QuestionI have a 99 F-250 SuperDuty...please explain the differance between D and E. Why, if the stated load of a tire is say, 3300lbs @ D, and 3200lbs@E, why aren't they interchangeable?
And if it is used mainly for suburban travel (no construction use), but only for occasional pulling of a travel trailer ( tongue weight of 700lbs, total wt. 8000lbs.
Thank you,
Craig Doty
AnswerCraig,
There are a number of reasons why a tire might not be suitable.
Not enough load capacity: Load capacity is determined by the amount of air in a tire. So a larger tire - one that has more interior volume - and a stronger tire - one that can hold more pressure - have larger load carrying capacities. The difference between a Load Range D and a Load Range E is that the casing of the tire is a bit stronger - and there are a number of ways to do that, but typically a stronger ply cord is used.
Based on what is in your question, it sounds like you have a larger tire (dimensionally), but it's a Load Range D and that it has more load carrying capacity than the smaller Load Range E. Based purely on load carrying capacity, this ought to be an acceptable usage.
BUT!!!!
There are other considerations:
A tire is mounted on a rim and the rim has to be a suitable width for the tire. Usually the stock rims limit what tire you can put on. I suspect this is the problem here.
I'll bet you have LT235/85R16 LR E's on the truck now and would like to put on LT285/75R16 LR D's. Unfortunately, the stock rim is a 7" rim and the LT285's need a minimum of a 7 1/2" rim.
Another consideration is the amount of space under the fender. There may appear to be plenty of space when the vehicle is sitting still, but the tire CAN NOT touch anything when the vehicle is in motion. That means the entire range of suspension and steering travel has to be check - and that's something that is usually beyond the ability of the average tire shop, so they usually err on the side of caution.
Hope this helps.
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