17" tyre sizes

[ritch_w]

I'm looking to change up from 15" alloys with 195/60/15 tyres to 17" alloys, but am slightly confused with what tyre size to get... I seem to remember that Ian had 225/45/17s, but when checking with a tyre size calculator (http://www.tyresave.co.uk/tyresize.html) get the following results;

Tread Width Profile Height Wheel Diameter Overall Tyre Diameter
195 mm 60% 17 inches 24.21 inches 615 mm

225/45/17 Difference in Diameter: percentage = 3.09% actual = 19 mm
215/45/17 Difference in Diameter: percentage = 1.63% actual = 10 mm
205/45/17 Difference in Diameter: percentage = 0.16% actual = 1 mm
225/40/17 Difference in Diameter: percentage = -0.49% actual = -3 mm

my interpretation of this is a postive % will give a actual higher speed than what the speedo shows.......

whats also confusing is the v6sport uses 215/45/17 and the v6-24 is 195/60/15 which is a 1.63% difference, but would both models have differently calibrated speedos? (i dont think so....)

what size to go for? and which size will maintain speedo accuracy????

[psbarham]

i'm running 225/45/17's on my v6 and the speedo is only 2 mph fast at all speeds according to the gps , so better than factory , the ride was also much much better

[Nick Mann]

Having experienced 215 45 17's on the V6 Sport, and 235 45 17's on the VR4, I would say go for a bigger wall and a better ride.

My speedo reads 4% over now on 235's, but the ride is better and I think the tyres will wear pot hole abuse for longer.

[ghanda]

Interesting. I was running the standard 16's with a mph/kmh convertor, but with the limiter still in place. I replaced this with a Eurospec convertor/delimiter and I was reading fast.
Replaced the wheels with 17's and widened the tyres to 235/45/17's.
Net result? At 140, the true GPS reading is 141.5!!
So pretty damn accurate the whole way up.

[Gly]

im running 215/40/17s. i like the look of a lower profile tire
a little on the hard side when i hit a pot hole... so i try to avoid them

[Freddy]

I have just purchased some 18" wheels and got the tires sized to the factory diameter. Prior to that I was running 215/40/17 which, I have found out now, tends to make the speedo over read by 8km/h @ 100km/h. The correct sizing makes the car feel stronger somehow. Torque seems to match up with the revs better and fuel economy is definetly better as well. Food for thought.