& it has VERY OLD Firestone 7.00 X 15LT trailer (or truck?) tires on it-I've read that the closest size is a ST225/75R15 load range C, D, or E-BUT I've also read that ZERO trailer tires are made in the US anymore, and the Canadian made Goodyear Marathon tires are just as bad as the Chinese ones. I still have a basically brand new set of 4 Dayton Quadra SE P235/75R15 extra load rated tires that have a narrower than standard (for the size) tread-who votes for using those instead of junk Chinese made trailer tires? Opinions?
I just bought a boat today...
- Thread starter bullwinkle
- Start date
- Status
I say, run the slightly narrower tires you have & don't worry. Just remember the old saying: a boat is a hole in the water that makes money disappear.
Boat = Bring over another thousand.
They ought to be fine.
They ought to be fine.
Here's a picture, see if this works-
http://s87.photobucket.com/albums/k129/meb727/?action=view¤t=photo.jpg
http://s87.photobucket.com/albums/k129/meb727/?action=view¤t=photo.jpg
A 7.00-15LT has a load carrying capacity of 1710# at 50 psi for a Load Range C. That's a total of 6840# for the 4 tires. I think there ought to be a 15% over-capcity in the tires - and since about 15% of the weight of the trailer is supposed on the tongue, the weight of the trailer and the boat (and everything you put in the boat (fuel, ski equipment, collers, and the beer in the coolers) should not exceed 6840#.
A P235/75R15 has a load carrying capacity of 2028# at 35 psi - and since it is on a trailer, you need to derate the load capacity by 10% to 1844#. So that's good!
Just be careful that there is enough room for the tire as it will deflect as the trailer corners. Let's do a size comparison:
A 7.00-15LT is 8.0" on a 5.5" rim with a diameter of 31.8".
A P235/75R15 is 9.3" wide on a 6" rim (9.1" on a 5.5" rim) with a diameter of 28.9".
So while there is going to be enough room under the fenders, the trailer may not provide enough romm width-wise. Please check that out!
A P235/75R15 has a load carrying capacity of 2028# at 35 psi - and since it is on a trailer, you need to derate the load capacity by 10% to 1844#. So that's good!
Just be careful that there is enough room for the tire as it will deflect as the trailer corners. Let's do a size comparison:
A 7.00-15LT is 8.0" on a 5.5" rim with a diameter of 31.8".
A P235/75R15 is 9.3" wide on a 6" rim (9.1" on a 5.5" rim) with a diameter of 28.9".
So while there is going to be enough room under the fenders, the trailer may not provide enough romm width-wise. Please check that out!
Unfortunately, every ST225/75R15 trailer tire I've used (Power King, Freestar, Carlisle, and Goodyear Marathon) on my company's tandem equipment trailer has been JUNK-extremely weak sidewalls, maybe good for 10K miles max, zero puncture resistance, and wear out like rubber marshmallows! Strangely enough, the (mostly) ancient 14.5 inch 8 & 10 ply rated bias trailer tires that I run on my old open 5' X 10' mobile home single axle utility trailer wear like iron, don't leak air, and last until chunks of rubber start flying off! Then it's off to the rural mobile home guy to spend $10 on another one (including the wheel)!
Bullwinkle hit it on the head!
Seems every so called 'trailer' tire I ever bought was garbage as well.
Seems every so called 'trailer' tire I ever bought was garbage as well.
Originally Posted By: CapriRacer
..........A P235/75R15 has a load carrying capacity of 2028# at 35 psi - and since it is on a trailer, you need to derate the load capacity by 10% to 1844#. ........
The OP says his tires are XL rated. Is max capacity rated at 50 psi, instead of 35 psi? Is there still a 10% derating for trailer use?
..........A P235/75R15 has a load carrying capacity of 2028# at 35 psi - and since it is on a trailer, you need to derate the load capacity by 10% to 1844#. ........
The OP says his tires are XL rated. Is max capacity rated at 50 psi, instead of 35 psi? Is there still a 10% derating for trailer use?
Last edited:
That is too nice of a boat to take a chance and run car tires even if they are XL's. I agree with FZ1 use only trailer specific tires for your boat.
Also 14.5" tire takes a different hub and would not work on your trl.
Also 14.5" tire takes a different hub and would not work on your trl.
Originally Posted By: SubLGT
Originally Posted By: CapriRacer
..........A P235/75R15 has a load carrying capacity of 2028# at 35 psi - and since it is on a trailer, you need to derate the load capacity by 10% to 1844#. ........
The OP says his tires are XL rated. Is max capacity rated at 50 psi, instead of 35 psi? Is there still a 10% derating for trailer use?
No, the max capacity fro XL tires is rated at 41 psi - however, it might say 50 psi max on the sidewall.
And, yes, the 10% dertaing applies to both SL and XL.
Originally Posted By: CapriRacer
..........A P235/75R15 has a load carrying capacity of 2028# at 35 psi - and since it is on a trailer, you need to derate the load capacity by 10% to 1844#. ........
The OP says his tires are XL rated. Is max capacity rated at 50 psi, instead of 35 psi? Is there still a 10% derating for trailer use?
No, the max capacity fro XL tires is rated at 41 psi - however, it might say 50 psi max on the sidewall.
And, yes, the 10% dertaing applies to both SL and XL.
Trailer tires are frequently junk, but they also run over curbs, drag against things, get dipped in salt water, sit in the sun for months at a time without moving, etc.
I have found that if I replace the trailer tires every couple years, regardless of tread depth, I don't have a problem. I do a lot of miles towing trailers, on some I wear the tires out, others I don't, but thinking of them as having an expiration date has been the end of tire failures for me.
I have also heard repeatedly that you should not use car or truck tires instead of trailer tires. I guess in some cases not-trailer tires can bounce more and cause more sway due to softer sidewalls and tread that is not optimized for going straight.
I have found that if I replace the trailer tires every couple years, regardless of tread depth, I don't have a problem. I do a lot of miles towing trailers, on some I wear the tires out, others I don't, but thinking of them as having an expiration date has been the end of tire failures for me.
I have also heard repeatedly that you should not use car or truck tires instead of trailer tires. I guess in some cases not-trailer tires can bounce more and cause more sway due to softer sidewalls and tread that is not optimized for going straight.
The best option on a trailer, if they'll fit, are 16" highway rib tread Load Range E light truck tires, with Michelin XPS Ribs probably the pick of the litter. If they'll fit, switching to 16" means buying new wheels and maybe new trailer hubs to get the correct lug pattern.
Most people don't balance trailer tires, except horse trailer tires, and that can be problematic. I've seen trailer tires bouncing down the road which can't be good for tire life. Many trailer wheels are so cheaply made that the center pilot hole is not in the exact center of the wheel. These cannot be correctly balanced between cones on the balancer and must be mounted on the tire shop's lug-centric adapter...if the tire shop has one and if you can convince the tire buster to use it. Dyna Beads balancing beads can work well--I use them in my motorcycle tires without other weights and on my pickup in addition to dynamic balancing.
Most people don't balance trailer tires, except horse trailer tires, and that can be problematic. I've seen trailer tires bouncing down the road which can't be good for tire life. Many trailer wheels are so cheaply made that the center pilot hole is not in the exact center of the wheel. These cannot be correctly balanced between cones on the balancer and must be mounted on the tire shop's lug-centric adapter...if the tire shop has one and if you can convince the tire buster to use it. Dyna Beads balancing beads can work well--I use them in my motorcycle tires without other weights and on my pickup in addition to dynamic balancing.
- Status