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The Doctor's Archives

Inflation . Tire Application . Tire Facts . Tire Maintenance
Tire Performance . Tire Specs . Tire Wear . Unidirectional Treads

Dear Tire Doctor,

We manufacture aftermarket over the road trailer suspension parts.  Some of our products effect tire wear and we are working on a project to reduce tire wear.  I need an estimate on approximately how long and or miles the fleets will run new tires on a over the road trailer and approximately how long and or miles will they run recapped tires on a trailer. view reply >>

I have a 2002 Kenworth T2000 that was involved in an accident in January 2005. The right front end was hit by a dump truck that lost control at about 40 mph. Just about everything has been replaced in that corner, plus the tractor has had a front end alignment and a three-axle alignment twice.  Since the accident, I've replaced the right front tire three times because the outer shoulder constantly wears too fast and cups sometimes. Could this be from something that measures out but doesn't? Maybe the shock? Please help me. view reply >>

What causes my left front steer tire size 285/75R24.5 to wear just the outside edge of tire? view reply>>

The inside tires on my front drive axle are wearing every other row of tread badly. Both the inside and outside of the tires are wearing evenly. The air pressure is correct in both. How can a tire wear every other row of tread and not all rows on the same tire? view reply >>

What causes the right side of the steer tire to wear in different spots along the outside rib? The tire is on a 2003/379 Pete with a 271" wheelbase. view reply >>


Dear Tire Doctor,

We manufacture aftermarket over the road trailer suspension parts.  Some of our products effect tire wear and we are working on a project to reduce tire wear.  I need an estimate on approximately how long and or miles the fleets will run new tires on a over the road trailer and approximately how long and or miles will they run recapped tires on a trailer.

Appreciate your help. Ken

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Dear Ken,

Thank you for allowing Bridgestone to be of assistance.

Before trying to answer your question, we must emphasize that there are multiple factors that influence tire life on trailers; route, type of equipment, tire size, maintenance, speed, driver habits, etc. For instance, a standard tandem axle trailer may achieve twice or more the tire life of a spread axle trailer.

That said, let's assume:

Dry Van - standard tandem axle trailer

LP 22.5 tires @ properly maintained air pressures

34,000-lb. maximum tandem load

Long distance, over-the-road operation

Normal operating speeds

Tire life predictions: (These will vary not only from fleet to fleet but from trailer to trailer)

Original equipment quality new tires = approx. 200K

Economy grade new tires = approx. 170K

Premium retread on virgin casing = approx. 160K

Economy retread on 2nd+ cap casing = approx 125K

No one fleet operates exactly as the other. Some fleets run only new tires while others exclusively retreads after the original equipment tires wear out. Still other fleets have no set pattern either way.

We realize this is not a very definitive, concrete answer. There are so many variables that a more definitive answer could only be provided on a fleet-by-fleet basis after considerable research.

Best regards, Tire Doctor


Dear Tire Doctor,

I have a 2002 Kenworth T2000 that was involved in an accident in January 2005. The right front end was hit by a dump truck that lost control at about 40 mph. Just about everything has been replaced in that corner, plus the tractor has had a front end alignment and a three-axle alignment twice.  Since the accident, I've replaced the right front tire three times because the outer shoulder constantly wears too fast and cups sometimes. Could this be from something that measures out but doesn't? Maybe the shock? Please help me.

Sincerely, Jerry

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Dear Jerry,

Thank you for the opportunity to be of assistance.

First off, you do not mention how many miles the truck has run since the repairs, so we can’t determine how quickly the right-front wear is occurring. Also, you do not mention replacing the left front tire, so we will have to assume that the left-front tire has not required replacement during this time period.

First let’s discuss outer shoulder wear to the right-front steer position.

The most susceptible tire position for irregular wear is the outer shoulder of the right-front steer tire. Much of this has to do with steering geometry, road crown and steering component placement and design. However, it is not reasonable that the right-front tire should require replacing three times during the life of the left-front tire.

Items that can contribute to right-front steer tire outer shoulder wear:

1. If examination of the left-front tire shows no side force wear then a likely culprit would be a positive camber angle on the right-front.

a. Was the steering axle replaced as part of the repair?

b. Did the alignment shop give you a print out of the alignment specs, as received readings, and after- alignment readings?

c. If you do have such a print out, make sure the right-front CAMBER angle is either 0 or slightly negative. Any positive setting will lean the top of the tire out and wear the outer shoulder on the tire.

d. If the right-front does have a positive camber angle, the axle should be replaced (do not bend the axle as this voids any warranty).

