Post by
Larz »
https://forums.nicoclub.com/larz-u216291.html
Fri May 17, 2019 2:47 pm
You are right in considering the effect of sidewall on the ride comfort. I went from the OEM 245/45 to 255/40's and there is no noticeable difference in ride comfort or road noise. The benefit of using the wider 255 size is all about handling and grip. The size of the sidewall had no effect, but going from a 40 to 50 sidewall is two sizes higher which might actually make enough difference to soften the ride quality. You will still have the same OEM suspension, so it's hard to say if it will make a big difference though. Changing to adjustable aftermarket struts might be an idea, but very expensive and may void any warranty you have.
Remember this: Right now, your car is at the OEM spec'd ride height. That ensures the car will drive, steer, and handle at optimum performance and safety. If you keep the same wheel size, you must keep the ratio of (sidewall height / tread width) the same to maintain the OEM ride height: (265/35) = (255/40) = (245/45) = (235/50). If you want a size 50 sidewall, you will need to use a 235 tread width. 235/50/20's can be found on Land Rover, some Jag XJ-L's, etc so they certainly won't be dangerous or inappropriate for a Q70 sedan. They will, however, be more expensive and probably available only from higher quality brands like Michelin, Pirelli, etc.