Ford CMP axle ratios?

[Hanno Spoelstra]

Guys,

I don't have my references at hand. So can anyone on here help me with the axle ratios for the F30 and F60L with 10.50-16 tyres?

Are they the same as on the F60L with 11.00-20 tyres, or is there a difference?

Thanks,
Hanno

[Grant Bowker]

Based on the Instruction Book, Ford Special Pattern Vehicles Built for the British War Department, Third Edition (8th printing, not dated) The axle ratios are:
F8 4.11
F15 6.67
F15A 6.5
F30 to F60 (all variants) and FAT and rear engine 7.16

[Hanno Spoelstra]

Thank you, Grant!

So the 10.50-16 and the 11.00-20 tyres have (approx.) the same rolling diameter?

Hanno

[Grant Bowker]

As always when discussing CMP Tires, there are variations of actual dimensions by maker within the same nominal size.
Based on the AEDB Design Record, 10.50-16 tire diameter ranged from 37.4 to 38.2 inches and 10.50-20 ranged from 41.3 to 42.3 inches. All diameters given are for tires that are inflated on rims but not mounted on vehicles as the reduction from "free" diameter to "loaded radius" varies depending on the weight (vehicle plus load) the tire is carrying.

[Hanno Spoelstra]

So the difference in nominal size is roughly 4 inches. I guess this could be less with the larger tyres being compressed under a higher load. Apparently this difference was not worth to introduce yet another axle ratio.

[Howard]

Hanno,
I take it from what you are saying, that you are assuming that all of the different trucks had the same target revs at a given speed?
I would have thought it perfectly reasonable to expect the heavier trucks to run at higher revs, making use of the available power in the upper rev range, versus the smaller that would be less unhappy chugging along at lower revs.
(Boy, this stuff is difficult to put into words, isn't it!?)
H