[gsbaker]

I'm having a useful back-and-forth email conversation with my favored wheel/tire provider, Tire Rack. They are not recommending a square setup. I am awaiting a more detailed answer, but I think they have an issue finding a narrow-ish rear snow tire that can meet the load requirements of our portly i4s.

I'll keep you posted.

My goodyear ultragrip performance plus (bmw OE) has a load rating of 100, which is 1764 lbs. The size is 245/45R18 square.

how narrow do you want?

 

[Dyno]

My goodyear ultragrip performance plus (bmw OE) has a load rating of 100, which is 1764 lbs. The size is 245/45R18 square.

how narrow do you want?

I was just researching this. Ideally, you'd want a skinnier tire if you want the best snow performance. In our case, that might be a 225/50R18. The Michelin version has a load rating of 1709 lbs, so it should be OK. The overall diameter is good, as well. However, based on what I've seen on my summer tires, those skinny tires might wear really fast on the rear.

245/45R18 has plenty of load capacity as you point out, so it seems you could put together an 18" square package with either 225's or 245's.

However, a 245/40R19 tire does not quite meet the load rating bogey of 1709 pounds for the rear, so strictly-speaking, you can't make a 19" square configuration work unless you want fat 255's all around, but who wants that?

Tire Rack is only recommending staggered 245/255 combos at this point (either 18" or 19").

Good news regarding wheels, though. Aftermarket choices are starting to appear.

 

[toosteeley]

Good news regarding wheels, though. Aftermarket choices are starting to appear.

There are lots of aftermarket wheel choices available. Have been for a while

 

[Dyno]

I am finding conflicting information on the topic of square winter wheel/tire packages. Neither the retail tire stores nor my local BMW dealer are recommending a square setup. They are not saying "it's not advisable". They are just silent on the matter without explanation. They all recommend 245 F and 255 R in either 18" or 19" diameters.

But then there's this, from page 295 of the owner's manual...

Although it stops short of saying that an 18" 225/50 or 245/45 square setup is "recommended", it certainly implies it's OK.

On the other hand, the very same document says this...

So, if you adhere to the "divide the tire load by 1.1" guidance to winter rear tires, the only sizes that comply are the 255 options. This may be what the tire stores are seeing when they are sticking to a staggered recommendation.

BUT, my 255/40R19 OEM Pirelli P-Zero summer tires don't meet the "divide by 1.1" rule either! So, it's obviously not a hard-and-fast rule.

I've come to the conclusion I've overthought this. I may just flip a coin.

 

[skydog]

Very confused now as to whether 18” square is OK or must be staggered.

 

[toosteeley]

A square winter setup is just fine.

 

[gsbaker]

I am finding conflicting information on the topic of square winter wheel/tire packages. Neither the retail tire stores nor my local BMW dealer are recommending a square setup. They are not saying "it's not advisable". They are just silent on the matter without explanation. They all recommend 245 F and 255 R in either 18" or 19" diameters.

But then there's this, from page 295 of the owner's manual...
View attachment 33756

Although it stops short of saying that an 18" 225/50 or 245/45 square setup is "recommended", it certainly implies it's OK.

On the other hand, the very same document says this...
View attachment 33757

So, if you adhere to the "divide the tire load by 1.1" guidance to winter rear tires, the only sizes that comply are the 255 options. This may be what the tire stores are seeing when they are sticking to a staggered recommendation.

BUT, my 255/40R19 OEM Pirelli P-Zero summer tires don't meet the "divide by 1.1" rule either! So, it's obviously not a hard-and-fast rule.

I've come to the conclusion I've overthought this. I may just flip a coin.

Here is a link to our discussion of winter wheels last year.

Snow on my M50 ❄️

I got some snow on my i4 M50 😅 By the way, I don't already buy winter tires 🙈 So I drove with summer tires by -8°C on snow and the car handle it pretty well! Electric and xDrive (or 2+2) are really amazing!

www.i4talk.com

BMW was offering a winter wheel set for the i4 that was a square 245/45R18. The individual tires were rated as 100 or 1764.

