which means the converter would not fit.
The advice in the bike shop was to get a new bike :-(
I'm considering filing the bottom bracket shell smooth if the dimensions of the converter would fit.
Has anyone any advice? Any similar story? Or anyone with a converting part (i believe there was one made in the 80's)
Any help would be great :-)
05-11-11, 01:48 PM
Have you open up (remove the crank from ) the BB to see if it is treaded ? If it is a standard astabula bottom bracket then yes your converter kit will work . In my 30 years of serving repairs I have never see a treaded astabula bottom bracket . I like to see a photo of your if it is.
05-11-11, 01:55 PM
I agree I never saw a threaded one either, however I don't think I ever worked ona Swedish bike. I suspect the guy at the shop either has no imagination or just does not know what he is doing.
05-11-11, 02:28 PM
Thanks a mil for the responses. I reckon I will go back to the shop tomorrow and ask another guy. In the meantime I tried to open it and look for myself http://imgur.com/a/AVajE. But I cant get that metal ring on the outside off. I'm guessing if its like a normal bike do I use a hammer and screwdriver and knock it out from the opposite side? Unless its one of these so-called threaded bbs...
another query - if its not threaded and I buy the converter component, is there a danger that it wont fit anyway? Are bottom brackets varied sizes, esp old ones? I think mine is about 4-5cm diameter (cant say exactly as the crank arm is in the way.
I will let you know what the shop says...
Thanks again, always amazing help on this forum :-D
05-11-11, 04:26 PM
I am not sure if the shelles are different sizes, I know there are different cranks. that metal ring is the cup and they are just pressed in and can be carefully tapped out
05-11-11, 04:42 PM
what you might be seeing is a dustcap . once you remove the cone ( turning it clock wise ) the metal cap should just slide out . it hard to said from your photos . the cone is the ring with the dimples in it. use the tool if you have it or a hammer and a punch to move it.
05-11-11, 04:47 PM
ok ,just look at your latest photos , just use a punch and hammer out the cups . do it from the backside of the cup. they might be hard at first but a few good blows at different points will do it. once out clean up the bottom backet and put in your converter .
05-12-11, 03:36 PM
Hey, so quick update - went to several bike shops today. They all confirmed its a threaded bottom bracket shell. The cups are screwed in, requiring a special tool to open them. its a type of wrench with teeth that grip the holes you can see here (http://imgur.com/a/9PO3H). As I dont have that tool and you cant buy it anymore, I dont have the cups off to show you a picture!
Its also a 48mm diameter bb shell, meaning the converter from harris cycles wont fit :-(
I'm guessing no one has encountered this but if they have please post your advice/experience!
Thanks for all the advice :-)
05-12-11, 04:00 PM
The threaded Ashtabula-like bottom bracket shell is for a Fauber crank. There is a thread on it's removal :
I don't know anything about the Fauber bicycle company, but a friend of mine is a collector and he has a Fauber frame from around 1920 or earlier. The BB shell on his Fauber is the same size as for Ashtabula cranks but is threaded and has a notch cutout. His guess is that the cutout is to show that the cups are threaded and not pressed-in. Because he does not have or found a Fauber crankest, we were looking at it and trying to figure out how to adapt the BB shell to accept an Ashtabula crank or a modern converter. No answer yet though, and we hadn't tried too hard. It just came up when we were yakking away and then passed by.
If you do find a solution, please do post about it.
edit : I just googled Fauber and here's a bit more information and a picture of the Fauber crank.
05-12-11, 04:23 PM
Jebejava - thanks for the thread - once i had the proper name i had a bit of search. found these converters from a finnish company:
the company's website is http://www.pyoratohtori.fi/ and they're listed under KASETTIKESKIÖT
I am happy as a pig in ****. i'm heading back to the bike shop tomorrow to see what they think.
Thanks again :-)
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