Z4M Coupe tire size question

[ManoSpeed]

So I'm getting ready to purchase winter tires and am reading my Z4M manual and it states the following:

Front: 225/45 ZR18 (30PSI)
Rear: 255/40 ZR18 (32PSI)
225/40 R18 92 V M+S (33PSI front/38PSI rear)


Is BMW telling me that for winter tires I need to get a non-staggered setup of size 225/40 R18 92 V M+S? Initially, I was thinking simply get the same OEM sizes in a staggered setup for a winter tire, but now I'm not sure.

Any ideas?

[esqu1re]

I have winter rims for the z4m, and they're all 8.0 in but with different offsets in the back so they don't have that shrunken look. I don't know if that's what you're asking.

Edit: I don't know whether that 225/40 R19 92v M+S pertains to the winter rims they have for sale for the Z4 or the stock rear rims.

[ManoSpeed]

Actually, I am not changing rims. I am leaving the OEM rims on. I just want to put on winter tires. In the manual they are giving me the following:

Front: 225/45 ZR18 (30PSI)
Rear: 255/40 ZR18 (32PSI)
225/40 R18 92 V M+S (33PSI front/38PSI rear)

I assume the first two entries are the stock OEM wheel sizes (staggered setup). The M+S (mud+snow) is listed in the 3rd entry. Is BMW recommending I get the following tire size for winter driving for all 4 wheels?

225/40 R18 92 V M+S

[esqu1re]

Maybe someone who knows for sure can chime in, but I know that you don't want to go too wide for winter tires. Wider tires in the snow are not good because you'll be "hydroplaning" over the snow---instead of going through it, you'll be going over the snow. Hence, BMW's snow rims for the z4 are 225's all around.

Now, with that said. I don't know if 225s will fit over the rear tires or whether BMW is recommending you put 225's on the back of stock tires.

[dekaliber]

There's a very small selection of winter tires in the staggered stock setup, which is probably one reason BMW is recommending the non-staggered setup for all 4. What esqu1re said is also correct -- you want narrower tires for good snow traction. Actually, a 225/40R18 tire is supposed to fit on a 9" wide wheel whereas a 225/45R18 only goes up to 8.5", which is probably why they're suggesting a smaller aspect ratio.

[ebruder]

The comments about going narrow are absolutely dead on. I am running 215/55VR-17 Dunlop Winter Sport M3 on dedicated 17" winter wheels all the way around. The is compared to my summer tires of 235/40R-18 and 265/35R-18. I didn't down size to save money, but to get the grip in winter time that I need, but the money savings on the smaller tires covered a significant amount of the cost of winter wheels. When you add in the cost (and tire stress) of mounting and unmounting, I believe you will be way ahead with a dedicated winter package.

Even if you choose to stay with 18's and stock wheels, go skinny and higher aspect ratio.

EB

[ManoSpeed]

Thanks for all the input, but can anyone confirm that BMW manual is recommending I use the following 225/40 R18 92 V M+S (33PSI front/38PSI rear) size on stock OEM rims for a winter tire setup?

[ebruder]

Originally Posted by ManoSpeed

Thanks for all the input, but can anyone confirm that BMW manual is recommending I use the following 225/40 R18 92 V M+S (33PSI front/38PSI rear) size on stock OEM rims for a winter tire setup?

If that is what is written, that is what they are recommending, however it is not necessarily the best set up by far. Going square, however, is just fine.

EB

[dekaliber]

FWIW, I ran 225/40R18 Dunlop Wintersport 3Ds front and back on my Z4 3.0si with ZHP wheels (8x18 front, 8.5x18 back) with no problems for 2 winters. (Same setup is being put on the ZHP in a couple of weeks.) Lots of people emphasize narrower and smaller wheels, but I found 18" not too different from the 17" setup I had used for the first year.

[ManoSpeed]

Originally Posted by dekaliber

FWIW, I ran 225/40R18 Dunlop Wintersport 3Ds front and back on my Z4 3.0si with ZHP wheels (8x18 front, 8.5x18 back) with no problems for 2 winters. (Same setup is being put on the ZHP in a couple of weeks.) Lots of people emphasize narrower and smaller wheels, but I found 18" not too different from the 17" setup I had used for the first year.

Sounds good; The non-staggered setup suggested by BMW is actually $110 dollars cheaper than the staggered summer size setup, if I were to try that out in a winter tire. I'm going go to ahead and get the 225/40R18s.

