View Full Version : BSA Bobber Hardtail Dimensions?

12-04-2015, 8:42 PM
I am building a 65 BSA bobber. I bought a basket case that had a hardtail welded on, and it was hacked off. Maybe it's more like a half a basket. I am using a Triumph rear hub laced to a harley 16 wheel (so I will be using Triumph axle plates). Up front, I am using a 30's BSA M20 girder front end with a 19 wheel.

I know from lurking here that it is critical that I get the drop correct so fork trail is positive while the bottom frame rails are parallel to the ground.

My questions: How do I determine the correct stretch and drop so that the engine sits properly (so that frame and cylinder fins are parallel to the ground)? When I mock it up how do I pull the necessary dimensions so I know which hardtail to buy?

Has anyone had success with with a David Bird or Factory Metal works weld on hardtail that strecthed/dropped while not tilting the engine? If you could supply the dimensions used that would be a big help.


12-14-2015, 6:16 AM
Heres a photo of the girder front loosely mocked to the frame. Still waiting for a proper front axle so I can set the parts in a jig.

12-14-2015, 6:05 PM
How tall are you? It's all about building a bike that fits you. Seems those bikes were designed more for guys 5ft 4 inches tall. Taller types may need longer stretch and such so the knees aren't blocking the mirrors. LOL! And who sez the engine/frame66073 can't be tilted?!?!?!