Hello,

A short question:
Is there a difference in the angle of the steering head
Between The girder and telescopic fork models?

Thanks,
Noam.

email (option): noam10@gmail.com

Hi Noam...The short answer...No

M Series BSA frames for both girder and telescopic forks share the same steering head angle of 27 degrees...

Incidentally A, B, C and D Series models also have the same common steering head angle...

However, for M Series Models the frame front downtube is different for girder and tele equipped versions...

This means you can fit girder forks to a telescopic fork frame but not the other way round...Ian

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

Hi Ian, Thanks !

I was wondering, because as you mentioned, the frames for girder and tele fork are different:
The front down tube of the subframe for the girder fork goes all the way down to connect to the rear subframe,
Whilst for the tele fork, the same tube connects to the top of the engine plates…

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I have this 1960 BSA M21, which was made in the past a chopper, but with WM20 500 engine, and gear,
A good long dynamo and a good magneto, and a good carb (Amal 900 though, not the 276 ) I wrote about it in the past.
It is running well. the reason I bought it is that with all of the above and clear title, the cost was like an engine, maybe plus magneto..

Here it is as bought.
Very hard to handle with this long fork, huge angle and small clip on handlebars..

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Anyway, the rear chassis is unchanged, but the front one, as cut, enlarged, and anything you can imagine.
The rear wheel is 16” balloon Harley tire, with a BSA rigid frame hub…
The front telescopes were made from 2 welded telescopes welded together through a tube.. very danger, as you can see at photo.

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I managed to buy a Suzuki front fork, cut the hub out of the wheel, got a new 19” rim and shorter spokes, and laced it to match the fork.
(I had to do that as the 19” front wheel measurement is in the licenses, and would not pass MOT with the 21”)

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Bottom line is, that now the front is too short, and the bike sits low.
I can cut and change the frame again, or just replace the front frame with an original frame, which I would probably do.
I do not trying to get anything original with this one,
Just street legal and safe to drive.

By the way, why a telescopic fork cannot be mounted to a girder frame? What is the difference?

Cheers,
Noam.

email (option): noam10@gmail.com

Hi Noam..With girder forks as the forks move under compression the wheel moves away from the frame...

With tele forks it moves towards the frame...

That is why the downtube on tele fork frames was shortened, pulled back and attached to the top of the engine plates, to avoid being hit by the wheel/mudguard...

There'll be contact if those forks are fitted to a girder frame...Ian

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

Thanks Ian.

I'm glad I've asked and that you gave this answer..

I almost decided to use the girder frame with the Suzuki tele forks,
As also the current, altered chassis is a girder fork front subframe,
But with much longer forks and this huge angle, there was no contact...

Thanks,
Noam.

email (option): noam10@gmail.com