235/45R17 — 796.3 revolutions per mile, and what it governs
A sport-saloon fitment, and the size at which the 17-inch 45-series family is at its most useful.
Metric notation · Passenger touring
- Overall diameter
- 25.33 in
- 643 mm
- Section width
- 9.25 in
- 235 mm
- Sidewall height
- 4.16 in
- 106 mm
- Aspect ratio
- 45%
- sidewall as a share of width
- Wheel diameter
- 17 in
- the hole in the middle
- Circumference
- 79.6 in
- 2021 mm
- Revolutions per mile
- 796.3
- geometric, not measured
- Revolutions per km
- 494.8
- geometric, not measured
- Typical load index
- 82–99
- 1047–1709 lb per tire
A passenger tire's load index tracks its air volume, and volume tracks section width and sidewall height. Sizes in this class sit in the band that carries a typical two-tonne car with its rated payload across four tires.
The load-index range shown is the band this CLASS of size is typically produced in — not a list of what is in stock for this exact size today. Load index and speed symbol are printed on the sidewall of the specific tire you are holding, and the required minimum is on the placard of the specific vehicle you are fitting. Read both.
Nearest real sizes in imperial notation, same wheel
- 32x11.50R1732.00 in tall+6.67 in
- 33x10.50R1733.00 in tall+7.67 in
- 33x12.50R1733.00 in tall+7.67 in
Compare any two sizes, including ones this site has no page for, in the comparison tool.
25.33 in tall, 9.25 in of section width, 4.16 in of sidewall, 79.6 in of circumference. The geometric revolutions-per-mile figure is 796.3.
Sport-oriented saloons and coupes account for most of the fitment, along with the wider rear half of some staggered sets. It is one step wider than the class default of 225/45R17 and one step narrower than 245/45R17.
What each 10 mm does to the revolution count
| Size | Diameter | Revolutions per mile |
|---|---|---|
| 215/45R17 | 24.62 in | 819.2 |
| 225/45R17 | 24.97 in | 807.6 |
| 235/45R17 | 25.33 in | 796.3 |
| 245/45R17 | 25.68 in | 785.3 |
Each rung costs roughly eleven revolutions per mile. That is the number every wheel-speed-derived reading in the vehicle is scaled by — speedometer, odometer, trip computer, and the wheel-speed comparison that stability and traction systems run on. It is also the figure the axle ratio multiplies against to produce engine speed, which the gear ratio calculator works through.
Moving from 225/45R17 to this size is a diameter change of 1.40%, which puts an indicated 70 mph at an actual 71.0 mph and adds a mile and a half to every hundred the odometer records.
The closest code in the catalogue
215/55R16 measures 25.31 in against this size's 25.33 in: 0.06%. A 16-inch tire with 4.66 in of sidewall and a 17-inch tire with 4.16 in, standing the same height and 0.79 in apart in section width. Both are inside a tenth of one per cent of the same rolling diameter.
Sidewall and rim
4.16 in is a middling figure for a 17-inch performance fitment — more than 225/45R17's 3.99 in, less than 215/50R17's 4.23 in. It gives the casing enough material to tolerate a range of rim widths without the stance changing dramatically, which is part of why this size is a common aftermarket choice.
The same reasoning applies at the other end of the wheel range: a wider casing at the same aspect ratio needs a wider rim to sit at its nominal section width, and a narrow rim pulls the shoulders in and makes the tire measure taller than the figures above.
Load index and speed symbol both vary between tires marked 235/45R17; the load and speed index decoder reads a service description directly.
Related
- 32x11.50R1732.00 in tall
- 33x10.50R1733.00 in tall
- 33x12.50R1733.00 in tall
Class: Passenger touring. Every figure above is computed from the size code, not stored — see how these numbers are calculated.