Sidewall vs volume for dampening (1 Viewer)

[highfructose]

Would any engineer minded folks care to comment on whether the damping offered by tires comes from the height of the sidewall (and thus slight crushing of the tire when you hit a bump), the total volume of the air (and thus temporary stretching of the totality of the tire when hitting a bump), both, or some other combination?

I’m considering 285 75 r17 and 295 70 r18…one which has a bit more sidewall while the other (I think) a bit more total volume inside the tire.

I’m wondering which one (load range e) would offer the softest ride at 35 psi.

 

[OSS]

I’m no engineer, but the way I understood it (maybe incorrectly) is that the taller the sidewall, the potentially cushier the ride when aired down.
But every tire, no matter the size, will ride harsh at high psi.
Tires with taller sidewalls handle worse at lower pressure than smaller sidewall tires.
The higher the load rating, the more harsh the tire will ride when compared to a similar tire with a lesser load rating.
I know from experience that a Load Range C tire rides a lot nicer than a Load Range E.
Has to do with sidewall flex.

 

[grinchy]

If you’re after a compliant ride focus in on ‘flotation’ tires. Most are 12.5” wide but you can find in 10.5 and 11”.
These almost always have a 121 load or less, so you get the sidewall height and the more complaint ride. The 295/70 will have a 129 load.

 

[bloc]

The higher the load rating, the more harsh the tire will ride when compared to a similar tire with a lesser load rating.

I'd add, *at the same tire pressure*. OP isn't asking about them but some tires are offered in non-LT flavors and these can get away with quite low pressures while supporting the same load as those LT's, and this will drastically impact ride quality as you note.

Good points in general though.

 

[highfructose]

If you’re after a compliant ride focus in on ‘flotation’ tires. Most are 12.5” wide but you can find in 10.5 and 11”.
These almost always have a 121 load or less, so you get the sidewall height and the more complaint ride. The 295/70 will have a 129 load.

Sort of looking for the perfect around town ride but with the potential to increase air pressure for a stiffer less floaty ride on the highway.

(Within the oem wheel/tire weight envelope for an lx570 of approximately 76 lbs to 86 lbs):
There are c rated tires in the 285 75 r17 range which offer 8.45” of sidewall but will need to ride at 35 psi minimum (50 max).

There is a eurometric 295 70 r18 116 that offers 8.15” of sidewall but can be run at 30 psi (44 max).

The c rated offers a maximum tire load 23% over stock while the 116 load eurometric is 12% over the maximum load of the oem tire.

Based on my limited understanding of this topic, the higher potential load capacity is roughly analogous to how “tough” the tire is…how much abuse can the carcass, when properly inflated, “manage” without risk of failure.

So the load c is a tougher higher psi tire but may offer a harsher ride…unless the slightly extra sidewall offers a bit more flex.

And the 116 load tire may offer a nicer ride though at the sacrifice of a bit of tire toughness (and this particular recon grappler tire, for all I know, may howl on the highway-it’s a new tire and there isn’t much real world data on it).

It would be nice to know how “tough” a 116 load tire is compared to a load c. I’ve seen one brief video from cooper showing how tough their tires are in one test…

 

[bloc]

There is a eurometric 295 70 r18 116 that offers 8.15” of sidewall but can be run at 30 psi (44 max).

While this will technically support the load without nuking the tire, you’ll find that it will wallow around everywhere and not handle cornering or emergency maneuvers well. That is a significantly larger sidewall at lower pressure than stock, and that tall/soft sidewall just can’t support a vehicle this heavy when cornering. I ran P285/70r17 as low as 27psi which is also “safe” but it was not confidence inspiring, to say the least.

Not really an issue if you only do this on gravel, but any road miles may be asking for trouble.

 

[scottm]

My stock tires at stock pressure felt wallowy. Wife and I spent a week driving out east in the new truck and she liked the ride. New taller, skinnier AT all-weather Nokian tires at same pressure are less wallowy, still soft, a bit noisier, but that pressure is too low for these tires to run all the time. At proper pressure of 42psi, new tires are quite hard, to the point they bounce and lose grip on bumpy curves at highway speeds, wife doesn't like the ride, I don't love it. But they are awesome in slush and snow at highway speeds at the higher pressure.

For long drives with the wife, I air down for her comfort and we like the ride, I notice a little noise. For slush or rain, and for my weekly long drives where I don't know what I'll encounter, I air up to 42 or more and they are quieter and stiffer, less comfortable. I don't air down for around town, not worth the effort.

These are heavy and hard tires, no getting around it. I don't think soft ride is volume or height, it is stiffness and that is a combo of how they are built and air pressure. At max pressure of 80psi, I can't imagine how unpleasant that would be, and how fast the tread centers would wear.