Load Range H Steer Tires

While tire shopping for new steer tires, I noticed that some tire models come in a Load Range H (G is standard for 22.5 and 24.5). My tractor is running Michelin 275/80R22.5's (G rating) right now, and they have some issues. The 275/80 size is kind of rare (I think Michelin made it up) and I'll be looking for a 295/75 for a replacement to match my drives. Here's where it gets interesting for me.

Most steer axles are rated at 12,500lbs - give or take, and that works great for most tractors. My tractor is a Volvo 780 with a Cummins engine and a 13 speed, and it puts alot of weight on the steer axle. I think the bobtail weight on the steer axle is somewhere around 11,200lbs.

The truck is equipped with a Wabco Air Ride steer axle, rated to 13,200lbs. I'm trying to figure out whether this gives me any slack on the scales - where 12,000lbs is the limit in most states I travel. It also brings in the question of Load Range H tires, to match the capacity of the axle.

Load Range G tires are rated to 6,175lbs (single) and that adds up to 12,350lbs. This seems to be just fine for those 12,500lb axles on most trucks.

Load Range H tires are rated to 6,610lbs (single) and adds up to 13,220lbs - and that matches the 13,200lb steer axle max I have.

I'm sure the H rating will ride stiffer, because of the added plies, and that doesn't make me a happy camper. But the real question is, are there allowances at the scales for the added rating? The difference in ratings also limits my choices, and it has to raise the price on the tires, would it be worth it?

To include some details, I pull a dry bulk hopper trailer on regional (and some long haul) runs. I run at 80,000lbs - or as close as I can get to be legal. Alot of the customers have a dirt or gravel yard to load and unload, and I have to run deep tires on the drives - or risk getting stuck. The steer tires have to be able to handle rough surfaces (sometimes railroad tracks - although I try like heck to avoid it), and alot of highway miles.

Thanks in advance for your help and advice.

 

The main issue I'm having with the steer tires is an uneven ride, sometimes it feels like they're out of balance. I've had them spin balanced, and it didn't change a thing. It comes and goes, but it basically feels like they're out of round, or they have flat spots. They are starting to air check some, but hopefully they'll pass my DOT inspection this month.

When I bought the truck last February the steer tires were about 70%, so I left them alone, and the drives were recaps so they got replaced. After that, the truck stayed parked until October (long boring story). Everything else was fine on the truck (luckily), but the steer tires felt like they'd flat-spotted - bouncing and shaking the hood.

I've had to run them because I still don't have the money to buy tires, but they need to be replaced before I tear something up. So I'm just going to force the issue and get them changed sometime next month, along with an alignment and some front shocks. I figure it's best to do it all at once, and then sometime soon down the line I need to pick up some Centramatic ring balancers.

The air ride axle is a different feel, and it took some getting used to. I don't see that it makes a difference going down the road - still pretty stiff on large bumps (and OK on I40 feels like railroad ties). The only benefit I've seen so far is on rough terrain at low speeds, it moves easier than a sprung axle and smooths some of it out. The air bags are starting to rip, one is leaking badly right now, and they'll be $550 to swap out. So there's definitely a downside. As far as the feel on the road, it's like the difference between a classic car and a new one - with the air steer being the classic - some of the steering feel is lost in the difference.

Running more weight on the steers isn't something I'd like to do, it has to do with the balance on this tractor. I've heard from alot of people that between the set-back steer axle, the added weight of the Cummins and 13 speed, and the fact that it's a 780, it's going to be nose heavy no matter what. Even with the tanks (2x150) slid back to the drives, it still rides at 11,200lbs on the steers with full tanks and no trailer. I plan to add an APU when I can afford to, carry chains on a carrier, and maybe add a cattle guard because I run in the sticks alot - and I'm worried the steer axle will be over 12k without a load. I guess I'll find out when I get that far, and deal with it then!

Thanks for the advice everyone, I'll plan on going with Load Range H tires - maybe it'll get me some slack when I need it. I plan to stick with Firestones to match my drives, and it looks like the FS507 is about my only choice for now. Who knows, they might even stand up better to the farm terrain I wind up on sometimes!

 

I've been running my steer tires at 105 (I think max is 110 - I'll have to check the sidewalls), and the rest at 100. Since I've got to run these for another month or so before I can afford to change em, I'll try running them at max. They can't get any worse, and maybe they'll roll round for a change.

Yeah those front airbags are really close in, being nearly under your feet! I'll bet that would wake you up in a hurry trying to figure out what's what. One of mine has been leaking air for about 15,000 miles - talk about a suspense story I'll have them changed out before I roll again, as there's no way I can pass a DOT with that going on.

 

Talls would help this truck alot, what gears are you running in your drives? It'll be awhile before I swap over - what with the cost of wheels and tires, etc. If I knew height wasn't a concern (it's not with what I'm doing) I would've gone with 11R's myself. Your truck has got to be way up there with 11R24.5's - got a picture?

And good to know on the fuel mpg, I get about 6mpg running at 80k - I just hope that won't change when I flash the ECM at the next service. How's the ISX at 535? Mine pulls well at 475, but sometimes I think more power would keep my foot lighter.