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Old 02-01-2020, 08:55 AM   #7
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Cool Re: Effect On Handling of Tires With Different Speed AND Load Ratings on SAME Axle?

Originally Posted by CapriRacer View Post
First, THEE most contributor to sidewall stiffness is
inflation pressure. You get a much harsher ride when you
add inflation pressure than you get between load ratings of
the same make/model tire.

Plus. load ratings and speed ratings aren't necessarily tied
to sidewall stiffness - BUT - higher speed ratings TEND towards
stiffer sidewalls in order to get better handling (quicker
response.), but not always, and there are so many exceptions,
it's almost wrong to say what I just said.

Load ratings are a bit more difficult to explain. If we are talking
about passenger car tires, sidewall stiffness (that is ride harshness)
varies more between makes and models, than between Standard
Load (SL) and Extra Load (XL) - and as I explained above, the
difference of a single digit load index in the same size is not really
a difference.

But in LT tires (ones that use Load Range), within a given make
and model, a higher load range will have a stiffer sidewall - BUT -
that stiffness will be over shadowed by the inflation pressure.

Put another way, if I operate a Load Range C tire at 50 psi, it will
ride harsher than the same make and model tire in a Load Range
E at 40 psi.

What an education! Thanks!

As far as the 93V thing goes, the tire decal on my Accord does specify that load & speed, yet now, ten years after its assembly, that combo seems scarcer than hens teeth - at least in the size tire this Accord requires. I'm a stickler for specs, Capri, that's why I pushed that point. But given what you said, I guess I can deal with 94V, especially if I routinely haul bagsa cement, ay'know whadd I mean?

So your suggestion is, watch those pressures. And that I do, weekly, let alone monthly.

An anecdote:
Over a decade of helping out family, friends, and colleagues with their vehicle's tire pressures, I have noticed the following pattern:

45% of folks tires are overinflated, 45% are underinflated, and about 10% are anywhere near OEM or specified cold pressure!

Most of those that do regularly check, at least once per month, are of the school that 'higher pressure is better'. Many even run the Max Cold numbers on their vehicles, or, at least 5psi over what is specified on their vehicle's load and tire placards. You pretty much know whose car we all pile into for long trips - and it's not one of those!

Those that don't check, or even know what a gauge looks like, their tires are all over the map: One tire, spot on. The other, waaaay overinflated, and the remainder, somewhere around 20-25psi. smh.. And they're complaining about having a hard time controlling their car, or thinking it needs aligning, etc.

Then I come along, do what I have to do, and to them, it's like I put all new tires & suspension parts on the thing! smh They never realized that their vehicle could actually handle! And we're not talking Mazzos and Beemers here, just every day whips.

Capri: How do we pull vehicle operators in from the two inflation extremes?

Everyone would enjoy driving more, be less grouchy and road-rageous, and help the planet also!

Last edited by RidingOnRailz; 02-01-2020 at 11:50 AM.
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