9.00 X 16 tyres are the correct size for the WW2 3/4 Ton WC Dodge trucks and quite a few other vehicle types including the 15 cwt British range ( WOT2 , CS8 and others ). Not forgetting the Canadian CMP 15 cwt models. I guess that most MV enthusiasts have heard stories from fellow enthusiasts about the problems encountered when fitting new 9.00 X 16 tyres . These tyres do seem to present some odd dimensional characteristics and when the time comes for a new set of tyres for your much loved green machine, it pays to be informed before handing over your money . The main problem with 9.00 X 16 tyres seems to stem from a distinct difference in British and U.S.A. standards. U.S. specification 9.00 X 16 tyres are often very difficult to fit on the standard wartime British and Canadian War Office (WO) pattern split rims . The British 16" WO pattern split rim was developed pre WW2 and the WO rim specifications do not seem to match up with contemporary rims from other sources. The WO rims are actually slightly wider in diameter ( approx. one quarter inch ) at the point where the inner edge of the tyre bead rests. The WO seems to have decided to go with its own way of doing things, this attitude was to cause some headaches during WW2 as we shall see.
Wartime tyre manufacturers were aware of the problem as various old 9.00 X 16 tyres I have come across have been marked with scripting moulded into the sidewalls e.g., 'FOR BRITISH WHEELS ' or 'FOR AMERICAN RIMS' . To add to the confusion , one example has been found marked 'FOR CANADIAN WHEELS '. To get around the problem , some present day MV owners have resorted to drastic measures . Some restorers have been reducing the diameter of WO rims by turning them down slightly, the other popular method is to cut the beads of tyres with a sharp knife - remove a thin slither of bead . Some owners just take the problem to a professional tyre fitter who has all the gadgets on hand to squeeze on tight fitting tyres. The only thing is , what happens if you need to remove a tyre for a repair job out in the field and it has been squeezed on under high pressure in a cage . . . . much swearing and cursing ensues .
Most MV collectors seem to accumulate much junk and I am no exception. I have , over the years , saved quite a few old 9.00 X 16 tyres of various brands and dates . Brands like ‘INDIA SUPER TRACTION’, branded with the WD broad arrow that I found on a derelict 1941 Morris CS8, . In order to make some sense of the problematic dimensional dilemma, I decided to measure some old 9.00 X 16 tyres and rims . At least, this would provide some basis for explaining the mystery. The results are in no way to be interpreted as being one hundred percent accurate, but, they do provide a basis for working out the strange anomalies that exist in WW2 vintage 9.00 X 16 tyres. As a starting point , I measured the bead diameter at the outer and inner edges of the bead face . The bead face ( the horizontal face ) on 9.00 X 16's is usually around one and a half inches wide . I then measured the diameter of various rims at the point where the bead rests against the rim flange .The results I got tend to say that the U.S. standard tyres marked ‘ FOR AMERICAN WHEELS, ‘ do have a smaller inner bead edge diameter compared to the British made wartime brands I measured. The smaller inner bead edge diameter is a result of the bead on U.S. tyres being at a angle ( approx. five degrees ) , the bead actually slopes inward , toward the axle line . The wartime British tyre beads showed little angle, maybe one or two degrees at the most . It is very interesting to note that the post WW2 manufactured Ferret scout car RF ( Run Flat ) tyre I measured was dimensionally the same as the WW2 U.S. standard type , this would explain why the post WW2 manufactured DUNLOP TRAK GRIPS are difficult to fit onto WW2 British/Canadian WO rims. Also, the lightweight alloy Ferret rims do measure up as having a smaller diameter at the point where the inner bead edge rests , compared to the heavy steel WW2 vintage WO rims .The most important thing to remember is, in the post WW2 years , tyre manufacturers ( including British makes ) tended to adopt the U.S. five degree angle standard for 9.00X 16’s. It’s easy to become confused when buying tyres that look like they should fit , only to find that you have been caught out . Maybe the best thing to do is take along a rim with you , and check things out , on the spot at the tyre dealer . It is impossible to be definitive on this topic, in reality, tyres would have varied dimensionally due to various circumstances . There were so many different brands around during WW2 , many are long extinct . I hope these observations will be of use to anyone considering a new set of 9.00 X 16 tyres. Hearing of tyre blowouts on restored MV's , is , unfortunately becoming more common . Remember, it's not worth taking risks with 60 year old tyres At some rallies I have attended , I have seen old cracked tyres on otherwise nice vehicles . It only takes one nasty incident on a busy motorway for us all to be branded as cowboys who play with big toys so please do the right thing and make sure your tyres are up to standard.
Written by : Stu. D. Baker |
