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[Flumazenil]

I remember reading an article that stated that 18's with the same brand tire actually performed better than the 19" counterparts. Is this true for those of you who have both rims? Seems to make sense due to less weight of the 18's.
The 19's of course look hot.

[quality_sound]

All things being equal yes, they should. But the 19s weigh less so it's not so cut and dried.

[VBM3]

I run 19's on the street and 18's on the track.

[FruitCake]

18s all day long!

[kitw]

Normally 19s are heavier, but the M3's wheels are sort of unique in that the bigger wheels are lighter... combined with the shorter and stiffer sidewall, they handle pretty nicely. Surprisingly the 19s ride well too, I'd say even better than the crappy runflats on our 335i

[bobbyd1961]

the 19s run leaps and bounds better than the runflat 18s on my old 335. 19 rims a whole lot better looking than 18s

[OMID INC]

i thought the 18s weightd the same as the 19s. forged typically lighter than cast. 19s are forged, 18s are cast

think about this too... there is more rubber on the 18s v the 19s. = more weight from rubber and more air inside the tire. (people frequently forget that air does weigh something and so do the damn rubber from the tires)

at this point i would say that brand of rubber would have the most to do with performance. 1-3 pounds per wheel will do NOTHING for 90th percentile of intermediate drivers.

[Finnegan]

Weight issues and forged vs. cast aside, the 18s handle just as well and have a better ride than the 19s. I've had both stock 18s and 19s on the car--both with PS2s.

It comes down to looks; I tired of the 18s, now have 19s.

I think it's pretty much a given from the track rats around here 18s are the best for that application.

[MTROIS]

Originally Posted by VBM3

I run 19's on the street and 18's on the track.

+1

[starkraven]

I run 13s, bitches. Sweeet!

[OMID INC]

Originally Posted by Finnegan

Weight issues and forged vs. cast aside, the 18s handle just as well and have a better ride than the 19s. I've had both stock 18s and 19s on the car--both with PS2s.

It comes down to looks; I tired of the 18s, now have 19s.

I think it's pretty much a given from the track rats around here 18s are the best for that application.

but for what reason? maybe superior tire selection and price? there are 19s that are super light and would constitute use of tires with smaller sidewall for increased precision in handling. just something to keep in mind.

not to say you cant throw 285/30s on 18s.. but you know.

[skierman64]

BMW engineers say that 18s are slightly faster at the track than the 19s. I'm not sure of the reason. That was said back in '08 when the M3 was first sold in the US.

[Finnegan]

Originally Posted by Finnegan

I think it's pretty much a given from the track rats around here 18s are the best for that application.

Originally Posted by OMID INC

but for what reason? maybe superior tire selection and price? there are 19s that are super light and would constitute use of tires with smaller sidewall for increased precision in handling. just something to keep in mind.

not to say you cant throw 285/30s on 18s.. but you know.

The reasons, if I recall correctly and we're talking track, are:

Greater tire selection in 18s, somewhat cheaper too; forged 18s are lighter than forged 19s (all things being equal--and it's a rough generalization). Price: Apex makes a nice form flowed cast wheel in 18s (up to 18 x 10) that seem to get good reviews and don't cost and arm and a leg. The rationale there is that you'll go through some wheels (and tires ) if you track the car a lot (bend a rim, off track "excursions", wear and tear), so why pay an arm and a leg for wheels for the track?

I think this thread probably belongs in the "Wheels and Tires" section. Also, there are much more knowledgeable folks around here on this topic than me, and what you see above is what I've gleaned (or recall gleaning) from the real experts....

[fatpanda]

Originally Posted by Finnegan

The reasons, if I recall correctly, were:

Greater tire selection in 18s, forged 18s are lighter than forged 19s (all things being equal). Price: Apex makes a nice form flowed cast wheel in 18s (up to 18 x 10) that seem to get good reviews and don't cost and arm and a leg. The rationale there is that you'll go through some wheels (and tires ) if you track the car a lot (bend a rim, off track "excursions", wear and tear), so why pay an arm and a leg for wheels for the track?

I think this thread probably belongs in the "Wheels and Tires" section. Also, there are much more knowledgeable folks around here on this topic than me, and what you see above is what I've gleaned (or recall gleaning) from the real experts.

+1 id say just buy watever u think looks nice, price aside. Like the other thread on grey vs silver rims... theres no conclusion..

