Tire Tread Depth Rule for Entire Axle?

Steer axle yes, any other axles no. It doesn’t make it right IMHO, but at my company it’s not up to me.

 

I always replace both steers at the same time. No matter what. Drives I’m not as picky about. I try to match the same side. I generally replace a set at the same time because that’s the way they wear. But, the spider gear will compensate for whatever few 32nd’s difference there is. But steers will affect handling

 

I always did steers at the same time, I don’t have a specific reason for it. I don’t have any scientific proof but I would think a big difference from duals on one side to the other side would cause the differential to have to compensate for the size difference. I don’t know if that would be true or not, and I haven’t stayed at a Holiday Inn Express in a long time.

 

Main thing when mounting duals is matching height. I’ve seen big difference in brands despite being same size. A shorter tire will skip and get flat spots

 

Reputable tire shops won't put tires of too great a depth difference on the same axle. i.e., if 3 tires on the axle are at 6/32 they won't put anything greater than 10/32 or 12/32 with them.

 

This website says 4/32 between tires or sides of axle is max.
Tire Wear | AcuTread Tire Service | Retreading Manufacturers

 

Back in the Bias tire days we were given a measuring stick that gave outside tire diameter and had to mount two tires together that were within 1/2 inch of each other for best wear.

I haven't seen a device like that since radials took over.

We were taught to use matching tread [had some funky trailer recaps] style for each side but no comparison to the other side of the axle.

But bias tires had flats so often that a lot of drive and trailer duals were changed frequently.

Flat tires used to be a REAL delay problem with Monday's being the worst.

Chemical Leaman tracked tires [loved to brand new tires!] by branding numbers which were used on tire change cards describing position and on/off numbers that was stapled to the RO going to the office. Pre-deregulation staffing allowed such minute bean counting.

 

no, there is no rule. The regs are for individual tires, not axles.