[albertw]

Originally Posted by 4Hockey4

I feel like folks are convincing themselves that run flats are even in same world as Michelin PS4s. My new Pirelli run flats, and wifes Conti run flats were crap, brand new.

If you are using 50% of the cars ability on the street only...accelerating a few hard times straight...sure.

But pushing in mtns and light track work, PS4s is a 10 street tire, run flats maybe a 5. I played with Pirelli pushing car hard once, that was a mistake.

There are plenty of reasons to have RFT's, performance is not one of them.

I'm puzzled that you appear to be concerned that a tiny minority of 2-series drivers think the Pirelli runflats are an acceptable tire. Why does this matter to you?

I'm also puzzled that you think your fact-free opinion would change the minds of such people. What you wrote sounds suspiciously like "I ran way too fast into a turn, scared myself badly and blamed the tires rather than the driver."

My experience is that the Pirellis lose traction gradually and predictably. My comparisons are to another car (C5 Z06) which is lighter and has much wider tires, so I'm not sure they are valid. For what they are worth, the breakaway characteristics of the Pirellis are similar to an extreme performance summer goflat tire, the Toyo Proxes T1R. (I wore out two sets of those. I bought them because they were reputed to be much less noisy than the original F1 Supercars, and was delighted to find they had less traction as well so sliding the car was easier). I also ran one set of Michelin AS3, which on that car had a noticeably more abrupt breakaway (not scary, but noticeably different) than the T1Rs and my current Pirelli runflats on my M240i.

I'm not clear on why you think the runflats are "crap", but I am pretty sure it is not because of their behaviour at the cornering traction limit.

I've ordered a pair of Pirelli PZero All Season Plus goflats to replace my two worn out runflats, for three reasons: 1. They are likely the best possible match for the two good runflats, and that might let me wear them out safely. 2. With the goflats on the front, I will have the best possible test of whether replacing runflat with goflat improves steering feel, or whether the reputed benefits stem mainly from the more typical switch to new, different tires. 3. The test report comparing the Pirelli and AS3+ on TireRack rates them as very similar, with the Pirelli a better road tire and the AS3+ more capable on the track. A more recent test of the AS4 indicates it is similar to the AS3+ with more traction. The extra traction of the AS4 is a negative for me, as it means higher speeds are needed to slide the car. The most important observation in the comparison is that the Pirellis steer a bit heavier, so maybe more tire feedback will break through the numbing effect of the electric steering. I will post a report in a couple months when I've evaluated the change.

[Neverlost99]

Depends 1. Do you like cracked wheels? 2. Do you like rough noisy ride 3. Do you like been stuck in South Georgia when you are 51 miles from Macon?

[4Hockey4]

Originally Posted by albertw

I'm puzzled that you appear to be concerned that a tiny minority of 2-series drivers think the Pirelli runflats are an acceptable tire. Why does this matter to you?

I'm also puzzled that you think your fact-free opinion would change the minds of such people. What you wrote sounds suspiciously like "I ran way too fast into a turn, scared myself badly and blamed the tires rather than the driver."

My experience is that the Pirellis lose traction gradually and predictably. My comparisons are to another car (C5 Z06) which is lighter and has much wider tires, so I'm not sure they are valid. For what they are worth, the breakaway characteristics of the Pirellis are similar to an extreme performance summer goflat tire, the Toyo Proxes T1R. (I wore out two sets of those. I bought them because they were reputed to be much less noisy than the original F1 Supercars, and was delighted to find they had less traction as well so sliding the car was easier). I also ran one set of Michelin AS3, which on that car had a noticeably more abrupt breakaway (not scary, but noticeably different) than the T1Rs and my current Pirelli runflats on my M240i.

I'm not clear on why you think the runflats are "crap", but I am pretty sure it is not because of their behaviour at the cornering traction limit.

