Fuel economy - run flat versus regular tyres

[Andywhy]

Hi all,

Has anyone changed away from run flat tyres to regular tyres and seen a change in fuel economy? I was driving a UX with 17" wheels for months but now have a UX with 18" runflats and there seems to be about a 3-5mpg difference in fuel economy, so I just want to see if anyone else has noticed this if they've swapped?

Thanks

[rayaans]

9 minutes ago, Andywhy said:

Hi all,

Has anyone changed away from run flat tyres to regular tyres and seen a change in fuel economy? I was driving a UX with 17" wheels for months but now have a UX with 18" runflats and there seems to be about a 3-5mpg difference in fuel economy, so I just want to see if anyone else has noticed this if they've swapped?

Thanks

Too many variables to consider but it makes sense if the fuel economy has worsened

larger wheels / tyre combo is heavier. Even more so with runflats compared to normal tyres

[Andywhy]

Thanks for the response.

I've measured over my commute which is basically identical every day. The second UX gets noticably a few MPG less and that's all I can put it down to.

[ColinBarber]

1 hour ago, Andywhy said:

Thanks for the response.

I've measured over my commute which is basically identical every day. The second UX gets noticably a few MPG less and that's all I can put it down to.

It's a combination of both wheel size and heavier tyres is the cause. Don't expect to get 5 mpg back just from changing the tyres.

[Peter UX]

The official figures (mpg and co2/mile) do vary across the trim levels of the same engine. That's one of the reasons I went for 17" wheels (the other being the taller tyre walls offer more protection against curbing... Fingers crossed) 

[Andywhy]

Yeah I did see a difference but I hadn't realised it would impact it that much. I do think it's mainly the rolling resistance and weight of the run flat tyres over the increased size. Everything I've researched says that the size and tiny increase in width shouldn't really impact it that much, it's more likely to be the rolling resistance which is category D for the run flats versus A for a regular tyre. I think when it comes to getting new tyres I'll stick regular ones onto it.

[Roger Bill]

Blackcircles list a few alternative run flat tyres for the UX250h havinhttps://www.blackcircles.com/tyres/225-50-18?runflat=1 Most have rolling resistance ratings of C or D.

According to this, the impact on fuel economy of tyres with different rolling resistance ratings can be significant especially at higher speeds:

https://www.fleetnews.co.uk/news/2014/6/18/real-world-tyre-economy-ratings-out-of-step-with-labelling/52721/

[Andywhy]

Thanks. I did find the same info and that's what prompted my original question. It's quite a significant percentage - I read 17% extra resistance which can result in 5% fuel economy hit, which equates to about 2.5mpg for the UX. Admittedly it doesn't sound like a lot but in the long term it is.