[gkski]

Which tire wears quickest on a 430i xDrive? Seems my right rear wears faster than the other 3. I would expect the fronts to wear quicker than the rears. I have been rotating front to rear, but I notice measuring across the 4 channels that the right rear is at 5/32 while the other three tires are at 6/32.

 

[Doug Huffman]

Alignment, alignment, alignment, inflation, rotation.

I recommend aligning to 0.02º toe-in all around and balanced left and right camber midrange all around.

32 00 Wheel Alignment F36 / 4WD Series

Observe test conditions!
Front axle:
Total toe-in		0° 14' ± 12’
Total toe-in adjustment*		0° 14' ± 4'
Toe difference** single wheel between left/ right		max. 12'
Camber (difference between left/right max. 30')		- 0° 20' ± 30’
Camber adjustment*		- 0° 20' ± 25’
Toe difference angle (difference between left/right max. 30’)		- 1° 26'
Castor angle		(difference between left/right max. 30')
Front wheel offset		0° ± 15'
Maximum steering angle
‐ Inner cornering wheel	Ca. °	38° 06'
‐ Outer cornering wheel	Ca. °	32° 18'
Rear axle:
Total toe-in		0° 18' ± 12'
Total toe-in adjustment*		0° 18' ± 4'
Camber (difference between left/right max. 30')		-1° 23' ± 25'
Camber adjustment*		-1° 23' ± 5'
Geometrical driving axis		0° ± 12'
*Note: To minimise adjusting errors (measuring inaccuracies), use a narrower tolerance for adjusting toe/camber. **Note: Toe difference front axle = criterion for steering wheel inclination

 

[gkski]

Does the BMW dealer alignment fit the bill? I'll probably need new rubber next year. Still question which tire sees the most wear. Somewhere I read that the right rear wore the fastest.

 

[Autoputzer]

Your right-rear tire wear is not necessarily indicative of misalignment. If your tread depths are fairly even across the four circumferential channels of each tire, that means your alignment is good and your tire pressures are what they should be.

It's normal for the right rear to wear faster. Even with xDrive, the rear tires get between 60% and 65% of the power.

When you take a sharp right turn, the right rear tire gets more of the engine's torque than the left rear tire. When you take a wide left turn at speed, the right tires get more weight and therefore more wear than the left tires. My tires on the right-rear wear roughly twice as fast as my tires on the left-front.

BMW has changed their minds several times about tire rotation: don't, left-to-right only, front-to-back only, and my favorite: "consult a BMW center."

Doing a four-tire rotation pattern would even out the wear between all four tires. Since your rear tires get most of the power, use the RWD rotation pattern. Since G20's don't have full-size spare tires, skip the spare position (go from LF to RR).

After 35k miles, Frau Putzer's X3's average tread depths between tires only varied by 0.44/32". Even then, the deepest tread was on the left-front (6.28/32") and the least deep was on the right-rear (5.84/32"). After the current rotation stint, those differences will be just about wiped out.

BMW passenger cars tend to wear the inner half of the tread more. BMW SUV's tend to wear the outer half of the tread more. There are logical explanations for this: BMW spec's more negative camber for the rear wheels of passenger cars. SUV's have a higher center of mass and therefore more body roll in turns. SUV's tend to have higher aspect ratio tires, causing the tires to tuck under more when turning.

Uncle Dougie's attachment of your car's alignment spec's calls for a nominal front toe-in for each wheel to be 0° 07' (or 0.11°) ', and 0° 08' (or 0.13°) for the rear wheels. The nominal value for toe for each wheel is the total toe divided by two. BMW alignment spec's have ridiculously large tolerances. Uncle Dougie's recommending setting your toe to be just within those tolerances (0.02°) That would make any excess wear on the inner half of tread, typical on BMW passenger cars, even worse. Those small toe-values would likely be beneficial on a BMW SUV, though. Uncle Dougie has an X5.

I precisely measure my tread depths when I rotate my tires. Both of our BMW's have spare tires, so it's easy for me to do a DIY tire rotation. (You need a spare tire as a place holder.) Here are the tread depth and tread wear data sheets for the last rotations on my 535i (79k miles) and Frau Putzer's X3 xDrive 30i (35k miles). The 535i's tires wear more on the inner half of the tread. The X3's tires wear more on the outer half of the tread. Both right-rear tires wore more than the left-front tires: 140% more on the 535i, 90% more on the X3.

BMW 535i:

BMW X3:

 

[gkski]

Except we're speaking of a 2019 430i xDrive convertible (F33)?

 

[Autoputzer]

Except we're speaking of a 2019 430i xDrive convertible (F33)?

You know what they say about BMW's.... "Same sausage, different sizes."

Like Frau Putzer's X3 xDrive 30i, you should expect your rear tires to wear 30% to 50% faster than the front tires. On my RWD 535i, it's more like 140% more.

You should also expect the inner half of your rear tire treads to wear more than the outer half, like my 535i's do.