I've ordered a pair of Pirelli PZero All Season Plus goflats to replace my two worn out runflats, for three reasons: 1. They are likely the best possible match for the two good runflats, and that might let me wear them out safely. 2. With the goflats on the front, I will have the best possible test of whether replacing runflat with goflat improves steering feel, or whether the reputed benefits stem mainly from the more typical switch to new, different tires. 3. The test report comparing the Pirelli and AS3+ on TireRack rates them as very similar, with the Pirelli a better road tire and the AS3+ more capable on the track. A more recent test of the AS4 indicates it is similar to the AS3+ with more traction. The extra traction of the AS4 is a negative for me, as it means higher speeds are needed to slide the car. The most important observation in the comparison is that the Pirellis steer a bit heavier, so maybe more tire feedback will break through the numbing effect of the electric steering. I will post a report in a couple months when I've evaluated the change.

I feel like folks are convincing themselves that run flats are even in same world as Michelin PS4s.

lol you do you.

[Sportstick]

Originally Posted by Neverlost99

Depends 1. Do you like cracked wheels? 2. Do you like rough noisy ride 3. Do you like been stuck in South Georgia when you are 51 miles from Macon?

I hope never to experience #1 or #3, but with the Primacy3 ZP, I recently learned that #2 is far from inevitable. I would have agreed about #2 when I had the OE Pirelli RFTs. They are not all the same.

[Australian Bimmer]

I like having runflats. My wife and I have only had 4 punctures in 12 years (she drives Minis), but each time we were able to keep going and get the car to a tyre shop or the dealer the next day. I really like that for convenience and safety. Plus, my wife has never changed a tyre in her life.
Two of those have been repaired, two had to be replaced.
When I travel long distance, I carry a couple of spare tyres (not wheels) in the trunk (the ‘boot’ here in Australia). In Australia, no one really stocks RFs and most tyre shops have to get them in from their warehouse. This way, as long as I can access a garage with the ability to change a tyre, (plenty of those, even in more isolated places), I can keep going, even if the punctured tyre is quite badly damaged and can’t be driven on for long.
I am happy with the ride/handling/mileage in my car with adaptive suspension. I have gotten 45,000 km out of my Bridgestone rears which will need replacing soon and the front pair still have around 20,000 km left in them.
Tyres in a big plastic bag still allow plenty of other stuff to be put in the boot. I have also strapped my spare tyres in the back seats using the seatbelts.

[msej449]

Originally Posted by 4Hockey4

I feel like folks are convincing themselves that run flats are even in same world as Michelin PS4s. My new Pirelli run flats, and wifes Conti run flats were crap, brand new.

If you are using 50% of the cars ability on the street only...accelerating a few hard times straight...sure.

But pushing in mtns and light track work, PS4s is a 10 street tire, run flats maybe a 5. I played with Pirelli pushing car hard once, that was a mistake.

There are plenty of reasons to have RFT's, performance is not one of them.

I think that you're possibly in danger of making exactly the false inference that I mentioned: You're changing from a worn Pirelli runfalt to a new Michelin go flat and concluding that 100% of the poor comparative behaviour of the old tyre is because it's a runflat. Nothing to do with a change to a completely different manufacturer/tyre and nothing to do with a change from worn to new. If you're changing three things at the same time, how can you know which elements go to make any improvement?

I've 'pushed' my Continental runflats through many Alpine routes where any mistake would mean deiving off the side of a mountain and been completely confident they're up to the task.

[cristo]

I changed the new RF Pirellis that came
on the car to new NRF Michelin PS4S tires
soon after we got our M240i F23
and there was a world of difference in
performance and comfort (same wheels).

[TrboMike]

blah blah blah

The op asked opinions on if he should get rid of the OEM runflats.

The OEM runflats have very stiff sidewalls (which makes them "run" when "flat") and blow out the sidewall very easily on potholes. Also because of the sidewall stiffness they upset the suspensions ability to control the car in cornering, which is why most people feel they make the car handle like shit.

