My Current Tires
Goodyear Endurance
Maintenance Videos and Articles
- Goodyear Tire Maintenance – https://www.goodyearrvtires.com/helpful-videos.aspx
What Causes Tire Blowout
- Overloaded tires.
- Over and Under-inflated tires
- Improper Weight Distribution
- Tire Age and Dry Rot
ST vs LT Tires
ST Tires:
ST, or Special Trailer, tires are intended only for trailers. They have been designed as a “follower” tire, and must never go on the drive or steer wheels. Their stiffer sidewalls are engineered to handle the tall loads of a travel trailer or fifth wheel on straights and in turns but not the stresses generated by steering and acceleration.
- have stiffer sidewalls, in general.
- have higher load ratings than their vehicle tire counterparts.
- endures more “scrub” or that act of scuffing the side of the tire that might happen in tight places or hitting a curb.
LT Tires:
If driving off-road the stiffer sidewall of a bias ply LT tire may hold up better while the greater flex of a radial ST tire will work better for highway driving, especially at higher interstate driving speeds.
Buying a higher load range stiffens a sidewall, so an LT tire with Load Range D, E or F is advisable on heavier trailers.
If You Switch to LT, make sure an LT’s load capacity — for example, the number 125 in the tire size 275/70R18, 125R,E — is equal to or greater than what the trailer manufacturer specifies. LT tires typically have a lower load capacity than ST tires. The 125 indicates a load capacity of 3,640 pounds per tire. Consult a load capacity chart. Also, check to see that the trailer wheels can handle the maximum pressure.
- Light Truck tires
- Thinner, softer sidewalls
- Less stiff and will absorb road shocks more
Tire Size
An ST205/75R15 tire size like I have now will have a section width of 8.1 inches and an overall diameter of 27.3 inches.
An ST225/75R15 will have a section width of 8.9 inches and an overall diameter of 28.4 inches.
So the larger size is 0.8 inches wider and 1.1 inches taller. On the height though only half of the height needs to be considered so it will be 0.55 inches closer to the underneath part of the fender.
Tire Age
Check the DOT number. The end of the DOT number has four digits, usually surrounded by a circle shape. The first two numbers are the WEEK of manufacture, the last two numbers represent the YEAR. So if the numbers are 2417 that tire was manufactured on the 24th week of 2017. Tires are meant to be replaced after 5 years of use REGARDLESS OF TREAD..
Tire Pressure
If using the original tires that came with your trailer, then follow the sticker on the trailer. It is never appropriate to underinflate or over-inflate a trailer tire for any reason. The label on your trailer should be followed up to the max rating on the tire.
An LT tire likely has a lower maximum pressure than a similarly sized ST. Any tire pressure sticker on your trailer wouldn’t apply to LTs. If you go with LTs, inflate to the maximum pressure embossed on the sidewall. Avoid over or underinflating, and don’t overload your trailer.
The pressure number molded on the sidewall of tires is NOT the “Maximum Allowable” pressure. It is the Cold pressure necessary to support the Maximum Load capacity for that tire. In reality, the pressure number molded on the tire sidewall is the Minimum needed to provide for the support of that load. Increasing the cold pressure above the number on the tire sidewall will NOT increase the tire rated load capacity per industry practice, standard, and guidelines.
If the pressure increases because of increased Ambient Temperature or because the tire gets hot from being in the Sunlight or the tire gets hot from being driven on, that increase is considered and accounted for by tire design engineers. The increase is about 2% for each increase of 10°F in tire temperature. Even a temperature increase of 100F ( 20°F to 120°F for example) would only result in about a 20% increase in tire pressure and undamaged tires can tolerate a greater pressure increase than 20%.
Load Rating
Tires have varying weight load ranges (a letter code system) and overloading a tire beyond its weight capacity also causes heat to build up.
Most tires have two-ply polyester cord sidewalls, and some are three-ply. Not all plies are the same. Plies are sheets of rubber encasing fabric threads that are twisted into strong strands, or cords. Depending on weight and thickness, those plies may be intended for lighter duty, as on a car, or for handling heavier loads, as on a truck.
Decades ago, the number of plies would increase on truck tires, sometimes to 10 or even 12. The letters used for load range today are intended to represent stiffness equal to multiple plies, not the actual number of plies.
LOAD/INFLATION INFORMATION FOR ST METRIC TRAILER TIRES
| Tire Size | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 60 | 65 | 70 | 75 | 80 |
| ST175/80R13 | 905 | 1000 | 1100(B) | 1190 | 1270 | 1360(C) | ||||||
| ST185/80R13 | 990 | 1100 | 1200(B) | 1300 | 1400 | 1480(C) | ||||||
| ST205/75R14 | 1170 | 1300 | 1430(B) | 1530 | 1640 | 1760(C) | 1850 | 1950 | 2040(D) | |||
| ST215/75R14 | 1270 | 1410 | 1520(B) | 1660 | 1790 | 1870(C) | ||||||
| ST205/75R15 | 1220 | 1360 | 1480(B) | 1610 | 1720 | 1820(C) | 1940 | 2040 | 2150(D) | |||
| ST225/75R15 | 1430 | 1600 | 1760(B) | 1880 | 2020 | 2150(C) | 2270 | 2380 | 2540(D) | 2620 | 2720 | 2830(E) |
| ST235/80R16 | 1720 | 1920 | 2090(B) | 2270 | 2430 | 2600(C) | 2730 | 2870 | 3000(D) | 3130 | 3260 | 3420(E) |
Speed
Driving faster than the tire’s speed rating (also a letter code) will also drive up the tire temperature. IF the ST tire has NO markings, the MAX SPEED RATING OF MOST TRAILER TIRES IS INDUSTRY STANDARD AT 65 MPH. The Goodyear Endurance has the HIGHEST TRAILER TIRE speed rating of 87 max.
Additional Considerations:
- If you have a tire lose more than 20% of its air while sitting, then the tire might be compromised by static compression, i.e. it sat, without being rotated which put forces on the tire it was never meant to have. The tire should be removed from the rim and inspected INSIDE the tire to establish its integrity before being deemed acceptable.
- If you buy new tires for your rims, you can choose to have them balanced if you prefer. Remember that many trailer wheels are centered by the position of the lug bolts (these wheels are lug-centric) and not the center bore of the wheel. For best results, have them balanced using a pin plate adapter. This mimics the way a lug-centric wheel is mounted to a hub.
Camper Original Tires
WestLake, 15-Inch D-Rated, Two axles (TIRE ASSY ST205/75R15 LRD WESTLAKE RADIAL 15 X 6-5-4.5 BLACK)
- Vehicle Class: ST – Special Tire (Trailer Tire)
- Nominal Section Width: 205mm
- Aspect Ratio: 75mm
- Fabric Carcass: Radial
- Rim dimensions: 15″ diameter x 5″ wide
- Bolt pattern: 5 on 4-1/2″
- Wheel bolt size: 1/2″-20
- Wheel capacity: 1,820 lbs
- Pilot diameter: 3.19″
- Offset: 0
- Tire size: ST205/75R15
- Section width: 8″
- Outer diameter: 27.1″
- Tire capacity:
- Load Range: D
- Ply rating: 8
- Maximum load: 2,150 lbs at 65 psi
- Tread depth: 10/32″
- Maximum speed: 75 mph (speed rating L)