From 18 to 17 inch on NC 2.0

Hi, my front tyres were used due to a bad alignement so i decided to go from 18 to 17 inch with a new set of wheels and tyres and…what an amazing difference that is.
I bought the car with those 18 inchers and i test drove it as such …as i had no reference point to compare (never dorve an NC before) i was satisfied with the ride …until now that is ;the car feels more comfortable (as expected), the car feels a lot more planted (gone is the “nervous” behavior on uneven Belgian roads…) and my cornering speed is improved a lot especialy in the rain. As there’s more rubber the curbing damage will also be minimalised. Beside that the tyres are half the price , was 150eur (Falken 225 35/18) and now 76 eur (Uniroyal rainsport 215 40/17). I know this comparision is not “general” as the ride quality of the tyres also influences its behaviour but as far as i’m concerned ; i’m a happy fiver (once again…)
Just wondering; would a 16 inch setup be even better or is 17 inch the better compromise?

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They should be 45 profile not 40.

I don’t know much about the 16s but the 17s usually wear a 45 profile tyre so you’re still a little short on sidewall with your 40s. The 16s wear a 50 profile so a little more sidewall to play with. AFAIK the weights of the standard wheel/tyre combination is the same with the 16 and 17.

225/35 = sidewall = 225*.35 = 78.75mm [18s] total wheel diameter 614mm

205/45 = sidewall = 205*.45 = 92.25mm [17s] Total wheel diameter 616mm

205/50 = sidewall - 205*.5 = 102.5mm [16s] Total wheel diameter 611mm

215/40 = sidewall = 215*.4 = 86mm [your current tyres] Total diameter 603mm

I use 215/45 on 17s so the sidewall is 96.75mm which I reckon gives almost the ride quality of the 16s with the arch filling size of the 18s. Total wheel diameter 625mm

Not sure if this has been any help to you. I hope it is!

215/40R17 should be fine.
I believe the NC was originally equipped with 205/45R17.
Therefore, the only issue now if that the speedo will read 60mph when @b_w is doing 59mph.

The speedo already over reads in a standard car therefore the reduction in sidewall will increase that. 215’s bring true speed closer to speedo speed but still under.
True speed at 60 indicated on 40’s will probably be closer to 56 mph.
Plus more of the harshness the op was trying to remove.

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Ian is right about the speed variation, which are small either way round on the 18" or 17" but as you pointed out b_w’s post sort of suggests ride is a factor. The main variance is likely to be the weight of the 18" rims plus Rainsport’s wet perfomance.

Nick d; indeed it’s 45 and not 40.
It is also the only 215-17 inch combo in rule with our tecniical control (mot to you guys) in Belgium.
My choice was also partly aestethical as my 18 inchers had those “fake” bolts which is not my cup of thea (to tuning-alike for me…)
A happy 17 incher…

The tyre it would have been delivered on is 205 45 17.