IMO I wasnt upset with the grip they offered, but after blowing out two of them on tiny nothing potholes and seeing how much it cost to replace just one, I was glad to get rid of them. And once I did I noticed a HUGE ride and handling improvement even with low grip snow tires which I contributed to not having iron sidewalls. My runflats were not worn or bald when I got rid of them, two of them were fairly new thanks to blowouts.

This is why most people hate them, and get rid of them, and why most replies in this post say that.

[Sportstick]

Originally Posted by TrboMike

This is why most people hate them, and get rid of them, and why most replies in this post say that.

The logic seems to be that the OEM runflats are unsatisfactory, therefore all other runflats will be as well. By making an aftermarket purchase of Michelin Primacy3 ZP for my 3 Series, I found this logic is flawed. However, the entire category is not comparable to the PS4S of course.

[4Hockey4]

Originally Posted by cristo

I changed the new RF Pirellis that came
on the car to new NRF Michelin PS4S tires
soon after we got our M240i F23
and there was a world of difference in
performance and comfort (same wheels).

My run flats were new and others almost new. World of difference indeed.

like I said running around streets, 50% ish push, fine..I did not have any issues, on track, medium runs...no way. PS4S, issues gone. (well still have plenty of driver ones lol, but meh not professional)

However, the entire category is not comparable to the PS4S of course.

that was really my only point...but again, someone really wants us to believe they are. RFT's have many purposes, top performance is not it...

I remember talking to Tire Rack rep when I was considering AS3+ (before I knew) great combo tire, and asked about TR reviews. He said to take with a grain of salt, that they make all tires seem "close" cause otherwise they wouldnt sell the selection. Maybe not true, and I quote "the AS3+ is a great tire for the first 80%, its the last 20% where you will want the PS4S" and obviously the AS3+ is even step above RFT.

Car was the same except tires and forged rims. Same track, same weather really, 70 and overcast. Night and day. Based on what I've been told, not much of that had to do with new Titans.

Cheers and let us know what you think when you get them. Fun discussion, if not interesting

[msej449]

It's because I'd consider switching to goflats that I'm pressing the point, and am concerned that comparing the worst runflats to the best goflats doesn't really help me or the OP decide. Because no one can tell us what % of the improvement when moving from, say Pirelli runflat to Michelin goflat, is down to runflat>goflat versus Pirelli>Michelin. And begs the question of whether I couldn't get the majority of that improvement just by switching to the best runflat available?

For example, If I could get a 20% handling improvement from changing runflat brand, versus a 30% improvement changing to goflats, then I'd stick with changing to a better runflat. The +10% wouldn't justify dropping the runflats, but for some, it would, which is fine. But if the best runflat only gives a 5% improvement while the best goflat gives a 35% improvement, then it's a completely different situation.

But unfortunately, and not surprisingly, no one seems to have ever done an apples-for-apples swap. So we tend to have these circular arguments where people keep re-stating how much better the goflat orange is than the runflat apple. And doesn't answer the questions (a) whether there's a better choice of runflat apple out there and (b) if there is, how much better would the goflat equivalent be?

Personally, I think that the Pirelli P7 is completely the wrong tyre for a performance 2 Series, and the PZero Summer is not at all the right tyre. The PZero Summer has always been intended for heavier cars and the 2 is really at the very edge of being a match. So yes, if the OP has the PZero fitted then I'd say that there should be a better summer tyre to be found in runflat form. I don't doubt that there are also better tyres in goflat form as well. But no one seems able to say just how much better they might be than the best runflat. And thus help decide whether losing the runflat capability is worth it.

[4Hockey4]

Please stop pressing, myself nor anyone else were comparing used worn RFT to new PS4s.

The Conti's were NOT OEM and brand new and the Pirellis were slightly used.

