Author Topic: Thorn Raven Tour BB--shimano only?  (Read 1907 times)

David Cox

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Thorn Raven Tour BB--shimano only?
« on: July 21, 2005, 01:47:13 AM »

I'm a new owner of a Thorn Raven Tour and currently in the process of building it up-- but I've hit a road block.  I tried two bottom brackets ( an IRD sealed cartridge and a Primo Powerbite euro ) both bottom brackets will not thread into the drive-side of the shell. I took the eccentric BB to a local bike shop today and they grabbed a Shimano sealed cartridge off the shelf and it threaded right in--no problem.
I find it puzzling that only a Shimano BB would work.  Am I really required to use only Shimano?
I welcome your thoughts and insight.

Best regards,
Portland, Oregon


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Re: Thorn Raven Tour BB--shimano only?
« Reply #1 on: July 21, 2005, 08:41:11 PM »
I'm no expert but it occurs to me that in England at least bottom brackets are available in 'English' and 'Italian' threads. I'm pretty confident that Thorn EBB's are 'English' threaded. Is it possible your non-fitting brackets were the other type of thread?

I'd imagine you'd be able to fit most makes of cartridge bracket with whatever flavour of taper, spline or whatever connection to the cranks you need or desire. Just make sure that you also get the right width (68 or 73mm seem to be the usual options - my new Raven Tour uses 68 mm) and axle length. The Rohloff chainline is supposed to be 54mm unless you are using the 13t sprocket. If you are using the chainring on the outer position of a triple chainset, a combination of crank/spider and axle which gives you a 47.5mm chainline should be right because the outer ring should be about 7.5mm further out.

Hopefully the above information is of some use to you.


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Re: Thorn Raven Tour BB--shimano only?
« Reply #2 on: August 25, 2005, 06:46:22 PM »
Sounds like you lucky you didn't "screw-up" the tread. ;-)

Go for English 68mm, I suspect you can any BB you would want, it this size.

Getting the chainline right is a bit of a trail adn error. You and also slide the Eccentric BB from side to side a mm or two to get it right.