Using your factor of 1.1 is equivalent to distributing 55% of weight to the rear axle.

From the specs the gross vehicle weight is 6030lbs for the M50 or the xdrive40. (6200 if you add curb weight plus max payload. Gross axle weight is 3100, times 1.1 is 3410, divided by 2 is 1705.

I bought one of the winter sets that had goodyear ultragrip p+. The sidewall is stamped with 100H for 1764 lbs at 124 mph.

There is nothing wrong with a square set as long as you get the weight rating for the rear wheels.

 

[ssh]

My M50 winter setup from BMW is exactly the same as @gsbaker's. I ran them all winter last year on all my trips to Copper and around town. I think I'll get one more season from them.

 

[Dyno]

I agree with you guys and will likely order four 245/45R18 Michelins in the next day or two, but it bugs me that the math of the owner's manual doesn't support this choice.

1. Locate the maximum tire load and the Gross Axle Weight Rating on the B-Pillar
   • Max tire load for 245/45R18 100H Michelin X-Ice Snow = 1764 lbs
   • GAWR (rear) = 3417 lbs (from the aforementioned door sticker)
2. Divide tire load by 1.1
   • 1764 / 1.1 = 1604
3. Tire load (divided by 1.1) must be greater than one half of GAWR
   1. 1604 is NOT greater than half of the GAWR (rear)
   2. The tire of this example does not meet the criteria (Pretty close, though. Close enough for me, anyway)

It seems to me that the "divide by 1.1" thing is a way to get a 10% safety factor on the load rating.

Again, I suspect this is what the tire retailers (or at least the ones I looked at) are seeing when they recommend 255's for the rear.

 

[gsbaker]

I agree with you guys and will likely order four 245/45R18 Michelins in the next day or two, but it bugs me that the math of the owner's manual doesn't support this choice.

1. Locate the maximum tire load and the Gross Axle Weight Rating on the B-Pillar
   • Max tire load for 245/45R18 100H Michelin X-Ice Snow = 1764 lbs
   • GAWR (rear) = 3417 lbs (from the aforementioned door sticker)
2. Divide tire load by 1.1
   • 1764 / 1.1 = 1604
3. Tire load (divided by 1.1) must be greater than one half of GAWR
   1. 1604 is NOT greater than half of the GAWR (rear)
   2. The tire of this example does not meet the criteria (Pretty close, though. Close enough for me, anyway)

It seems to me that the "divide by 1.1" thing is a way to get a 10% safety factor on the load rating.

Again, I suspect this is what the tire retailers (or at least the ones I looked at) are seeing when they recommend 255's for the rear.

I still think the safety factor is not needed, unless the tire rating, not the tire retailer, specifically says that it needs to be downgraded.

typically published ratings include their own contingencies. So if a tire is rated to carry 1764 lbs (100 rating) that means that 99.99% of ttires will truly carry that much.

in addition, you have to add 1200 lbs of payload to get 1705 lbs load on a rear tire. This means four hulking passengers plus six suitcases at 70 lbs ( airline max bag). You could hardly get that much into your car, so why worry?

As @ssh has pointed out, many of us drove last winter on this tire rating without issue. Even BMW dealers recommended these specs.

So you are in good company if you follow suit.

 

[Veyrix]

I'm now 95% sure I'm just going to get the BMW OEM package 18'' square setup (858M with good year ultra grip). I have 20'' wheels but based on conversations here, the sports brakes are the same on the i4 regardless of what wheel package you get (assuming you get the m sport brakes of course). I was thinking about tire rack but I think I'm a sucker for the BMW label....

 

[toosteeley]

^ Do you have the rear fender flares? If so, the front calipers are actually M Performance, not M Sport, so slightly larger.

