another performance suspension question

[3liter1]

Anyone know why they would recommend the 18' wheels......this is from the BMW website....

For optimum ride quality, BMW Performance Suspension should be used in combination with 18" tires. Part number for springs may vary depending on vehicle model and options. Consult your BMW Center for more details. Components included: • 2 Front struts and mounts• 2 Rear shock absorbers• Front sway bar, 26.5mm in diameter (replacement of the rear sway bar is not required)• Rubber sway bar mounts for front/rear• Small parts (mounting hardware, covers and dampers)

[CMSS2000]

Most likely BMW developed the Performance suspension using 18" wheels.

[mosx]

I remember reading that BMW did crash testing with 19's on the performance suspension and it didn't meet their standards...

[cwg]

maybe they feel the combination of the short stiffer sidewalls on the 19 inch wheels will produce a ride which is too harsh when combined with the stiffer suspension of the performance suspension

[tgxmike]

I'm running 17 in wheels with the full performance suspension on a 128i and it if F-ing amazing. No plans to go to 18s, but def going up in tire size to 225/45/17 all around.

[Dackelone]

Originally Posted by mosx

I remember reading that BMW did crash testing with 19's on the performance suspension and it didn't meet their standards...

Where did you read THAT?

[3liter1]

Originally Posted by tgxmike

I'm running 17 in wheels with the full performance suspension on a 128i and it if F-ing amazing. No plans to go to 18s, but def going up in tire size to 225/45/17 all around.

thanks -that's great input. i am running 17's also
Are you experienceing a bit of understeer now at the limit?

[mosx]

Originally Posted by Dackelone

Where did you read THAT?

"We asked BMW Accessories Development Manager Stephen Zoepf why a larger-than-stock diameter isn't offered. "We extensively test our wheels and tires to meet a crash safety standard and decided that 18 inches is the largest we're willing to offer for the 1 Series, 19 for the 3 Series. Anything larger runs a risk of pretty catastrophic damage."

http://www.mwerks.com/artman2/publis...formance.shtml

[Diver]

Better skip the catastrophic damage. I wonder what happens?

[Dackelone]

Originally Posted by AudiS4

Anyone know why they would recommend the 18' wheels......this is from the BMW website....

For optimum ride quality, BMW Performance Suspension should be used in combination with 18" tires.

I think it might have more t do with the TUV over here and the legal obligations that comes with.

I remember backin 2002 or so... Porsche said you could install larger wheels on the Boxsters. Porsche even went thru TUV type approval so owners could retrofit the larger turbo look wheels back then. I think they were 18"s or 19"s - I do remember they were the "996 turbo-look" hollow spoke design wheel. I forget which ones really (28"s or 19"s).

Anyway... Porsche wrote this is writing that an owner can do this. Some people did so... got the added TUV paperwork for their cars(registration) they bought. And then a few years later these cars with larger wheels started to have body cracks appear - around where the shocks mount to the body. Porsche had to buy buy all these cars quietly over here. BC... they put it in writting that you COULD mount these larger wheels. So... lesson learned. BMW could be doing the same thing... saying one use "these size wheels" not others we offer for other models.

Dackel

[mosx]

Originally Posted by maxnix

Doesn't bode well for the 1M then, does it?

In any case, one must remember that a tire's sidewall is part of the spring equation also, as is tire pressure. Sorter sidewalls are generally stiffer. See RFT here.

1M has a wider wheel base in the front, so it won't be the same.

[SiN55]

18" is just fine IMHO, why bigger?

[cwg]

If you take what BMW says at face value: "for optimum ride quality" then I think they beleive that going up to 19 inch wheels especially with rft wil make the ride too harsh and they will get complaints