USGI 7:50x20 Tire chains

[pfarber]

USGI, but not original issue, for $125 per axle you can put chains on your Jimmy.

http://store.colemans.com/cart/tire-cha ... -2041.html

Its a stock photo on the page... all the tire chains used that pic.

[WWII TRUCK]

And remember, they have to be made for NDT tires to fit correctly, anyone buying GI Chains for same size commercial tread will find them too small.

[pfarber]

The site lists the chain dimensions... 29 inches for the cross chains... I don't have a CCKW 7.50x20 tire handy but a little over 2 feet wide sounds right.

Places do sell chain tension devices (aka springs) that can take up the slack, if any, and provide a nice tight fit.

[WWII TRUCK]

GI size chains do not always fit the same size commercial tires, as Gi tires have a smaller cross sectional profile. Commercial chains will have slack. GI Chains are issued without tighteners.

[pfarber]

GI size chains do not always fit the same size commercial tires, as Gi tires have a smaller cross sectional profile. Commercial chains will have slack. GI Chains are issued without tighteners.

I just saw this year old post and have laugh at this knucklehead. 7.5x20 is different than 7.5x20? HAHAHAHAHAHAHA

I can dig up OODLES of pictures of CCKWs in civvy tires that are 7.5x20. During the war they used whatever was round, held air and fit on the rim... that would include civilian 7.5x20 civvy tires.

Thank god I booted this maroon off the site. With wisdom like 'it might not be the same size, even though its the same size' let him booger up the other boards with this drivel.

[motto]

I'm sorry Paul but what this fellow has said will be based on his personal experience as is what I am about to say.

I have been involved in running trucks on 7.50x20 tyres for around 40 years and I can tell you for a fact that there are significant variations in cross section of these tyres from different manufacturers. As a result of this experience I would strongly advise against running tyres from different makers on the same axle or in particular buddying them up as duals. The same goes for any tyres on a CCKW rear end as there is no power divider and any variation between tyres will result in wind-up between the two axles. Wind-up is something you definitely don't want as it results in accelerated wear on the drive train as well as the tyres and also reduces fuel economy. I recollect that in one of the TMs there is a picture of a fellow using a large calliper to compare tyre diameters on the rear of a CCKW.

The worst case I personally encountered was when I borrowed a friends '42 model 1-1/2 ton Chev 4x2 truck to pick up another vehicle a couple of hundred miles from home. I had noticed that one set of duals had mis-matched tyres. Though both were nominally 7.50x20 one was hardly touching the road. The truck did the unladen outwards journey ok but fifty miles into the return trip the larger diameter tyre that was carrying more of the load suffered a blowout.

Even now if you compare an Indian made Speedwell 7.50x20 to an STA 7.50x20 you will notice that the Speedwell has a smaller cross section.

**( This is not bullshit Paul, you owe that man an apology) ** Delete this line if you wish to allow the post.

David

[pfarber]

I don't delete posts and welcome any discussion.

What this gent is saying is true. Yes, the TMs do make it clear that the MAX difference in diameter for duals is 3/4inches in circumference and 1/4 inch in diameter (TM31-200 Maintenance and Care of Pneumatic Tires and Rubber Treads, April 1, 1943 P16 para 15).

If your friend was allowing daylight under his tires because he didn't PM the truck than how does that make what I say wrong?

From the mold a new tire, from the same manufacturer should be within 1/8th in diameter, well under the 1/4 inch limit. If you start talking mixed manufacturers or used tires then yes, measure away.

7.50x20.. notice there is no way to tell the height of the tire?

[pfarber]

Yes, the TMs will state that you shouldn't mix TREAD PATTERNS (run NDTs with NDCC or street)...

Same TM31-200 P16 para 15a "tires must be the same size, tread design and tread wear".

But running Goodyears and Firestones? Run'em. As long as the above is still holds true.

[pfarber]

I would strongly advise against running tyres from different makers on the same axle or in particular buddying them up as duals.

David

Please prove this statement. You may have confused tread design (which I agree) or tread wear. But it matter not who made the tire.

Where I work there are over 300 trailers on the yard, and there are over 30 trucks a day with goods coming and going. I will bet you a warm diet soda that the vast majority are not running 'all goodyears' or 'all firestones' or 'all X, Y, Zs'. When the mobile tire shop rolls in to fix rented trailer tires, his rack has a good mix of manufacturers.

[motto]

Hi Paul and thanks for putting up my post

As an owner/operator I have a vested interest in maximum tyre life. The same does not apply to an outside contractor with his mobile shop. He will simply not be that picky. Especially as trailers are far more forgiving on tyre sizes since there is no drive line wind-up to consider. So long as dual buddies are close to the same that's good enough but I would think a lot of your trailers are now running on super singles anyway. I'll bet you that warm diet soda they are a lot more careful with what goes on the tractor unit.

There are very few makers of 7.50x20 tyres left now and even fewer making bar treads but over the years there have been quite a few. In this country I have seen Olympic, Dunlop, Hardie, Alliance, Hancook, Nankang, Speedwell, Firestone, Goodyear and US Royals and probably more. The differences in diameter, not only actual but maybe more importantly rolling diameter can be quite significant. Different ply ratings also comes into it and I find the best policy is not to mix tyres if you can possibly avoid it.

David

[pfarber]

All new users are moderated for 5 posts so I can make sure they are not spammer. You should automatically be moved to the 'regular users' after your 5th post. If you make 6 or most posts that don't automatically appear let me know and I can check it out.

I honestly don't want to see contrary, but things change from place to place and nothing is ever black and white.

There is only one NDT tire maker... its in PA, Specialty Tires of America. I don't know if they sell to the public, but these are the tires everyone is selling. For a while there were some imports.. but I think the quality was poor, and the are not carried any more.

7.50x20s are common farm/ag tires. They are not NDTs, but street treads are available.

The difference in diameter is a non-issue if you know your truck and have the proper manuals. My M35A2 had 10 tires and I don't think any of them were within the 1/4inch limit. It drove fine and I never had an issue... but I would certainly not run with 9 out of 10 tires touching the ground. I slowly was able to buy tires to get things more or less 'in spec'. That truck scared me into doing pre-start walk arounds and checking tires/inflation (the old 'hit it with a wooden club' trick is an easy way to tell if you are underinflated).

NDTs are horrible tires. On road they suck, on a wet roads they suck more.