2021 Audi Q3 tire size

Most common factory size

P235/55R18

Tire sizes by trim

Source marks: one source

2021 Audi Q3 tire size by trim
Size	Trims	Width, mm	Sidewall, % of width	Rim, in	Diameter, in	Sidewall, in	Revs per mile
P235/55R18	40 TFSI Premium Plus AWD, 40 TFSI Premium AWD	235	55	18	28.18	5.09	716
P255/45R19	45 TFSI S line Premium Plus AWD, 45 TFSI S line Premium AWD	255	45	19	28.04	4.52	719

What P235/55R18 means
Part	Number	Meaning
Type	P	Passenger car tire.
Width	235 mm	Tread width. 9.3 in.
Sidewall	55	Sidewall height is 55% of the width.
Construction	R	Radial tire.
Rim	18 in	Fits 18 in wheels.

Within 3% of the stock diameter. A common shop guideline, not a maker spec.

Sizes within 3% of P235/55R18
Size	Rim, in	Diameter, in	Change	Speedo reads at 60 mph
235/50R19	19	28.25	+0.3%	59.8 mph
235/60R17	17	28.10	-0.3%	60.2 mph
255/50R18	18	28.04	-0.5%	60.3 mph
255/45R19	19	28.04	-0.5%	60.3 mph
215/65R17	17	28.00	-0.6%	60.4 mph
265/45R19	19	28.39	+0.8%	59.6 mph
315/40R18	18	27.92	-0.9%	60.5 mph
225/65R17	17	28.52	+1.2%	59.3 mph

Sizes within 3% of P255/45R19
Size	Rim, in	Diameter, in	Change	Speedo reads at 60 mph
255/40R20	20	28.03	-0.0%	60.0 mph
255/50R18	18	28.04	+0.0%	60.0 mph
225/45R20	20	27.97	-0.2%	60.1 mph
315/40R18	18	27.92	-0.4%	60.2 mph
235/55R18	18	28.18	+0.5%	59.7 mph
285/35R20	20	27.85	-0.6%	60.4 mph
235/50R19	19	28.25	+0.8%	59.5 mph
225/55R18	18	27.74	-1.0%	60.6 mph

Checked against 292 factory sizes listed for 2009-2027 US models.

Tire pressure is on the driver door sticker. Not in this data.

Optional wheel packages may differ.