Cracked K2 Razorback RSX Rear Strut & Seat Stay

[rigmarole]

Good morning all,

I was a member of this forum many moons ago, with my K2 Proflex 3000, unfortunately it's been retired now (still in the garage) as I outgrew 26" wheels and a 'way big' frame and needed something larger! (I've had a custom 29er made now and it fits much better)

My girlfriend however has just become the owner of the K2 Razorback RSX (from 2000), unfortunately I am potentially in a a lot of trouble as her rear strut/seat stay is showing signs of cracking!

The crack is at the rear, near to the hub, where it bolts to the swing arm. I understand this is a fairly common problem as the aluminium is quite hard and brittle, and is probably a result of over tightening the bolts.

I have had a word with Callum at Rapid Descent Scotland and am on the search for a new strut. The version I have has the Noleen Mega Air shock (not the Fox shock of later versions). As far as I understand all the struts between different frame sizes are the same.

So far, as well as Callum, I have been in contact with K2 (who have no spares) and also Crosslake Sales (who say they have no frame parts). I am also talking to a bicycle frame builder, but this I hope is the last resort.

If anyone can offer assistance, be it repair ideas or sources of new/working struts, it would be greatly appreciated. It's a beautiful bike and it would be such a shame to take it out of action.

Kind regards,

Rigmarole

[Willie_B]

http://minneapolis.craigslist.org/csw/bik/1852396493.html

Not mine, not even sure it is what you need.

[Thunderchild]

Calling Terry(Shovelon on this forum).  Has to be 7000 series aluminum; maybe he can weld it.  Post a picture if possible of the cracks.  Oh yeah, Terry fixed a crack in my Evo.

Thunderchild

[rigmarole]

I'll get some photographs posted and give Terry a message. There's not terribly much to see though. Just small a line long near the weld.

At the moment I've been calling machine shops to get a part made to re-weld at a slightly different point. Thought it's amazing how many people just say "No, we won't do it"... it's like pulling teeth!

Callum said it was some sort of composite material and it wasn't weld-able, so a new part would be needed.

Thanks for your help anyway.

Willie... I think that bike is too new to be a donor bike. Apparently the geometry is different on the newer ones. I'm not 100% sure though.

[Colin]

I believe that some Razorback seat stay strut tubes were Thermoplastic/Carbon Fibre

Is that what you mean by "composite"?

Col.

[rigmarole]

Hi Col,

The seat stay strut tubes are aluminium and not carbon fibre.

As for what 'composite' means I am not sure, I can only assume the ends are made of something a bit weird... I am relaying information, Callum told me this is what a welder told him.

Sorry for the vagueness, the ends haven't broken off fully yet, and until I find someone that can make a new part I don't want to fiddle with it too much.

Cheers,

Jonathan

[rigmarole]

For a better idea here is the side of the strut:



Here, is a top view of the strut:

[shovelon]

If you notice the structure is a weldment. So obviously it is weldable. Could be a casting, but weld repair would only make it stronger. There is probably a threaded insert on one side which would have to be replaced.

[rigmarole]

Hello all,

I couldn't find a replacement strut but (after much searching) have found a willing machine shop and welder local to me that are going to see what they can come up with... out of a more durable aluminium as well. It seems the aluminium (identified as being probably a casting) is just too hard for it's own good. A lump of machined aluminium should do the job better!

I'll post with updates.

Cheers,

Rigmarole

[rigmarole]

Hello All,

As an update, the strut was fixed about 10 months ago by a local engineering genius here in York. The gentleman in the shop knew his stuff and was willing to save my bacon when others would have written the bike off.

Here is the photograph with the new and improved machined piece welded into place before painting.



The bike has been perfect ever since and is still going strong! The girlfriend is pretty happy too.

Rigmarole

[w2zero]

Nice job. 

Yessirree, this ain't rocket surgery but it is definitely welding science...

[02gf74]

good stuff, we all love a happy ending