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Discussion Starter · #41 ·
There's a glimmer of hope. I searched online and across tyre dealers in my city and found perhaps the only viable non-RFT option that fits my car's current wheel size (fronts 275/45/r20, rears 305/40/r20). The tyre is Hankook Ventus S1 Evo 3 summer tyre. Not as good as the Michelins, but I hope better than Nankang. Does anyone have experience with these Hankooks from the standpoint of ride quality, tread wear, etc.?
Below are the technical specs... I guess these won't last long, but that's a compromise I'll have to accept

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They're run-flats, too.

The treadwear ratings are really only reliable for comparing tires of the same manufacturer. But, 220 is really low.

My hatred of run- flats would make me buy 9" wheels for the back and get some Michelin non-run-flats.
 

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The TPMS devices can also sense and report the tire temperature in addition to the pressure. I don't remember if this readout is stock or not (I enabled temperature readout with Bimmercode), but with that enabled, it shows the current pressure, the ideal pressure (assuming you've told it the actual tires you have), and the tire temperature. So, if you have driven the vehicle, or say one side is sitting in the sun and the other in shade, the computer in the X5 will tell you the 'ideal' pressure to put into each tire based on the tire's individual current temperature.
 

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Discussion Starter · #45 ·
They're run-flats, too.

The treadwear ratings are really only reliable for comparing tires of the same manufacturer. But, 220 is really low.

My hatred of run- flats would make me buy 9" wheels for the back and get some Michelin non-run-flats.
You're right they are RFTs! what a bummer. Hankook's website does not mention they are RFTs, at least it isn't obvious on their website. Plus they are priced exactly in the non-RFT range, I mean the fronts 275/45/r20 are exactly the same price as the non-RFT Nankang and Nitto, and the rears 305/40/r20 are 25% below the Bridgestone Alenza RFT... so I never thought they would be RFTs. Anyway, back to square 1
 

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Discussion Starter · #46 · (Edited)
You really want the front and rear rolling diameters to be the same. Otherwise, your stability control will be confused, but that's not the worst of it. Different rolling diameters, even from different tread depths of identical tires front and rear, will tear up the clutches in your xDrive transfer case. The BMW repair manual spec's a maximum of 2mm difference in tread depths front and back.

Do whatever you want, but if it was me I'd bite the bullet and get matching 9" wide wheels for the back and then get some quality (e.g. Michelin) non-run-flats all the same stock size (275/45-20). With AIR (alignment, inflation, rotation), your tire worries would be over for the next 100000 km.

New OE wheels can be bought for $650 each in the US.

Genuine OEM BMW Wheel Part# 36116883757 Fits 2019-2021 BMW: Up To 35% Off On Every Order And Guaranteed Fit When You Enter Your VIN | Genuine BMW MINI Parts
With 275/45/20 on the rear, the sidewall is 4.9" vs 4.8" with 305/40/20, but that difference in sidewall height (and rolling diameter) I suppose is acceptable, but not a sidewall of 5" with 285/45/20 on the rears.

I've read everywhere that 275/45/20 has a section width of 10.8" and is approved for rim width between 9" - 10.5". It may end up with a straight (rather than stretched) side wall but I don't think the rims should bulge and should be safe. In the absence of non-RFT options in 305, moving to a squared setup of 275/45/20 non-RFTs on current rims (front 9", rear 10.5") seems most logical to me
 

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With 275/45/20 on the rear, the sidewall is 4.9" vs 4.8" with 305/40/20, but that difference in sidewall height (and rolling diameter) I suppose is acceptable, but not a sidewall of 5" with 285/45/20 on the rears.

I've read everywhere that 275/45/20 has a section width of 10.8" and is approved for rim width between 9" - 10.5". It may end up with a straight (rather than stretched) side wall but I don't think the rims should bulge and should be safe. In the absence of non-RFT options in 305, moving to a squared setup of 275/45/20 non-RFTs on current rims (front 9", rear 10.5") seems most logical to me
I looked up a Michelin PS 4 SUV (high-performance, summer) and a Michelin Premier LTX (touring, all-season) in that size on TireRack.com. It says they will fit on a 10.5" wide wheel. But, you will not be able to rotate the tires front-to-rear. That relatively wide wheel and relatively narrow tire will mean that when you scuff a curb, you'll scuff it with the wheel instead of the tire.

