9.00-16 U.S. versus British wheels

[Mike Kelly]

I have two seemingly identical 900x16 tyres . They are probably of WW2 vintage . One of them is marked FOR AMERICAN WHEELS , the other is without this marking . I think they are trailer tyres .

Anyway , I carefully measured each tyre to work out any possible differences . I measured the bead diameter from both the inner and outer edges .

You can deduct your own interpretation but , it appears to me that WW2 American tyres did not fit British rims .

Another tyre I have isa post war Ferret T24 run flat . Its dimensions are same as the AMERICAN WHEELS marked tyre . I believe that the post war T24 's are actually made using the U.S .specs . This is why those Simex St24' s are a tight fit on Canadian / British WW2 rims .


Mike

[Mike Kelly]

the results from my measuring

Mike

[gordon]

The US wheels had a 5o bead on the rims, British ones didn't.

In practice, it does seem like you can fit them either way, as I put British tyres on a couple of my Dodges, but these were modern ones which may have the angle...

Gordon

[Pete Ashby]

That five degrees is a real pain. I fitted British R/F's on my C15A and had to buff the bead, it's thick so you don't get near the cords, it took me nearly a day a wheel


I have heard of people who turn the rims down but I'm not too keen on that myself

Pete

[Mike Kelly]

Yes, its common practice here for restorers to have their CMP rims turned down 1/4" in diameter to accommodate the U.S. spec 900x 16's , it doesn't seem to cause any structural harm to the rim . I have never heard of a rim collapsing .

It's a odd fact that the post WW2 Dunlop T24 RF tyres were made to the U.S .specs . The Ferret alloy rims are slightly smaller in the bead diameter than the wartime steel version .

Mike

Originally posted by Mike Kelly
Yes, its common practice here for restorers to have their CMP rims turned down 1/4" in diameter to accommodate the U.S. spec 900x 16's , it doesn't seem to cause any structural harm to the rim . I have never heard of a rim collapsing .

It's a odd fact that the post WW2 Dunlop T24 RF tyres were made to the U.S .specs . The Ferret alloy rims are slightly smaller in the bead diameter than the wartime steel version .

Mike

Like Pete I'd be wary of turning rims down even a whisker.

As far as we can deduce the 5 deg "English" bead angle allows for a tyre to become loose immediately it is broken away from the rim flange making removal more easy assuming that the well is also set at 5 deg.

US and Canadian tyres seem to have a 0 deg bead angle and so need encouraging all the way off.

Run-flats are another matter, here the sudden loosening is a definite disadvantage and the rim needs to be a 0 deg angle to keep the tyre in place with the spreader. Also by its very nature, field replacement is less of an issue.

You'll also notice that Ferret T24s have a rim type designation on the tyre wall, doesn't it say something like "for H section rims" or something like it ?

R.

[Hanno Spoelstra]

Mike,

Thanks for your research and pictures. For me it puts an end to the debate on why these tyres & rims don't mix & match: it isn't so much a case of the 0° versus 5° degree bead angles, but the considerable difference in bead diameter.

Originally posted by FV623
You'll also notice that Ferret T24s have a rim type designation on the tyre wall, doesn't it say something like "for H section rims" or something like it ?

See my page on 9.00-16 tyres for your pictures of a R.F.H.S.2 tyre. The side is clearly marked "TO FIT 6.50 H RIMS ONLY".

Regards,
Hanno

[Rolf S. Ask]

Have I missunderstood it when I say that Canadian vehicles where made by British specs, but the wheels/rims used where the "normal" US/Canadian spec in diametres??

Rolf

[Tony Smith]

As well as the Ferret, these rim sizes are also used on Land Rover 130" Defenders and the various 101" Forward Controls. Seems like the WW2 rim specs were dropped by the British after the war. Does anyone know of a postwar British vehicle that used 0 degree bead tyres?

[gordon]

When LR 101's were being obseleted hereabouts I bought some little-worn ones from a dealer. Some of them went on my Command Car, and I think another four are still on that C15A cargo truck that Hamish still has for sale. We had no problems in getting them on to either wheel type.

Gordon

[Mike Kelly]

Today , I measured one of the Ferret light alloy rims against a WW2 rim from my Morris CS8 .

Results :

The Ferret rim : The narrower outer split half measured 15 3/4" at the point where the two halves join , a slight angle is evident towards the bead shoulder on the rim edge .

The WW2 Morris CS8 rim measured at the same point is 16"

A definate difference in size .

I am 100% convinced that WW2 British made tyres were 0 degree bead type ( both RF and normal pneumatic types ). I have looked at the DUNLOP TRAK GRIPS on the CS8 rims here , they are marked S for synthetic RF1 and they are very old , these are 0 degree as is the WW2 Michelin tyre, marked - Made in England I have .

It seems the post war TRAK GRIPS made in the 1950's and 60's went to the 5 degree bead , that is why the Ferret rims are narrower. Try fitting Ferret TRAK GRIP RF tyres on a Morris or CMP , tight fit isn't it .

By the way , I have 14 ( yes fourteen ) CS8 rims here ! As far as I can tell there is no physical difference to the CS8 rims fitted with RF tyres .

To add to the story , in the early 1980's I found two brand new 900-16 OLYMPIC made in Australia directional bar treads , these were made until the early 1970's for our aging 25 pounders . These tyres fitted on a WOT2D easily . So I guess some 0 degree tyres were still being made post WW2

Is everyone confused now ?

Mike

[Mike Kelly]

Originally posted by Rolf S. Ask
Have I missunderstood it when I say that Canadian vehicles where made by British specs, but the wheels/rims used where the "normal" US/Canadian spec in diametres??

Rolf ,

Reading Bill Greggs excellent 'Blueprint for Victory ' . He says at one point , the British sent some 900x16 rims to Canada , and that the Canadian built rims were to be made to the British specs .

As far as I know the Canadian type is similar if not identical to the British ones , I have not got a C15A / F15A rim here to measure up . The C8AX rims all have tyres on them so I cannot access the vital points to measure

Mike

[Vic Eaton]

HI THERE MIKE
Icame accross this problem of the 5o on my C15 WHEN FITTING BRITISH TYRES and at the time knew very little about these trucks so i just turned the 5o off the rim and have never had a problem since that was seventeen years ago.
vic eaton uk.
PS it made one hell of a noise on my lathe.