2. If examination of the left-front steer tire shows side force wear, or, if the alignment print out confirms no positive camber to the right-front.

a. Check your other alignment settings on the print out.

b. Total TOE should be at 0 when loaded. Traditionally alignments have been set between 0.030” to 0.060” with 0.040” considered industry norm. However, studies show that any excessive toe-in is very penalizing to tire wear.   

c. The rear axles should be parallel and as close to 0 thrust as possible. Normally, if an axle can not be set exactly to 0 (due to shim thicknesses) it is set to the closest possible setting to 0 but thrusting to the LEFT. This helps the truck compensate for road crown. If you have any thrust angle to the RIGHT in the drive axles, it will accentuate the effects of road crown. Then you’ll have to compensate by turning the steering tires to the left, which could result in outer shoulder wear to the right-front tire and inner shoulder wear on the left-front tire.

d. Finally check the caster setting. Caster is not normally a wear issue, however, after a wreck the caster stands a chance of being grossly incorrect. Normally caster is set about 1/2-degree higher on the right than the left to compensate for road crown. The Technology and Maintenance Council recommends a setting of 3-1/2 left, 4 right. If your settings vary, caster can cause a pull in the vehicle, and that pull has to be compensated for by correcting with the steering wheel, and thus causing shoulder wear.

3. If all of the above check out perfectly, you might consider checking your trailer – it may have been also damaged in the accident. “Dog-tracking” can affect steer tire shoulder wear as well.

As far as the cupping, this is normally something that can cause a bounce; Check to make sure the shock absorber is warm to the touch after operating, and make sure the wheel wasn’t damaged in the wreck.

Hopefully this has been of help to you. If you have any further questions, please contact us.

Best regards, Tire Doctor


Dear Tire Doctor,

What causes my left front steer tire size 285/75R24.5 to
wear just the outside edge of tire?

Regards, Louis

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Dear Louis,

There could be a variety of reasons for your tire wear.  Since we can only speculate, we recommend having your tire inspected by a qualified tire professional.

One-sided wear, which sounds like what you are describing, can be caused by improper camber and drive axle misalignment.  Worn kingpins, improper bearing adjustment and excessive axle loads can also cause shoulder edge wear.

We recommend you get the vehicle to an authorized Bridgestone Firestone dealer and have the tire inspected.

Regards, Tire Doctor


Dear Tire Doctor,

The inside tires on my front drive axle are wearing every other row of tread badly. Both the inside and outside of the tires are wearing evenly. The air pressure is correct in both. How can a tire wear every other row of tread and not all rows on the same tire?

Regards, Scott

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Dear Scott,

Anytime there are irregular wear patterns on a tire, it is the result of unequal forces being applied to various areas of the tire's footprint.

This can occur due to a number of conditions, including but not limited to: Air pressure vs. load, tire diameter match and alignment.

Unfortunately, it is impossible to diagnose your particular wear condition sight unseen. We are copying your e-mail to our field engineer in your part of the country. He will contact you within the next few days so he can visually inspect your tire.

Regards, Tire Doctor


Dear Tire Doctor,

What causes the right side of the steer tire to wear in different spots along the outside rib? The tire is on a 2003/379 Pete with a 271" wheelbase.

Thank You, Robert

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Dear Robert,

Thank you for this opportunity to be of service.

From the description of the irregular wear that you give, its sounds like you are describing what the Technology & Maintenance Council defines as Cupping/Scallop (Shoulder Wavy) Wear.

TMC describes the appearance as: "Localized cupped-out areas of fast wear creating a scalloped appearance around tire on the shoulder ribs. May progress to adjoining ribs." TMC gives the 'Probable Cause" as: "Usually a result of moderate to severe assembly out of balance condition, improper rim/wheel mounting or other assembly non-uniformity. Can also be due to lack of shock absorber control on some suspension types as well as loose kingpins and improper bearing adjustment. Underinflation can also cause this condition."

We hope this answers your question.

Best regards, Tire Doctor


The Doctor's Archives > Inflation . Tire Application . Tire Facts . Tire Maintenance
Tire Performance . Tire Specs .
Tire Wear . Unidirectional Treads

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