Tires

Your line of thinking is reasonable. Typically an 11R22.5 casing takes less abuse for the types of service it encounters than its bigger brother. However, when buying caps and casings it is impossible to determine the amount of abuse the casing took in their previous life so the assumption will not always hold true. Most retreaders do a rigorous evaluation of all casings prior to retreading. If your 12R22.5 are recapped by a reliable retreader then you should not have to worry about casing integrity.

Switching to an 11R22.5 will force you to make a few trade-offs that are most likely not worth it. First you will have to manage two different tire sizes in your fleet. Second switching to the 11R22.5 you will loose significant load carrying capacity dropping from 7390 lbs to 6610 lbs at 120 psi inflation. Exceeding these limits is not only unsafe but would be even more damaging to your casings than the typical abuse encountered in your mix serviced concrete application.

Flat spots can appear for a number of reasons such as an unbalanced break system, new brakes causing high friction and most often aggressive braking. You are correct if the flat spot is not too severe, dual trail tires can be positioned such that the flat areas are 180 degrees from each other. Flat spots that go deeper into the tread but have not exposed the steel belts or show other signs of casing damage can be retreaded and put back in service. If however, the skid damage has exposed the belts then discard the tire.

The TMC puts out an excellent resource called “Radial Tire conditions Analysis Guide” this resource covers every conceivable tire condition lists probable causes and gives recommend corrective actions. You might want to check it out and keep it as a handy reference – I do!

Ralph-

The decision to remove a tire from service is dependent upon a number of factors and each fleet/operator will weigh these criteria differently depending upon their own preferences and policies. Some of these factors include wheel position, type of service, tire condition, truck maintenance, and willingness to retread.

Looking at wheel position, your 8/32 rule is a common guideline for steer tires. If you manage your tires for retreading, pulling your steer tire with more non-skid enhances casing life enabling a new life as a drive or trail tire. Driver satisfaction and truck responsiveness are other common reasons to pull steer tires at 8/32 or higher. On the other hand, fleets who do not favor retreading, or have high miles/32 requirements, will commonly run a steer tire out to 5/32-6/32 given an even wear pattern. A quality steer tire like the G395 LHS will have excellent wear patterns enabling longer run out before pulling the tire. In the drive position, even wearing tires often run to 4/32 before being pulled from service. Similarly trail tires are often run out to 2/32 before removal.

Various service applications will place different demands on the tire affecting the recommended amount of non-skid at removal. For example, a truck running a regional route may keep a tire in service longer than a line haul truck who puts more demand on the tire and is farther from service locations. Also, poor truck maintenance can result in a 12/32 tread for the majority of the tire, but have an outside shoulder with less than 8/32 thus requiring removal.

A good resource for best practices is the "Recommended Maintenance Practice Manual" put out by the American Trucking Associations. http://tmc.truckline.com

Thanks for the question Ralph