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Napier tyre size (Beaded/Clincher)

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We are restoring a 1907 Napier, and I am having difficulty deciphering the tyre size required for the car. The car requires beaded edged / Clincher tyres, and I measured the rims (the car came with no tyres).

The rear is: (mm) ( +- a few mm error)

Outside diameter: 675

Inside Diameter: 628

Outside Width: 98

Inside width: 67

Which would mean a 880 x 120 tyre.

However the fronts measure: (mm) ( +- a few mm error)

Outside diameter: 707

Inside Diameter: 675

Outside Width: 74

Inside width: 51

I cannot find the correct tyre size for the front. Can anyone help with this?

The rims are full metal wire wheels.



PS: Also looking for acetylene lamps for the car (reproduction would do). Any clues as to who makes them? thx.

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  • 2 weeks later...

The tyre sizes used by Napier for 1913, which is the only listing I have.

There were five variants of the four cylinder model , which mostly either had

815x105, or 915x105 for customers requiring higher ground clearance. the exception was the 15 Extra Strong Colonial model, which had 915x105 standard, and 1020x120 optional as above.

The 30 hp 6 cylinder, which is much like a 15 four cylinder engine with an extra block of 2 cylinders, had 895x135 (which is around 23 inches wheel diameter where the tyre fits ), and 1020x120 high clearance.

The two largest 6 cylinder models, which are generally known as the 45 and 65hp models had the same sizes, except that the 65 used 1000x150 on the back for high clearance.

Now what you find on a car will often be a consequence of someone swapping wheels because of tyre availability issues, or bcause wheels have been re-spoked with different rims.

To me the metric measurements mean very little for tyres if you have something less common. The wheels I have for my 1911 Type 38 4 cylinder require a 28 inch inside diameter tyre, and are un-altered Napier wheels; but I do not know if that corresponds to either 915x105, or 1020x120, or neither. I reckon I need imperial measurement 36"x 4" tyres. Going back some years, both Lester and Universal listed this size in both Clincher (beaded edge) , and in straight side: So it is almost certain that someone has the moulds, and probably a few people might need to clamour for them for a small run to be made. The problem is that a lot of American cars with the largest wheel sizes like this had rings on both sides of the wooden wheel rims, which could be reversed for either straight side or beaded edge tyres, and many people prefer straight sided. Rudge Whitworth wheels only have one-piece beaded endge rims, and we have little option but to use the correct tyres.

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