20inch Runflats vs 18inch non-runflats

[Richard77]

I’m shortlisting cars to replace my current x3 and the favourite is the NX.

I really want one with the head up display and a few other options that come with the versions with 20inch runflats. Can anyone comment on the ride quality on 20inch run flats vs 18inch runflats? My current x3 is on non runflats and it really helps the ride quality, something that’s really important to me. It’s sometimes hard to pick this up from a short test drive. 

Has anyone swapped runflats for regular tyres and was that ok with insurance company?

[rayaans]

You don't need to inform the insurance company if you change from run flats to non run flats as long as they're the correct size / speed rating and load rating

[Ken R]

I have covered over 16000 miles on 20inch run-flats and have no complaints regarding ride quality or noise levels. Previously ran a NX300H on 18inch no run flats and honestly think they are very comparable overall. Downside is cost of replacement of run flats. Had to replace one tyre recently and it cost £364. That said my journey was uninterrupted!

[malcolmw]

We have been very impressed with the ride quality on our NX350h Premium Plus Pack which has the 20inch run-flats. It is smoother than our previous NX300h Takumi which had the 18inch conventional tyres.

Having said that, our Aston DB9 had run-flat Bridgestone Potenzas as standard and they were very harsh. Changing to Michelin PSS was a revelation.

[WhiteHart]

I have done just over 3000 miles in my NX450 with 20in run flats and it’s been a good ride, I could be imagining this but I think it’s quieter than my old NX300. 

[Tickedon]

I have the 20” run flats. Absolutely no complaints about noise or comfort on my NX 450h. 

Though my previous car was an Audi A4 with relatively small profile 18” tyres, so most things would be an improvement 

[Andy B]

15 hours ago, Ken R said:

I have covered over 16000 miles on 20inch run-flats and have no complaints regarding ride quality or noise levels. Previously ran a NX300H on 18inch no run flats and honestly think they are very comparable overall. Downside is cost of replacement of run flats. Had to replace one tyre recently and it cost £364. That said my journey was uninterrupted!

I couldn't have put it better - having also had a NX300h with 18s before. I can't feel or hear any discernible difference between the two cars.

The only drawback is, as Ken says, the higher cost of replacing the run-flats. Plus I feel that they are more prone to damage from potholes; etc. due to their composition (I have already had to replace one tyre due to this - at a cost of £280 - and have only done just over 10,000 miles).

[MarcG]

I have spinal injuries following an RTA. I had a BMW 5 Series with 18" rims because of the softer ride. My 450NX came with 20" Run Flats and the ride comfort is better than the BMW

[BillSt]

I had an X3 with runflats. Changed to non runflats and found big difference. Was very concerned initially that my NX450h+ came with 20” runflats and was expecting to need to swap them for 18”. But found it OK. Most of my usage has been in Spain with rather better roads than U.K. however.

[Richard77]

Thanks all for the comments, really helpful. I think the run flats will be fine but suspect I’ll swap them for non run flats eventually. I see they have 50 profile tyres so that will help with ride comfort too. 

[BillSt]

With my X3, the biggest gain was the road noise when I changed to non runflats. With the  silenced windows of the NX Takumi, the road noise is so much lower anyway. The main reason I might lose the 20” runflats will be the difficulty getting replacements if I did get a puncture. 18” 50s are much easier at the moment.