Big wheels kill MPG?

[davidjames]

Hello, first time posting here. Proud owner of a new 6.1 150 DSG Highline panel van since January

So naturally first thing I did was replace the 16in wheels with 20in wheels on 275mm wide tyres. However I really noticed the MPG drop and that's been highlight by going back to the stock wheels with winter tyres. Where I was getting high 20s or low 30s on a 70mph motorway run with the big wheels, I'm now getting low 40s at the same speed

Are big wheels just slow? Is it because they are heavy or the tyres really wide?

Wondering what is the best compromise of looks/style and fuel economy for next summer when the winters come off? Maybe an 18in?

Would love to hear others thoughts on this and any recommendations please

 

[Pete C]

If the circumference has changed then the mpg calculation performed by the van will be wrong.
Are you measuring mpg from the trip computer or from driving a known distance then measuring the fuel used ?

Pete

 

[davidjames]

Ah that is interesting - I've now down the same motorway journeys and I'm definitely get more mileage out of the smaller wheels, up to 150-200 miles extra on a full tank

Also the van seems to drive better as well, less lethargic when accelerating and more nimble steering. I guess that's the wide tyres to blame there?

 

[huw169]

275’s are far too wide for the front. Makes the steering shit for anyone who is a keen driver. Most won’t notice.
And as mentioned due to the increased rolling radius you will be travelling further than the Van thinks you are which is why both the dash and tank to tank will tell you it’s down.
Don’t get me wrong, they are less efficient, but probably not by as much as you think.

 

[F2JON]

Hello, first time posting here. Proud owner of a new 6.1 150 DSG Highline panel van since January

So naturally first thing I did was replace the 16in wheels with 20in wheels on 275mm wide tyres. However I really noticed the MPG drop and that's been highlight by going back to the stock wheels with winter tyres. Where I was getting high 20s or low 30s on a 70mph motorway run with the big wheels, I'm now getting low 40s at the same speed

Are big wheels just slow? Is it because they are heavy or the tyres really wide?

Wondering what is the best compromise of looks/style and fuel economy for next summer when the winters come off? Maybe an 18in?

Would love to hear others thoughts on this and any recommendations please

Wrong size tyres possibly?? I reckon you’re running 275/40/20 as a guess ?

 

[Gavinda]

You'll not be able to trust the milage the van reads with the larger wheels as they're taking you further with each revolution.
With 16" wheels 1 mile is around 760 revolutions.
With 20" wheels the same mile is only 704 revolutions.
That's around a 7% difference, you'll need to account for this to get a true understanding of the difference in mpg regardless of how you calculate it.

 

[Samro]

MPG has gone down the pan since I changed from my 19" wheels to 17"!

I think that the op is correct in that the original wheels and tyres will show more mpg, (Due to genuinely being better on fuel, but also because of reduced rolling diameter makes trip computer tell fibs.)

Big BFG tyres on my 17" wheels allow me to drive into a wet field and have a chance of getting back out. MPG wise they score low and are frankly not even very good for grip in freezing conditions.... but wet fields are no longer an issue.

I think my 255/45 r19 (with Goodyear Eagle F1 tyres) return comparable MPG with the OEM Devonport Bridgestone combo that came with my van.

It's courses for horses I guess, as the BFG Tyres are a win for me over the winter on grass, which is what I need for my camper.

The 19" wheel combo is what I need for the summer months, as these look cool. (God knows that I need all the help I can get on the "looking cool" front!

 

[Fluff34567]

Problem with changing wheel size and trying to calculate mpg is its always going to be incorrect unless your new wheel size is within 1% of original. Or you exclusively use GPS data and the distance between full tanks, ignoring whatever the computer says.

 

[dubber36]

I'd say I saw a 2-3 mpg drop on the MFD when I went from 235-55-17 to 255-45-19.

Without looking it up, the new wheels are around 3% larger, so taking into account the extra weight and the speedo discrepancy, that's to be expected. In fact, the computer is probably more accurate than it was before as the speedo is bang on with GPS now. When I do brim to brim mpg calculations, the MFD says 33mpg and the maths says 32mpg, so close enough to trust the computer.

 

[Samro]

I'd say I saw a 2-3 mpg drop on the MFD when I went from 235-55-17 to 255-45-19.

Without looking it up, the new wheels are around 3% larger, so taking into account the extra weight and the speedo discrepancy, that's to be expected. In fact, the computer is probably more accurate than it was before as the speedo is bang on with GPS now. When I do brim to brim mpg calculations, the MFD says 33mpg and the maths says 32mpg, so close enough to trust the computer.

I would agree. When I made the below statement, I had accounted for the difference the 3% change in diameter.

I think my 255/45 r19 (with Goodyear Eagle F1 tyres) return comparable MPG with the OEM Devonport Bridgestone combo that came with my van.

In contrast to this my BFG KO2's have crucified my MPG. This wheel/tyre combo I am using, means that my speedo and GPS speed are 100% matched, but my Long Term Average MPG on the MFD has fallen to 26-28 MPG from around 31-33MPG.

No other changes to the van have been made since fitting what are now my winter wheels.

(This isn't unexpected and I am happy that the BFG tyres are achieving exactly what I needed, albeit at the cost of fuel economy.)