JMasterK

Planning to replace my 285 / R45/ 20" with 285/ R50 / 20" due to much better selection of tires and brands and prices about 50% less. For the additional 1.5cm of extra tire height, has anyone done this and had problems with the low tire pressure warning light going off ? Audi service warned me this could occur (no guarantee either way) and will not shut off alarm light if it occurs due to safety reasons. Anybody out there try this different tire size and have this problem ?? THANKS!

uberwgn

Why would the rolling diameter of the tires set off the warning system????

itiongo

So, your tire pressured is lower, or is the TPMS is complaining about your tires due to the change in height?

Lectoid

I don’t think he has yet, said he was planning to and wanted opinions.

But like uber said, it should be fine because the Audi compares the two tires rotation to figure out if one has less pressure. So in theory you could put Jeep tires on there as long as they match across the axel and have the same pressure, it should be fine.

JMasterK

Audi service claims the taller tires rotate less and this triggers the low pressure sensors. I find that hard to believe but wanted to see if any other owners had this issue when changing tire size Thanks

the_duke

Audi service is wrong.

Lectoid

I suppose you could test this by lowering all of your tires to 20 lbs and seeing what happens. I’d stay on slow/private roads though. Don’t recommend high speeds.

RickObe

That could be true if you don't do the TPMS reset after installing the new tires. But if you reset the TPMS in the MMI, it will be fine.

What about wheel well clearance. Has that been evaluated?

dht34

Just picked up the Q7 and have the same 285/R45/20 run flat tires. I'm looking to replace these tires with cheaper non run flats alternative tires. Did you ever replace them with 285/R50/20 tires? Would there's be any issues with the change in height/aspect ratio to the speedometer and odometer reading wrong, and possibly causing issues with the ABS system?

Read that any changes to the tire aspect ratio (wheel/tire) combo has an overall diameter/circumference that should be maintained with 3% of (+/-) the original spec.

What non run flat and cheaper alternative tires can be mounted on the same OEM rim, specifically, the 285/R45/20 run flat tires?

Trevor K

This is correct. All of the OEM tire/wheel combinations have slightly different total circumferences as well as snow tires people put on their cars all the time without trouble. Just be sure to reset the TPMS after install. The Audi TPMS works by reading the ABS system's wheel rotation counter and will sense when one wheel begins to rotate at a different rate than another wheel (excluding steering angles, etc.).