interesting read on LT tire capacity

Lots of Stuff wrote:
I suspect their has always been a reserve built into any LT tire.
Any reserve is most likely equal to the comfort level to litigation for a tire manufacture.
Looks like maybe the government wants to involve itself into that decision.
But for consumers tire sidewall load ratings are the only thing to go by when figuring loads on LT tires.

This is the way I see it.

I don't see any suggestions that this reserve should cause us to behave differently, but are some of you saying that you should use up the 10% reserve?

I added 19.5s to add an extra reserve before the reserve. :) Any guess at what the reserve is on 19.5s?

I suspect their has always been a reserve built into any LT tire.
Any reserve is most likely equal to the comfort level to litigation for a tire manufacture.
Looks like maybe the government wants to involve itself into that decision.
But for consumers tire sidewall load ratings are the only thing to go by when figuring loads on LT tires.

CapriRacer wrote:
Just so we are clear on a point:

P type tire used in LT applications (that is, on an SUV, pickup, van, or trailer) have to be derated by a factor of 1.1 - and that is now the rated capacity of the tire.

For LT tires, the rated capacity is printed on the sidewall of the tire.

If you want to talk about "Reserve" capacity (that is , unused capacity), then for P type tires, that reserve is based on the derated capacity. Put another way, in P type tires, the 1.1 factor is NOT used for "reserve". It is used because the operating conditions are different between trucks and cars.

I completely understand what you and others are saying. What do you and others think of this statement and what does it mean.

"Applicability and LTVs--Given the increasing consumer preference for using light trucks for personal transportation purposes, NHTSA is, for the first time, requiring light trucks to have a specified tire reserve, the same as for passenger cars, under normal loading conditions. The agency is also extending the tire performance requirements for passenger car tires to LT tires (load range C, D, and E) used on light trucks."

This is what makes me think there is a reserve. I am just curious.

Just so we are clear on a point:

P type tire used in LT applications (that is, on an SUV, pickup, van, or trailer) have to be derated by a factor of 1.1 - and that is now the rated capacity of the tire.

For LT tires, the rated capacity is printed on the sidewall of the tire.

If you want to talk about "Reserve" capacity (that is , unused capacity), then for P type tires, that reserve is based on the derated capacity. Put another way, in P type tires, the 1.1 factor is NOT used for "reserve". It is used because the operating conditions are different between trucks and cars.

I snipped this from the NHTSA report.

Applicability and LTVs--Given the increasing consumer preference for using light trucks for personal transportation purposes, NHTSA is, for the first time, requiring light trucks to have a specified tire reserve, the same as for passenger cars, under normal loading conditions. The agency is also extending the tire performance requirements for passenger car tires to LT tires (load range C, D, and E) used on light trucks.

I believe if you read the whole article it says the p type tires need a 15 percent reserve and there saying here that light truck tires would need the same. Again that's JMHO

grip wrote:
I'm not seeing a 10% safety factor mentioned. According to Tirerack P-metric and Euro-metric tires must be de-rated by 9% when used on a pick-up. NHSTA says 10%. LT-metric tires can be run at the sidewall listed weight at the listed pressure.

Good point on capacity reduction for P tires on a truck.
P tires on a trailer are also included in the capacity reduction per the 571.110/.120 FMVSS.

"When a passenger car tire is installed on a multipurpose passenger vehicle, truck, bus, or trailer, the tire's load rating shall be reduced by dividing by 1.10 before calculating the sum (i.e., the sum of the load ratings of the tires on each axle,....Snipped

"On the other hand, LT-metric sized tires were specifically developed for use on light trucks and provide the full tire load capacity branded on their sidewall. "

This quote tends to support using just the sidewall Rated Weight for LT tires.

dave17352 wrote:
This is a short interesting read on load capacity of LT tires. It appears to me that LT tires have a built in safety margin of 10%, as these trucks are regular used to haul loads. I don't know how to make a clicky.


http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=70

http://www.nhtsa.gov/cars/rules/rulings/UpgradeTire/Final/

this makes it look like 15%

I'm not seeing a 10% safety factor mentioned. According to Tirerack P-metric and Euro-metric tires must be de-rated by 9% when used on a pick-up. NHSTA says 10%. LT-metric tires can be run at the sidewall listed weight at the listed pressure.

My read on this is that if you use passenger tires on a van, SUV or truck, you should derate the capacity of the tire by 10% or 15% based on the links you provided. If you were to use a light truck tire on a sedan, station wagon or coupe, you could exceed the weight on the tire ratings slightly and still be safe.