[duluthtwo]

Any suggestions for most reliable run flats for M240i?

[Kernel Kurtz]

Not sure what you mean by most reliable. I'd expect any of the major brands make good quality RFT tires.

FWIW, I've had Bridgestone Potenza summers and Pirelli Sottozero winters on both my current and previous cars and have had no issues.

[Twoforty]

After driving BMWs on runflats for the last 10 years, I could not believe the difference when I bought my latest car which came with conventional radials!
It's like night and day between the comfort of the ride, even on 19's.
Never again will I tolerate runflats

[Kernel Kurtz]

It is a personal preference thing to be sure. RFTs are heavy, and they have a harsh ride due to the stiff sidewalls. And they are expensive. On the plus side that stiff sidewall gives them great turn-in, and there is a value in never having to be late for anything while changing to a spare in a rainstorm or blizzard.

I would not presume to tell people if they should use Xbox or Playstation, IOS or Android, or CD or LP (showing my age). Do what works for you.

[dradernh]

Originally Posted by Kernel Kurtz

CD or LP

Don't forget 78s and 45s!

[delvec03]

There are no reliable run flats.

I had two side wall ruptures on 18" wheels within 2 years of BMW ownership. Compare that to the other 12 years of conventional tires with no sidewall ruptures, also on 18" wheels.

It's a no brainer. Ditch them.

You'll get a smoother and safer ride.

[msej449]

People change from one brand of worn runflats to a completely different brand of new goflats (i.e. change three things) and for some reason ascribe 100% of any improvement only to the goflat transition. Across this and the UK 2 Series forums there are almost no cases of people making a like for like swap i.e. from one brand of runflats to exactly the same brand and exactly the same wear goflats.

Take a look at this video comparing exactly the same tyre and compound etc. in goflat, runflat and gunge form:

The conclusion? That for the latest generation of tires, there is almost no difference between runflats and goflats. What little difference there is is relatively minor: The runflats are slightly better on moderately uneven road surfaces and in steering sharpness and slightly worse in terms of feedback at the limits of adhesion. So yes, if you track the car then you'd want goflats - but then you'd probably want a separate set of track tires anyway.

For me, what this means is that the primary choice of tyre is back to being
1. Do I go for one all-season year-round or separate winters/summers? and
2. Which is the specific tyre that is currently the best of its type?
And if the answer to '2' is tyre 'X' then if I can get it in runflat form, that's what I'll do, as there's no downside for public road driving.

[delvec03]

Originally Posted by msej449

People change from one brand of worn runflats to a completely different brand of new goflats (i.e. change three things) and for some reason ascribe 100% of any improvement only to the goflat transition. Across this and the UK 2 Series forums there are almost no cases of people making a like for like swap i.e. from one brand of runflats to exactly the same brand and exactly the same wear goflats.

Take a look at this video comparing exactly the same tyre and compound etc. in goflat, runflat and gunge form:

https://youtu.be/sTRn1E1uF6c

The conclusion? That for the latest generation of tires, there is almost no difference between runflats and goflats. What little difference there is is relatively minor: The runflats are slightly better on moderately uneven road surfaces and in steering sharpness and slightly worse in terms of feedback at the limits of adhesion. So yes, if you track the car then you'd want goflats - but then you'd probably want a separate set of track tires anyway.

For me, what this means is that the primary choice of tyre is back to being
1. Do I go for one all-season year-round or separate winters/summers? and
2. Which is the specific tyre that is currently the best of its type?
And if the answer to '2' is tyre 'X' then if I can get it in runflat form, that's what I'll do, as there's no downside for public road driving.

Clear You've never gone through the transition. I encourage you to bite the bullet! You can always change back 🤔

I'll start with the sidewall ruptures. That's irrevocable.

Then there's the ride. How can you say that going from a worn in runflat to a new goflat isn't making a fair comparison? If anything, it sets up in favor for the runflat. The tire stiffness goes down over time, so if we did what you proposed and compared a used runflat to a goflat this comparison should greatly favor runflats. But even with a worn runflat (softer than new) compared to a new goflat (new, thus very stiff) the goflat provides a more comfortable ride.

[Kernel Kurtz]

Originally Posted by delvec03

I'll start with the sidewall ruptures. That's irrevocable.

And also anecdotal. I've never had a sidewall rupture on any tire, RFT or not, in 42 years of driving. Maybe you are just unlucky.

[msej449]

@delvec03 Lets ignore the wear factor - how much improvement came from changing the brand and how much from changing to goflats? No one can tell me. In the past, I was genuinely interested because I would have changed if someone could have given me a definitive answer. But they couldn’t.

Logic alone says if you change two things and get an improvement, you can’t be sure that it’s a result of only one of them. You just don’t know - you can't assume that your ride improvement was anything to do with the switch to being goflat (and of course, conversely, I can’t know if it was anything to do with the brand change).

And anyway, surely the whole discussion is moot now, given that the latest generation of runflats is pretty much as good as their equivalent - note equivalent - goflat?

What I'm more interested in now is which brand of runflat might be better than my current S001 runflats.