You were smart or lucky to get a square set-up with your 430i xDrive. Staggered set-ups and smart AWD's don't go well together. Slight differences in front and rear rolling diameters result in a slow, steady grind on the xDrive transfer case's clutches. BMW spec's a maximum tread depth difference of 2mm (2.5/32"). With a staggered set-up, the front and rear tread depth differences exceed that long before the front tires are worn out. With a square set-up and a four-tire rotation pattern, you can keep those differences down below 0.5/32".

 

[gkski]

So, you're suggesting the four-tire rotation with the fronts crossing to the back? Isn't my car generally front wheel drive? I guess I have just been doing front to back rotations even though I do not believe my Pirelli Cinturato P7s are directional tires.

 

[Autoputzer]

So, you're suggesting the four-tire rotation with the fronts crossing to the back? Isn't my car generally front wheel drive? I guess I have just been doing front to back rotations even though I do not believe my Pirelli Cinturato P7s are directional tires.

Yep, use the RWD, four-tire rotation pattern: LF > RR > RF > LR > LF

Your 430i xDrive still sends about 63% of the engine's power to the rear wheels. Only about 37% of the power goes to the front wheels, and that varies from 0% to 37%. At interstate speeds, your car is pure RWD.

Directional tires have pretty much gone out of vogue, with the exception of winter tires. Directional tires have a "V" tread pattern. The point of the V on top of the tire (12 o'clock) should be pointing in the forward direction.

Your all-season tires may or may not be symmetric. Asymmetric tires have an inside and outside sidewall, and they're marked as such. They're fine rotating in either direction.

The all-season tires on Frau Putzer's X3 are symmetric. After 35k miles (and some alignment problems), the average depth in the outer channel was 0.5/32" less than the inner channel. At 35k miles, roughly the half-life of the tires, I had them flipped on the wheels. I'm still getting some extra wear in the outer channel, typical of BMW SUV's. Flipping the tires on the wheels will let the deeper side channels catch up with the original outside channels. By 70k miles, the inside and outside channel depths should be just about identical. I did this as sort of a science experiment. It's not cost effective, though. Tire flipping costs between $100 and $200. I'll still have to buy a set of tires for the X3 before we sell it at around 100k miles.

 

[Autoputzer]

I've added a new calculation to my "Tire Whispering" spreadsheet above:

Average Side Channel Wear Difference / Average Wear

For a "perfect" alignment this value would be 0%, meaning that the inside and outside channels wear at the same rate, at least over a four-tire average.. For the X3's 10k miles to 17k miles rotation stint, this factor was 39%, indicating a misalignment. After the alignment, the factor was reduced to just 12% for the 17k miles to 24k miles rotation stint. For the 24k miles to 32k miles rotation stint, the factor crept up to 17%. I did a short rotation stint from 32k to 35k miles. The factor for that stint was 24%. I'll see what trend is at my 43k-mile rotation and decide if a second alignment is warranted.

If I get a second alignment, I'm going to try Uncle Dougie's trick of reducing the toe values.

 

[gkski]

Turns out the Pirelli Cinturato P7 ASRs are asymmetric so wouldn’t that mean that if you swapped the LF to the RR, the sipe pattern will be rotating opposite to how it was?

 

[Autoputzer]

Turns out the Pirelli Cinturato P7 ASRs are asymmetric so wouldn’t that mean that if you swapped the LF to the RR, the sipe pattern will be rotating opposite to how it was?

Yes, they would be rotating in the opposite direction, but the outside sidewall is still the on the outside and the inside sidewall is still on the inside.

Here's the tread pattern.

Yes, there are sort of half-V's in second and third tread blocks in from the outside sidewall. They would flush water to the inward-adjacent circumferential channel or the outward-adjacent circumferential channel, depending on which side of the car they're mounted on.

Similarly, the outside tread block also has some directionality, and would either flush water to the sidewall or to the inward-adjacent circumferential channel, depending on which side of the car they're mounted on.

I guess you could call this "mild-directionality," mild enough to be ignored. They don't sell left P7's and right P7's.

Here's some oddball tire that is both directional and asymmetric. With this tire, they'd make left and right versions. This one is the left version. The half-V on the inner half of the tire flushes water toward the inner sidewall. The outer half of the tread does very little water flushing. It's optimized to provide dry-pavement performance, particularly when turning. In a turn, the outer half of the tread on the tire on the outside of a turn does much of the work. So, this left tire's outer tread would be doing much of the work in a fast right turn.

So, do a LF > RR > RF > LR > LF rotation pattern and your four tires will wear evenly.

 

[Autoputzer]

Instead of "mild-directionality," maybe a better term would be "local-directionality."

Tires rotating in the opposite direction is beneficial. It cancels feathering by causing feathering in the opposite direction. Feathering is caused by engine torque, and also by toe and braking.

The reason there are different FWD and RWD rotation patters is to counter severe feathering incurred on the drive axle (or primary drive axle) first, followed by gentle feathering in the opposite direction on the non-driven axle (or secondary drive axle), and then with severe feathering back on the driven axle (or primary drive axle) in the opposite direction of the previous stint on the driven (or primary drive axle).

