jimhead

I may be a weird, I'm trying to figure out how to add run-flat tires to my 2019 Q7 prestige. I just don't want to roll the dice about being stranded and overly inconvenienced should a flat happen 5 or 500 miles from home. It doesn't seem like anyone makes run-flat tires in 285/40 R21 size.

Currently I carry around a spare tire on a trailer hitch for road trips, but it's a sub-optimal solution. It blocks rear visibility, camera and parking sensors, and it is a hassle to swing it out of the way in order to open the trunk.

I don't think the ride quality difference of run flats will be a big deal to me. My car has the air suspension option, and frankly I have a hard time telling the difference between dynamic and comfort aside from the visual change in ride height.

Would downgrading to 20" be the only option? I'm a little reluctant to do that only because I've gotten used how nice the larger 21" wheel size looks in my eyes. Maybe if there were a cool 20" after market wheel style?

jimhead

Seems like there are options for 21" in narrower sizes.

275/40 R21 : -3.6% narrower, -1% smaller diameter
275/45 R21 : -3.6% narrower, +2.3% bigger diameter

NoVA_A6

The only tires advertised as run flats in 21" are Vredestein Quatrac Pro's.

jimhead

I searched around, but I can't find any information online that says these tires are run flats.

NoVA_A6

You're right, you can get the run flats in 20's but not 21's.

PsyQ7

Confirming this too -- I just put 285/45r21 Quatrac Pros on my Q7, didn't mind RFTs, but they were not an option.

keg97

Which option is better? I'm assuming the bigger diameter will result in a wee little more cushion than the stock 285/40/21 while the 275/40/21 would be the slightest bit firmer than the stock setup. Correct?

andrewbrion

Correct. I am using 275/40/21 and that size looks and works great.

PsyQ7

Just to add - I just moved from 285/40r21 to 285/45r21 - subtle but noticeable increase in softness esp over potholes. Makes the wheel look better in the arch too, fills in a little more.

notes and photos in my thread

jimhead

Oh interesting! Thanks for sharing this. Looks like 285/45 R21 all season run flats do exist on Tire Rack -- Bridgestone and Continental.

Softer over potholes and filling in the arches better sound like wins to me. Any issues with rubbing? It's a 3.7% increase in diameter according to the tire size calculator. Speedo will be off by 2.2 mph at 60 mph .. not the end of the world. Ride height will increase by 1.1", which will make it more challenging for family members of shorter stature to climb in and out. Now this has got me thinking of how to relocate the air suspension load lowering button in the trunk to be next to the driver.