I just had the 35k service done and I got a nx350 loaner while they did that and replaced the rear dome light. The loaner along with other loaners I’ve received seem to have a better ride quality than my nx350h. The only difference I see is that I have the 20 inch wheels since. All the loaners have had the smaller wheels with thicker tires but still run flats. I’ll probably be due for tires in another 10k miles by the end of the year. Would it be possible to switch to slightly thicker tires? Would that mess with anything such as correct mpg or mph readings? Any recommendations on tires?

 

You can switch to 18" wheels, the std 18" and 20" wheel and tire sizes for the NX are cross compatible without issue. Now if you try to get a taller sidewall tire on the same rims you have now, then yes, there will be speedo errors and potentially clearance issues. The other option of course is to get non-RFTs which tend to have softer more forgiving sidewalls.

 

Michelin Cross Climate 2 or Pirelli Scorpion AS Plus 3. I have the CC’s and my wife the Pirelli. Both are excellent. The CC’s are quieter and the Pirelli have a slightly better road feel. Expect about 1 - 2 mpg drop with the CC’s.

 

Are these also run flats? Since we don't have spares, I would be hesitant to get anything else.

 

No those are not run flats, they are regular tires, that is why people are like them, because they run better and smoother and quieter etc. Depending on where and how you drive, think about your tires this way. Sure things happens, but in the last 10 years, how many times did you have a flat tire that you had to replace? If you maintain your car and tires you will most likely would never have a flat tire. But in case that you do, you can always call road side assistance, you can have a pump in your car and you can always pump some air if there is a small leak, or keep some plugs on hand and repair on the go. What I am trying to say, get the regular tires and just drive, do not worry about flats

 

Ditto! For those of us with the 20" rims there are few options in non run flats. However, I replaced my Bridgestone Alenza run flats after just 1,000 miles with Pirelli Scorpion AS3 Plus tires and the improvement in ride comfort and handling is dramatic. These tires also perform admirably in rain and light snow. You have to move up to a 245 width (that buys you a tad more sidewall too) but they fit no problem.
Another non-run flat replacement to consider is the Yokohama XCV which is available in the 20" OEM size (235x50x20). It gets good reviews but I ended up going with the Pirelli's because I had them before on a previous vehicle and knew how well they performed. I was afraid of buyers remorse if I went with something else. Good Luck!

 

I get it, for most, it's put the tires in and don't worry about it. I work in real estate with builders and developers so I'm pretty much always driving by or into home construction sites and getting nails and other things in my tires. I also use the vehicle for road trips where one is more likely to have a blowout and not just something stuck in the tire, like a nail or whatever. I've already had one tire replaced on the current set because of this. I'm definitely more on the **** it mentality side of things but this is our main vehicle for all the things so I want to be a little extra careful and for the same reason, have the ride be as comfy as possible. Has the taller sidewall on the Pirelli Scorpion messed with your speedometer?

 

Only slightly in that when I set the cruise control (which is when I'm driving at 70 mph plus) I notice that the indicated speed on the hud is 1 mph lower than the set speed for a sustained period but then "catches up" to set speed. But that may or may not be due to the slightly larger diameter because I did not use the cruise control much with the oem tire. I spoke with tire rack and searched the web and all gave thumbs up as to the use of the 245mm tire without concern. Installer confirmed no rubbing issue in executing full steering wheel turn after installation.
Below are estimates of the differences between the two tire sizes from a calculator you can find online.

Tire Size Calculator

Tire Size Comparison Calculator. Use this calculator to compare the sizes of two tires both numerically and visually.

Result

Tire 1: 235/50R20
Tire 2: 245/50R20
Difference:
Tire Height (Diameter) 29.3 in 743 mm, 29.6 in 753 mm: 1.35%
Sidewall Height 4.6 in 118 mm, 4.8 in 123 mm: 4.26%
Tire Width 9.3 in 235 mm, 9.6 in 245 mm: 4.26%
Tire Circumference 91.9 in 2,334 mm, 93.1 in 2,366 mm: 1.35%
Revolutions per Mile 689.5, 680.3: 1.33%. Revolutions per Kilometer 428.4 422.7 1.33%
Speedometer Difference: Tire 1 (mph or km/h): 20 40 60 80 100 120. Tire 2 (mph or km/h): 20.3 40.5 60.8 81.1 101.3 121.6