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Discussion Starter · #1 · (Edited)
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?
 

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Happily Driving
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Runflats ruin everything. Switch and you might be pleased. Don't forget the spare...
 

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Get an alignment. This can correct issues exactly as your describing. At minimum it’s not a terrible idea and is way cheaper than tires and wheels. If your issue persists then maybe look into tire/wheel options
 

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You must have some non oem rims on your car. The standard tire size for 20” wheels on the g05 are 275/45/20 all around. Perhaps consider 45 series sidewall tires? In addition those massive 315/35 wheels with high unsprung mass and with such little sidewall sound far from ideal. If I were you, since you like the X5 so much, I would put the standard 275/45 tires (and rims) all around as well as non rf tires.
 

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I went from run-flats to non-run-flats on my F10 535i, and it transformed the car. Leaving the dealership's parking lot, driving down the ~3/4" (~2cm) discontinuity between the driveway and the street gutter, the ride quality difference was so much that I stopped to check the air pressure in the tires before the long drive home. The pressure was fine.

Circum''s right. The stock 20" tire size is 275/45-20. If the rims are the same front and rear, go with the 275/45-20's all around, and rotate them every 6k to 8k miles. That will make them wear roughly the same, and it will keep your xDrive transfer case clutches happy..

Nitto makes a lot of odd-ball size tires to cater to the customizers. That might be why you can only get Nittos in 275/40-20's.

By going to the stock size of 275/45-20, you might find a better selection of tires, in addition to getting a better ride.. I'd recommend Michelins. I have a process for adjusting my pressures to achieve even tire wear (average side wear equals average middle wear). I've found Michelins will wear evenly with less pressure. Michelin makes the Premier LTX in that size. It's an all-season (standard performance) tire, but it will easily last 100,000km (62k miles) with proper AIR (alignment, inflation, rotation). They also makes a high-performance Pilot Sport 4 SUV. They're more expensive, might ride slightly worse, and will wear out a lot faster (maybe ~40,000 km, if you're lucky)..

The Premier LTX's are also symmetric. So, if you get more outside wear than inside wear even after an alignment, common with BMW SUV's, you could have them flipped on the rims at their half life (~50,000 km), and maybe get an extra 10,000 km out of them.

Michelin also makes a lot of OE-spec' tires in that size for BMW, Volvo, and Porsche. They're crazy expensive and not worth the extra money.
 

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Those broad 20” tires are often prohibitively expensive . You may find it equal or even cheaper to get a used set of 19” wheels and new tires than just new 20” top tier tires.

Imagine what that will do to your ride quality!


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Why drive anything else
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I personally remove my RFT the minute I purchase a car. Here are a couple of options for OEM 20" Rims. If you but normal non RFT's on a 20 you will be fine and it will greatly improve the ride and comfort. It is an expensive endeavor to purchase replacement rims and then new tires for it. If you got the links and the model year is correct you can change it to yours.



 

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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.
 

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Discussion Starter · #10 ·
Thank you all for your responses. I'm really impressed by your feedback. It's embarrassing I posted the wrong tyre size in my OP! Circumnavigator is correct, the fronts are 275/45/R20, the rears 305/40/R20, and rims are style 738. It's the combination of a heavy car, standard (non-air) suspension, run flats, and the very subpar road quality that is contributing to the poor ride experience on the rough inner roads. The car drove like this ever since I took it from the dealership with 512 km on the odometer, so I don't think it's an alignment issue. I wanted to check if anyone has replaced to non-run flats with 20 inch wheels and what level of improvement (if any) they experienced and in what aspects. Does it result in a smoother ride? less jostling? is the difference significant or minimal.. I understand these things are subjective, compounded by the one variable that cannot be standardized, the difference in road quality across the world
 

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You might also want to consider going 275/45 in the rear too for best results.
Circum's on to something else here, too. TireRack.com shows the 20" wheels on a G05 X5 40i only being used with a square set-up, with 275/45-20 wheels on US spec' X5's.. Those 305/40-20's have almost the same rolling diameter, but they might not be what came on the vehicle. Somebody might have put them on to look cool. They might be too wide for the OE rim, causing them to behave oddly.

BMW tends to put narrower wheels on SUV's than on passenger cars, at least on the base or mid-range tire and wheel packages. The F25 (previous generation) X3 and the G01 (current generation) X3 both use 245/45-19 tires, but the G01 actually comes with narrower wheels than the F25 did. This actually makes sense in the real world, since the tires will rub against a curb instead of the wheel scraping against the curb.

Before buying tires, check to see if front and rear wheels (not tires) are the same size. Maybe BMW sells a staggered 20" set-up outside the US. But, I'd bet not.

TIreRack.com's website says that Bridgestone 305/40-20 Alenza 001's need a wheel 10" to 12" wide.