Keep going, you've seem to convince yourself. lol but unlikely anyone that has put a performance tire on their sports car and pushed will ever agree. GoFlt Fanboys lol holy fuck this thread is HOF

Stay safe on those mtn roads ! (you are looking to confirm your purchase and all your research, or looking to argue, and why many folks have not countered you...few have ...either way I'm out )

[albertw]

Originally Posted by msej449

But unfortunately, and not surprisingly, no one seems to have ever done an apples-for-apples swap. So we tend to have these circular arguments where people keep re-stating how much better the goflat orange is than the runflat apple. And doesn't answer the questions (a) whether there's a better choice of runflat apple out there and (b) if there is, how much better would the goflat equivalent be?

Good to see the question stated this clearly. However, I think it is actually a lot more complicated, and none of the fans of extreme performance summer goflats seems to be capable of even beginning to address the complexities. I've stayed with the thread hoping to get some useful information, but none has appeared. I don't really expect it to, but I thought I would be more explicit about what is missing in case someone is thoughtful enough to address even just one or two of the issues.

I can think of at least four aspects of tire performance that are relevant to running at faster than 80% of the traction limit, and these can vary depending on whether you are braking and turning, accelerating and turning or just turning at a constant speed. So there's a dozen variables that matter, and I'm sure that to a tire engineer there are many more.

If you are content to follow the herd, then ditching the runflats is obviously the easy thing to do. If you want to make a rational decision, then you need to consider that how you rank the importance of the variables might be quite different from someone else's ranking. Thus the average goflat fanboy's gut feeling is pretty well useless if he can't break it down into how specific attributes differ.

For example, the draconian excessive speeding laws here mean that I never accelerate hard or even at all out of a corner, because in corners with an advisory speed of 50 km/h (30 mph) I'm already near the excessive speed threshold, and I can't even reach the traction limit while staying below 120 km/hr in most corners labelled 60 km/h. So how easy it is to maintain control while accelerating and turning is completely irrelevant to me. If that's an important reason for favoring extreme performance summer goflats but the fanboy is unable to articulate it, then his opinion is less than worthless to me. It's deceptive.

Another example is any attribute that makes it possible to go faster into, through, or out of a corner. I don't race. My objective is to have the most fun in the most corners, so anything that forces me to go faster to have fun is a negative, not a positive. Someone who wants to post fast laps on the track will have substantially different priorities.

[Australian Bimmer]

17 years of run flats, Minis and BMW, live 50 kms (30 miles) out of town, 2 km of gravel (unsurfaced) road to get to our property, and I have never had a blow out, a cracked rim or a damaged side wall. Have had one bent rim on a Mini but also had another 3 on my Holden SsV (sold in the USA as a Chevrolet SS) which runs go flat tyres. (When I got new tyres fitted to it the tyre guy called into the workshop to show me that 3 of my rims where slightly buckled).
So, I dunno why several posters have had this experience. Our roads are pretty bad.

[albertw]

I don't understand why runflats should be more likely to allow potholes to damage the rim. It seems to me that a stiffer sidewall should spread the load over a longer section of rim, making damage less likely. ( I'm not an engineer, and my picture of the load distribution could be wrong.)

I wonder whether maybe something else is going on. Perhaps the average driver is less diligent about avoiding potholes when driving on runflats, because they know they won't be stranded by a blowout.

[dradernh]

Originally Posted by albertw

I wonder whether maybe something else is going on. Perhaps the average driver is less diligent about avoiding potholes...

I know a driver who regularly hit every pothole and major imperfection on the paved / unpaved road she lived on. When this was pointed out to her, she indicated that she had no idea hitting or not hitting things that could damage tires, wheels, and suspension components was a thing. This was a pretty bright woman, too. Her tires were not runflats.

Some people are just really hard on the physical objects in their lives, and they don't want to be bothered taking care of most of them. Explaining why she chose home furnishings requiring little maintenance or care, a woman once said to me, "I live hard." That was the best explanation of the mindset that I've heard.

