Sidewall stiffness an independent factor in ride quality or not?

[NY2LA]

Since my New Year's resolution is not to ask any more about tires here, I figured I'd post one more tire thread while I still have time.

I read in an article the other day that stated ride quality is the same at any given PSI among LT tires of any load rating. Ie, a D load tire at 45 PSI will have the same ride characteristics as an F load at the same PSI, assuming they both can be safely operated at that PSI.

What do people think of this claim? It doesn't make intuitive sense to me. Just because two tires are at the same pressure, that wouldn't seem to mean that they flex in the same way if they have differences in sidewall stiffness when encountering a bump. Or would it?

It seems like the answer to this question could affect people's choice of tire for the 200, as there are LT options ranging from C to F for our truck. I too am still thinking about what approach to take with tires and suspension once I get the Blizzaks off my 200, so I'm trying to wrap my head around issues like this.

 

[grinchy]

Well, I have e rated 129 load lt tires and at the right psi they feel great. If I run them a couple psi low, they are too soft, and a couple psi high they are too stiff. The window is very narrow, like 2 or 3 psi wide.

When I ran 125 load e rated lt tires, the window where they felt acceptable was a wider psi range, like 5 or even 7 psi.

of course there are other variables than the load index. The 125 were hybrid tread but two ply sidewalls, and the 129 are at tread and 3 ply sidewalls. And they are 2” different height, weigh 15 lbs different etc.

summary I suspect load index informs the ride more than c d e or f rating.

I expect further discussion to provide better insight than this.

 

[Madtiger]

Good thread...been wondering the same. I have BFG KO2 285/60/18 118/115S Load range D. I really like the ride even at 46 psi. I swear that it is not that much different from stock OEM Dunlops...but i could be remembering wrong.

 

[Taco2Cruiser]

Since my New Year's resolution is not to ask any more about tires here, I figured I'd post one more tire thread while I still have time.

I read in an article the other day that stated ride quality is the same at any given PSI among LT tires of any load rating. Ie, a D load tire at 45 PSI will have the same ride characteristics as an F load at the same PSI, assuming they both can be safely operated at that PSI.

What do people think of this claim? It doesn't make intuitive sense to me. Just because two tires are at the same pressure, that wouldn't seem to mean that they flex in the same way if they have differences in sidewall stiffness when encountering a bump. Or would it?

It seems like the answer to this question could affect people's choice of tire for the 200, as there are LT options ranging from C to F for our truck. I too am still thinking about what approach to take with tires and suspension once I get the Blizzaks off my 200, so I'm trying to wrap my head around issues like this.

I have to agree. Load rating is a change of the number of plys on the thread, not the sidewall.

The number of plys on the sidewall can change ride stiffness, like going from a 2 ply to 3 ply sidewall. That said, some tires just ride harder. Take Cooper STT Pros vs BFG KM3. Both with 10 ply thread ply (E rated) and 3 ply sidewalls. The STT Pros just fell stiffer when under the same truck (but better in every terrain if you ask me). Go to Nitto Ridge Grappler vs BFG KO2, Ridge Grapplers are a bit stiffer. All the same tread and sidewall ply, just how different companies make their tires.

On a 3rd gen Tacoma access cab I built for guy to live in for the foreseeable future. I wanted to put E rated tires on it, but he wanted C rated tires. Same exact tire, just different load ratings. Well, we did what I recommended and put E rated on it. He did a two week shake down, and said it was too stiff, and I switched him to C rated. He did another shake down, and came back and said that he couldn’t tell a difference and wanted to remount the E rated. He set out for Colorado, annndddd... flipped the truck. It drove all the way back to me, the insurance company totaled the truck, and he bought a double cab long bed, and we built it, again (this time with a big Alucab on the back. So when it came time for tires, I was like, “C or E?” He said, yeah, couldn’t tell a difference in ride, but the C did “squish” more when aired down. But with his weight, and trying to get him down to no higher than 20 psi off road, I felt more comfortable with him on a E rated.

But again, just thread ply count changes, I’ve never experienced that.

 

[Willie G]

Found this : Tires – Sidewalls vs Air pressure | Automotive Thinker - Discussing the finer points of automobiles

Hope it is useful.

 

[Taco2Cruiser]

Found this : Tires – Sidewalls vs Air pressure | Automotive Thinker - Discussing the finer points of automobiles

Hope it is useful.

I didn’t see anything in that article about thread plys, just sidewall. Did you mean to post that article or was it a wrong copied link?

 

[bloc]

My understanding is sidewall stiffness is a very small percentage of overall “tire spring rate” compared to what is provided by inflation pressure. And when you consider what happens to even a very stiff sidewall tire when deflated to 5psi vs 15, you can see that the tire pressure is a critical factor in what is actually suspending the vehicle.

 

[TeCKis300]

I would strongly disagree with the OPs articles assertion. Perhaps they may be making the point that pressure makes a larger impact, which it does, but I would agree with your intuition that sidewall load rating also makes it difference. A lesser factor, and maybe not enough for everyone to appreciate, but there are qualitative ride differences.

We know that ply rating doesn't necessarily correlate to physical plies any longer with modern tires. What I have found is that higher load rating tires may differ more incrementally in their plys, with the steel belts having more cords per inch and perhaps heavier gauge cords to handle higher pressures. Plys may be incrementally heavier and stiffer/stronger/less chip resistant compounds to hold up to loads.

I recall a story with BFG KO2s in the Raptors development. BFG only had LR-E KO2s. Engineers at Ford were not satisfied with the ride quality, and being a large enough customer, sent BFG requirements for a LR-C variant. Which is why you see the Raptor size tires LT315/70R17, as one of the rare larger sizes with both C and E load variants.

I would also say that tire sidewall geometry on wheels have an impact to ride. Taller obviously as there is more sidewall. But wider relative to wheels can help too as the sidewall is more rolled over and able to deflect more readily vs a square fitment.