On Sun, 2 Apr 2017 05:32:04 -0700 (PDT), wrote:

Watch out for speed rating.
If you car OEM calls for a speed rated
tire, they may try to force you
to that more expensive choice.
Looks like even the online guys do that
if you search by vehicle le type.

Your point is valid which is that a speed rating (e.g., W or V or Z) can be
used as a marketing tool, and which may not necessarily have anything to do
with tire safety.

The speed rating isn't about speed anyway - it's about temperature - which
is really about dissipation - which is a function of heat generation at
speed - all of which is determined by vehicle size, weight, road friction,
and, of course, speed.

Therefore, IMHO, anyone who takes the speed rating literally, is a fool.
It's all about how you use the tires and how they're constructed.

In effect, there is no such thing as a "speed rating" since the speed
rating that a passenger tire receives is really a "heat rating" or more
correctly, a measure of the heat-generation-and-dissipation rating, where
the generation of heat is greater at speed due to the double flexing of the
sidewall happening faster and faster as speed increases.

If you're comparing two tires for construction, you first look at the load
range before you even bother to look at the speed rating or temperature
rating. Any tire that is below the load range of the OEM tire is not a tie
you should consider (and which nobody reputable will sell to you anyway).

Along with the load range, you can look at the "ply rating", which is in
terms of standard load (SL), light load (LL), extra load (XL), etc. which
gives you a further indication of construction.

After the load and ply ratings, you have the temperature rating (which is
related to speed as described above) and the speed rating itself (which is
really a heat-generation-and-dissipation rating).

All these specs intertwine to prove a pretty good indication of the
construction of the tire.