GlampingWithCats.com

Time to Make the Donuts!

Sparta, WI, August 2025

Time to buy the donuts would be closer, but they are tires, not donuts. A diet does strange things to your mind… mmmm, glazed all weather radials…

Some of the pictures are not perfectly focused, but they are good enough to see what is going on. If you were not aware, a penny can be used to check your tread depth. If you can see the top of Lincoln’s hair, you need to replace the tire. If they ever change the penny, the tire companies will probably lobby to have Lincoln’s head further from the edge, so you have to change your tires more often. Even if the tread is not worn out, the general guideline is that RV tires should be replaced every five years for safety.

Driver side front is low tread
Passenger side front is low tread
Driver side rear tread is fine
Passenger side rear tread is fine

Currently, the front RV tires are getting close to worn out. These tires are more worn on either outer edge than the middle. This can be for several reasons, including cambered axle. Since the front axle is cambered, there is a good chance that it is not an issue.

Not surprisingly, it will probably be expensive to replace the tires. Even cheap RV tires are about $150 each as a minimum. Good ones are probably closer to $250+. Higher rated ones are closer to $300+. More surprisingly, tires are confusing. Being lighter, passenger car tires are a lot simpler and weaker. For larger and heavier vehicles, you need to worry about dimensions, load rating, load index, and speed rating. The tires that are currently on the RV are Goodyear Endurance ST235/80R16 123N/119 Load Rating E.

These values are:

(Type)(Width)/(Ratio)(Build)(Diameter) (Single Load)/(Dual Load)(Speed)

FieldValueMeaning
TypeSTSpecial Trailer
Width235Width of the tire (between sidewalls) in mm
Aspect Ratio80Ratio of sidewall height to width
BuildRRadial construction (R for Radial, D for Bias)
Diameter16Inches between the bead seat areas
Single Load Index123Load index for single axle use (3420 lbs)
Dual Load Index119Load index for dual axle use (3000 lbs)
Speed RatingNMaximum safe speed (87 mph)
Load RangeEPly-rating and max load pressure (10-ply, 80 psi)

Clearly, they have selected these tires to be strong enough to hold up the RV.

Dual axle max load is 3,000 pounds. Four tires, so 12,000 pound max. The RV has two 6,000 pound axles for a 12,000 pound max. The trailer is 14,000 pounds… Nope, they selected the cheapest weakest tires for the job. The hitch pin weight is about 2,000 pounds, so they are counting on the hitch taking part of the tire load. I guess they expect that we will never go up hill, down hill, over a bump, or through a pothole.

These are the tables of values for the various tire specifications. They are limited to subsets in the relevant range for the RV.

Load Index Table (subset)
Load IndexRate Max LoadLoad IndexRated Max Load
11426011223307
11526791233417
11627561243527
11728331253638
11829101263748
11919981273858
12030861283968
12131971294079
Speed Rating Table (subset)
Speed RatingMaximum Speed
G56 mph
J62 mph
K68 mph
L75 mph
M81 mph
N87 mph
P93 mph
Q100 mph
Load Range Table (subset)
Load RangePly RatingMax Load Pressure
B435 psi
C650 psi
D865 psi
E1080 psi
F1295 psi
G14110 psi
ST235/80R16 LR E Inflation Table (subset)
PSILoad Rating
352090 lbs (B)
502600 lbs (C)
653000 lbs (D)
803420 lbs (E)

The ply rating does not indicate an actual number of plies. It is a strength rating based on tire construction with the number of plies using an outdated construction method. The “ply” is just a unit of strength, like feet is a unit of distance.

Some people buy different tires, but there appear to be some considerations related to this. These are the guidelines and concerns that are discussed in the forums and guides. Of course, opinions always vary.

  • Never put on a tire with lower ratings than the original manufacturer tire
  • Brand matters, but opinions vary
    • Better: Goodyear, Michelin, Sailun, Hercules, Carlisle (new), Hankook, Maxxis
    • Worse: Westlake, Carlisle (old), Deestone, Thunderer, Power King, Triangle, Castle Rock
  • Tire construction matters
    • All polyester
    • Polyester with steel bands
    • All steel
  • Higher rated tires
    • have higher tire pressure which
      • can put more stress on the RV frame due to being stiffer
      • can exceed the hub pressure rating for the tire bead
    • can have larger dimensions which
      • may not leave enough gap between the tires
      • may change the height of the RV
    • may need to run at reduced pressure for lower weigh loads
    • may need to buy new rims to handle the higher pressure on the bead
  • Tire style matters
    • Tire companies claim
      • ST tires are specifically rated for trailers, not to flex for comfort
      • ST tires are designed for sustained load with stronger sidewalls
    • Some people that use LT tires (for light trucks) claiming
      • ST tires are rated at exactly their maximum capability
      • LT tires are underrated to give a safety margin

A possibly concerning thing that I noticed is that the tires are not the same distance apart on either side. This could just be that the cambered wheels are not quite lined up, but it may mean that the axle was installed slightly skewed. This could be part of the cause of the greater wear on the front tires.

It seems like the options from the acceptable brands are:

This is still going to take a little more research, but it at least compiles most of the information that we need in one place. Additional notes will be added here.

JM

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