[albertw]

Originally Posted by msej449

It's rare to find anyone who has replaced their runflats with goflats that are (a) exactly the same tyre brand (b) exactly the same tread depth. Basically, they're changing three things at the same time: 1. runflat>goflat 2.worn>new and 3. brand#1>brand#2, and then ascribe all the handling improvement to just one of those three - the swap from runflat>goflat.

BMW Forums are full of threads endlessly discussing how much better various other brands are than the one fitted as originals from the BMW factory. There' so much feedback on this that it's hard not to be convinced that the ex-factory tyres are really far from ideal. Almost every I-swapped-to-goflat-and-my-life-changed-for-the-better post cites such a change in tyre brand, plus a swap from worn to new, and then blames the original tyre as bad 100% because it's a runflat.

I can report on some of these questions. I needed to replace two Pirelli runflats that wore out the centre of the tread early because of an excessively high recommended pressure for the rear tires. I wanted to try goflat tires while staying with all seasons for less cornering traction than I would get with high performance summer tires.

The two best choices seemed to be Michelin AS4 and Pirelli PZero All Season Plus. I went with the Pirellis based mainly on TireRack's comparison tests which rated them as the better street tire. They have less traction (a plus for me) and heavier steering that was still responsive and precise. I hoped that the heavier steering would let more feedback past the numb electric power assist. They were also rated as giving a slightly softer ride with less noise. (The new tires went on the front and the half-worn runflats were moved to the rear.)

A report on their behaviour at the traction limit will have to wait until my favourite mountain roads are suitable for aggressive driving. What I can say definitely now at 35 psi front:

The switch has made very little difference to the dead spot on centre. I can move the wheel slightly to the side and the car will start a very slow turn, and I get no resistance from the wheel. If I let go of it, the wheel does not move back to centre and the car continues to turn slowly.

There might be a very small improvement in steering precision at moderate corner speeds - 150% of the corner advisory speed - or I might be fooling myself. It's a barely detectable difference at best.

The steering is somewhat more responsive to abrupt inputs. That's nice when testing but pretty well irrelevant in real world driving where chicanes don't exist and one wants to enter corners smoothly.

There is no improvement to the zero feedback from small irregularities in the road surface while cornering at moderate speeds.

The tires are definitely more compliant over small bumps. Since the runflats are only slightly harsher riding than my wife's RAV4, the improvement is trivial to me.

[60_Driver]

This thread started out great. Seems like it got a bit lost in the arguments. I learned a few things anyway.

[Pray for Mojo]

I went from the factory Pirelli runflats to Michelin Pilot SS within a month of owning the car. I found the difference to be fairly significant. The runflats rode appreciably worse and handling was pretty marginal for a 320hp car. This was 7 years ago, and I have 100k km on this car now with zero flats nor any patches or plugs. My colleague on the other hand is fully in the runflat cult and has replaced at least 5 tires on two vehicles in the same time period.

When I sold our GTI, I swapped the spare runflats on it, so the new owner had fresh rubber. They rode like complete shit compared to the worn factory Dunlops and braking felt worse.

There's a ton of risk adverse people out there that will tolerate having their fillings rattle out everyday for the 1/5000 chance they get a instant pressure loss flat. I've had one flat tire like that in 20 years of driving. I could have even avoided that one instance, if I trusted my gut 5 mins earlier and got out to check the TPMSless tire in -30.

Our X3 came with runflats and if the tires weren't $500+ each to replace they would be gone by now.

Getting a tow isn't the end of the world, especially if you live in the city. A life of compromises isn't as enjoyable as throwing caution to the wind and taking the occasional lumps.

[albertw]

[QUOTE=Pray for Mojo;27384884]
There's a ton of risk adverse people out there that will tolerate having their fillings rattle out everyday QUOTE]

This is incomprehensible to me. Of the cars I've had in the last 40 years, I'd rate the harshness of the ride of my 84 Buick Century as a 1, my 01 Corvette Z06 a 10. On that scale my wife's RAV4 is a 2. My 05 Altima was a 1.5. My M240i in comfort mode with Pirelli runflats is a 2.5.