 

[Veyrix]

^ Do you have the rear fender flares? If so, the front calipers are actually M Performance, not M Sport, so slightly larger.

Oh no you just ruined my day now as I have to go back to the drawing board on this . Yes I do have the fender flares.....oh boy....But seriously thank you for letting me know!!

 

[Veyrix]

Just to follow up on this, my service and parts department says that when they enter my VIN number every option that comes up will fit. They did confirm I do have the m performance brakes (vs the m sport brakes) but that the 18'' square setup will work (858M with Goodyear ultragrip)

 

[toosteeley]

Yes, I believe @Technic confirmed 18" BMW wheels will fit the M Performance calipers. You should be fine.

 

[Veyrix]

Thanks, yes I'm going to order the 18'' but jeez it's not like there is a lot of space now with m performance calipers and the 20'' wheels. As @techwhiz said a while ago, I can't fit much than a finger between the brakes and rotor and the inside of the wheel.....

 

[Technic]

Yes, I believe @Technic confirmed 18" BMW wheels will fit the M Performance calipers. You should be fine.

BMW states that the M Performance brakes (374mm rotors) of the M50 20" wheel option fit OEM 18" wheels minimum.

• OM Performance 18-Inch Brake System
• Description:
  4 Series M Performance Brake Kit - with Red calipers. Requires at least 18" wheels. Kit includes M Performance front and rear brake calipers, pads, rotors, sensors, and installation hardware.

 

[First EV]

Thanks, yes I'm going to order the 18'' but jeez it's not like there is a lot of space now with m performance calipers and the 20'' wheels. As @techwhiz said a while ago, I can't fit much than a finger between the brakes and rotor and the inside of the wheel.....

I went down a size on my current car with performance brakes. They said it would fit and it did, but there isn't even enough room for the wheel balancing weights to clear. They had to be put further back on the wheel. Looks kinda cool with the brakes filling nearly the whole opening though.

 

[ssh]

I agree with you guys and will likely order four 245/45R18 Michelins in the next day or two, but it bugs me that the math of the owner's manual doesn't support this choice.

1. Locate the maximum tire load and the Gross Axle Weight Rating on the B-Pillar
   • Max tire load for 245/45R18 100H Michelin X-Ice Snow = 1764 lbs
   • GAWR (rear) = 3417 lbs (from the aforementioned door sticker)
2. Divide tire load by 1.1
   • 1764 / 1.1 = 1604
3. Tire load (divided by 1.1) must be greater than one half of GAWR
   1. 1604 is NOT greater than half of the GAWR (rear)
   2. The tire of this example does not meet the criteria (Pretty close, though. Close enough for me, anyway)

It seems to me that the "divide by 1.1" thing is a way to get a 10% safety factor on the load rating.

Again, I suspect this is what the tire retailers (or at least the ones I looked at) are seeing when they recommend 255's for the rear.

FWIW, the BMW package with the Goodyear Ultra Grip Performance + has a load rating of 100H, as well:

GOODYEAR ULTRAGRIP PERFORMANCE + | 245/45/R18/100H | Winter

GOODYEAR ULTRAGRIP PERFORMANCE + Winter for 245/45/R18/100H tire size. Ultimate grip in all winter conditions

www.goodyear.eu

 

[Veyrix]

Thanks, yes I'm going to order the 18'' but jeez it's not like there is a lot of space now with m performance calipers and the 20'' wheels. As @techwhiz said a while ago, I can't fit much than a finger between the brakes and rotor and the inside of the wheel.....

I went down a size on my current car with performance brakes. They said it would fit and it did, but there isn't even enough room for the wheel balancing weights to clear. They had to be put further back on the wheel. Looks kinda cool with the brakes filling nearly the whole opening though.

Thanks! This is helpful and that sounds cumbersome. Did they have to take the wheel off and rebalance again with the restrictions of where you can put the weights?