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[808E90]

I've been thinking about this for some time now and I still can't make up my mind! Here's the problem ...

I sold my stock 18"s and got two new sets of wheels: 20" Advan RS-Ds and 18" Advan RG-IIs. When I first bought them I was thinking I could use the 18" as a back up or track set and the 20" as my everyday set. I’ve been so busy at home with our newborn that I really don’t see myself going to the small track that we have. The 18s also makes the car sit low and I go places with huge dips. The ride on the 20s is kinda harsh on our Hawaii roads and I'm just not to happy with the look.

I am now thinking of selling the two and getting one nice set of 19” wheels. I would have the comfort, performance and I could really use the space that the second sets take up too. I was looking into some BBS LM-Rs but the 19" wheels look so small on the E90!

Here link to a few pics of both wheels:
http://www.m3post.com/forums/showthr...&highlight=JDM


Thanks!

[skierman64]

It seems strange that the 18s would make the car sit lower. The outside diameter of the tire should be the same regardless of the wheel size. For example the 18s should have more tire sidewall to make up for the smaller wheel diameter. Are you running stock sizes on the 18s?

[Lemans_Blue_M]

Sell both of your current sets and get the OEM 19's plus a few other mods.

[drivendriver]

Originally Posted by skierman64

It seems strange that the 18s would make the car sit lower. The outside diameter of the tire should be the same regardless of the wheel size. For example the 18s should have more tire sidewall to make up for the smaller wheel diameter. Are you running stock sizes on the 18s?

Just what I was thinking and wondering.

[808E90]

Originally Posted by skierman64

It seems strange that the 18s would make the car sit lower. The outside diameter of the tire should be the same regardless of the wheel size. For example the 18s should have more tire sidewall to make up for the smaller wheel diameter. Are you running stock sizes on the 18s?

Originally Posted by drivendriver

Just what I was thinking and wondering.

Sorry ... I meant that it sits lower then the 20s

[skierman64]

Originally Posted by 808E90

Sorry ... I meant that it sits lower then the 20s

There shouldn't be a difference between 18s, 19s, and 20s on ride height assuming the proper size tires are being used.

[isugoo]

Originally Posted by skierman64

There shouldn't be a difference between 18s, 19s, and 20s on ride height assuming the proper size tires are being used.

Most of 20 tire setups have bigger overall diameter.
I think because most of 20" wheels for M3 application are 9-9.5F and 10-11R. So people tend to go with 255/30, 285/30 (245/30F, 265/30R will be pretty stretch look) and those setups have bigger overall diameters than our stock 18/19 tire diameters.

[Lemans_Blue_M]

Originally Posted by skierman64

There shouldn't be a difference between 18s, 19s, and 20s on ride height assuming the proper size tires are being used.

Your right, there shouldn't be a difference if the tire dimensions stay the same. (regardless of the wheel diameter)

BUT, here's the problem...

There are 'fitment gaps' in the tire sizing charts between 18", 19" and 20" tires. It's impossible to line these tire dimensions up perfectly, as you increase wheel diameters and widths beyond the stock OE sizes.

Everything gets out of wack, and you end up somewhere in between two tire sizes that you don't really want. At that point, you have to choose the more aggressive tire size (which may rub), or the more conservative tire size (which will transmit more NHV to the cabin).

And to make matters worse...the tire with the exact dimensions you want...is simply too wide (or narrow) for the wheel you bought.

[ben@tirerack]

That pretty much sums it up right there, especially when you have to consider staggered front/rear sizes. Maintaining front to rear proportionality adds yet another headache.

255/30R20 and 275/30R20 are a little wider, not too much taller, and will not rub (assuming wheel offsets are reasonable). Max wheel widths would be 9.5 Front and 10 rear.

[MTROIS]

Given the roads on which you drive... keep your 18"s!! They have more side walls and you will have a lower chance of bending them + quality of the ride + cheaper tires available + more choices for track tires available = more comfort and money in your pocket...