[GrussGott]

So i've got an M4 and of course have the big wheels and wide tires ... but in getting a 45e hybrid it occurred to me that the 19s will be lighter (and ride better) with the thinner tires providing less rolling resistance ...

The same with the brakes/rotors/calipers - the non-M brakes would be lighter ...

So the question is, any genius nerd types have a theory on the efficiency difference? Minimal-to-none or small-but-noticeable?

My thinking is, doesn't look quite as nice but if I'm buying an efficiency car shouldn't I go with the highest efficiency options? Maybe I'm overthinking it ...

[m3_08]

kind of agree with you. I plan to order 20" with all season....middle between pretending performance 21" and too small to me 19".
Same applies to M painted brakes.
To me its a comfortable economical city vehicle and for performance joy ride I have another cars.

[X5 45e]

I have 20 inch summer (740M) and 19 inch winterwheels. Both rft. If I could do it again I would also take 20 inch winterwheels. For me the comfort is more or less the same. 19 looks a bit to small although the ferric grey I have look better than the bright silver ones.

I didn't want 21/22 inch for comfort. Belgian roads are very bad.

I don't see any difference in economy.

The CO2 increases and mpg decrease with larger wheel size on paper. In practice other factors are more important.

The major difference in fuel / electric economy will be your driving style en even more charging habits. Winter temperatures reduce the electric range a lot.

Charging as much as possible is the only way to have good mpg.

[Lionel Hutz]

Smaller, lighter wheels and narrower, less grippy tires will 100% make a difference in efficiency. For example, the Model 3 takes a ~22 mile hit to its max range when equipped with the 20" performance wheels vs. the 18" standard wheels.

Brakes maybe some but likely not as noticeable as much of the mass is non-rotational.

[X5 45e]

Originally Posted by Lionel Hutz

Smaller, lighter wheels and narrower, less grippy tires will 100% make a difference in efficiency. For example, the Model 3 takes a ~22 mile hit to its max range when equipped with the 20" performance wheels vs. the 18" standard wheels.

Brakes maybe some but likely not as noticeable as much of the mass is non-rotational.

That is 6,5 % of the range for the long range version. That is significant on paper. Or is this your own experience? The economy of the x5 is also better on 19 inch wheels than on 22 inch.

I just wonder if in practice numbers will be the same. Like mentioned other factors are equal or more important.

My fuel economy is better now on staggered 20 inch than on non staggered 19 inch winter tires.
The difference in electric efficiency in the summer is caused by the higher temperatures. So it is difficult to compare.

And if you want to be really green: don't by a car at all but use a bicycle and public transport. Or a least don't by an X5 or even a Tesla but a small car with a small engine. Tesla's also have a high carbon footprint in production of the car and electricity.

So bottom line. Take the wheels you like. And buy an X5 with a 45e 6 cylinder while it is still possible.

[X5 45e]

I found a test (car and driver 2010) comparing fuel economy and acceleration on 15 - 16 - 17 - 18 - 19 inch wheels on the same car. Both decrease with increasing tire size.

I presume this can be extrapolated to the X5?

[Lionel Hutz]

Originally Posted by X5 45e

That is 6,5 % of the range for the long range version. That is significant on paper. Or is this your own experience? The economy of the x5 is also better on 19 inch wheels than on 22 inch.

EPA test ratings

[GrussGott]

Originally Posted by m3_08

kind of agree with you. I plan to order 20" with all season....middle between pretending performance 21" and too small to me 19".

Yeah, I think I'm with you - I plan to do a lot of roadtripping with this vehicle and took a look at replacement tires:

* The 20" still have a square setup which helps a bunch
* The 20" wheel stock tire 9" width is the same as the 19s
* The 20s look better and probably don't weigh all that much more all-in (with the tires)
* The tire availability is much higher with the 20s vs the 19s or 21s, seeing way more options on tire rack, etc
* The 20" tire replacement set is equal or cheaper than 19s

So I think I'll take your advice and build with the 20s - then I can get my favorite all-season/winter tires, Nokians, as replacements.

