Warning to OEM 640M owner.

[My2ndBMW]

I have purchased the OEM BMW 640M Winter Tire package from the dealer and had them installed.

Everything looked fine from the outside but when I got home and checked it carefully, my 9” wheel were mounted in front and 8 ½ at rear. No big deal as it fits but not right so I had them fix the mistake next day.

BTW, you have to place a small mirror behind the spoke to see the difference in parts# because visually it looks identical from outside with square tires setup.

Part# for Rear wheel should starts with 9J and Front wheel should starts with 8 ½.

[JoeFromPA]

Damn, I guess that's confirmation of what I was trying to figure out: that the 9" would fit in the front and you could order a square setup and run it with tire rotation.

[justinstephen]

This is awesome news to me. I'm planning on buying the 9" rears for all around. Were there any side effects that you saw?

[evanescent03]

Originally Posted by My2ndBMW

I have purchased the OEM BMW 640M Winter Tire package from the dealer and had them installed.

do you have photos? what specs on the tires?

thanks!

matt

[My2ndBMW]

Originally Posted by justinstephen

This is awesome news to me. I'm planning on buying the 9" rears for all around. Were there any side effects that you saw?

It definitely rides softer than PSS but other than that my M3 with Continental rides like Lexus in Comfort (suspension) setting. This is not a bad thing in a crappy road that we have here.

[My2ndBMW]

Originally Posted by evanescent03

do you have photos? what specs on the tires?

thanks!

matt

I don’t have a photo of my car but here is a photo of another forum member with 640M on F80.

http://f80.bimmerpost.com/forums/sho...&postcount=146

640M package comes with Continental ContiWinterContact TS830P 255/40 R18 tire.

[stonecliff]

Originally Posted by justinstephen

This is awesome news to me. I'm planning on buying the 9" rears for all around. Were there any side effects that you saw?

The parts manager at my dealer agreed with this approach also and I ordered 4 of the 18" rears. Should have them in a couple of weeks and will let everyone know if there is an issue.

[Falafel Combo]

Would'nt running a square setup mess up the steering and handling geometry? You want to take all that engineering and throw it away so you can save a few bucks on tires?

Any other merits to a square setup maybe I'm missing???

[stonecliff]

Originally Posted by Falafel Combo

Would'nt running a square setup mess up the steering and handling geometry? You want to take all that engineering and throw it away so you can save a few bucks on tires?

Any other merits to a square setup maybe I'm missing???

The 641M/640M rears are the exact same wheel as the 437M/513M fronts (ET29). The only difference between the front and rears on the 641M/640M set is 2mm of offset.

If BMW was recommending a staggered tire setup for the 641M/640M, I might agree. But they are not, and there is no way that 2mm of offset will mess up the steering and handling geometry. Especially since they are the same as the summer fronts anyway.

[jbtco]

Originally Posted by stonecliff

The 641M/640M rears are the exact same wheel as the 437M/513M fronts (ET29). The only difference between the front and rears on the 640M set is 2mm of offset.

If BMW was recommending a staggered tire setup for the 640M, I might agree. But they are not, and there is no way that 2mm of offset will mess up the steering and handling geometry. Especially since they are the same as the summer fronts anyway.

My 640m's are 1/2" different in width between front and rears wheels stamped 81/2" for fronts and 9" for the rears, though same tyre size recommended.

[stonecliff]

Originally Posted by jbtco

My 640m's are 1/2" different in width between front and rears wheels stamped 81/2" for fronts and 9" for the rears, though same tyre size recommended.

In this case, it's not the wheel size that matters; it's the tire size. Since the tires are the same size in all four corners, only the offset affects steering geometry. And 2mm is a pretty minimal difference, increasing front track by 4mm total.

[jbtco]

Originally Posted by stonecliff

In this case, it's not the wheel size that matters; it's the tire size. Since the tires are the same size in all four corners, only the offset affects steering geometry. And 2mm is a pretty minimal difference, increasing front track by 4mm total.

Why then do BMW make the wheels different sizes ?

[stonecliff]

Originally Posted by jbtco

Why then do BMW make the wheels different sizes ?

Great question. And the related question is "why did they change the offset from the recommended summer to winter wheels when they are putting the same size tires on them?"

