Bigger wheels - reduced MPG and performance?

[Rael]

I fitted some 19's at the weekend, and since then I've not been achieving as high an MPG than with the 18's fitted...is this normal? The rolling radius is only 1.55% difference, as the tyres have changed from 225/40/18 to 235/35/19. And I'm not sure if it's just my imagination, but it feels slightly slower too.

Not sure if this helps, but I also now get a fair bit fo road noise, and my old front tyres were worn bald on the inside edge.

 

[noktoto]

Lower MPG and reduced performance? That's because your new wheels are heavier and wider.

 

[Rael]

They didn't feel much heavier when I was putting them on, but perhaps you're right. I just can't believe its knocked 5-6 mpg off! I'm wondering if it's worth it...trouble is they look incredibly sexy!

 

[s1l3nc3r]

Wheels heavier and wider which now means they will be creating more friction so more drag.

Road noise will be down to them being wider..bald on the inside edge points to tracking issues...

 

[jcp]

Sounds wrong- is the difference in rolling circumference factored in to your mpg figures? Your speedo and mileometer will be wrong as may your fuel computer. You need either to measure full to full after a known distance as for example sat nav trip computer read out or a journey which you have accurate distance figures for.

 

[Rael]

So I could have tracking issues? Could have been caused by my other half walloping the curb in my old wheels grrr! Should get that checked out I guess?

jcp - excellent point...the fact that my speedo is now out "could" mean my computer is out too, as this, I assume, works on the car's speed. Mileage is difficult to track as, again, I would have thought the miles on the car will now be being affected by the larger rolling circumference.

 

[jcp]

A garmin gives what seems accurate readings of speed and distance so try that- you could borrow one if you don't have one although I find mine indispensable and it was not expensive. You could do the arithmetic with some thought if you assume the speedo was correct. Mine isnt especially precise with an error -about 5% compared with the GPS speed. The car flatters performance by about that amount.

 

[hon_n_gem]

The wheels might not feel as heavy, but a lot of the weight is further from the centre and hence more fuel is required to turn them.

 

[JayTse]

RAEL - Obviously theres a few bad point of fitting larger wheels on your motor... BUT it does look damn sexy... that point alone would make it worth while...

so whatever you do, just keep the 19s on

 

[ZBOYD]

I run 19's and they do effect the MPG ever so slightly but not vastly, more apparent round town but not so much on the motorway.

I chose 8J x 19" wheels, they are commonly 8.5J x 19" in most other styles. By running a narrower wheel I can still use a narrower width of tyre.

So instead of the usual 235x35x19 I chose to use 225x35x19.

The standard 18 inch wheel uses 225x40x18, the tyre drag should be similar and the rolling circumrance should make less than 1% difference.

 

[Nath.]

Does it really matter, you could have saved your money and bought your other half some flowers every week for a year.

You chose to buy the 19's and now you're nit picking about 1 or 2 MPG loss

IMO some people are way too interested in the little MPG screen, it's a false reading any way, do the maths and you will go APE

 

[Rael]

Thanks for all your replies guys.

I think I've been almost convinced that the MPG reading won't be that accurate any more, and also that the looks should take precedence over the practicalities!

I will get my tracking sorted though, and may try and borrow a Garmin or similar. I guess I was just too excited about getting bigger wheels I didn't consider anything other than aesthetics! And maybe I was right

 

[Rael]

Nath - didn't see your response when I replied.

If it was 1-2 mpg, I wouldn't have even bothered posting. As I said, it seems to be at least 5-6 in the first few days - I do the same journey every day.

 

[Nath.]

My guess would have been 1-2 MPG, if it's more than that I would say that you have very heavy 19's.

Put them on the bathroom scales and see the weight difference between the 2