Its obvious how load range affects tire load capacity, but how do higher and lower load ranges effect offroad performance

[LocalmotionSC]

I'm curious how higher load range tires fair offroad. If you have a high GVWR vehicle you don't really have a choice in the matter, but I'm still curious what tradeoffs are made in going with a higher load range tire. They generally run much higher PSIs (sometimes upwards of 120 psi), does this mean they cannot be aired down to the same extent as lower load range tires? or that the rated load decreases with lower psi's? I wonder how higher ply counts effect strength and/or flexibility?

 

[rayra]

typically higher ply counts go directly to resistance to puncture, a stiffer carcass and less rolling resistance (combined with higher pressures). But typically A/T tires are a softer 'grippier' rubber compound which doesn't mesh well with sharp rocks etc when running underinflated.
But since most 'ExPo' vehicles tend towards being overloaded, the higher load rating is the more important aspect. You can still air them down just fine. You'll have to ask the rock crawlers for the finer aspects of running a near empty tire and issues related to load rating.
what it really comes down to is there isn't an single 'best' factor. Depends on your intended uses and needs, the reality that most of these vehicles are used overwhelmingly ON-highway, your preferences and available budget. And speaking of that, a few simple choices can double or halve your total costs. A relatively useless additional 7mm of ground clearance can cost you a lot more money.

 

[jadmt]

I run e rated tires on a 4 door Wrangler and air down to 10-15 psi off road And get good traction. Lowering psi does lower load capacity and toyo has a formula for showing how load capacity drops with lower psi. an e rated tire most likely won’t give ultimate off road traction like a lower rated tire because the stiffer carcass won’t wrap around rocks as easily but I have never been limited by traction and I would rather have the added puncture resistance.

 

[javajoe79]

Worth noting is the load rating really comes in to play at speed and definitely relies on the correct psi. If you’re not traveling fast enough to build up heat in the tire, you can be aired down and not damage the tires. If you have bead locks you can go really low.

 

[luthj]

As far as traction goes, the softer the sidewall, and the rubber compound, the more conforming, and the better the traction. Of course that means the tire is easier to damage, and has a lower max pressure, and thus load at speed.

Airing down should be measured as a proportion of sidewall height compared to properly inflated for highway speeds. Using just pressure does not take into account vehicle load.

A tires load rating is primarily driven by sidewall flex. The more the sidewall flexes, the more heat builds up. Reducing sidewall flex means higher pressure. To handle higher pressure the tires carcass/sidewalls get thicker/stiffer. This is why heavy truck tires can handle 100+PSI, and are very heavy to hold the pressure/weight.

 

[billiebob]

running a tire matched to the GVWR is the best option

If your vehicle is rated to run C Load Range, running D or E will make the ride harsher and send more of the shock, vibration thru the chassis. Running the correct tire will add reliability, durability to your rig..... so will staying under your vehicles GVWR.

 

[grogie]

If your vehicle is rated to run C Load Range, running D or E will make the ride harsher and send more of the shock, vibration thru the chassis. Running the correct tire will add reliability, durability to your rig..... so will staying under your vehicles GVWR.

I had always heard that too. With running Goodyear MT/Rs, I went from 32" Cs to 33" Es and noticed no difference in ride.