Hard to imagine that BMW would think it is a problem to put snow tires on the stock 437M wheels, no?

[jbtco]

I wonder if it has to do with being able to fit chains which is I think a requirement in some places.

Or maybe just a ploy to sell more wheels.

[My2ndBMW]

I am very surprise that I am the only 640M owner with 9” wheel mounted in front and 8 ½ wheel mounted in rear by mistake.

Anyway, I am no expert in steering/handling geometry so I personally decided to stick with BMW’s recommended staggered winter wheel setup.

I do love my stock 19” wheel but 640M(18”) isn’t all that bad. Especially, I find it easier to clean than stock 19” because of less surface area and spoke design.

[remmib]

Originally Posted by stonecliff

Great question. And the related question is "why did they change the offset from the recommended summer to winter wheels when they are putting the same size tires on them?"

Hard to imagine that BMW would think it is a problem to put snow tires on the stock 437M wheels, no?

They might have changed the front offset since the front wheel is 8.5" and not 9".

On the F10 the 18x8 is ET30 while the 19x8.5 is ET33.

[Mikster]

Originally Posted by My2ndBMW

I have purchased the OEM BMW 640M Winter Tire package from the dealer and had them installed.

Everything looked fine from the outside but when I got home and checked it carefully, my 9” wheel were mounted in front and 8 ½ at rear. No big deal as it fits but not right so I had them fix the mistake next day.

BTW, you have to place a small mirror behind the spoke to see the difference in parts# because visually it looks identical from outside with square tires setup.

Part# for Rear wheel should starts with 9J and Front wheel should starts with 8 ½.

I was wondering the same thing, since I also got the 640M. Where exactly should i look for the part number...behind which spoke?

M

[My2ndBMW]

Originally Posted by Mikster

I was wondering the same thing, since I also got the 640M. Where exactly should i look for the part number...behind which spoke?

M

You place a small mirror behind the spoke to see the part number. I haven’t checked it since I had it corrected by the dealer but I remember it’s a first left (or right) spoke from the valve stem. The part number begin with either 9J (rear) or 8 ½J(front).

[jbtco]

Hopefully mine are on the correct ends of the car as I put them on myself. TPMS reset seems straightforward per idrive and pressures showing the same as my trusty Longacre gauge. On 20 mile trial run with temp at around 8C on damp greasy roads revealed no issues, ride (on the pilot Alpins on 18s as opposed to PSS on 19s) seemed a bit smoother I would say sport setting for suspension feels about the same as comfort previously.

We will probably have a warm winter here now and render all this a waste of time.

[MasterC17]

Originally Posted by Falafel Combo

Would'nt running a square setup mess up the steering and handling geometry? You want to take all that engineering and throw it away so you can save a few bucks on tires?

Any other merits to a square setup maybe I'm missing???

I'm not quite sure what you're getting at here. This is for a winter tire and wheel setup, I don't think anyone is trying to save a few bucks on tires. Second, a square setup has historically been a superior tire setup to the staggered tire setup for handling purposes.

[Mikster]

Originally Posted by My2ndBMW

You place a small mirror behind the spoke to see the part number. I havent checked it since I had it corrected by the dealer but I remember its a first left (or right) spoke from the valve stem. The part number begin with either 9J (rear) or 8 J(front).

Guess what-- dealer DID screw up!
I used a mirror to look behind the spoke on each wheel. The spoke you need to look at is immediately to the right ( counterclockwise) of the tire valve.
He had the 9 inch wide wheels (9J) on the front, and the 8.5 inch (8-1/2J, not 8J) on the rears.
Going to swap them tomorrow.

M

[01ON19]

Originally Posted by Mikster

Guess what-- dealer DID screw up!
I used a mirror to look behind the spoke on each wheel. The spoke you need to look at is immediately to the right ( counterclockwise) of the tire valve.
He had the 9 inch wide wheels (9J) on the front, and the 8.5 inch (8-1/2J, not 8J) on the rears.
Going to swap them tomorrow.

M

Same with me. Correct on one side, wrong on the other. This even after I told them front and rear wheels were different sizes. I specifically said the wheels and NOT the tires were different sizes.