[phillipp]

What would you say are the pros and cons of 20" wheel size vs 21" option with regards to ride and handling?

[cpt]

There are lots of variables, but in general the 21" setup will be heavier. Someone measured the Audi OEM 20" and 21" wheels + tires and the total weight difference is ~13kg (21" being heavier).

In terms of how this additional rotational weight impacts acceleration and handling, I found this controlled experiment quite useful as a frame of reference:
https://www.caranddriver.com/feature...-wheels-tires/

- As wheel size increases, acceleration and fuel economy get worse, while braking distance improves
- Cornering (skidpad g-force) improves as wheel size increases, but peaks at 18" and tapers off at 19" in this particular setup

[advantage20]

Originally Posted by cpt

In terms of how this additional rotational weight impacts acceleration and handling, I found this controlled experiment quite useful as a frame of reference:
https://www.caranddriver.com/feature...-wheels-tires/

- As wheel size increases, acceleration and fuel economy get worse, while braking distance improves
- Cornering (skidpad g-force) improves as wheel size increases, but peaks at 18" and tapers off at 19" in this particular setup

So 18" is the sweet spot performance-wise on a Golf, which is a C-segment hatchback; going bigger will lower performance and ride comfort for the sake of bigger wheel style.

I assume that same sweet spot would typically be 18"-19" on a D-segment mid-size sedan (e.g. 3 Series) and 19"-20" on an E-segment executive sedan (e.g. 5 Series), which are designed for bigger overall tire sizes; and that going for the bigger rim option within that 1" range will have smaller potential negatives than on a Golf, since the bigger the tire is to begin with, the more incremental each extra inch of rim will feel within that given diameter. So if for example 20" happens to be the optimal size on the 5er but one really likes the style of those 21" that are being showcased, perhaps the negatives of the 21" will be minimal, especially coupled with the more high-end adaptive chassis you can get on a 5er compared to lower segments. The biggest considered option needs to be tested in real life, I guess.

[phillipp]

Okay. The more I learn the more I'm confused. BMW says best range is with the 19" wheel and range gets worse with larger wheels. Well, if tire diameter stays same regardless wheel size, then how is range affected?

If you have a 19" wheel the tire has more sidewall. If you have a 21" wheel the tire has less sidewall. But tire diameter is same irrespective of wheel diameter. What am I missing?

[advantage20]

Originally Posted by phillipp

Okay. The more I learn the more I'm confused. BMW says best range is with the 19" wheel and range gets worse with larger wheels. Well, if tire diameter stays same regardless wheel size, then how is range affected?

If you have a 19" wheel the tire has more sidewall. If you have a 21" wheel the tire has less sidewall. But tire diameter is same irrespective of wheel diameter. What am I missing?

The overall tire diameter does stay the same when you opt for a larger rim size, however as the rim's diameter increases, so does the rim's width, and consequently the tire's width as well, meaning there is a wider patch of tire being constantly in contact with the road. Which provides better traction/grip under acceleration, braking and cornering, but by that same token, 1) permanently increases rolling resistance, therefore requires more energy expenditure to maintain a certain speed, and 2) permanently increases the weight of the wheels themselves to begin with, and a higher unsprung rotating mass means yet more energy expenditure.

Then again, the step from 20" to 21" on a 5er is likely more incremental than, say, the step from 18" to 19" on a Golf. Unless 21" really happens to fall way beyond the sweet spot, which you should check the given numbers for again and test drive in any case. To be fair though the bi-color M Sport 20" already look fine and just big enough, don't they?

[phillipp]

Originally Posted by advantage20

The overall tire diameter does stay the same when you opt for a larger rim size, however as the rim's diameter increases, so does the rim's width, and consequently the tire's width as well, meaning there is a wider patch of tire being constantly in contact with the road. Which provides better traction/grip under acceleration, braking and cornering, but by that same token, 1) permanently increases rolling resistance, therefore requires more energy expenditure to maintain a certain speed, and 2) permanently increases the weight of the wheels themselves to begin with, and a higher unsprung rotating mass means yet more energy expenditure.

Then again, the step from 20" to 21" on a 5er is likely more incremental than, say, the step from 18" to 19" on a Golf. Unless 21" really happens to fall way beyond the sweet spot, which you should check the given numbers for again and test drive in any case. To be fair though the bi-color M Sport 20" already look fine and just big enough, don't they?

Your response is well presented and very reasonable. Thang Kew.

[phillipp]

New question - what are "mixed" wheels and tires? When configuring the new i5 there are options for A/S (all season of course) and mixed on what appear to be the same wheel design.

[arkhi]

Originally Posted by phillipp

New question - what are "mixed" wheels and tires? When configuring the new i5 there are options for A/S (all season of course) and mixed on what appear to be the same wheel design.

They're performance tires. Comes with an increased speed limiter to 155 mph.

[Llarry]

Originally Posted by phillipp

New question - what are "mixed" wheels and tires? When configuring the new i5 there are options for A/S (all season of course) and mixed on what appear to be the same wheel design.

"Mixed" is BMW's term for staggered wheels and tires: For instance, 245/40R-20 front and 275/35R-20 rear. These have the same overall diameter. As arkhi says, they are also usually summer/non-A/S performance tires.

I see an error in the G60 i5 pricing guide, they call the 19" non-staggered setup mixed; it is not.

[BMW012]

in general, bmws have offered mixed (staggered) all seasons as well.

[tsbrown]

Originally Posted by arkhi

They're performance tires. Comes with an increased speed limiter to 155 mph.

When I ordered my G30 540i with A/S tires I didn’t realize it forced me to a lower speed limiter, 130 mph I believe. Disappointed, I searched for ways to get this increased to 155, just to have it, but it is hard coded to the car from the factory and can’t be changed. Reality is I’ve probably never been over 100 in the car and so this hasn’t been an issue. If you really want the 155 limiter order the mixed performance tires.

[tsbrown]

Any idea what the wheel offsets are for the 20” wheels? Usually can find them on RealOEM but haven’t found them yet…too early. I like some of the 8 series wheels better and might swap for them if they fit.