Tire tread wear pattern

[sermis]

I put 2 new Firestone Hawk 9.00 20’s on the front of my deuce. I drove it about 3000 miles with the tires and noticed a cupping wear pattern on the tread. Both sides of the tire seamed to wear about the same. Also both tires seamed to have the same wear pattern. What is the cause? Bad shocks, out of balance?
If you look close you can see how it cups on the outside of the center.

 

[rizzo]

if you run your hand over the tire does it catch one way and go smooth the other?

 

[rizzo]

tire wear info

http://www.michelintruck.com/michelintruck/toolbox/videos-demos.jsp#FundamentalsofTireCD

 

[cranetruck]

This tendency is aggrevated by the two tandem axles in the rear being coupled together without an interaxle differential. The result is a lot of scrubbing in the front, especially with duals.

 

[builder77]

Interesting link.
I took these pics of wear pattern of my front tires. As you can see from the pics the wear is heavier on the back side of the lug. The left of the pic is the toward the front of the truck. I also found the same wear pattern on a few of the rears, but I suspect those are from tire rotation. I am guessing this is likely normal.

 

[marksgarage2]

Mine did the same thing in 3000 miles. Since I went 11:00-20 and singles I don't see any wear patterns as before.

 

[clinto]

Mine does the same thing. I guess I will have to start rotating them per the OM.

 

[JDToumanian]

I've got the same kind of wear on my front tires, too...

That's why I'll be installing one floating axle shaft and locking hub on one side of one of my rear axles before I get new tires. Unlock it for pavement, lock it for off-road. I'll paint it OD and I don't think it will spoil the original look of my truck too much. I don't want to remove the inter-axle drive shaft because I drive in a lot of sand, and it would be a p.i.t.a. to have to bolt it in every time before I go off road.

If the locking hub and shaft don't pay for themselves within one set of tires I will be surprised!

Jon

 

[rizzo]

wear like that can be from alignment. if both are wore in opposite directions it is from the alignment of the rear axle. same direction or only one tire- the front axle alignment.

 

[cranetruck]

Mine does the same thing. I guess I will have to start rotating them per the OM.

Clinto, when you rotate the tires, take two good ones from the rear for the front. If the front tires are not matched you will develop shimmy in a hurry.

I got 12,000 miles on my fronts before putting them on the rear axle(s).

Mine always start to "cup" on the outsides and should last another 12,000 miles on the rear axles.

One problem with the use of only one driving axle is the increased wear on the tires on that particular axle.

Jon's suggestion is a good one, but the best solution is an interaxle diff (locking), but where to get one....

 

[ken]

Alignment would be pretty tough. The rears float side to side on the leaf spring pads. Toe in as the only thing we can set without some special equipment.
Steve try pulling off a front shock and see if it still has any restance. I swapped to some monroe gas charged shocks and it took alot of that cupping away. Also check and see if your kingpin bushings are wore. Not to mention tie rod and draglink. Also check and see if the steering box is wore. Just get some one to turn the steering wheel back and forth while watching the pitman arm. If it goes up and down or side to side while tring to turn it's probally time for new bushings. All of these can lead to a small wooble and cupping. I've thought about adding a steering stablizer to the tierod but haven't had time to tackle that one yet.

 

[clinto]

I will eventually do an Ouverson lockout on one of the rear axles, but that's low on the priorities list.....................

Does anyone have the civvy part # for a good pair of shocks?

 

[sermis]

Both have been pulled and dismounted. I did not mark direction but the wear is the same on both tires. I think it was towards the back of the tread. No odd wear on one tire and not the other that would indicate alignment. I did not notice any shimmy in the front. I am going back with the 15.5 / 20’s so wanted to try to fix any problems before shy start and ruin my new tires.
Ken, do you have the shock number.

 

[cranetruck]

I have civy shocks on mine, I'll check later. The studs were larger in dia and the mounting holes had to be reamed out some.

 

[emmado22]

Seems like civy shocks are the way to go then, correct?

 

[clinto]

Seems like civy shocks are the way to go then, correct?

My thoughts were that they might be a slightly higer quality/rate and that I wouldn't have to pay shipping

 

[Scrounger]

One can get that wear pattern if the toe-in is off. If the front tires are toed-in to far it is like driving on the outside edge of the tread. The front of the tires should be about 1/8” closer than the back. The measurement and adjustment must be done under load; the tires have to be on the ground. If one doesn’t have turntables a couple of pieces of plywood and some Tyvek, the house wrap stuff, will do. It is best to use new tires properly inflated and to have a helper.
Jack up one side and draw a fine line around the center of the tread with some chalk or a soap stone. Take the Tyvek and cut about a dozen pieces 12”X 12” square and place them stacked under the tire and on some plywood, lower vehicle. Repeat other side. The Tyvek is very slippery and the tires will rotate easily. There is a whole section in the manual on this, but a close enough way is to measure the distance between the drawn lines on the very front and very back of the tires. Adjust the tie rod end till the front is 1/8” closer than the back. It helps to turn the tires after adjustment and before measuring. Once set tighten tie rod end.

 

[cranetruck]

The shocks I use are slightly larger than the originals and are marked "Meritor T112 7SA".
The mounting hole had to be enlarged to accommodate the larger stud dia. A Unibit did the job.

Image shows my right front tire after almost 5,000 miles of highway driving. Only one driving axle and 1100-20 NDCC's. The typical "cupping" is beginning to appear, visible towards the bottom of the picture.
My front end alignment is per spec and I even tighten the front wheel bearing nuts a bit more than called for to reduce its effect on camber.

On my last set, I remounted the tires on the "rims" so that the worn edge ended up on the inside. This caused a severe shimmy, so it's better to move them to the rear and get a new set up front.

I hope to get 15,000 miles out of the current fronts, before moving them to the rear.

 

[ken]

I kept one of the boxes that the shock came in. I'll look for it and get you the #. They were monroe gas charged. And they seem to work well. The studs were the same diameter as the orignal shock. I'll hunt for the # when i get back to houston.