Speed rating and load rating

[Gecko123]

Two years ago I was going to purchase some General Grabbers tires. I ordered them and they arrived at the tire store. When it came time to install them the tire tech said my vehicle is original rated for H rated tires and the Grabbers are only T rated and I had the option to not have them installed. I decided not to install them because I thought there must be reason they warned me. They don't gain anything for telling me this of course.

Any way what are your thoughts. Is it critical to have H rated tires. I assume they are stronger and not that anyone would go beyond an T rated tire speed on a 4runner that would be nuts.

Is there more flex on a T rated tire?

 

[ebg18t]

I wouldn't worry about the lower speed rating.. I don't think I have had my truck over 75mph. I just worry about load rating. My current tires are only 'Q' rated. You will find many Offroad (MT) and AT tires fall into the T, R and Q categories.

Quote from tirerack.com
link to below info:

Beginning in 1991, the speed symbol denoting a fixed maximum speed capability of new tires must be shown only in the speed rating portion of the tire's service description, such as 225/50R16 89S. The most common tire speed rating symbols, maximum speeds and typical applications are shown below:

L 75 mph 120 km/h Off-Road & Light Truck Tires
M 81 mph 130 km/h Temporary Spare Tires
N 87 mph 140km/h
P 93 mph 150 km/h
Q 99 mph 160 km/h Studless & Studdable Winter Tires
R 106 mph 170 km/h H.D. Light Truck Tires
S 112 mph 180 km/h Family Sedans & Vans
T 118 mph 190 km/h Family Sedans & Vans
U 124 mph 200 km/h
H 130 mph 210 km/h Sport Sedans & Coupes
V 149 mph 240 km/h Sport Sedans, Coupes & Sports Cars

 

[berettashot117]

which grabbers did you get? the red letter or the AT?

 

[Gecko123]

i didnt end up getting them. I got michelin latitude HP instead

 

[JB.]

Two years ago I was going to purchase some General Grabbers tires. I ordered them and they arrived at the tire store. When it came time to install them the tire tech said my vehicle is original rated for H rated tires and the Grabbers are only T rated and I had the option to not have them installed. I decided not to install them because I thought there must be reason they warned me. They don't gain anything for telling me this of course.

Any way what are your thoughts. Is it critical to have H rated tires. I assume they are stronger and not that anyone would go beyond an T rated tire speed on a 4runner that would be nuts.

Is there more flex on a T rated tire?

First off, I think the tire guy made a mistake. I doubt any 4th gen ever came with H rated tires. I don't even think they came with T rated tires. Maybe in the later years. My '05 Limited came with S.

The refusal to mount anything with a lower speed rating is just a liability concern that is up to the particular shop.

H speed rating has traditionally been the threshold where tire construction has included one or more cap plies laid over the steel belts to restrict centrifugal tire growth at high speed which can weaken the belt bonding eventually resulting in a belt separation (throwing the tread). H rated tires also marked a spot where there was a significant reduction in tire failure rates. It wasn't a smooth curve. There was a big reduction starting at the H rating threshold. They are simply more robust tires and the failure rates, even at moderate speeds, are lower than lesser speed rated tires.

Safety practices have changed a lot in recent years accelerated, I gather, by Ford/Firestone. Most recently designed SUV tires (to the degree I've looked) at lower than H speed rating (which is the vast majority) have cap ply construction which narrows the failure rate gap with H rated tires and affects the consistency of the meaning of speed ratings lower than H. Given an S rated tire with a cap ply vs a T without, I'd take the S, but the point seems to be becoming moot as the trend seems to be toward nearly universal inclusion of such construction. The presence of a cap ply was my only non-negotiable filter when buying tires the <a href="http://www.toyota-4runner.org/performance-zone-tires-wheels-exhaust-superchargers-more/89432-ongoing-review-revo-2-lt-load-e.html#post779793" target="_blank">last</a> time, not so much because of a huge safety concern, but simply because it seemed silly not to take advantage of such a simple and effective feature.

So that you don't have to wonder how much some poster on the internet knows, much of this information comes from <a href="http://www.toyota-4runner.org/general-discussions/110300-ask-tire-engineer.html" target="_blank">this</a> guy.