. . . can anyone provide me with the angle between the two tubes of the lower fork? I need it to have a mounting bracket machined for a disk brake caliper. I need something more precise than what I would get by measuring.

email (option): jonny.rudge@verizon.net

Are the girder forks even strong enough to support disk brake use?

email (option): vinver@ns.sympatico.ca

here here,you're going to kill yourself

email (option): richardholt@rocketmail.com

email (option): braunz@paradise.net.nz

The Norton's do have the benefit of side check springs. I'm not sure if George actually uses that bike on the road though? Ron

email (option): ronpier@talk21.com

probably a front brake disc off a honda 50cc should well big enough if not maybe too big any bigger and i would wear a gum sheild to help when i go over the handle bars

Hi John..You'll scare yourself sh****ss if you don't fit a new spring and do something about the lack of rebound damping..However, I would be interested to know how you resolve the problems with this modification...mail me when you get to testing time would you?...Ian

The forks should be able to cope with a disc brake..they fit them to Harley Springer forks which are broadly similar...Ian

My thanks to all of you who are concerned about my well-being. I think I know of the consequences of the higher stopping power (including the collapsing spring problem), but higher ultimate stopping power is not my reason for wanting a disk brake. My reason is the lesser effort required in normal braking situations. I face New York City stop-and-go traffic every day and, on bad days, needing higher squeeze effort every few seconds sometimes results in fatigue. With a well-adjusted disk brake I only need the light effort of one finger, instead of needing the entire hand to squeeze the devil out of the brake lever.

email (option): jonny.rudge@verizon.net

a harley springer has a shock absorber

I have fitted a BSA 8 inch brake into my girder forks gives good braking with no problems, not the same as a disc but the forks seem strong enough.

Well then, as long as you paint it green..
But getting to the original question, you may well need to measure the angle on your own fork, probably the specs are one thing but 70 years of abuse can change the shape somewhat.. and what one guy measures on his fork may not be the same as your example. I would think it will be a custom one off job anyway, so you woule likely need to let the welder have the fork to make the bracket.

Vince

email (option): vinver@ns.sympatico.ca

Oh, no. No welding, for many reasons. One is that I want to keep the bike capable of being easily restored to original specs, without grinding, etc. Another is that I wouldn't trust welding such a critical part as the fork without annealing it, and that simply makes it too costly and too troublesome. In fact, I don't even know if it is possible since most of the joints on an M20 are brazed and the high heat of the annealing process may well weaken or even destroy any brazed joints that may exist on the fork - I don't know if there are any. I intend to have a bolt-on bracket machined, which will hug both tubes of one side of the fork, onto which bracket the caliper will bolt on. That's why I need the exact angle. I can measure the OD of the two tubes with sufficient accuracy to have good fit along the length of the bracket but if the angle is wrong the contact area will be diminished and one or both fork tubes may become dented, either in the process of fitting the bracket or by the fact that one tube will bear all or most of the braking force.

email (option): jonny.rudge@verizon.net