Size Conversions
Popular Alternative Tire Sizes
For an equivalent size, a HIGHER load range tire can always be substituted:
- ST225/75R15 LR D Marathon substituted for ST225/75R15 LR C Marathon
- Match inflation pressure to load carrying requirements using load and inflation tables
Some manufacturers use slightly different size designations. Popular RV tire size equivalents:
- 235/80R22.5 = 245/75R22.5
- 255/80R22.5 = 265/75R22.5
- 275/80R22.5 = 295/75R22.5
Converting from 8R19.5 to 225/70R19.5:
Many RV owners are converting from 8R19.5 to the newer, more popular 225/70R19.5 size. In most cases
this can be done successfully. The following guidelines should be consulted to determine if this conversion
can work for you. Before making a final decision to convert, we recommend contacting your local Goodyear RV
tire retailer to verify that all considerations have been met.
Advantages = more even wear, improved stability
Conversion Checklist (8R19.5 to 225/70R19.5 only):
- Check with the vehicle manufacturer to ensure approval of the tire/wheel clearance and fitment
- Verify that rim width is compatible to run the 225/70R19.5
- A wider minimum dual spacing is required and should be confirmed
- Due to a tire diameter and static loaded radius difference there will be an increased number of revolutions
per mile which will mean that the vehicle speedometer and odometer will read approximately 2.5% high. Because the difference in
RPM is less than 3%, however, no changes to gearing would generally be required.
Tire Size |
Type |
LR |
RIM |
Min. Dual Spacing |
Width |
Tire Diameter |
Static Load |
RPMs |
Speed |
Load Inflation Single Dual |
225/70R19.5 |
G670 RV |
F |
6.00RW, 6.75, 6.75RW |
9.7 |
8.6 |
32 |
14.9 |
644 |
75 |
3640 lb @95 psi
3415 lb @95 psi |
225/70R19.5 |
G670 RV |
F |
6.00RW, 6.75, 6.75RW |
9.7 |
8.6 |
32 |
14.9 |
644 |
75 |
3640 lb @95 psi
3415 lb @95 psi |