History of 10.50-16 tyres

[Andrew H.]

Doesn't 10.5" refer to their width? If so, it would not indicate height.

[Andrew H.]

The modern equivalent of the original 10.5 X 16 tyres as used in WW2 is 262/75/R16 (10.5' X 25mm = 262mm). In other words, the tyre is 262mm wide and the chord is 75% of that = 196mm deep. Also the rim at 16" X 25mm = 400mm. Therefore the diameter must be 196mm + 196mm + 400mm = 792mm or 31.68 inches.

Thats the arithmetic, but we found that modern 262/75/R16 tyres looked too small on our LRDG truck (based on WW2 photos) and we had to go another size up before we got a tyre diameter that "looked right".

[Lang]

Andrew

The reason they did not fit was all the old tyres were basically 100 height ie height of the tyre is the same as the width. They had various specialist odd-ball heights but you would expect any normal tyre of the period to be equal height/width.

This construction was so standard across the auto industry that tyres used to be measured by height with no wheel size ie 30x3. Everybody knew that the tyre was the same height as width so they knew that the 3 inch wide tire would go on a 24 inch rim (height of tyre top and bottom subtracted from overall height.

When they started with radial they messed with profiles so your 265/75 is only 3/4 as high as it is wide. To match the !0.50 you would need a 265/100 which I doubt is made.

As you found out we are now forced to use over wide tyres to get the original height if we want something off the shelf or go to the few specialists around the world still building 100 profile bias construction tyres.

Lang

[Grant Bowker]

The AEDB design record gives outside diameters for 10.50-16 tires that vary by brand:
Pneumatic cross-country 37.4-38.2 inches (2% variation)
Pneumatic highway tread 37.0-37.6 inches
Run-flat cross-country 37.6 inches

[Andrew H.]

Originally Posted by Lang

Andrew

The reason they did not fit was all the old tyres were basically 100 height ie height of the tyre is the same as the width. They had various specialist odd-ball heights but you would expect any normal tyre of the period to be equal height/width.

This construction was so standard across the auto industry that tyres used to be measured by height with no wheel size ie 30x3. Everybody knew that the tyre was the same height as width so they knew that the 3 inch wide tire would go on a 24 inch rim (height of tyre top and bottom subtracted from overall height.

When they started with radial they messed with profiles so your 265/75 is only 3/4 as high as it is wide. To match the !0.50 you would need a 265/100 which I doubt is made.

As you found out we are now forced to use over wide tyres to get the original height if we want something off the shelf or go to the few specialists around the world still building 100 profile bias construction tyres.

Lang

Thanks Lang!
Thats good information I didn't know.
We are still working on a plan to get your tyres across the ditch (a friend has a large yacht)
Andrew

[Lauren Child]

Originally Posted by Lang

Andrew

The reason they did not fit was all the old tyres were basically 100 height ie height of the tyre is the same as the width. They had various specialist odd-ball heights but you would expect any normal tyre of the period to be equal height/width.

This construction was so standard across the auto industry that tyres used to be measured by height with no wheel size ie 30x3. Everybody knew that the tyre was the same height as width so they knew that the 3 inch wide tire would go on a 24 inch rim (height of tyre top and bottom subtracted from overall height.

When they started with radial they messed with profiles so your 265/75 is only 3/4 as high as it is wide. To match the !0.50 you would need a 265/100 which I doubt is made.

As you found out we are now forced to use over wide tyres to get the original height if we want something off the shelf or go to the few specialists around the world still building 100 profile bias construction tyres.

Lang

I hit this problem with 1050R20 being 75% hieght versus 1050-20. I'd assume the same is true for other sizes, with the "R" being shorthand for a lower profile.

[Ilian Filipov]

Thanks for your answers guys, you're really awesome!

[Lang]

Lauren

The "R" stands for RADIAL and is not a size indicator.

For instance, the very common 7.50x16 used on Landrovers, Landcruisers etc for 50 years was a 100 profile (height equals width) tyre.

The world moved on, so for about 20 years in the 70/80 period they designed a new radial construction tyre to match equal height and width of the old bias construction. They called it 7.50R16

As those old vehicles were superseded by modern types wanting wider profile tyres without increase in rolling diameter we started to see the width-height relationship change with percentage profile measurements.

For those old vehicles still operating, they now have to go to the 235/85x16 which is the same height as the old 7.50x16. The difference is that it is 235mm (instead of 7 1/2 now about 9 1/2 inches) wide but, only 85% of that in height, to achieve the same diameter as the old tyre.

All the various commercial tyres (and most car tyres too)of whatever size went through that progressive change.

Lang

[Tony Smith]

Originally Posted by Lang

Lauren

The "R" stands for RADIAL and is not a size indicator.

Lang

Almost universally, Radial tyres with R in the size are 78% aspect ratio.