**********s | Black Z4 w/M6 Wheels

[Dammmittt]

I'm not sure I follow. You're saying that the gap between the inside edge of the rim and where the tire sits is wider than stock, so that makes up for the 1/4 inch of radius he lost with the low AR tires?

[SapphireBlackG01]

Correct me if I'm wrong, but isn't the entire purpose (of the particular wheel sizes that Ron gave us) to preserve the overall stock diameter, even with the new wheels?

They both come out to about ~22.5 inches or so. Or close enough.

The way I look at it, I guess, is that yeah, the M6 rims are an inch bigger than stock, but the tire sizes you would buy for it are an inch shorter, therefore negating any significant difference except sidewall compliancy.

I would imagine the reason that Mako's wheels look fine without a drop, is because the stock wheels and tires also look fine without a drop, and Mako's overall diameter is the same. He simply has more metal surface area to keep things shiny and interesting.

[SapphireBlackG01]

Originally Posted by GP20

Its wheel gap is actually wider than stock since the overall tire diameter is less than stock tires.

How do you figure? Tire height is less, but wheel size is more.

Originally Posted by GP20

The car sits lower slightly, but the wheel gap is also larger slightly which is another reason (other than simply visual tricks) that makes a car look like a 4x4 when one upsizes the rims.

No, I think the reason a car looks like a 4x4 when you upsize the rims, is because upgrading from 16's/17's to 19's without the appropriate tires will, in many cases, actually LIFT the car an inch or two, because with the larger overall diameter comes a larger distance between the axle and the ground.

[SapphireBlackG01]

Originally Posted by Dammmittt

I'm not sure I follow. You're saying that the gap between the inside edge of the rim and where the tire sits is wider than stock, so that makes up for the 1/4 inch of radius he lost with the low AR tires?

A drop really though would be more than just lowering the overall diameter of the wheels/tires to bring the car closer to the ground.

It would involve lowering the springs etc to bring the car closer to the wheels instead.

[GP20]

Originally Posted by xxpaintmepunkxx

How do you figure? Tire height is less, but wheel size is more.

Tire sizes & tire overall diameters:

Stock Z4M tires:
225/45/18 - 659.63 mm
255/40/18 - 661.16 mm

235/35/19 - 646.93 mm
265/30/19 - 641.35mm

245/35/19 - 654.05 mm
275/30/19 - 647.44 mm

If you go with either 235/265, or 245/275, you're decreasing the overall tire diameters, hence why the car now sits closer to the ground, and why the wheel gap is now bigger.

No, I think the reason a car looks like a 4x4 when you upsize the rims, is because upgrading from 16's/17's to 19's without the appropriate tires will, in many cases, actually LIFT the car an inch or two, because with the larger overall diameter comes a larger distance between the axle and the ground.

Nope. The car doesn't need to be lifted an inch or 2 to give you that 4x4 look. In many cases the car actually sits closer to the ground than before. Like I said, the 4x4 look is mainly just a visual trick.

[GP20]

Originally Posted by xxpaintmepunkxx

I would imagine the reason that Mako's wheels look fine without a drop, is because the stock wheels and tires also look fine without a drop, and Mako's overall diameter is the same. He simply has more metal surface area to keep things shiny and interesting.

It's the style of his rims that plays the visual trick like I've been talking about. Both sets of the rims in the picture are 19". Which do you think look bigger?

[MakoBimmer1]

Originally Posted by GP20

Which do you think look bigger?

[SapphireBlackG01]

Originally Posted by GP20

Tire sizes & tire overall diameters:

Stock Z4M tires:
225/45/18 - 659.63 mm
255/40/18 - 661.16 mm

235/35/19 - 646.93 mm
265/30/19 - 641.35mm

245/35/19 - 654.05 mm
275/30/19 - 647.44 mm

If you go with either 235/265, or 245/275, you're decreasing the overall tire diameters, hence why the car now sits closer to the ground, and why the wheel gap is now bigger.

You're going to have to explain the math to me, because the way that I did it, it shows the opposite effect. Total diameter increasing, because the increase in wheel size more than offsets the small decrease in tire height.

Correct me if I'm wrong.


18 inch wheel + 3.986 (225mm*0.45) inch tire = 21.986 inches diameter
18 inch wheel + 4.015 (255mm*0.40) inch tire = 22.015 inches diameter

19 inch wheel + 3.375 (245mm*0.35) inch tire = 22.375 inches diameter
19 inch wheel + 3.248 (275mm*0.30) inch tire = 22.248 inches diameter


It seems to me that there's some error in your numerical work, because a 650mm diameter is more than 25 inches across, and I would think that size is a bit large to fit in the wheel well of any Zed, M or otherwise.

[ronn888]

Originally Posted by xxpaintmepunkxx

You're going to have to explain the math to me, because the way that I did it, it shows the opposite effect. Total diameter increasing, because the increase in wheel size more than offsets the small decrease in tire height.

Correct me if I'm wrong.