I hate doing things half-ass. When I solve a problem, I want to solve it profoundly and only do it once. I'm also big on rotating tires so that all four of them wear out at the same time. If it were me, I'd still buy some OE 9" wheels for the back and some non-RFT Michelins, and be done with it.
 

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Discussion Starter · #48 ·
I looked up a Michelin PS 4 SUV (high-performance, summer) and a Michelin Premier LTX (touring, all-season) in that size on TireRack.com. It says they will fit on a 10.5" wide wheel. But, you will not be able to rotate the tires front-to-rear. That relatively wide wheel and relatively narrow tire will mean that when you scuff a curb, you'll scuff it with the wheel instead of the tire.

I hate doing things half-ass. When I solve a problem, I want to solve it profoundly and only do it once. I'm also big on rotating tires so that all four of them wear out at the same time. If it were me, I'd still buy some OE 9" wheels for the back and some non-RFT Michelins, and be done with it.
I agree with you on doing it the right way with the correct wheel size etc., but cost is prohibitive and there is a huge markup on everything here, especially on European imports. A 738 wheel that costs USD ~600 in US easily costs north of USD 1500 per wheel here.

If I opt for squared tyres 275/45/r20 on staggered wheels (front 9.5" wide, rear 10.5" wide), I'll share pictures.

A big thanks to everyone for taking the time to answer my queries
 

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I have a G05 with 20 inch tires with runflats and it drives great - although I do have the air suspension which is a little soft. I seem to be imn the minority but I have no ploblem with the runflats.
As HotGrbg suggested you may want to think about an alignment. I would discuss with the dealer, there is no way the G05 should handle as you are suggesting.
I just took delivery on a 2022 40i msport. I have steel springs and stock run flat Pirelli tires. The ride is great, and I like the feeling of not being stranded on the road with a flat.
 

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Hi everyone
Can anyone share their experience with switching to non-run flat tyres? My recently purchased like-new (< 500 miles) x5 40i has 20" Bridgestone run flats with regular steel suspension (no air suspension, no adaptive suspension). The fronts are 275/40/R20, the rears 315/35/R20 (edit: fronts 275/45/R20, rears 305/40/R20). The road quality where I live is average, and I didn't have the opportunity to test drive the car extensively prior to the purchase. I find its ride quality unpredictable. The car struggles on uneven roads, where it tosses me a bit, but on poor roads it has a jarring ride, unacceptable for a car at this price point. I drove the car for 2000 miles, lowered the tyre pressure to the minimum acceptable, and while that improved the ride quality by ~10%, it still is unacceptable to me. The whole experience has been disappointing because there is so much else to like about the current generation x5, but now I'm considering selling the car. As a last ditch effort, I'm looking into the option of switching to non-run flats. Where I live the only affordable option is Nitto tyres. My question is, considering that these are 20" wheels, does switching to a non-run flat make a significant difference? It will be an expensive experiment with uncertain results, therefore I'm hesitant. I've read people saying it doesn't make a big difference on the 20" because of the suspension setup. I've considered downsizing to 19" rims although it is a major cost, the car will look far less appealing, and it may still not solve the problem... or should I just sell the x5 and look somewhere else?
run flats have a thick and stiff side wall, so is harsh ride for sure and if you have a flat they are not good after that, you will need a new one. the sidewall will be damage most likely. I use Fire-hawk from Firestone on my Z4 best tires after other ones with no good experience. on a smaller rim les Unsprang weight is better and for matching overall diameter of OEM tires ,you will have more meat on the tire for softening up the ride. also the wider the tire it will wander on irregular road.
 

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I took mine off of my 2020 X5 as soon as I got it..It runs so smooth now.. I also had the dealer order me a spare....Mine have 20 inch with same size on all 4 corners...I dont see the reason for bigger on the back.
 

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Heat can destroy any tire. Flex can increase heat, so with a RFT, in addition to help hold the vehicle up, limiting the flex keeps the heat down, so they'll last longer and is one reason why you should drive slower with a flat on a RFT. BUt, some manufacturers have figured out ways to help dissipate that heat, so they can allow the sidewall of a RFT to be a bit more flexible. IOW, not all RFT are created equal, and your results may differ.
 

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I just took delivery on a 2022 40i msport. I have steel springs and stock run flat Pirelli tires. The ride is great, and I like the feeling of not being stranded on the road with a flat.
Agreed this is my wife’s ride and I have a better peace of mind knowing she won’t get stranded.
 
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