Calculator
Winter tire size calculator
Winter tires on a smaller wheel cost less, ride better and grip better in snow. The catch is finding a size that keeps your speedometer, ABS and gearing honest. Enter what is on your door placard and we do the search.
Result
The best match on a 17 in wheel is 225/60R17, -0.4% from your factory diameter.
| Size | Diameter | Change | Sidewall | Width | True speed at an indicated 60 mph | Fit |
|---|---|---|---|---|---|---|
| 225/60R17 | 27.6 in | -0.4% | +11 mm | +0 mm | 59.8 mph | Best match |
| 215/65R17 | 28.0 in | +0.9% | +16 mm | -10 mm | 60.6 mph | Best match |
| 205/65R17 | 27.5 in | -0.9% | +10 mm | -20 mm | 59.5 mph | Best match |
| 195/70R17 | 27.7 in | +0.0% | +13 mm | -30 mm | 60.0 mph | Best match |
| 235/60R17 | 28.1 in | +1.3% | +17 mm | +10 mm | 60.8 mph | Within 2% |
| 225/65R17 | 28.5 in | +2.8% | +22 mm | +0 mm | 61.7 mph | At the limit |
| 215/60R17 | 27.2 in | -2.1% | +5 mm | -10 mm | 58.7 mph | At the limit |
| 235/55R17 | 27.2 in | -2.0% | +6 mm | +10 mm | 58.8 mph | At the limit |
Load and speed check
Add your factory load index to check the new tire’s capacity. It is the two or three digits after the size on the sidewall, before the speed letter.
This tool computes geometry. It cannot see your brakes, fenders or suspension. Confirm any fitment with a tire shop before you buy.
The wheel checklist
New tires need new wheels, and the wheel is where winter setups go wrong. Six numbers decide whether a wheel fits.
Bolt pattern
Must match exactly. 5×114.3 mm is not 5×112 mm, and no adapter makes it so. The pattern is on the wheel’s spec sheet and in your owner’s manual.
Center bore
The wheel’s bore must equal or exceed your hub diameter. Larger needs hub-centric rings so the wheel centres on the hub, not on the lug nuts. Smaller does not fit.
Offset
Stay within about 5 mm of the factory offset. The same width and the same offset put the tire exactly where the factory tire sat, so there is nothing new to clear.
Wheel width
A 225 mm tire is approved for rims from 6.0 to 8.0 in wide; the measuring rim is 7.0 in. A rim near the middle of the range keeps the sidewall shape the tire was designed for.
Brake clearance: the base-trim rule
A smaller wheel has to clear the brake caliper. The best evidence is the factory itself: if a lower trim of your model year ships on the wheel size you want, that size clears the brakes on your car, unless your trim has larger brakes. Going below the smallest factory size needs a test fit.
TPMS
Direct systems need a sensor in each new wheel, matched to your car. Indirect systems, which watch the ABS wheel-speed sensors, need only a reset after the swap. Your owner’s manual says which you have.
Worked example
Worked example: a Forester on 18 in wheels
A 2019 Subaru Forester Sport ships on 225/55R18, while the base trim of the same year ships on 225/60R17. Run through this calculator, the best-matching 17 in size is 225/60R17, -0.4% from the factory diameter. The base-trim wheel proves a 17 in wheel clears the brakes, and its offset and bolt pattern are the ones to copy. That is the whole answer, and it took three forum threads to find it.
The math, shown
Sidewall = width × aspect ÷ 100. Diameter = wheel × 25.4 + 2 × sidewall. Change = (new diameter − factory diameter) ÷ factory diameter. True speed = indicated speed × new diameter ÷ factory diameter.
Questions people ask
Why put winter tires on smaller wheels?
Three reasons. A smaller wheel takes a taller sidewall, which absorbs the potholes that hide under snow and protects the rim. A narrower tire on that wheel puts more weight per square inch on the snow and cuts through to the road instead of floating. And a 17 in winter tire costs less than a 19 in one, usually enough to pay for the steel wheels.
How much can the overall diameter change?
The industry rule is 3%. The speedometer, odometer, ABS and stability control all read wheel speed and assume the factory diameter, so a bigger change puts them off. Under 2% is the conservative target and is almost always available. Anything over 3% needs a clearance check and will read the speed wrong.
Can a winter tire have a lower speed rating than the factory tire?
In the United States the tire industry accepts a lower rating on winter tires, provided you never exceed it, and Q (99 mph) or T (118 mph) is common. Some automakers require the factory rating be kept; German brands often do. The load index is not negotiable: it must be equal or higher.
Do I need new TPMS sensors for winter wheels?
If your car has direct TPMS, yes: each wheel carries a sensor and the car expects to see four that match. Many shops sell winter wheels with sensors fitted. If your car has indirect TPMS, which infers pressure from the ABS sensors, there is nothing in the wheel and you reset the system after the swap.