[quality_sound]

Even with a lighter, larger wheel there will still be more weight nearer the outside of the wheel. The farhter away from the hub the weight is the harder it is to start and stop the wheel it is. This is why the 18s can weigh more but still be faster or get better mileage, assuming you're using the same tires with the same compounds.

[OMID INC]

i assumed we were talking about oem 18s vs oem 19s. thats why i mentioned forged vs cast 19s and 18s.. either way.

[quality_sound]

Even using the OEMs the example is still true. The smaller the wheel gets the less important the weight becomes. Honestly, I think that's the reason that the 19s are forged and the 18s aren't.

[donovan]

Blah..just wrote a page on a topic similar to this.

18:
A. Lighter
B. Tires cost less
C. Cheaper to purchase and wider selection (my opinion)

19:
A. Potentially could look better
B. Expensive Tire
C. More Weight
D. Tire rub is suspesion to low.

[Richbot]

Originally Posted by quality_sound

Even using the OEMs the example is still true. The smaller the wheel gets the less important the weight becomes. Honestly, I think that's the reason that the 19s are forged and the 18s aren't.

Word. This has been gone over a bunch of times elsewhere.

Since the tires are almost identical, and the wheels are very close in weight it makes an apples-to-apples comparison (almost) possible, if we can believe Tire Rack's specs for the PS2's

245/40-18 24lbs
265/40-18 27lbs

245/35-19 24lbs
265/35-19 25lbs

At 26.3" tall, the 265/40-18 has about 4" from the bead to the tread. The 265/35-19, at 26.3" tall, has about 3.5" from the bead to the tread. So while it weighs less, the weight of the tire is concentrated in 3.5" instead of 4". A moment of inertia calculation would still probably put the 19's at a lower MOI than the 18's for the rear wheels, but that's probably much more tire dependent than wheel dependent, as the PS2's just seem to be exceptionally light in that particular size.

For the fronts, because they're also working with 0.5" less distance from bead to tread, the 19's probably pencil out a lot closer to the same.

Still, all other things being equal, the 19's probably are a little easier to accelerate than the 18's, mostly because of the heavy rear tire that comes with the 18" package. Also, can't forget that the difference in sidewall between the 18's and 19's only affects the sidewall weight, the weight at the tread cap and across the carcass is probably roughly the same whether it's a 19" tire or a 15" tire as long as the overall diameter and tread width are about the same. So while more weight is concentrated further out, it's only 0.5" worth of whatever the sidewall weighs, not 25 pounds.

But when it comes to unsprung weight and how hard the suspension has to work, the 19's have a clear advantage, because that number is only really about dead mass and not rotating mass.

Intuitively, once you start getting in to a car with this much power and weight, a taller sidewall for the rear tire starts to make a lot more sense than a shorter one. Probably why the performance difference between the 18's and the 19's isn't greater, since the 19's are clearly both lighter and easier to spin up and slow down.

As soon as you start going aftermarket, buying 19's doesn't make any sense to me at all if you're looking for outright speed around a track. Better tire choice, lighter wheels, lighter tires, plenty of brake clearance, cheaper, easier to mount.

[quality_sound]

Originally Posted by donovan

Blah..just wrote a page on a topic similar to this.

18:
A. Lighter
B. Tires cost less
C. Cheaper to purchase and wider selection (my opinion)

19:
A. Potentially could look better
B. Expensive Tire
C. More Weight
D. Tire rub is suspesion to low.

More weight towards the edge, yes, but not necessarily more overall weight.
There is absolutely no difference in tire rub if the offset and widths are the same.

[BMWMFAN27]

Originally Posted by Flumazenil

I remember reading an article that stated that 18's with the same brand tire actually performed better than the 19" counterparts. Is this true for those of you who have both rims? Seems to make sense due to less weight of the 18's.
The 19's of course look hot.

I was told the 18's perform better, but I am sure everyone will have their own opinions and reasons as to why or why not.

[curveball99]

I have a set of 18" Volk on order and prior to buying, I consulted with a few 'experts' that had a lot of race/track experience and was surprised that they unanimously recommended going with 18's. I was initially set on buying 19's myself because I thought they would look better. I have to admit, however, that the 18's have actually grown on me and now I prefer the look of the 18's. The blue M3 in the pic below is on 18's and the AW on Volk TE-37SL's.