[rickst29]

Complex reply.

Older '2518' models (if I recall correctly) were built with a "3500 lb" axle, which provided adequate height for only 14" tires before the diameter of the tire would rub against the of the wheel well.

In many cases, owners could add the "lift kit", raising the body and frame about 1-1/2" higher above the axle. That increase in height has generally been adequate to allow for the use of 15" tires on those models.

But newer models (including this 2023, and probably yours as well) are built with a "5200 lb" axle. The axle itself is taller and stronger, creating about 1" more height between the pavement and the "top of the wheel well" -- also allowing for 15" tires. I have an older 2619 built with the larger axle of that year, and use 15" tires with no "lift kit" and without rubbing issues.
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But, if you have changed the "15 inch" tires, the diameter at the edge of the outside of the rubber tread might not be the same as "OEM" tire size. The outer sizes of 15" tires are described by the first additional number in the size specification as follows:

"225/75R15" is typically about 28.3" tall, that might be to close (and allow rubbing). If you switched downwards in size to "205/75R15", the tire would be less tall( 27.1" total) and also a bit less wide (about 8.1", down from about 8.9")

HALF of the that difference (roughly .6 inches) would be a reduction between the wheel hub and the top of the wheel. The other reduction on height would be between the wheel hub and the pavement, lowering the wheel (and your TM body) about .6 inches closer to the ground.

Most of the tires in that size are load range "D", which is roughly 2150 lbs per tire. That figure is right at the limit for a fully loaded 2518 (4580 lbs mus about 320 lbs of tongue weight). But a few tires with that smaller size are also available as load range E tires.
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The other possibility is that your torsion bar axle has "worn down", reducing the angle of drop between the axle body (containing the spring bars) and the mount hub arm. If that has happened due to overloading or component failure, the angle is too flattened at even light loading - the mount hub is to high in comparison to the axle, the and large-diameter tire can rub.
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Repair or replacement of a failing axle is costly. If If your current tires are 225/75 R15 and the axle seem "mostly OK", it would probably be most cost-effective to simply switch to tire size 205/75R15, while maintaining the same load rating (D or E).

I don't know the method attachment for the current axles on more recent TM models. If they are bolted the frame members (rather than welded), a small spacer like the old "lift kit" might solve the problem (although the original lift kit, built for the "3500 lb" axle, is probably not exactly the right size to set between the bigger axle and the TM frame)