I had no trouble at all with comfort driving 600 miles a day for a week in the Z06 (except for noise - I needed noise cancelling earbuds for more than 30 minutes on the highway in that car). The M240i on funflats is almost Cadillac plush in comparison.

Do you funflat haters really want a sporty car that rides like a Sedan de Ville?

[TrboMike]

How do they make a runflat tire be able to be driven on with no air in it? Either the sidewalls are super thick/stiff to be able to handle the weight of the car without compressing or they put a hard rubber ring inside the wheel to take the weight of the car.

So a runflat will always be heavier than an equivalent non-runflat.

A runflat will always have an extremely stiff sidewall (compared to an equivalent non-runflat) so that it will still be able to be driven on with no air. This causes the sidewall of the tire to become part of the springweight of each corner. The sidewall becomes more a part of the suspension work than a non-runflat. Also the stiffer sidewall is less compliant on potholes which can cause the rim to be more easily damaged or the sidewall itself to be more easily damaged (compared to a non-runflat).

Albert, you seem to be very worried about the OEM runflats being unfairly compared to any other tire (runflat or not) because the OEMs are worn or the other tire more sticky fgor the getgo. I'm not saying that at all. I'm saying a tire that is designed to be a runflat is loses its ability to absorb bumps and poorly effects the spring rates of a car (compared to an equivalent non-runflat).

What you gain is not having to change a tire or having to have a spare in the trunk. What you lose is the suspension's ability to control the car, the risk of damage to the tire and rim, and the cost of replacing an expensive runflat.

I'm glad you went to tirerack's comparison tests and read input about tires. You should google the reviews of how runflats poorly effect a car's handling (not from grip, from the stiff sidewall) and why so many car reviewers hate them.

The OP wanted to know the benefits and negatives of the OEM runflat tires and possibly switching to something else.

[Sportstick]

Originally Posted by TrboMike

How do they make a runflat tire be able to be driven on with no air in it? Either the sidewalls are super thick/stiff to be able to handle the weight of the car without compressing or they put a hard rubber ring inside the wheel to take the weight of the car.

So a runflat will always be heavier than an equivalent non-runflat.

A runflat will always have an extremely stiff sidewall (compared to an equivalent non-runflat) so that it will still be able to be driven on with no air. This causes the sidewall of the tire to become part of the springweight of each corner. The sidewall becomes more a part of the suspension work than a non-runflat. Also the stiffer sidewall is less compliant on potholes which can cause the rim to be more easily damaged or the sidewall itself to be more easily damaged (compared to a non-runflat).

Albert, you seem to be very worried about the OEM runflats being unfairly compared to any other tire (runflat or not) because the OEMs are worn or the other tire more sticky fgor the getgo. I'm not saying that at all. I'm saying a tire that is designed to be a runflat is loses its ability to absorb bumps and poorly effects the spring rates of a car (compared to an equivalent non-runflat).

What you gain is not having to change a tire or having to have a spare in the trunk. What you lose is the suspension's ability to control the car, the risk of damage to the tire and rim, and the cost of replacing an expensive runflat.

I'm glad you went to tirerack's comparison tests and read input about tires. You should google the reviews of how runflats poorly effect a car's handling (not from grip, from the stiff sidewall) and why so many car reviewers hate them.

The OP wanted to know the benefits and negatives of the OEM runflat tires and possibly switching to something else.

Although you have many valid points, I do not think it is accurate to generalize to this degree. Depending on the application, some runflats do much better than others, just as among non-runflat tires there is wide variation in capability. As I noted earlier, replacing mediocre OEM runflats from Pirelli with aftermarket Michelin Primacy3 ZP improved all aspects of performance, from ride quality to handling to quietness. For the application on our 3 Series family car, which does not ever experience "9/10ths" driving style, the suspension and tire create a system that performs excellently. This may not apply to an enthusiastically driven 2 Series, but that makes the point that generalizing reduces the accuracy of the comments.