Bottom bracket question; swiss thread??

[stumpjumper1990]

I have a nice -barely used- K2 A99 frame waiting for some mud and snow. I started putting it together with some parts in the shed. I tried to put the bottom bracket in, but it did not fit. I only have some BSA thread versions, so I thought it would need an italian thread. I could not find any 68 mm italian versions and on http://www.sheldonbrown.com/bbsize.html#threading I saw that there are no 68 mm italian thread brackets! It's definitely 68 mm, so what can it be?? swiss thread?

I don't know where these K2 frames were made, but when they are for sale, most of the time they come from Switzerland or Austria. I even have an old swiss brochure of it, so I think it's swiss thread..... :?: :?:

Anyone any ideas??

 

[danson67]

Dear Stump,

K2 was prety much a US company, I think, so I'd be surprised if it had either a French or Swiss BB shell. The 68mm length does indeed rule out Italian (70mm). But, it might just be a BSA that needs a good clean...

Firstly, you should be able to check the thread directions. If the thread on the right of the frame runs in clockwise, you have a French BB. (weird) If the right is threaded anti-clockwise (LH thread) it's a BSA or Swiss BB. The left side threads are identical on French and Swiss standards

If the right side is LH thread, just to make sure it isn't a BSA thread...check the thread pitch. A BSA thread has 24 rotations per inch, the French and Swiss systems have a finer 1mm pitch (25.4 rotations per inch).

Find a standard 6mm bolt, (Canti bolt etc.) This has a thread of 6mm diameter x 1.0mm pitch. Push the bolt thread into the BB thread, the pitch should match, with the gap between the theads staying the same along its length. It the thread is BSA the bolt threads won't match, as the BSA has a coarser pitch, so the gap will vary and the bolt will tend to sit on top of the BB thread. If you've got a standard 1" threaded pair of forks around (not Raleigh), that thread is also BSA with 24 threads per inch, so you could use that as a gauge too. This should match a BSA BB thread perfectly.

So:
BSA = 1.375" (34.9mm) x 24Tpi (1.06mm pitch) Left Cup RH thread, Right cup LH thread
Italian = 36mm x 24Tpi (36 x 1.06) Left Cup RH thread, Right Cup RH thread.
French = 35mm x 1.0mm (25.4Tpi) Left cup RH thread, Right cup RH thread.
Swiss = 35mm x 1.0mm (25.4 Tpi) Left Cup RH thread, Right Cup LH thread.

Kind of complicated, but I hope it helps

All the best,

 

[stumpjumper1990]

Thanks Dan,

That really helped a lot..... problem is that I now know for sure it's a BB with swiss thread! :cry:

I'll get some phone pics of the bike on. But take a look at my other K2 (look at my signature). These are not the K2 bikes as we know them. Also on the K2/Proflex forum these bikes are not known. As far as I figured out, these bikes were made in Switzerland, so the swiss thread is logical!

Problem is; were to find a swiss thread BB?

Cheers,
Bart

 

[stumpjumper1990]

Here's a bad pic (damn phones) of my K2 A99!

 

[Tad]

You could try a threadless BB? There are a couple of makes out there.

http://www.tritoncycles.co.uk/products. ... 3339&rs=gb

Mavic made one too.

 

[stumpjumper1990]

And another!

 

[stumpjumper1990]

You could try a threadless BB? There are a couple of makes out there.

http://www.tritoncycles.co.uk/products. ... 3339&rs=gb

Mavic made one too.

Yeah, thought of that too! But not willing to give up on the search just yet....

 

[Tad]

Phil wood's your man

http://archive.roadbikereview.com/00/0EFB5B7F.php

http://www.philwood.com/products/bbpages/bbcups.php

 

[Dhphat]

I'm pretty sure its not a Swiss BB. I don't think any one has used that since the late 70's.

 

[stumpjumper1990]

I'm pretty sure its not a Swiss BB. I don't think any one has used that since the late 70's.

You might have a point there! :?

I will have another good look at it.... perhaps the thread is just worn.... :cry:

A threadless BB might be the solution in the end.....

Will let you know! Thanks for all the help!