Bigger steer tire

[Hammerhead]

(09-05-2016 )sbtrucking Wrote:  Hey fellas,

Does any one run bigger steer rim and tire?
With the roads being a mess lattely beating up our trucks and comfort I
want try new combo on steers and maybe on drives, plus driving team and sleeping mostly wile rolling hopping I can smooth things out a little.

I just got 22.5 x 9" alcoa steers and have on the way Yokohama 104ZR spec2
20 ply 315/80/22.5 tires, hope to run them at 80-85 psi

Also on the rears I want swap lo pros with 11r 22.5 16ply so I can drop the pressure few psi and smooth the rear end also.

What are your thoughts on this?

Steering tires:
I run big (385's) steer tires, for work not comfort. I'm a heavy haul application.
Go to a tire shop and actually look at the info on the sidewalls, 385's REQUIRE 125psi! With wide base tires having such large tread faces, they need high pressure to support the center of the tread face because the sidewall is much further away.

I have friends that run northern Canada that do exactly what your thinking. They run 385's on 12k axles with 90psi on the pavement and drop to 80 for the gravel road. If you want to run them for comfort, you have to understand that there will be a price to pay;
First: they are more expensive because there's more tire.
Second: running lower pressures means you will get less tire life. I highly recommend using "Tire Life" in them, it's a liquid that cools the tire and rim, and actively balances the tire. Tire Life is a brand name and I use three bags in each tire.
Third: change your front hub oils to a high quality synthetic oil, and plan to change this regularly. A standard 12k front axle will support these tires, IF you don't increase the weight load factor, but there is incredibly more drag with a wider tire and lower pressures and your bearings and oils will pay the price, particularly in the temps you operate in TX. Consider spec'ing a 14,600 front axle with a 16,000 steering pump and cooler on future trucks to help with longevity.
Fourth: a 315 really isn't big enough to notice a big difference, they've tried that and they now run 385's. With tires this wide you will need the rubber fender extenders to keep tire spray down.
Now here's where the math gets tricky, because these big tires with lower pressures ride softer their tires costs have gone up, but other maintenance costs went down. In their application and road conditions fuel economy isn't really reliable (1000's of miles on gravel roads that when wet throw any calculations out the window) but yours will be, and I'd like to know what you find.

The overlooked drive suspension
There is actually big improvements to be made here. Depending on your suspension. If you have OEM suspension you might be limited with what I'm about to tell you, but if you have Other suspension (ie: Neway, Hendrickson) you have more possibilities. Most suspensions have several different ratings, pay attention to that. If you have the KW 8 bag 40k axles and suspension, the 46k air bags USED to (in the 90's) fit into the 40k, check the measurements closely!
But what difference is that Hammer? They don't just rate suspensions higher for shits-n-giggles because of the axles, they make them stronger. And to support more weight, without overpressurizing the air bags they use a larger diameter bag. Larger diameter means more surface area. Larger surface area with equal pressure means more support, or INVERSE larger surface area for equal load means LESS pressure for equal support. In other words less pressure in your bags means they are softer and they ride nicer! This means you may have to do some homework, I spent about an hour looking through the parts book before I found a "suitable replacement" for my old '90 Pete with Air Trac, but I found one that was 1 1/2" larger in diameter that fit and bolted in, what an amazing difference! That's why I run 52,000lb suspension with 46k axles in my heavy haul application, to get good ride, because I'm routinely loaded to 40,000 or more on my drives. 40k for me is 57psi, I'd bet your higher than that at your legal 34k.
Not all suspensions have alternatives, remember that when your spec'ing your next truck...

Good luck, and ride SOFTLY