MB: 18" vs 19" ride quality
 

I'm about to get some new wheels for my wife's SL500. the stockers are 17s. I'm debating 18 or 19s. 19s obviously look way better, but I'm just worried about the ride quality.. and thinking maybe i should stick to 18s. she drives 40km one way to work.

any advice?

Bigger the wheel, the heavier the ride will be

It will be noticeable in roughness driving changing from the thicker sidewall of the 17's but the difference between 18 and 19 themselves will be minimal. The biggest factor will be the chance of damaging the rim itself from pot holes and stuff. The thinner the sidewall the more likely your going to get bent rims. If your doing a lot of commuting (and being a female driver) I would likely stay with the 18's and have that little bit extra cushioning of the extra sidewall thickness.
Also 19" rubber for whatever reason is always more expensive than 18" and 20" I guess it's a supply and demand type of thing.
One final thought on an SL500 you could easily roll on 20" rims if you were really just going for the look. I'm sure you could find some decent wheel and tire packages for 20"
Berz out.

That's a good point, I never thought about the fact that 19" rubber would be more than 20"..

Either way, thanks for the tips. I'll stick with 18s. 20s could work, but I think they will make the car look more modified than she would prefer.

Too bad many stock AMG wheels come in 19.. :(

Im currently riding on 19s...asthetically it looks way better. Ride quality is okay at best...It will deff feel like riding in a tractor.

Im coughing up about 1000bux a year for a set of tires (lasts me about 16mo or so with a ghostrider camber kit) v12s.... in a 235/35/19 and 275/30/19

I have a c63 and just went from an 18" stock to a 19" and there is a slight difference. If it's only for your wife I'd go for the 18's. The other really good point is that 19" tires are far more expensive and harder to come by. When I needed mine the closest ones I wanted were at least 5-10 days away.

Good luck on whatever route you pick

Wider 18s will look better than narrow 19s remember. How modified might this car get? Bigger wheels and smaller tires exaggerate wheel gap quite a bit, so 19s or 20 not lowered would tend to look awful.

Go with 19's what's the point of moving from a 17 to an 18; mine's as well just get 19's. This was my though process when I bought wheels for my wife's C Class during the summer. Ride comfort was compromised a fair bit with the smaller sidewall but she didn't notice it. I barely drive the car and I noticed it instantly. An SL should easily fit 20's if you want to go that route!!!
I've got some 19" iForged Wheel sitting around if you're interested; I'll sell 'em Cheap!

I wouldn't go larger than 18", not with the roads we have here.

I haven't noticed any ride quality difference between 17" and 18" wheels, but 16s definitely feel softer. Keep in mind tire prices - they'll be a bit pricier as you go past 18".