Bridgestone Alenza 001 RFT | 305/40RF20 (tirerack.com)

SoCal's link says that the 738 wheel is 9" wide.

BMW X5 (2019-2020) 20x9 Aluminum Alloy Machined with Grey 5 Double Spoke [86459] : StockWheels.com - OEM Wheels & Used Rims
 

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Discussion Starter · #14 ·
Thank you once again. This exchange has been an eye opener. I suspect style 738 is offered in staggered configuration here, and the rears might be 10.5 inch wide. There are several non-RFT options in size 275/45/20 to fit the front 9" wide wheels, but none thus far in size 305/40/20 for the rears. Nitto tyre's website claims their size 275/45/20 is compatible with rim width 8.5-10.5", so I might be able to install their 275 on the rear wider (10.5") wheels without the need to change the rims. Otherwise it will be a dead end for me
 

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Discussion Starter · #16 ·
Hmm. This is an example X5 drivers door placard that shows both the tire size and the wheel size (9.0J x 20) for the car. What does yours say?
Seems everything is different here. Attached is a picture of driver side placard, which isn't very helpful. The other just shows appropriate tyre pressure ranges for the various tyre sizes

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Discussion Starter · #17 ·
Circum's on to something else here, too. TireRack.com shows the 20" wheels on a G05 X5 40i only being used with a square set-up, with 275/45-20 wheels on US spec' X5's.. Those 305/40-20's have almost the same rolling diameter, but they might not be what came on the vehicle. Somebody might have put them on to look cool. They might be too wide for the OE rim, causing them to behave oddly.

BMW tends to put narrower wheels on SUV's than on passenger cars, at least on the base or mid-range tire and wheel packages. The F25 (previous generation) X3 and the G01 (current generation) X3 both use 245/45-19 tires, but the G01 actually comes with narrower wheels than the F25 did. This actually makes sense in the real world, since the tires will rub against a curb instead of the wheel scraping against the curb.

Before buying tires, check to see if front and rear wheels (not tires) are the same size. Maybe BMW sells a staggered 20" set-up outside the US. But, I'd bet not.

TIreRack.com's website says that Bridgestone 305/40-20 Alenza 001's need a wheel 10" to 12" wide.

Bridgestone Alenza 001 RFT | 305/40RF20 (tirerack.com)

SoCal's link says that the 738 wheel is 9" wide.

BMW X5 (2019-2020) 20x9 Aluminum Alloy Machined with Grey 5 Double Spoke [86459] : StockWheels.com - OEM Wheels & Used Rims
I think rim 738 comes in both 9 and 10.5" widths

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Very interesting! Based on the flag next to your profile, I’m assuming you’re in Saudi Arabia, so the wheel sizes are specific to that local market. I found an Australian link to staggered 20” 738 wheels with front width 9” and rear width 10.5”. I’ll assume this is exactly what you’ve got. I’m that case, it looks like a 305 width tire is probably the safest width, as 275 or 285 width might make the metal part of the rim stick out. In any case, it’s unfortunate that you’re not able to find any non RF options in that size. If cost isn’t too much of a factor, it might be worth getting the 9 inch rims for the rear or better yet, downsizing the rims to 19” or 18” for maximum comfort. If that is the difference between you loving and loathing the X5, it might be a good option, especially if you’re not leasing. Either way, this has been very interesting and informative! 20 Inch Genuine BMW X5 G05 Style 738 Alloy Wheels Set of 4
 

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Discussion Starter · #19 ·
Thank you once again for your valuable responses. There is no non RFT option for size 305. Multiple manufacturers provide non-RFTs in size 275/45/20. The fronts are therefore not a problem and I'd rather go for a squared setup. Size 275 has a width of 10.8" and it fits a rim width between 8.0-10.5", but like Circumnavigator mentioned, it may be overstretched and look odd with the possibility of rim bulge on the rears. The other size is 285/45/20, but I don't think I should go for a squared setup with these as the fronts would be too wide and could cause unanticipated problems. I therefore looked into 275/45/20 for the fronts on 9" wide rims, and 285/45/20 for the rear for the 10.5" wide rims. The side wall for the rear will increase from 4.8" with 305/40 to 5.0" with 285/45, which I hope won't disturb the speedometer and other electronics too much. The latter also has a tyre width of 11.2", so the appearance should be more acceptable on the 10.5" wide rim.

Unfortunately, the only tyre available in 285/45 is the Taiwanese brand Nankang. I read that the brand is decades old and has popular affordable high performance tyres, but don't know how safe/durable/quiet they will be for a heavy crossover. The BMW dealer has stopped importing x5s with 19", so 20" is the only option. It's clear management is making decisions without considering the road quality. I also don't intend to purchase 9" rims for the rears. Looks like 2 hard choices, either these Nankangs or sell the vehicle, currently leaning heavily towards the latter
 

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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
 
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