18 inch wheel + 3.986 (225mm*0.45) inch tire = 21.986 inches diameter
18 inch wheel + 4.015 (255mm*0.40) inch tire = 22.015 inches diameter

19 inch wheel + 3.375 (245mm*0.35) inch tire = 22.375 inches diameter
19 inch wheel + 3.248 (275mm*0.30) inch tire = 22.248 inches diameter


It seems to me that there's some error in your numerical work, because a 650mm diameter is more than 25 inches across, and I would think that size is a bit large to fit in the wheel well of any Zed, M or otherwise.

I believe G20 is right... plug in the tire sizes in the calculator found on the top of this page:

http://www.e90post.com/forums/forumdisplay.php?f=12

[ronn888]

Ron, read somewhere on the grapevine that there may be M6 Reps that are forged coming sometime in the future from you guys... any truth to this? TIA

[GP20]

Originally Posted by xxpaintmepunkxx

You're going to have to explain the math to me, because the way that I did it, it shows the opposite effect. Total diameter increasing, because the increase in wheel size more than offsets the small decrease in tire height.

Correct me if I'm wrong.


18 inch wheel + 3.986 (225mm*0.45) inch tire = 21.986 inches diameter
18 inch wheel + 4.015 (255mm*0.40) inch tire = 22.015 inches diameter

19 inch wheel + 3.375 (245mm*0.35) inch tire = 22.375 inches diameter
19 inch wheel + 3.248 (275mm*0.30) inch tire = 22.248 inches diameter

To get the height of the side-wall, you took 225 (tire width) and timed it by the aspect ratio 45% or 0.45 and eventually got 3.986"; this part you did correctly. Now this is where you did the calculations wrong - you then proceeded to add the full length of the rim and only 1 end of the side-walls of a tire (3.986") together. You forgot about the opposite end of the side walls. To get the diameter of the wheel, the correction calculation would be:

(diameter of the rim) + (tire-width x aspect ratio) x 2

or

( (radius of the rim) + (tire-width x aspect ratio) ) x 2

[Ron@Modbargains]

Originally Posted by ronn888

Ron, read somewhere on the grapevine that there may be M6 Reps that are forged coming sometime in the future from you guys... any truth to this? TIA

Heh, I need to go chop that grapevine As of now, no truth about it coming out in the future. We talked about it at a meeting but that's it, just talk, I wouldn't expect anything for awhile if it was to happen.

[SapphireBlackG01]

Originally Posted by GP20

To get the height of the side-wall, you took 225 (tire width) and timed it by the aspect ratio 45% or 0.45 and eventually got 3.986"; this part you did correctly. Now this is where you did the calculations wrong - you then proceeded to add the full length of the rim and only 1 end of the side-walls of a tire (3.986") together. You forgot about the opposite end of the side walls. To get the diameter of the wheel, the correction calculation would be:

(diameter of the rim) + (tire-width x aspect ratio) x 2

or

( (radius of the rim) + (tire-width x aspect ratio) ) x 2

Haha, my mistake. Thanks for the clarification.

[montreal_bimmer]

car looks hot as hell with those M6 reps on....

nice job Ron....

[MakoBimmer1]

Wheel weights with tires:

Stock 18" wheel + tire: 50lbs (F), 55.5lbs (R)
Miro M6 19" wheel + tire: 49lbs (F), 54lbs (R)

Not bad!!!!

--Chad

[valdeztke]

How "bad" do these look in 18's?

I'm curious as I just picked up a Z4 and I'll only have it till MAR08. What other cars (335/328? possibly) will 19/ w/ the Z4 offset go onto?

[Ron@Modbargains]

Originally Posted by valdeztke

How "bad" do these look in 18's?

I'm curious as I just picked up a Z4 and I'll only have it till MAR08. What other cars (335/328? possibly) will 19/ w/ the Z4 offset go onto?

They don't look necessarly bad in 18, its just that I think most people prefer going to the bigger size like the 19's if they are going to go and get some wheels and tires. The offsets of the Z4 are high offsets so in 19, you are looking at 19x 8.5 ET35 and 19x9.5 ET40, If it was an MZ4 the rear would be a 19x9.5 ET20.

[JEllis]

I dont really understand the M6 wheel craze...

[Hawkeye]

That is because you have no style... or Zed

[albailey]

Originally Posted by JEllis

I dont really understand the M6 wheel craze...

dude, let your eyes go out of focus... it's a big flower! now do you get it?

not really my thing either, but they do look like they'd show less brake dust
with that dark interior and be fairly easy to clean. if they could be had in the
18 to 20lb range i'd like the look a little more

[yamazaho]

M6 wheels look perfect on the Z's, especially after a drop!!!

[Ron@Modbargains]

Originally Posted by albailey

dude, let your eyes go out of focus... it's a big flower! now do you get it?

not really my thing either, but they do look like they'd show less brake dust
with that dark interior and be fairly easy to clean. if they could be had in the
18 to 20lb range i'd like the look a little more

Yeah current M6 wheels in 18 are 22lbs I think, that if they went any lower in weight it would probably become unsafe.