Need advice!
I have a 2006 RL with A-spec shock absorbers and H & R springs.
I want to buy winter tires in a 235/50/18 size.
Would not hurt if this underestimation of the arch?

 

It will work, a little smaller diameter, difference of 2.2% which will throw off speedo, odo and probably be OK with the AWD software. Depending on where you are, I hear the killer snow combination, using your old 17's is 225/55-17. No diameter difference from stock, and much cheaper!

Good luck whatever you do...

 

235/50/18's are actually a little larger than stock diameter. Personally, I'm running 235/55/17's for my winter setup and have no issues with clearance but I'm not lowered either. They're close enough though <2% difference. As far as messing with the AWD system, it shouldn't really matter what size tire you run as long as you have the same size/make/model and similar tread depths at all 4 corners.

 

I also have the Michelin X-ice 235-55-17 was my winter-package. No clearance issue, i think it might be even high then my 245-45-18 summer-package.

*Kurenev- plz, let me know how much the H&R spring brings the clearacne down? and how it drives in the snow, and if ur A-Spec Lip is getting f-ed up?