I have managed to track down an 8" half width front hub for my M21 and need to get it built with new rims and spokes. Only thing is, the hub was supplied bare - does anyone know what the offset should be?

Thanks

Gary.

email (option): gj.owen@hotmail.co.uk

Gary assuming you are talking about girder forks. I have sent you details from the standards book.

Ron

email (option): ronpier@talk21.com

An 8" brake on an M21? That will be a tele fork model I would think..

Girder fork brakes are 7"...Ian

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

email (option): gj.owen@hotmail.co.uk

Yep I realised too late If all else fails, if possible, get your wheel builder to build it in the centre of the forks. Ron

email (option): ronpier@talk21.com

Can you measure the offset whilst wheel is in forks, if so I can measure the wheel in my B33 for you.

It is best done with a straight edge across the brake drum face with the brake plate removed, and measure down to the rim. I doubt you could measure it properly in the forks. Ron

email (option): ronpier@talk21.com

email (option): gj.owen@hotmail.co.uk

Gary you've opened up a real can of worms. I have measured both my B33 and Shooting Star both different. Not a very scientific way of measuring using a steel rule and by eye. On the B33 measuring from the rim to outside of fork leg N/S 2 11/16" O/S 3" Shooting Star N/S 2 3/4" O/S 3 1/8" So a slight offset towards the nearside, this could be down to the guys who did the wheels when I had new rims put on. Hope this is of some help.

The rim should be in line with the front down tube centerline and centrally placed between the fork legs...If you can work out an offset that gives you that result you'll be OK...Ian

Thanks to both Ians for their help. I think the advice to go dead centre between the forks makes perfect sense to me.

Gary.

email (option): gj.owen@hotmail.co.uk

This question comes up regularly. The standards book does not give a clear answer and the question of whether the forks are symmetrical about the steering column has never received a satisfactory answer either. A number of previous contributors, backed up by measurements they have taken, believe that the left fork is further away from the centre line to allow space for the speedo drive. I cannot confirm this.

I did some of my own measurements and compared them to measurements made by others. They tie up closely with measurements made by Hans Muller. I made a sketch and put it in the technical section under “Wheel Building”. Unfortunately it is all metric but I came up with an offset of 5/16” from the outside face of the brake drum to the edge of the rim. This seemed to be about right when I re-built my wheels.

email (option): pvlietstra@gmail.com

Hi Peter...Note we are talking telescopic forks in this case and the 8" '1/2 width hub' BSA front wheel with the aluminium brake plate...Ian

Hi Ian, your right. I didn't read the question. I guess the best would be to measure up and work it out from first principles.

email (option): pvlietstra@gmail.com