Tires: Tire Tread Design, closed shoulders, fleet operators

Question
QUESTION: Hello Barry,

I am curious about the difference between to types of tread designs commonly found in the market place and which of the two designs would apply best to a particular vehicles and their common usage.  The two different tread designs I am comparing are "open shoulder" and closed shoulder" patterns and which are best for commercial tow truck applications (towing of passenger and LT vehicles) as well as LT's (i.e. F-250)that experience semi-commercial use (i.e. general contracting, snow plowing, personal vehicle.  The climate is the Toronto area (winters include heavy snow).  I am curious because many new light trucks come with closed shoulder designs.  Are they that important and must they be replaced with closed shoulder designs?

Thank you

ANSWER: Mike,

This is kind of a long and involved issue, but I'll try to give you the highlights.  BTW, I'm going to confine my discussion to All Season type designs.  Traction, All Terrain, and strictly steer position tires are a different kettle of fish.

Open shoulder designs generally give better snow traction, but they tend to wear more rapidly and more unevenly.  This means that on steer positions, alignment becomes more critical - and since tow trucks typically make many sharp and complex maneuvers, this could be a problem.

Open shoulder designs also tend to give better fuel economy - mainly because they use less material.

But tires designed strictly for commercial usage tend to have closed shoulder design in order to reduce the wear issues, since cost is probably the most important item to fleet operators.


---------- FOLLOW-UP ----------

QUESTION: Great--I have a much better understanding of the two different designs, I'm just curious if you could have two tires with closed shoulders on the back of a tow truck and two tires with open shoulders on the front or visa versa or even 3 of one style and 1 of another etc..

thanks

Answer
Mike,

It is pretty common for the rear tires to be "traction" tires and the fronts to be "steer", so, yes, that is possible.

BUT

4WD's require tires that are very close in diameter, so it's best to have all tires be the same size, make, model, and state of wear.  Otherwise there is a chance of driveline stress and a failure.

AND

The general rule is to have tires in dualed applications matched as closely as possible.  This prevents one tire from carrying more of the load than it's mate.

AND

Any odd tire on a vehicle makes the vehicle want to pivot around that odd tire in emergency maneuvers.  The more different the odd tire, the more that tendency.