I'm using the frame dimensions pic from Henks CD to check my frame. The rear frame is whippy of course.

I drew lines on my work bench, set the frame up and have found it to be a bit tweaked, (engine sprocket and drive chain side). I'm using the other side as datum points.

The front part (to the downtube)is a bit low, the seat downtube intersection seems to have shifted forward by 3/8 of an inch. Looking forward from the rear wheel, there seems to be a bit of a twist.

Also, the rear section is wide so to put on the rear stand, I have to compress it.

When I bolt up, things bind horrendously.

Any and all suggestions to square this up will be appreciated.

Cheers,

Robb

email (option): britool51@hotmail.com

Hi Rob..It sounds like a lot of M20s...many seem to have had crashes, have had sidecars fitted or have spent time with the two halves of the frame separated (in that case the back of the frame is easily bent.)
They are difficult to straighten because datums are not immediately obvious. I didn't quite get what you were saying about the front of the frame...what follows might get you started with the rear...
If you have a good back wheel with the correct rim offset you can fit this as a complete assembly to the frame and tighten it up to the left hand wheel mounting lug.(looking from the rear.)Check before starting that the wheel mounting lug is vertical..if not straighten it up. With a gearbox also mounted in place you can then use a straight edge to check rear wheel sprocket to gearbox sprocket alignment. If that is out, that side of the frame must then be 'tweaked' to bring the two sprockets into alignment.
Once that is achieved the centre of the wheel rim should also lie on the same centre line as the front half of the frame.
If both those things look OK you can then 'tweak' the other side of the frame to produce the correct overall width for the rear of the frame. Everything at the rear should then be in the correct place....Ian

email (option): julie@wright52.plus.com

Hi Ian,

What you say makes a lot of sense. I just had not thought about the relationship of the gearbox sprocket and the rear hub. I've been on bikes since I was 16 years old, and this totally escaped me!

What do you think about the effect of torque on the frame from the gearbox and rear sprocket, and also when braking the torque arm? On MGAs (mine is a 58) this is a common malady allowing the rear axle to move. This gives some pretty squirrelly handling!

The pannier rack carrier is also bent. I know how this happened though. The nut (supposed to be castelated and pinned) on the flat arm came loose. It was my fault, as I had put just a regular nut on. DOH!

Thanks again for your help.

email (option): britool51@hotmail.com

Hi Robb...I have never had any problems that I could put down to torque effects. The whole thing (rear of the frame/wheel etc.) if assembled and aligned correctly bolts up to make a pretty rigid structure, despite some of the individual parts not being particularly strong when in isolation from the rest..it's a bit like the difference in rigidity between a flat piece of carboard and the same bit of cardboard folded up to form a box....Ian

email (option): julie@wright52.plus.com

Hi Ian,

I did a loose bolt up starting from front to rear. As I went along, I tweaked here and there to get things square. Going a step at a time, with gentle persuasion, pry bars, and a lead knock hammer from my MGA, did the trick. Straight edged ( 1/8 inch gage stock) on all for quadrants of the tubes also helped as I could see a bend easier.

I laid a tape measure out at certain points to see if they are level (per drawing) and sure enough, they were.

I now have the rear fender bolted in, all the stays have been straightened, using a borrowed Pannier rack stay from Henri, allowed me to set up the pannier rack (way tweaked)!

Ihave to come up with a decent paint color and final assembly will happen soon.

email (option): britool51@hotmail.com

Hi Robb..it sounds liker it all went according to plan...glad you got it sorted.
You and the bike should have the same destination in mind now!! ...Ian

email (option): ian@wright52.plus.com

Hi Ian,
I bought this bike outta the crate in 1970! It has survived w2 divorces, and a 4 year tour in the Navy.

Actually, I sold it when I went in service, and bought it back (unknown to me it was my bike) 4 years later ina garage sale for $25.00. When I applied for teh title, I asked who owned it before, and the lady said my name! I about dropped to the floor. Cool huh?

I'm using the same method on my seriousle kinked rear subframe from another bike, and it's coming alonh fine too.

email (option): Britool51@hotmail.com