Use the live comparison above to see the exact diameter, circumference, revs/mile, and speedometer error between 31x10.5R15 and 33x12.5R15. Change either size to explore a different pairing, or open the full Tire Size calculator to start from scratch.
Tire Size Comparison
31x10.5R15 vs 33x12.5R15
Diameter, circumference, revs/mile, and speedometer error for 31x10.5R15 vs 33x12.5R15, with a to-scale visual.
Metric (285/75R16) or inch (35x12.50R17)
Past +10% diameter, budget for a regear. Use the Gear Ratio calculator to check.
Tire Size Results
First Tire
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stock diameter
Second Tire
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new diameter
Speedo Error
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speedometer error
| Measurement | First | Second |
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31x10.5R15 vs 33x12.5R15: What Changes
On 15-inch wheels, the jump from 31s to 33s is the defining early-Jeep upgrade: a 33x12.5R15 adds two inches of diameter and two inches of width over a 31x10.5R15. On a TJ or YJ that typically means a short lift and a fender check, and the wider footprint transforms how the rig airs down and crawls.
Frequently Asked Questions
Do I need a lift to run 33x12.5R15?
Usually a modest one. On a TJ or YJ, 33s on 15-inch wheels commonly call for a 2.5–3 inch lift plus fender trimming to clear at full flex and lock.
Is regearing worth it for 33s on a Jeep?
Often, yes. The 31-to-33 jump is only about 6-7% in diameter (under the 10% rule of thumb), but many Jeeps still benefit because stock gearing is tall and 33s add rolling weight, so a regear restores lost low-end torque and highway drivability.