[NCRob]

Hi, I've read through vartious threads where different folks have ran both and been happy without complaints. Question though: Other than cosmetic or price, is there any "functional" advantage or disadvantage of one set over the other?

Personally, I will be running mine on Titan 7 7 TS-5 aftermarket wheels
(35 profile on all tires mentioned)

[Holset]

I would not go more than a 10mm front to rear difference it's not good for the centerdiff.

And installing larger diameter tires will make your car accelerate slower because of higher gearing but if you have lighter wheels you can mitigate some or all of that.

[pbonsalb]

295 makes the 3.15 diff like a 3.12 and 305 makes it like a 3.09.

[bcparker2]

Yolo and go 295/305. With stock 706m and suspension the front rub just a touch at like 2/3rds to lock and if you go past it clears. Can't speak to driving dynamics vs other sizes.

[Holset]

Originally Posted by Holset

I would not go more than a 10mm front to rear difference it's not good for the centerdiff.

And installing larger diameter tires will make your car accelerate slower because of higher gearing but if you have lighter wheels you can mitigate some or all of that.

I would like to add that i mean not over 10mm in width front to back or more specific not more than 1.1% circumstance like the stock tires have.

[pbonsalb]

Does the Idrive let you do custom wheel/tire sizes and if so does selecting this option merely correct the speedometer or also change the traction control front/rear difference slip allowance? Or am I confusing BMW with Porsche? If I am confusing the two, can a different tire size be programmed into an ECU with a high end scan tool?

If only a 1.1% difference is allowed, why does BMW say that square snow tires are OK? Is it that 0% difference is OK because the traction control slippage allowance goes the other direction? Square is 1.1% less difference than stock; 2.2% from 285/305 staggered is 1.1% more than stock.

[NCRob]

Originally Posted by pbonsalb

295 makes the 3.15 diff like a 3.12 and 305 makes it like a 3.09.

Hi, can you clarify for this newbie what those numbers mean?

[pbonsalb]

Stock differential is 3.15 ratio. Generally, the higher the number, the higher the performance because the rpm of the engine is higher and “more in the power and” at a given speed. With cars that make ridiculous torque at very low rpm like our twin turbo V8, you don’t need rpm as much to access power, so this is not as much of an issue.

A longer diff (lower numerical number) will give less rpm at the same speed and is typically less performance oriented and more fuel economy oriented. A shorter diff (higher numerical number) typically has the opposite result.

The differences we are discussing here are really minuscule. Very, very, very few drivers could feel any difference. Maybe it could be measured in tiny fractions of a second on a 2 or 3 minute race track. A bigger difference, like a 1/10 or more might be noticeable. Most drivers would need at least a couple of 1/10ths to notice.

On my E36 M3, I have run 3.15, 3.23, 3.38 and 3.64 so I studied and experienced a range of diffs in the same car.

[Holset]

Originally Posted by pbonsalb

Does the Idrive let you do custom wheel/tire sizes and if so does selecting this option merely correct the speedometer or also change the traction control front/rear difference slip allowance? Or am I confusing BMW with Porsche? If I am confusing the two, can a different tire size be programmed into an ECU with a high end scan tool?

If only a 1.1% difference is allowed, why does BMW say that square snow tires are OK? Is it that 0% difference is OK because the traction control slippage allowance goes the other direction? Square is 1.1% less difference than stock; 2.2% from 285/305 staggered is 1.1% more than stock.

In the Idrive i can choose between the stock and other tire sizes the other sizes is non specific though and also if you have summer or winter tires.

[pbonsalb]

I’ll have to check again. One of my cars has an option for custom.

[Holset]

Bmw sells Michelin winter tires setups in front 265/40-19 back 285/40-19 thats 2,6% difference in circumference and they also offers 265/40-19 front and back.
You can choose those specific dimensions in Idrive under winter tires.

Still i would not personally run more than 1,1% on summer tires.

[pbonsalb]

If 2.6% is OK, 0% is OK and 1.1% is OK, then I don’t see why 2.2% is not OK.

[Holset]

I think winter tires has more "give" and slip in them and if you choose those specific dimensions in Idrive i guess the car changes some settings to accommodate those tires?

[Maverik259]

Originally Posted by NCRob

Hi, I've read through vartious threads where different folks have ran both and been happy without complaints. Question though: Other than cosmetic or price, is there any "functional" advantage or disadvantage of one set over the other?

Personally, I will be running mine on Titan 7 7 TS-5 aftermarket wheels
(35 profile on all tires mentioned)

I'm running 285/295.

More tread on the road = more friction = more grip

Thicket side wall = less wheel gap = more rim lip protection from curbing

More Weight

More expensive

No option for BMW star in the rear 295.

Just my experience.

[pbonsalb]

275/285 are pinched in the 10.0/11.0 20” Titan7 TS5. The front still looks OK but the rear really looks bad. Definitely needs more rubber and I am not sure 10mm will be enough. Hopefully I can burn up these tires in the next year and buy wider PS4.

[NCRob]

Originally Posted by pbonsalb

275/285 are pinched in the 10.0/11.0 20” Titan7 TS5. The front still looks OK but the rear really looks bad. Definitely needs more rubber and I am not sure 10mm will be enough. Hopefully I can burn up these tires in the next year and buy wider PS4.

Yeah, Autotalent vendor recommended 305s on rear. Makes me wonder why Titan didn’t make the wheels to fit the OEM specs? At any rate, I still will likely get them for what appears to be a great value plus I definitely like the look of the larger tires. So I can sell my OEMs or just hold them to slap back on at lease end. Now I wish the car came with all seasons. That would be a perfect situation in my case!

[pbonsalb]

Wider is higher performance and most buyers of aftermarket wheels want higher performance. You can probably find stock size wheels if that is all you want. But with the wider wheels, I would run wider tires — if not at the time you buy the wheels, then when you wear the stock tires out. I did not want to buy $1800 worth of tires when mine have a decent amount of life left.

[NCRob]

So there is not a BMW star PS4 in 305, but any reason not to run the Ferrari spec at 2 lb weight savings over generic?

https://www.tirerack.com/tires/tires...PS4S&tab=Sizes

https://www.tirerack.com/tires/tires...4SXL&tab=Sizes

[pbonsalb]

Is there less tread depth?

[NCRob]

9.5/32” vs 9/32” if one couple tell a difference in this??

[pbonsalb]

No. I was just trying to come up with an explanation for the weight difference. Maybe the Ferrari is lighter so the load rating is less?

[NCRob]

Originally Posted by pbonsalb

No. I was just trying to come up with an explanation for the weight difference. Maybe the Ferrari is lighter so the load rating is less?

Ferrari is actually a little more load rated but the tread width is less: 10.4 vs 11.2

Still, 2 lbs seems like an awful lot. That being said, would we still want to use the Ferrari on our M5 for that weight savings? Or am I missing something which could definitely be the case as I know next to nothing on the matter myself