Steels vs Alloys + tyre size + tyre type = improved mpg?

[Ambrose]

So I’ve just recently swapped out my steel GP17 wheels, running 235/55/17 Cross Climates to Davenport running standard 215/60/17 Vancontact tyres and the changes is staggering. Previously I was getting approx 38mpg motorway miles whereas now, I am getting around 45mpg. So my question is, is this down to the wheels, tyre size, tyre type or a combination of all 3 factors?

 

[david173]

Less contact area with the ground, less friction but i would have thought the main differnece is the 215/60 are running a higher pressure and as they a commercial tyres have a stiffer side wall.
I had a similar experience with the same tyres you listed but in reverse both on devonports so I assume its mostly down to the tyre

 

[nigelcro]

So... this is interesting, and relevant as I am just making exactly this decision - 215/60/17s or 235/55/17s. MPG is probably the second most important criteria after ride comfort.
Are we saying that rather than have a Cross Climate or Cinturato All Season I would be better with a more commercial tyre running at a higher pressure.
I am guessing that high pressure might improve MPG but adversely affect ride comfort? In which case, as with everything else in life, you can't have everything and compromise is the order of the day?

 

[Ambrose]

On the 215/60, I do find the steering lighter and easier to drive in general but may have lost a bit of traction at the same time. Comfort-wise, feels pretty much the same.

 

[DXX]

have lost a bit of traction at the same time

Are you wheel spinning your van? I can do this in first gear if I drive like a knob but its not a reason to justify a tyre change imo.

 

[Lubrown]

Are we saying that rather than have a Cross Climate or Cinturato All Season I would be better with a more commercial tyre running at a higher pressure.

I think size matters.

I went from a commercial tyre (104/106 rating) to an XL (102 rating) all season tyre, but both the same 215/65R16 size.

Comfort, noise and dynamics/precision are totally different with the 102 load rated tyre being better at smoothing over bumps, much quieter in the cabin (despite the pass by noise on the labels being 69db for the commercial tyre and 72db for the all season) but the all season is Willie in terms of sharp directional changes and needs more steering wheel inputs I find.

However, mpg has proven about the same for me so far. Of course, a real comparison would be when these new tyres wear down the the tread depth the old ones had.

When these all seasons need changing I’m going back to a summer tyre just for the wet weather confidence. But I’ll stick with a 102 or 103 rating rather than commercial.

 

[Ambrose]

Are you wheel spinning your van? I can do this in first gear if I drive like a knob but its not a reason to justify a tyre change imo.

I drive like a fart but have managed to spin the wheels a couple of times when pulling in a junction - which I rarely managed in my previous setup