-----------
SIDE STORY:
Back in 2013 I had a set of Nokian WRs on an M3, drove them for 3 winters, then left them on into the spring / summer just to wear them out - those tires lasted almost the whole summer and I was beating the crap out of them with burn outs and canyon runs. Finally got to the point where I could see the cords on the very inside of rears so I dumped them, but it was kind of a Seinfeld/Kramer-runs-out-of-gas thing ... I was tempted to keep going ...

Anyway, Nokians are awesome all seasons and wear like iron is my point.

[hiluca]

Originally Posted by X5 45e

That is 6,5 % of the range for the long range version. That is significant on paper. Or is this your own experience? The economy of the x5 is also better on 19 inch wheels than on 22 inch.

I just wonder if in practice numbers will be the same. Like mentioned other factors are equal or more important.

My fuel economy is better now on staggered 20 inch than on non staggered 19 inch winter tires.
The difference in electric efficiency in the summer is caused by the higher temperatures. So it is difficult to compare.

And if you want to be really green: don't by a car at all but use a bicycle and public transport. Or a least don't by an X5 or even a Tesla but a small car with a small engine. Tesla's also have a high carbon footprint in production of the car and electricity.

So bottom line. Take the wheels you like. And buy an X5 with a 45e 6 cylinder while it is still possible.

did the 20inch 740m wheels come staggerd from factory or did you make that decision and if so how did you go about it ?

[X5 45e]

Originally Posted by hiluca

did the 20inch 740m wheels come staggerd from factory or did you make that decision and if so how did you go about it ?

Yes from factory.

In Europe 740M is 275 front and 315 back for summer tires.

If you order a winter set 740M it is 275 for the 4. I think to be able to put on snow chains ?

[hiluca]

Originally Posted by X5 45e

Yes from factory.

In Europe 740M is 275 front and 315 back for summer tires.

If you order a winter set 740M it is 275 for the 4. I think to be able to put on snow chains ?

i thought we we're getting all season runflats on the car ?
what size are those ?

[X5 45e]

Originally Posted by hiluca

i thought we we're getting all season runflats on the car ?
what size are those ?

I have 740m wheels.

315 back and 275 front

Mine are Pirelli P zero's rft. Those are not all weather. I presume in t stad they will give you the same as in the parking ( Flanders &#128540

[mmstw]

Originally Posted by X5 45e

I have 740m wheels.

315 back and 275 front

Mine are Pirelli P zero's rft. Those are not all weather. I presume in t stad they will give you the same as in the parking ( Flanders &#128540

So you are running wider in the rear than coming from the factory? 315/35R20? Might be interesting due to possibly wider selection of tyres.

[X5 45e]

Originally Posted by mmstw

So you are running wider in the rear than coming from the factory? 315/35R20? Might be interesting due to possibly wider selection of tyres.

No these are the factory installed. Sorry just had a look my mistake

305/40R20 in the rear
275/45R20 in front

[hiluca]

Originally Posted by X5 45e

I have 740m wheels.

315 back and 275 front

Mine are Pirelli P zero's rft. Those are not all weather. I presume in t stad they will give you the same as in the parking ( Flanders &#128540

haha thanks ;p

[Ian335xd]

Originally Posted by GrussGott

So i've got an M4 and of course have the big wheels and wide tires ... but in getting a 45e hybrid it occurred to me that the 19s will be lighter (and ride better) with the thinner tires providing less rolling resistance...

The same with the brakes/rotors/calipers - the non-M brakes would be lighter ...

So the question is, any genius nerd types have a theory on the efficiency difference? Minimal-to-none or small-but-noticeable?

My thinking is, doesn't look quite as nice but if I'm buying an efficiency car shouldn't I go with the highest efficiency options? Maybe I'm overthinking it ...

I would agree that the bigger and wider the tyre the more rolling the resistance but I was playing with the UK configuration and it shows that the 22" has the lowest gm/km and is 2g lower than the 20" which are narrower.

My only thought was the 22" are non run flat which would make them lighter?