[MJDBMW]

Originally Posted by SWOT1

Not on the stock rims... 265f 295r seems like the best setup. (you could always add 12-15mm spacers...)

Is anyone running 12mm spacers with the 265/295 ps4 setup? If so, any issues with handling or road noise that you care to share? Extra credit if you are running on mss springs with a 1 inch drop.

[_x3M_Competition]

Originally Posted by r33_RGSport

Interesting finding.

If OP is running without a spacer on the rear, I am very mind blown.

My HRE setup is 21x11 on the rear with 295/35-21 summer tires, barely have clearance to the inner wheel well.

I suggest OP to check the clearance before having a cut on the inside wall from rubbing.

Hey Ben,

Do you know if this tire setup will work with 15mm spacers f/r?

[r33_RGSport]

Originally Posted by cerebrallp02

Hey Ben,

Do you know if this tire setup will work with 15mm spacers f/r?

On my HRE setup, you can't run 15mm spacer since it is cut precisely for the car.

But, if you meant on the stock wheels, I have no idea if it will poke out or not with 15mm spacer.

[Kevlar]

If anybody is curious... 265/295 is the same size tire the 2020 Mercedez Benz GLC 63 uses.

[dkhm3]

I’m about to do this with Michelin’s. Any effect on mpg and handling~ like understeer?

Wheel size fits fine, our 21” wheels are the same size as the Glc63 so I am not sure why BMW decided to go so narrow.

I had swapped 295 rears on my 275 f80 and just all positives, no negative effects on mpg, plus tire wear improved because the tires were not so stressed.

[Max Well]

Originally Posted by dkhm3

I’m about to do this with Michelin’s. Any effect on mpg and handling~ like understeer?

Wheel size fits fine, our 21” wheels are the same size as the Glc63 so I am not sure why BMW decided to go so narrow.

I had swapped 295 rears on my 275 f80 and just all positives, no negative effects on mpg, plus tire wear improved because the tires were not so stressed.

Although BMW keeps much of their thought process tightly wrapped, I have no doubt that it is all about the aerodynamics, and the complex decisions that go into how a final product is delivered. As I shared in another thread, Ford's Aero 101 course ( saea.com.au/resources/Documents/aero101-SAE-A-Seminar.pdf ) provides background, with slide 19 indicating a 2010 BMW Study showed the following drag contributions: upper body 40%; cooling system 10%; underbody 20%; and tire/wheel/wheel arch 30%.

And in the M Division interview also shared previously ( bmw-m.com/en/topics/magazine-article-pool/how-bmw-m-tests-in-the-wind-tunnel.html ), Dr. Alexander Hennig states, "The basic aerodynamic shape of the bodywork has improved continuously in recent decades. This makes other factors, such as the aerodynamic optimisation of the underbody and the aerodynamic design of the rims, tyres and add-on parts, all the more important today. It is in these areas in particular that much more detailed aerodynamic work is being done today than in the past."

Undoubtedly the goal of the M Division is to settle on main performance roles each model will have, then maximize the aerodynamics within the framework of aesthetics (which surely demands compromises from both sides). Seems our F97/98 models were designed for high speed long track/Autobahn use and not short courses with tight turns like the M2 (where wider tires and fender flares become more important). Makes sense considering the higher CG associated with SUV/SAV designs.

In that Interview they talk about mm tolerances in their design, so I strongly suspect this wheel/tire/arch design is the one that provided the best aerodynamics. They could have easily designed around the the 265/295, and I would bet the design folks surely requested such for the aesthetic, but the aerodynamics must've proved substantially different for a strong argument to be made for the sizes provided on our production models.

All speculation, but I trust M Division's logic was sound and didn't occur by happenstance.

[evo-mike]

Yeah aero but cost was probably a highly contributing factor as well.

[dkhm3]

Originally Posted by Max Well

All speculation, but I trust M Division's logic was sound and didn't occur by happenstance.

While I don't disagree, one can't help notice the changes since Audi RS guy is running M is similar to RS- narrower tires, AWD, and heavier and heavier cars.

Van Meel's first M is the X3M.

https://www.autocar.co.uk/car-news/i...formance%20arm.

[RoWoX3M]

Originally Posted by MistaVauros

I'm jealous, lol 😏 I'm in MD and we are expecting snow next week, lol. However, I've been considering just running PS4S year around because my wife also has an SUV, so I figure if we need to go out in bad weather/snow, then we can just drive hers. 🤔

I'm also in MD and a new X3M owner. Mine came equipped with 21" contis. Planning now for the colder season ahead and can't decide between keeping the stock size in the Michelin Pilot Sport A/S 4 or going with the wider pirelli. In either case I'd be adding unsprung weight with an a/s tire but I'd be minimizing it in the stock sizes. Thoughts?

[evo-mike]

Originally Posted by RoWoX3M

I'm also in MD and a new X3M owner. Mine came equipped with 21" contis. Planning now for the colder season ahead and can't decide between keeping the stock size in the Michelin Pilot Sport A/S 4 or going with the wider pirelli. In either case I'd be adding unsprung weight with an a/s tire but I'd be minimizing it in the stock sizes. Thoughts?

So the Michelins a/s 4s are actually a pound lighter each than the stock contis. The Pirellis are surprisingly heavy at 37lbs for the 295/35/21s. That's 6lbs heavier than the stock rear contis. The 265s would be 3lbs heavier than the fronts. That's about 18 extra pounds, probably enough to see a noticeable difference in fuel economy and acceleration. Unlikely to feel any difference tho.

[RoWoX3M]

Originally Posted by evo-mike

So the Michelins a/s 4s are actually a pound lighter each than the stock contis. The Pirellis are surprisingly heavy at 37lbs for the 295/35/21s. That's 6lbs heavier than the stock rear contis. The 265s would be 3lbs heavier than the fronts. That's about 18 extra pounds, probably enough to see a noticeable difference in fuel economy and acceleration. Unlikely to feel any difference tho.

I saw that too on tire rack but when you go to the continental and Michelin websites the contis are about 28lbs while the a/s Michelins are about 32.

[BeyondVision]

so just wanted to check back in on this. Winter is coming in Michigan and thinking about putting Pirelli A/S on my non comp. I have 20's so I am assuming the 265 & 295 setup in 20's would also not have any issues on stock setup? Thanks.