Originally Posted by dave in edmonds
I went with the ExtremeContact DWS 06 in 225/45ZR18. The tire choice has more of an affect on ride quality than tire size. These tires actually ride much smoother and quieter than the almost new Kumhos that came on the car. I couldn't be happier with the ride.
Nice ride! In addition to looks, I think the oem rack may create wind noise on the highway, so on the prior '83 Saab 900, I had a removable rack (that was noisy on highways).
On my similar 04 hatch, I went with the later model side skirts that don't stick out as much ... going to work in bad weather I'd often get mud on calf area of pant legs, getting in & out, and I had a personal preference for the more subtle look.
IMHO, both tire size and brand have an effect on ride quality, to a limit. I would not expect much comfort from a 35 series tire with the typical ~25" OD. regardless of brand. I do have 215-55 DWS's, and for a z rated tire, the sidewalls are VERY flexible, and I agree that helps with ride comfort. I removed my very heavy oem 17" rims (23 lbs!) and installed 16" Mazda3 (16 lbs) rims, that with those tires, gives me some scratchless curb contact ability the oem 17" set-up did not have.
For comfort, in general, tire brand matters, as does type (all season, summer etc), as does aspect ratio. When I switched from 215-50-17 series to 215-55-60, I gained more sidewall height (more sidewall flex when hitting ridges on road surface, for a given tire brand/type), and the tire spec's listed the contact width as narrower. This is typical, but not without exceptions when you get into super low profile tires. The narrower patch helps foul weather traction, and softens the ride a bit.
My 215 mm DWS example: rim -- ratio -- tread width -- OD (~same)
16" -- 55 -- 6.9" -- 25.3"
17" -- 50 -- 7.0" -- 25.5"
18" -- 45 -- 7.3" -- 25.6"
Of course new tires with full tread depth, and the rubber not yet hardened with age, will give a big ride improvement over the same tire that's old & worn. Tread blocks are each springs, the more sipes the softer.
Shocks --- right now my oem shocks are brutal ... hit a speed bump and front end will rise the height of the bump! A friends Volvo S70 with new Bilstein Touring shocks rode very smooth, looking into them.