12:00-20 tyres
 

Has anybody ever used 12X20 bar tread tires on a CMP? I'm thinking of RPM and road speed, but braking concerns me with the greater flywheel effect.

1200-20
 

Many CMPs here have been fitted with these tyres as they were available cheaply.

They raise the road speed a bit which also means you have to change down sooner on hills, but don't seem to affect the braking or handling in any major way.

On a Ford CMP they can rub on the pitman arm on full lock.

Other than that they just don't look quite right, but that's an aesthetic thing.

Here's a former wireless signals converted with these tyres, and the rear wheels have been fitted reversed.

http://www.oldcmp.net/Images/stonker/stonker3.jpg

"Here's a former wireless signals converted with these tyres, and the rear wheels have been fitted reversed."
I noticed that when i cleaned up my 20 inch rims that it looked like the wheels could be put on iether way with the champfer(?) or bevel of the stud holes and the appearance of the tube valve opening on both sides. was there any purpose to this or just ease of manufacturing useing the same tooling?

The 'why'
 

As I recall... and this was some 35 years ago... the reason was so the back wheels didn't drop into the same ruts as the front thus helping traction. I can't remember what was done with the stems.

I know on some models, like the FAT that the front wheelbase is wider than the rear but that is without reversing the wheel rims.

1200x20 on C60S
 

Hi Harry

My C60s Pattern 13 was came with 1200x20 Michelins on the front end when it was surplused. Didn't drive it much that way but I did note a problem of clearance to the brake hose. Didn't see any other problems.

The truck has been running 1100x20s since I first put it back on the road 20 + years ago.

Cheers Phil

Bar Treads
 

Gday Harry,

Well sort of - these are 12.00 X 20's but in NATO bar tread pattern. They are a modern radial tyre.

Ive only ever used these on my truck. They also steer extremely well as in they dont have that old bar tread habit of wandering..

I live in a flatter part of Australia so the effect of a bigger tyre slowing her down when going up a decent ascent isnt a problem.

The brakes work fine (very well in fact) and when I did take the beast on a 16 hour epic to the coast, down some very steep descents, I simply selected a very low gear and kept it there.

Ive repeatedly had the steering on full lock and never had the tyres rub on anything.