Thursday, April 12, 2012

Tires and Rims Deciphered

When you get a vintage bike, you inherit the bodges of the owners before you. Some of these bodges are fantastic and merit preservation and others are aren't. I consider each bodge on my Norton Model 7 from several perspectives. First, I make sure that it is safe particularly in Houston, Texas. Second, I make sure that it s mechanically sound and that it is not a shortcut that will endanger the integrity of the bike. Finally, I view it from an aesthetic perspective.

I've mentioned it before on this blog that the bodges of previous owners are very much part of the bike's soul and I try to preserve as much as I can with the above criteria in mind. My bike came with a Manx style front fender  that seemed out of place with the lines of the bike.

My Bike

The Ideal

I personally feel that the original fender balances the lines and for that reason I have spent a great deal of time and money sourcing an original fender. Immediately upon its arrival I installed it and admired its lines. The problem arose when I quickly found that the front wheel wouldn't rotate freely. Inspection revealed that the tired rubbed against the fender bridge. Despair! Checking the rim and tire, I noticed that it was a 19 inch WM2 while the handbook indicated that the original specification was for a 21 inch WM1 wheel.

Well, how hard can that be to source I just found an NOS fender? Well, very hard. The rim itself is not common and after a great deal of searching I found what I was looking for at the Racing Norton Website. It's important  to realize that along with rim size  the dimple pattern and angle are relevant to proper fitment to the hub. The proper tire is not much easier to find in the 21 inch size. Currently, 21 inch wheels are favored by chopper builders because of the enhanced handling of it's larger size. Not really the look for a 1951 Norton Model 7 but I found what I was looking for at Universal Tire.

I turned to my friends at the Model 7 Forum on Yahoo. The conversation was confusing at first largely because a wheel, the combination of tire, rim, and hub, has several sizes associated with it. Not only that but for each type of rim has several different nomenclatures based on era and can accept several different tire sizes. I don't think I am alone when I say that too many choices proves confusing. In order to prevent others from suffering my travails I offer the Rosetta Stone of tire and rim sizes. Go here for a very help chart.

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