Correct PSI Rating for Westlake ST205/75R15 Radial Trailer Tire

Question:

Appreciate your answer on Westlake 205/75Rl15 tired, are they speed rated for 75 mile per hour, I usual cruise at 70 pulling with my trailer? Thanks Last question: I have a 2015 Chevrolet 2500HD diesel. When I purchased the truck I was told to make sure I have it the tow/haul mode so I have lights to the trailer. Is that correct, if I tow a lot less weight why must I use the tow/haul mode? But the main question is should I have lights to a trailer using my seven pin harness when not in the tow/haul mode? I can’t find anything in my truck handbook about this? Thanks for your time and effort on this question.

asked by: Jonathan B

Helpful Expert Reply:

I'm not quite sure why your dealer would say to put 80 psi in the Westlake ST205/75R15 Radial Trailer Tire # LHWL300 because they say to inflate it to 65 psi which gives you 2,150 lbs for the load rating. With 4 tires this puts you over the 8K max weight of your trailer that you referenced.

When referencing a "cold" trailer tire it actually means a tire that has had time to cool off from traveling. During travel the friction between the tires and the road builds heat inside the tires and the psi pressure increases. Once you have stopped for a while (like overnight) your trailer tires have time to completely cool off and are now considered "cold". So it really has less to do with outside temperature and more with the internal temperature of the tire (each 10 degrees Fahrenheit will only change the pressure by about 1 lb). If you don't already have a tire pressure gauge then I recommend the TireMinder # TMG-AAA-MULTI. I personally own one of these and it makes checking the pressure in my tires a breeze and I don't have to worry about misreading an analog gauge.

expert reply by: Jon G

Jonathan B.

4/24/2019

Jon G.

4/24/2019

Yes, the Westlake ST205/75R15 Radial Trailer Tire # LHWL300 does have a 75 mph speed rating. I took a look at the online owner's manual for your 2015 Chevy 2500HD and on page 9-39 it states that the tow/haul mode adjusts the transmission shift pattern to reduce shift cycling. It doesn't say anything about activating the trailer lights. You can easily determine if this is true or not by simply connecting your trailer wiring to your pickup and then testing your various light functions while someone stands behind you to see if the lighting comes on or not.