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1949 ZM20T Wheels

I have just aquired a civilian 1949 ZM20T. Rigid rear, tele front. Have both hubs but no spokes or rims.
Questions if you could help please:-
Wheel sizes 19 inch front and rear?
What size rims? Wm3 front and rear?
Any information on offsets appreciated?
Thanks in advance
Bryn

Re: 1949 ZM20T Wheels

Rim sizes are 19" both ends with a WM2 on the front and a WM3 on the rear...Depending on the bikes history you may either have the 7" front brake with a steel brakeplate or the 8" front brake with the aluminium brake plate....
Likewise with the back wheel...You should have the hub with the brake drum riveted to the side of it but you might have the QD 'military' type hub fitted, with the bolt on sprocket...The one piece hubs are impossible to get rear drum/sprockets for as well as being very awkward to change. Also the rear spindle has a design weakness...I've seen a couple of these (one my own) where the wheel spindle sheared at the point where it changes diameter...The spindles are also hard to find these days, so a wheel change should be something you might consider from a practicaliy point of view...Ian

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

Re: 1949 ZM20T Wheels

I have a 1950 which is identical to a 1949. And as Ian said, the rear brake drum/sprocket is unobtainable.

I have never heard of the spindle breaking but thanks to Ian I now have one more thing to be worried about when riding the bike!

Draganfly does have new rear wheel spindles if this happens.

Re: 1949 ZM20T Wheels

Sorry Bruce!...Did I mention the frame breakage and the and the bendy fork yokes....:laughing: :laughing: ....Ooops...Ian

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

Re: 1949 ZM20T Wheels

Ian,

What good news do you have next? The 7" front brake won't stop the bike. The forks have no dampening and the bike will leak oil? Please don't let this new owner know about the six spring clutch!

Anyway, I am assuming the wheel spindle breaks on the sprocket side? If so I am thinking of grinding a bigger radius there. I ride the bike a lot and would like to avoid this problem! I have access to a cylindrical grinder so it won't be a problem to do.

Re: 1949 ZM20T Wheels

Crickey!!!!!!!! What next???

Re: 1949 ZM20T Wheels

Don't panic!, it's just a bit of banter...I ran my rigid M21 to work on and off for years...I fitted a B33 engine later on (mine already had the 8" front brake and a Triumph clutch....An ultra reliable machine once previous lash ups were rectified and the chap I sold it to about 20 years back is still using it to ride to his work ...Ian:relieved:

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

Re: 1949 ZM20T Wheels

Now you got me thinking, I have the same model and Iam in the process of fitting a sidecar to it, which is an Australian made Dusting and quite heavy. This will obviously place more load on the rear axle. These were designed to haul sidecars with all the lugs cast in the frame.
I have fitted sidecar rated springs to forks and tapered bearings to headstock but can't do much to strengthen rear end.
Might be interesting once complete if it fails whilst belting down the highway!!

email (option): tknalder@iinet.net.au

Re: 1949 ZM20T Wheels

I don't want to get everyone worrying about their rear spindles...I have personally seen two broken ones and have had anecdotal evidence of another which I've no reason to disbelieve...
On the other hand I've been riding and involved with BSA singles for 45-50 years so I've had a while to get a problem and hear about a couple more!....:laughing: ....I don't think this is a very common problem, I merely mentioned it because it happened and it fell within the remit of the enquiry about wheels for this particular model...There are plenty of other problems that are more common!...Ian

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

Re: 1949 ZM20T Wheels

My bike is finished but isn't licensed as yet and after careful assembly oil leaks isn't a problem as yet, wet sumping is, which only means draining the crankcase into clean container and putting it back in the tank. Fortunately someone prior to me rebanded the sprocket and did a very good job. The rivets holding the drum still original and look perfect. The amount of miles it will do when sidecar is finished and attached will be minimal so I think it will out last me if its lasted 70 years to date without failure. As Ian said fit a wheel with bolt on drum, however where I am one would be difficult to find. I am aware of 6 spring clutches and have improved the drag when trying to find neutral by fitting a lever with 1 1/6th cable pull compared to original 7/8".

email (option): tknalder@iinet.net.au

Re: 1949 ZM20T Wheels

So now I am confused
Didn't the post war QD hubs revert to the counterbored bolts and flat holes used pre war ?
or did they continue to use the countersunk self aligning bols ?
I have seen both

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