QuestionI have a 1988 Prowler that I recently bought. The tires on it now are dry rotted and I need new ones. The tire size now is F78-15 which I looked up the conversion to 205/75/15. The problem I'm having is by reading all these Q&A sites, I'm not understanding what everyone is talking about. Do I go w/ SL,XL,LT,ST speed rating, what load letter??? The camper weighs 3,035 w/ 2 axles. Can you please tell me which tires to get??
Thank you.
AnswerLori,
The first step is to check the vehicle for a tire placard. It should list the original tire size and the proper pressure for that size.
Unfortunately, unlike cars and light trucks, I am not aware that anyone publishes tire info on RV's. But assuming the tires on there are the origin tires, they would be ST type tires - and they come in Load Ranges.
An F78-15ST has a load carrying capacity of 1385# at 35 psi (Load Range B# or 1710# at 50 psi #Load Range C). has a diameter of 27.3", and a width of 7.75" on a 5½" rim with an allowable rim width range of 5 to 7"
An ST205/75R15 has a Load Carrying capacity of 1480# at 35 psi (Load Range B) or 1820# at 50 psi (Load Range C) with a diameter of 27.1" and a width of 8.0" on a 5½" with an allowable rim width range of 5 to 6½". So except for the width, that is a good match - and the width is only slightly wider, probably not enough to worry about.
So your first step is to find the tire placard and see what the size and inflation should be. If you can't find the placard, look at the tire and see what Load Range it is and what the sidewall says the maximum inflation pressure is. Use those to determine which Load Range you need for an ST205/75R15.
- and, No! You can NOT use a passenger type tire! It must be an ST type tire.