Severe feathering followed immediately by opposite severe feathering could cause the tip of the feathered tread block to tear off. Wearing down the tip of the feathered tread block gently at first (with toe and braking) prevents the tip from being torn off in severe feathering in the opposite direction.

 

[gkski]

Because these tires are non-directional but however asymmetric, I suppose an installer mounting 4 new Pirelli Cinturato P7s doesn't even pay attention to what part of the tire is in the rolling forward direction when mounting the 4 tires?

Also, given that I am around 25K on these tires and as I said the RR is wearing fastest, and also that all of my previous rotations have been simple front to backs, it seems reasonable to take the LF tire which has the most tread of all and exchange it with the RR? If this somehow gets me to a more equivalent 4 tire measurement, at that point I could go forward with the RWD, four-tire rotation pattern: LF > RR > RF > LR > LF.

Of course all this time I thought my convertible was a front wheel drive car with AWD capability!

 

[Autoputzer]

Because these tires are non-directional but however asymmetric, I suppose an installer mounting 4 new Pirelli Cinturato P7s doesn't even pay attention to what part of the tire is in the rolling forward direction when mounting the 4 tires?

Also, given that I am around 25K on these tires and as I said the RR is wearing fastest, and also that all of my previous rotations have been simple front to backs, it seems reasonable to take the LF tire which has the most tread of all and exchange it with the RR? If this somehow gets me to a more equivalent 4 tire measurement, at that point I could go forward with the RWD, four-tire rotation pattern: LF > RR > RF > LR > LF.

Of course all this time I thought my convertible was a front wheel drive car with AWD capability!

On high-performance, asymmetrical tires the difference between the inside and outside is more apparent. With all-season asymmetrical tires, the installer relies on the "OUTSIDE" and maybe "INSIDE" stamped on the sidewalls. I had a tire guy put one on backwards once. It's not just the tread patterns that are different. Often, the rubber compounds in the inside and outside of the tread are different. My backwards-installed tire wore really fast on what supposed to be the inside but mounted on the outside.

Back around 2010, BMW did a marketing study that found about 80% of BMW 1 Series drivers thought their cars were FWD.

80 percent of BMW 1-Series drivers think the car is a front-wheel drive (motor1.com)

The second generation (F48) and current (U11) X1, X2, and 2 Series Gran Coupe actually are FWD or FWD with part-time AWD.

 

[gkski]

Interesting. So actually my 2019 X1 xDrive is a front wheel drive car with part time AWD while my 2019 430i xDrive is a rear wheel drive car with part time AWD.

I misspoke on the tire mounting. What I meant to say is once the Asymmetric non-directional tires are mounted and balanced correctly in terms of outside and inside mounting, the installer won't necessarily put them on the left or right side of the car. Non-directional, so nothing to stop them from grabbing any of the 4 tires and installing whereever.

 

[Autoputzer]

Your 430i xDrive is more accurately an "almost-full-time AWD."

That RWD-based xDrive completely disengages the front drive shaft at high speeds and during very sharp turns. In sharp turns, all four wheels are traveling at different speeds. Specifically, the average front tire speed is different than the average rear tire speed. That would cause the xDrive clutches to grind or cause the tires to grind against the pavement.

I'm not exactly sure why RWD-based xDrive disengages the front axle at high speeds. I suspect it's for fuel economy and to stop any small slippage and wear of the clutch discs while traveling over great distances. If you're going 80 MPH, you're probably on the Interstate or Autobahn, the pavement is clear of snow and ice, and you're going somewhere a long distance away.

That small slippage would be from very slightly different average front and rear wheel speeds. Those very slightly different wheel speeds would be caused by very slight difference in the tires' rolling diameters. The slight differences in rolling diameters would be due to different tread depths and different sidewall deformation (due to different weight carried by the tires and different tire pressures).

Yep, once the non-directional, asymmetric tire is mounted on a wheel correctly, it doesn't matter which side of the car it goes on.

If you still have 5/32" to 6/32" of tread depth after 25k miles, you're doing pretty good for run-flat tires. From Post #4, the average tread depth on Frau Putzer's X3's non-run-flat tires at 35k miles was 6/32". But the average inner channel depth was only 5.20/32". The average outer channel depth was 5.73/32". Because the tires are symmetrical, I had them flipped on the rims. That trick cost me $200, but it should let me get another 10k miles out of the tires. That's still not cost effective, since I'll have to buy new tires before we sell the X3, either way. My tire flipping was more of a science experiment and a tree-hugging exercise (delaying sending four tires to the landfill, and maybe preventing sending a complete set of tires to the landfill before the X3 is sent to the scrap yard.

 

[gkski]

I suppose that the 45psi for the rear tires and 38psi for the front tires to account for the convertibles hard top has some impact on tire wear as well.

With the snows I just had delivered for our X1, looking forward to directional tire rotation.