Thanks

[Nate2046]

I can't answer your question about whether its what BMW intended but I can confirm they'll fit on the stock wheels. I've run 225/40's front and back on the stocks for the last two winters. Have fun in the snow

[elerner61]

Originally Posted by dekaliber

There's a very small selection of winter tires in the staggered stock setup, which is probably one reason BMW is recommending the non-staggered setup for all 4. What esqu1re said is also correct -- you want narrower tires for good snow traction. Actually, a 225/40R18 tire is supposed to fit on a 9" wide wheel whereas a 225/45R18 only goes up to 8.5", which is probably why they're suggesting a smaller aspect ratio.

Quoting an old thread because I'm looking to put winter tires on my OEM rims (and one of my rears has a slow leak and little tread left).

I could not find any winter tires on TireRack in 225/40/18. There are a few in 225/45/18 which is the stock size for the fronts. The quote above saying the 225's with the higher aspect ratio would be less suitable for the wider rim in the rear is confusing to me. I would think that the taller sidewall would provide more "give" to mount on the wider rim.

Can someone explain why I'm wrong?

Thx.!

[dekaliber]

This is probably a good question for the Tire Rack guys. It's just what the specs say. I just looked though, and there are plenty of winter tire options for 225/40R18.

[elerner61]

Originally Posted by dekaliber

This is probably a good question for the Tire Rack guys. It's just what the specs say. I just looked though, and there are plenty of winter tire options for 225/40R18.

I see all those tires listed now as well. Hmmm, I must have messed up somewhere. Thanks for checking for me!. I'll post the question over in tires as well.

[ManoSpeed]

Speaking of winter, I don't think I'm going to be running the M this winter. The winter tires were fantastic and I never had a problem, but watching the guy get pounded by salt, water, snow, and debris from other cars just pains me so this year I'm opting to get a daily driver for 3-4K. I'm leaning towards the Subarus for their AWD capability and their very reliable boxes engines.

[epbrown]

Same here - I drove it that first winter, and winced every time I heard salt rattling against the underside, even though I was having it washed once a week (underside included). I still drive it on clear days, but typically drive my equally impractical but less-loved 2nd car during the winters since then (Smart Fortwo, Pontiac Solstice GXP and this year, BMW Z3 coupe.)

[BTM]

Anyone have pics of 225/40s on the 9" wheels? I remember that size being slightly stretched on my 8.5" E90 wheels...

I would personally go 235/40 or 245/40 all around

[djlogan33]

Originally Posted by ManoSpeed

So I'm getting ready to purchase winter tires and am reading my Z4M manual and it states the following:

Front: 225/45 ZR18 (30PSI)
Rear: 255/40 ZR18 (32PSI)
225/40 R18 92 V M+S (33PSI front/38PSI rear)


Is BMW telling me that for winter tires I need to get a non-staggered setup of size 225/40 R18 92 V M+S? Initially, I was thinking simply get the same OEM sizes in a staggered setup for a winter tire, but now I'm not sure.

Any ideas?

================================================== ======
BMW is right.
For winter tires, U want smaller & skinner tires, same size on all four corners, with good all-season tread.
They will not be as cool looking, but much safer.
Also, with the same size tires you can rotate them every winter and make them last much longer.

If I were you, I would find some inexpensive used 17" wheels and mount the winter tires on them.
I did this for many years before I got a daily driver (winter/bad weather) car.

My rack tires are smaller 17" tires that are all the same size.
Since I wear the left two tires much more than right two tires, I keep them rotated.

[aerobod]

Originally Posted by djlogan33

================================================== ======
If I were you, I would find some inexpensive used 17" wheels and mount the winter tires on them.
I did this for many years before I got a daily driver (winter/bad weather) car.

Be careful choosing 17" wheels for the Z4M. When I bought winter wheels for my Z4M, there was only one 17" wheel that Tirerack sold that would clear the front brake calipers and with that wheel you had to make sure the balance weights were either inboard or on the spokes to clear the caliper. Not liking the look of the only 17" that would fit, I just opted for one of the much wider range of 18" wheels that would fit.

Although BMW specifies a 225/40-18 standard winter tyre, if you don't plan on fitting chains, 225/45-18 works better from both a clearance and sidewall height perspective.