Class 8 Trucks: Wide-Base Tire Contact Patch Question

[Deaf Bob]

I do know I love hauling heavy scrap loads with my dualie flatbed over the singles 1 ton sprung pickup.
I get stuck less with highway tires on the dualie than I do with the sorta taction tired singles..

[SuperBuickGuy]

My guess is all of it applies (less rolling resistance, cheaper cost -8 rather than 16 tires to buy, better economy). The first truck tires were hard, non-pneumatic rubber strips, but they were all singles. When pneumatic tires came out, they were tube filled, split rimmed safety hazards. I'd bet, buried in some federal reg is the requirement for dual tires above a certain weight. I'm also sure there's also an amendment that allows single wheels - but, again a guess, we don't see retread singles...

Duals are a safety issue - anyone who's pulled a heavy trailer with a dualie rather than a single wheel knows that 4 sidewalls are better than 2. That said, tire design and construction has come a long, long way since the duals were required way back at the dawn of time.
I don't get the slick bit - more contact patch=better traction. Plus, what would you rather chain, singles or duals?

[milner351]

SBG don't forget the pressure on the contact patch.

Two narrow tires are quite likely to cut through snow / slush - where one wide one will tend to ride up on top and get you in trouble.

[200kss]

I've heard from a few drivers (owner operators) and fleets that super singles are better for fuel economy. We don't do any tire replacement work so I can't say on replacement cost, mpg or tire life differences. From a PM tech standpoint, I'd rather inflate 8 large tires than deal with trying to find the valvestem on the inner 4 tires that the last guy blocked by clocking the outer wheel incorrectly. If you've checked tire psi on duals you know what I'm talking about.

[Deaf Bob]

I've heard from a few drivers (owner operators) and fleets that super singles are better for fuel economy. We don't do any tire replacement work so I can't say on replacement cost, mpg or tire life differences. From a PM tech standpoint, I'd rather inflate 8 large tires than deal with trying to find the valvestem on the inner 4 tires that the last guy blocked by clocking the outer wheel incorrectly. If you've checked tire psi on duals you know what I'm talking about.

The famous "Oh where art thou"!

[realsteelfreak]

I drive a fuel tanker every day, we stay away from super singles so we don't get stuck on the side of the road. I have drove for a tank line running singles, didn't have any issues, but always the chance. In a perfect world singles seem great , but we can't put our or anyone else life at risk. Tractors and trailers that come with singles are designed and built with a wider axle or correct offset wheel , I have seen plenty of those wider axle units changed to duals, tires sticks out about 3'' on each side.
Tires that are say 11r22.5 or 24.5 are 11'' wide x 2. A lot of companies run a 295/75 tire. Some singles are 445/50's , sizes vary I have seen 515's on the front of heavy trucks like concrete or other big 10 wheelers . You cant really worry about tread width , you have to worry about load rating.
Just my thoughts.

[Caveman Tony]

Shooooooot... I thought this thread was about these.

[SuperBuickGuy]

SBG don't forget the pressure on the contact patch.

Two narrow tires are quite likely to cut through snow / slush - where one wide one will tend to ride up on top and get you in trouble.

mmm... the wide v narrow tire debate rages on

[Deaf Bob]

mmm... the wide v narrow tire debate rages on

Yep.. 2 FJ40's.. One with wide tires, the other with narrows.. Who goes where was traded off.. Never answered definitely...

[38P]

mmm... the wide v narrow tire debate rages on

What debate? Honeywell's Bill Watson explains it all in the simplest terms (at least for vehicles a lot smaller than Class 8s) http://www.hotrod.com/techarticles/t...er_comparison/ (scroll about 60% down to the question " For us non-physics guys, please explain F=uN"

The main effect of wide tires is to change the shape of the contact patch, not enlarge it. (The Archimedes Principle proves it) Of course, going from a long and narrow "patch" to a short and wide one can have many positive (and a few negative) effects, improved flotation on soft surfaces being one of them.

There's another good explanation of the "myths" about wide tires from the AutoSpeed e-zine from the "Land of Wonder, the Land Down Under" here: http://autospeed.com/cms/title_Tyres...5/article.html