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quote:Originally posted by Irlpguy
Quote:
quote:Originally posted by Tom S.
I'm merely repeating what the rep from Tredit told us at the rally. He said it is the result of the Ford/Firestone fiasco. In his words, it is not an advertised fact (I'm reading between his lines here: because they don't want the public to push the tires to that limit.) but the government told LT tire makers (he said nothing about passenger car tires, probably because we weren't discussing them, nor does Tredit supply them) to manufacture their tires with a 15% safety factor. If you want to correct him, I'll try to find his name and number, or you can come to next year's rally and call him out on it. Given his job, I'm pretty sure he an expert.
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Tom since you did not identify your "source", my reference was obviously not directed at anyone at Tredit. The link I provided is an official ruling, where interested parties presented their cases and rules regarding safety/reserve were set. The provision that automobile and LT manufacturers must not rate the capacity of their vehicles on the Max DOT load @ pressure rating of the tire, but must reduce that by what amounts to approximately 15% of the DOT rating. The tire remains rated at it's DOT rating not more and not less. Look at the tire stickers on any car or LT, you will never see the load rating as high as the DOT rating stamped on the tire, the recommended pressure and load will always be reduced. This is what for an LT tire provides the safety factor and load reserve.
There is no such requirement for vehicles using ST tires, if there were, manufacturers would only be able to set the load capacity based on 85% of the DOT rating. Because there is no ruling on anything but automobile and LT's, trailer manufacturers are able to rate their "vehicle" at the full capacity as stated on the tire.
Because Keystone puts Goodyear Marathon ST tires rated at 3402 on Dexter axles rated for 7k each, Keystone must reduce the GAWR on units with 7k axles down to 6750 so that the the least common denominator is taken into account, that being the tire. This is the case with all of the manufactured units using these tires on 7k axles. The law is that if you reduce the capacity of an axle with a tire rated less than the axle, then the VIN sticker must reflect that, it does on mine and any others I have looked at.
How is the mysterious 15% safety margin to be accomplished in an ST tire other than to have the DOT rating reduced by 15% when they are reflecting the load capacity on the VIN sticker.
I have provided a link to official documentation regarding reserve capacity and have asked that if anyone can dispute this or provide any other information that proves an LT tire has a built in reserve capacity to step up to the plate and provide it.
I suggest folks read the information I provided in the link.
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I suggest you read it too. From the summary:
(5) Tire Selection Criteria/De-Rating of P-metric Tires - the agency proposed retaining the de-rating percentage of 1.10 for P-metric tires used on non-passenger car vehicles and revising FMVSS No. 110 to specify that
the determination of vehicle normal load ("reserve load") on the tire be based on 85% of the load at vehicle placard pressure.
(emphasis added by me). Looks to me like the Tredit rep was right.
But then I'm no tire expert either.
