19 Inch tires!!

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Jun 1, 2007
Hello again-
Thanks for your help and opinions on my last posts. The wealth of experience from this forum really shows and is a great help. I am, again, restoring a 75 Mk3. The mechanicals and electrical pose no threat, even though it looks as if the previous owner "fixed" the wiring with a weed eater. New main harness....check and done. Can anyone point me in the direction of a 19 inch rear tire? I ran Avon Road Riders, a 90 90 19 on the front and a 100 90 19 on the rear. I love the feel of the road riders, but cant find anything bigger. I would like to run a 100 series on the front and at least a 110 on the rear, but as all you Norton hounds out there know, a rear tire at 19" is not an easy find. At this point, I am tempted to find an 18" wheel to open my options. Anyone???
I doubt you will find anything suitable for the rear in a 110-19 or larger. If you are set on a larger rear, you will need an 18 inch rim. Unfortunately, for a Mk3 this means a new custom drilled rim. With a pre-Mk3 you have the option of finding a good Atlas rim. Unless you are already planning on re-spoking both wheels, this seems like a lot of expense just to get one or two sizes larger. A 120/90-18 is as large as the Mk3 swing arm will allow without chain interference. This slows the steering considerably. I have done this on my Mk3 cafe racer and am seriously considering going to the 110/90-18.

If you are respoking both wheels and go to 18 inch front and rear you do increase your tire selection somewhat, but you would be hard pressed to beat the AM26's in my opinion. YMMV
I have used K81's for thirty years and they are still on my MkV750. They have always been more than adequate. However, I don't know if it is that I am used to the rounded profile modern tires from the 850 cafe bike, Ducatis and BMW, or if I am still a little unsure after losing the front end on my 850 Interstate last spring, but when I laced up new rims and spokes late this summer, I put a set of AM26's (100/90-19 front and rear) on the Interstate replacing the K81's. I feel more confident with them on tight twisty roads. It may be me, but they seem to change direction quicker than the K81's.

I'll keep the K81's for originality, but for my 850 mule and the cafe racer, I'll go with more modern profiles. YMMV
Why do you want bigger tyres, I run roadriders on 19" and can easily chamfer the footpeg rubbers and take off with no wheelspin. You only have 50 odd HP, a 100/90 will take a lot more.
One of the better changes I've made to my 72 Combat was to switch to a 18" rear. I mounted a 120/90 Dunlop GT 501. I know 50 HP is well under the acceleration capabilities of a 120 tire, but braking and cornering knows no such limits. I'm quite certain a 120/90 has a lot more contact patch than a 4.10.
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