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Most trailer tires don't wear out — they blow out. And nearly every time, it's down to two things the owner didn't check: how old the tire was, and whether it was carrying more than it was built for. Here's the stuff that actually keeps a load on the road, from a shop that lives in farm country.
Around here, trailer and farm tires aren't a niche — half of Chatham-Kent is hauling something. But they get treated like an afterthought until one lets go on the 401 shoulder with a load of hay or a side-by-side on the back. So let me walk you through what matters, in plain English. None of this is complicated once somebody tells it to you straight.
First thing: those letters in front of the size mean something. ST stands for "Special Trailer." An ST tire is built with a stiffer sidewall on purpose — it's there to carry vertical weight and resist sway, not to steer or corner. That's the opposite job of the P (passenger) or LT (light truck) tire on your vehicle.
So two rules. Don't throw old car tires on a trailer because they were free — they'll squirm under load and wear funny. And don't run ST trailer tires on the drive wheels of your truck — they're not made for it. Match the tire to the job.
If you remember one thing off this page, make it this: the load range has to meet or beat what your trailer needs. Load range is just an old "ply rating" written as a letter. Here's the whole chart:
| Load Range | Ply Rating | Roughly |
|---|---|---|
| B | 4-ply | Light utility |
| C | 6-ply | Small trailers |
| D | 8-ply | Mid-size / boat |
| E | 10-ply | Heavy / dual-axle |
| F | 12-ply | Heavy equipment |
| G | 14-ply | Goose-neck / big loads |
The bigger the letter, the more it carries — and the higher pressure it runs. To put real numbers on it: a common heavy size like ST235/85R16 in Load Range G (14-ply) is rated around 4,400 lb per tire at 110 psi. Four of those carry a serious load. Drop down to a Load Range D in that same size and you've got a lot less capacity, and a tire that'll cook itself if you overload it.
You'll find the weight your trailer needs to carry on its data plate (the sticker on the frame or tongue). If you're not sure, bring me the trailer's GVWR or just the current tire's full sidewall code and I'll work out the load range you need. Don't guess on this one — under-rating a trailer tire is how you end up on the shoulder.
This is the big one. A car tire usually wears out before it gets old. A trailer tire is the reverse — it sits parked in the sun for months, barely turns, and the rubber rots from the inside while the tread still looks brand new. People look at that deep tread and think they're fine, then it comes apart at highway speed.
Replace trailer tires every 5–6 years, full stop — no matter how good the tread looks. Check the DOT date code on the sidewall: the last four digits are the week and year it was built (so 0921 = 9th week of 2021). If your "like new" trailer tires are seven years old, they're not like new. They're a blowout waiting for a hot day.
Most trailer blowouts aren't from a nail. They're from heat, and heat comes from running underinflated. A soft tire flexes, flexing builds heat, and heat is what makes the belts let go. Run your trailer tires at the max cold pressure stamped on the sidewall — not the pressure you'd use on a car. Check them cold before a big haul, especially after the trailer's been sitting all winter. Five minutes with a gauge beats an hour on the shoulder.
One more: most ST tires are only speed-rated to around 65–81 mph (105–130 km/h). If you're towing faster than that, you're outrunning the tire. Slow down a touch and they'll last.
Ag tires are a different animal again, and honestly there's no shame in just calling and telling me what the tire's going on. A few basics so you know the lingo:
That last point is where we come in. We've got a second supplier specifically for trailer, ag, ATV and specialty tires, so we can get sizes the box stores will just shrug at. If you've got a number off the sidewall, we can probably find it.
What we do: we stock and source trailer, farm, ag and specialty tires, we'll figure out the right load range so you're not guessing, and we mount and balance them here. Rural Chatham-Kent is our backyard — we get what you're hauling. Take a look at our trailer tire and farm tire pages, or just call with a size.
Every 5–6 years regardless of tread, and sooner if you see cracking in the sidewall or tread. Trailer tires age out before they wear out because they sit so much. Check the DOT date code rather than guessing by how the tread looks.
Enough to carry your trailer's loaded weight with margin. Find the GVWR on the trailer's data plate, or give me the size and current load range and I'll tell you whether it's right. When in doubt, go up a load range, not down.
Not ideally. ST (Special Trailer) tires have stiffer sidewalls built for carrying and resisting sway. Passenger tires flex too much under trailer loads. If a trailer is spec'd for LT tires that's a different case — check the data plate, or ask me.
Almost always one of three things: they're too old (aged-out rubber), they're underinflated (heat build-up), or they're under-rated for the load. Fix all three — fresh tires at the right load range, aired to max cold pressure — and the blowouts usually stop.
Yes — through our specialty supplier we can get trailer, ag, ATV and implement sizes the big chains don't stock. Give us a call with the size off the sidewall and we'll track it down and price it.
Trailer tires are simple once you know the three things that actually matter: right load range, aired up, and not too old. Get those right and you'll stop having roadside surprises. Farm and ag is more specialized, but that's what we're here for — bring me a sidewall number and we'll sort it out.
Trailer, farm, ag and specialty sizes — sourced, load-rated right, and installed here. Call with a size off the sidewall and we'll price it.