Hello Folks,
I am driving a '21 GLE350 RWD, and the mileage reached about 14K miles.
I've noticed that a passenger-side front tire has almost worn out.

I'm thinking of Michelin Defender for the long-lasting tires at Costco, it seems that they are non-RFT.
Would it be okay if I change my tires to non-RFT?
Also, any recommendation of tires is welcome.

I am worried that it may cause any problem with my car.
Please help me out.

Changed my RFT to Defenders excellent choice smoother quieter driving

Assuming you're looking at tires in the same size with the correct load ratings, it shouldn't cause any problems at all. Just the opposite in fact. Non-runflats are less expensive and lighter weight, plus they last longer and they don't provide you with a false sense of security the way runflats can. Just make sure you also add a spare tire and/or emergency repair/inflator kit.

My 2020 GLE350 has run flat tires and I can't wait to get rid of them! Although I haven't looked in to actual pricing, I seem to remember seeing some comments here that the dealer actually had better pricing on tires. Even if I bought the tires somewhere else, I'd be very reluctant to trust a Costco or Sam's Club grease monkey to handle my rims and properly balance and torque the lug bolts.

Odd. My 2022 came with NON run flat Michelins….and a spare as well. It has to be the smoothest, quietest ride of any vehicle I’ve had. Including S580.

Please note that if your car is leased you may want to check with your dealer to ensure that when it is time to turn the vehicle in, you will not run into any issues with your new non RFT tires.

Non-runflats were available from the factory. The staggered 21's on my 450 are conventional/non-runflats, and I have a spare tire kit as well.

I wanted the standard, non upgraded 19’s. Came with the spare, the NONs…and they were Mich.
If you want smooth, non jarring, and quiet…the run flats are the kiss of death. Been down that road too often.

If your on good terms with your service advisor and give home a bottle of wine once or awhile he can give you a great price on tires and alignment. I’ve used big o tires too in so cal. They will beat dealer prices on tires and there open on Sunday which a big plus but there alignment is not great on my cars. Tried them once had to go dealer after a week to straighten out the car from veering to the right to much.

Correct. If leasing the vehicle with run-flats swap the tires first thing and store the original tires. Upon return swap them back again so that you don't get dinged for proper RFT replacement.

Oh yeah definitely or you or you will regret it when buying new ones for a car you have turned in.

I've bought tires several times through Costco and Sam's Club, with no problems ever.

Lately though, I've been buying from Tire Rack. The last time I tried to buy through Costco, they had to order them (C300) and when they came in the next week, they were non-runflats. So I went to Tire Rack, had the right tires delivered to a local shop the next day, and still saved money over Costco.

My 2015 350 ML came with Continental LX 20 (now LX 25) non runflats.
I'm on my 4th set @ 131,000 miles

The defender tires are great. They also sell a climate 2 tire that also doubles as a snow tire. I have seen a few vehicles in florida with them so the seem to stand up to the warm weather unlike the x-ice winter tires. The problem I ran into was i have 20" rims and it came with at 275 tire size. Defender isn't made in that size so I had to go up to 285 which is just a touch larger in diameter then the factory tire. The problem was that a lot of places would not give me that size because it was not listed on the door. Costco would do it because I could show that the tire was within their 3% rule but it was going to take a week or longer to get them without an guarantee delivery date. I have been using costco tires center for year and am very happy with them and their service but I wanted the new tires before my trip. Iwent to my local Mavis tire, spoke to the guy and they had fresh tires for me the next day. Not only that, they matched the costco price, I got a road hazard warrantee thrown in. I never thought those things were any good but I used Mavis for my wife's E350 and after she "scratched" the curb they did an adjustment and took care of it quickly without issue. As far as run flat, I never liked them. Driving around without a spare is a little nerve racking but I haven't gotten stuck with a flat tire in years! Just the other day, I stopped to help a guy in an acura who had a flat and was tryjng to fill it with air. It must have been a huge hole because my portable pump didn't work and the one that came with the car new couldn't keep up with the air loss. Finally after 20 minutes, we decided to change to the spare. When he went into the trunk and opened up where the spare tire was supposed to be, nothing. He had no spare and never checked it out for all the time he had the car. Unfortunately, because he didn't have a spare, he wound up having it lifted and taken to a local tire place to get it replaced. So, as much as I dislke runflats, they do serve a purpose.