How to straighten a Sub-Frame?

Monument

Hi,

I would appreciate advice on how to straighten the subframe from my racing motorcycle. The subframe is the rear frame of the bike - supporting the seat and up to the tail. In the crash the bike cartwheeled end over end so it was subject to a great deal of force.

In the attached pictures the surface is level so you can see the misalignment. The subframe is 700mm tall and 220mm wide at mid-height. It is made of square/rectangular box steel.

How can I bring it into alignment - what will I need to buy to do the job? It is an important structural part of the bike and must be square.

I would very much appreciate advice.

MitchellMc

Hi @Monument,

Whether it's a car or bike sub-frame, straightening requires specialised mechanical machines that hold the frame in position whilst making adjustments. Not only is a machine required, but you'd need to know what adjustments are necessary to pull the frame back into position. It's not quite as simple as just pulling it back in the other direction. Also, it would be best if you had this frame checked to ensure it's possible to re-align it and that there are no hidden stress fractures that need to be addressed. 

I'd encourage you to seek the services of a professional that can re-align this frame for you. It's not worth attempting this work at home and risking an accident due to something you've missed.

Please let me know if you have any questions.

Mitchell