Swapping 245/75/16 for 235/65/16 Tires: What the Chain Stores Won’t Tell You
Short answer: the load capacity is not the problem here
A Load Index of 121 — which is what the 235/65/16 tires in question carry — works out to about 3,197 lbs per tire. Multiply by four and you have roughly 12,800 lbs of total rated capacity. A 1993 D250 used as a daily driver that rarely sees 700 lbs of cargo doesn’t come close to stressing that number. The tires are not undersized for the job.
The national chain stores refusing the swap isn’t about safety math. Their corporate policy blocks anything outside the vehicle manufacturer’s original tire specification — a liability hedge, not a judgment call about whether the tires will hold. A local independent shop doesn’t carry the same policy burden and can make that decision case by case.
The diameter drop is what actually changes the truck
This is where it gets interesting. Going from a 75 to a 65 aspect ratio sounds like a small tweak, but the numbers aren’t subtle:
- LT245/75R16 overall diameter: approximately 30.5 inches
- 235/65R16 overall diameter: approximately 28 inches
That’s about 2.4 inches less overall, or roughly 1.2 inches less radius. The truck sits lower on these tires. On a vehicle already lowered 3.5 inches, that means the ride height drops a bit further — probably not a problem if the goal was a cleaner, tucked look, but worth knowing it’s cumulative.
The bigger practical effect is the speedometer. It was calibrated for tires measuring around 30.5 inches across. With 28-inch tires spinning faster for every mile traveled, the gauge reads about 8 percent high. At an indicated 60 mph, actual speed is closer to 55. Nothing dramatic, but real enough to matter if you’re pacing traffic or watching for posted limits on a longer drive.
Width is almost a non-issue
The width drops from 245mm to 235mm — a 10mm difference, under half an inch. Visually indistinguishable. No meaningful effect on load capacity or handling at the speeds and weights this truck will see.
What Load Range C actually means for this truck
Load Range C tires are built for light truck and commercial applications, rated to handle higher inflation pressures and sustained loads than standard passenger tires. Six-ply equivalent construction. They show up on cargo vans, service trucks, and exactly the kind of vehicle that gets loaded and driven hard on a regular basis.
For a truck carrying at most 700 lbs on rare occasions — especially one that’s been modified for aesthetics rather than payload — a C-range tire is more than adequate. The question the chain stores are asking (“is this tire rated for this vehicle’s GVWR?”) isn’t the same question as whether the tires are safe for how the vehicle is actually used.
Getting the swap done at a local shop
Independent tire shops handle non-spec swaps regularly. The conversation is usually brief: you’re aware these aren’t the factory spec, you want them anyway, can they mount and balance. Most will say yes without hesitation.
A few practical things to sort out at the appointment:
- The 235/65/16 mounts on 16-inch rims — a direct match, no fitment issue there
- Ask the shop to set inflation to the tire’s recommended pressure for your actual load, not the door jamb sticker (that sticker references the original 245/75 size)
- Once mounted, check for rubbing at full steering lock before any real driving — the lowered suspension combined with a narrower tire usually helps clearance, but it takes about 30 seconds to confirm
Ground clearance: the cumulative picture
Between the 3.5-inch suspension drop and now a tire that’s 1.2 inches shorter in radius, total ground clearance is well below stock. Fine for pavement, but worth factoring in if there are any driveway transitions or parking structures that were already marginal before the suspension work.