What does complicate this discussion, certainly, is that in Europe we simply don't get the sidewall rupture problem that so many in the US seem to complain about. It just isn't an issue. The debate has been exclusively around handling. I’d be surprised if your roads were universally so much worse than European ones. It’s something of a mystery as to why you get this problem and we don’t. One explanation is that it’s perceived and not real i.e. you don’t get any more sidewall damage than we do, you just ascribe it to being a runflat side-effect, when it isn’t: it’s just the result of damage during normal driving/parking: when it happens to a goflat, people just shrug and assume they damaged the sidewall in the normal course of events, but when it happens to a runflat, people blame it on being a runflat.

[aerobod]

Although I generally prefer conventional radials to runflats, I've probably driven 100,000km on run flats with no problems. I've actually had one equivalent tyre set in runflats and non-runflats on the same 3-series, Bridgestone RE050As. The performance overall was very similar with the only difference being slightly more harshness on small sharp bumps offset by slightly sharper turn-in due to the stiffer sidewalls of the runflats. These tyres were also used about 12 years ago, so tyre technology has moved on since then with back to back testing indicating little difference as @msej449 says.

Sidewall ruptures can happen to any tyre dropped into potholes (I've seen quite a few non runflats at our friends tyre shop with bulges and ruptures), the issue is likely more related to low profile tyres and/or specific tyre models and the poor quality of roads, than whether the tyre is a runflat or not.

[Kernel Kurtz]

Originally Posted by aerobod

Although I generally prefer conventional radials to runflats, I've probably driven 100,000km on run flats with no problems. I've actually had one equivalent tyre set in runflats and non-runflats on the same 3-series, Bridgestone RE050As. The performance overall was very similar with the only difference being slightly more harshness on small sharp bumps offset by slightly sharper turn-in due to the stiffer sidewalls of the runflats. These tyres were also used about 12 years ago, so tyre technology has moved on since then with back to back testing indicating little difference as @msej449 says.

Sidewall ruptures can happen to any tyre dropped into potholes (I've seen quite a few non runflats at our friends tyre shop with bulges and ruptures), the issue is likely more related to low profile tyres and/or specific tyre models and the poor quality of roads, than whether the tyre is a runflat or not.

My current S001 RFTs are noticeably better in most respects than the RE050A RFTs I had on a previous 335.

I'm pretty sure our roads here in Winnipeg are as bad as any you will find in any developed country, especially in the spring time with all the continuous day/night freeze/thaw cycles creating thousands of brand new potholes every day, and temporary "cold mix" patches that rarely hold for long. Inevitably that time of year brings massive numbers of claims to our public insurance company for wheel/tire and suspension damage, and I'm quite sure most of those people don't have RFTs (becasue you often see them at the side of the road just a ways past some large crater).

I've long since learned to a) drive with particular attention to the road ahead, leave lots of time and space in adjacent lanes to avoid potholes, and watch for cars ahead of you hitting them b) try to avoid routes that have older streets that are more likely to have defects (some of our streets are more patch than original road surface), stick to newer roads where possible, and c) be very wary of pools of water - you never know what it under them, and where there is water accumulation there is likely to be more of that freeze/thaw that gives rise to potholes. In fact some of the worst holes are often hidden in puddles.

Defensive driving is not just avoiding other drivers. Sometimes the roads themselves are your enemy.

[cooolone2]

No on RunFlats... Sorry, just NO!

It's meant to be driven, so drive it!!! Run flats take all the joy joy out of it!

Good Luck

[aerobod]

I'd expect better dry road grip and more sporty performance from a Michelin PS4S Zero Pressure runflat tyre than an AS/4 non-runflat, likely no measurable difference from a non-runflat PS4S.

[msej449]

I predict that quality mainstream tires will eventually only come in runflat form. If for 95% of vehicles and drivers there's little or no actual on-the-road difference between the runflat and goflat version, then it'll be much easier and cheaper for manufacturers to have one production line making the runflat version, rather than two, making runflats and goflats separately. It'll only take a year or two of one manufacturer with a big campaign announcing equivalence in handling but superiority in safety of their runflats before all the manufacturers will have to follow suit. High-performance road versions and track tires will still be produced in goflat form because the cars in question amplify even the small difference in handling, but you'll pay a premium because of the extra cost of a separate production line. And really cheap tires will be as they are now (a lot fewer components than a quality tire, hidden by how vulcanising anonymises the construction and with a funky tread pattern that's actually just random and not functional) plus will be goflat and non-gunked. Just a thought.

And what the video implies is that the gunge option can be applied to any tire, so you could see that included as standard as well. Or perhaps it's just something that in the future could be applied by the tire retailer at the point of sale, and offered as an option to any tire you buy?

[Kernel Kurtz]

Originally Posted by msej449

And what the video implies is that the gunge option can be applied to any tire, so you could see that included as standard as well. Or perhaps it's just something that can be applied by the tire retailer at the point of sale, and offered as an option to any tire you buy?

I'm not convinced runflats will ever be more than a niche market, primarily because they are more expensive to build and more difficult for tire shops to deal with, but time will tell.

As for the seal tire, a similar thing is already quite popular with cyclists and I have this on my mountain bike. Tubeless tires that have some latex injected through the valve stem which almost instantly seals any punctures, and I can say from first hand experience it works very well. In the bike application the main drawback is it is very messy to work with (and that also seems to be the main objection to products like Slime, which you can already add to regular tires to seal a flat), but that tire in the video looks like it would be much more friendly in that regard. Something like that would make tubeless bike tires much more easy to use as well. I do still wonder if the sealing properties degrade over time, and if it works even in very cold weather (both of which are issues with bikes). Will have to research that a bit more.