[adrian206]

I'm new to the forum and have a new to me 2015 m235i, It has run flats on it that will have to be replaced before too long. I had run flats on a 328i and felt like when I replaced them with standard tires the ride was a little smoother, I put a spare donut tire in the trunk and felt like it was a worthy trade off, space ect....

Opinions on run flat or no run flat? Standard tires quieter? Smoother ride?

[delvec03]

#neverrunflat

[TheSniper]

No on the run flats. They're awful.

[Sportstick]

Originally Posted by adrian206

I'm new to the forum and have a new to me 2015 m235i, It has run flats on it that will have to be replaced before too long. I had run flats on a 328i and felt like when I replaced them with standard tires the ride was a little smoother, I put a spare donut tire in the trunk and felt like it was a worthy trade off, space ect....

Opinions on run flat or no run flat? Standard tires quieter? Smoother ride?

I think the answer is more nuanced and depends much on your desires, expectations, and priorities. I notice that you mention two attributes, 1) smooth and 2) quiet. You make no mention of handling nor performance. You may have acquired a BMW for reasons other than the "ultimate" driving experience. As well, you may prioritize safety and security of you/your passengers if you had a flat tire in an unfortunate location moreso than going around corners quickly. No judgement...we each have our own prorities.

I have two BMWs (see signature) and chose RFT on one, and wouldn't dream of having them on the other. I replaced the harsh and noisy original Pirelli RFTs on my 3 Series with actually quite smooth and quiet Michelin Primacy3 ZP run flat tires for use as our family car. (Check the ratings on tirerack.com) You can easily understand the concerns for that use case with spouse, etc. possibly in some either urban or remote locations. OTOH, for my personal toy 2 Series, almost always with only me aboard and wanting to maximize performance, I chose Michelin PS4S which are not runflat but are probably about the best performance tire and also smooth and relatively quiet. I have a minispare in the truck with a jack kit. The car has no practical purpose in our household...it's my toy for fun driving and is always in reasonable locations.

Once you decide what the priority is for this car, the right choice of tire category will appear. If you decide the higher priority is on-the-road security of RFT to avoid a probematic location for a tire change, the Primacy3 ZP has been surprisingly pleasing although seems little known. The name has to match exactly when shopping...Michelin overuses the Primacy name quite a bit. If that situation does not concern you, unquestionably, non-RFT tires offer superior characteristics.

[leftoverture]

Exactly what sportstick said. My wife works from home most days, but a few times a month she must go into the office, which is in a very bad neighborhood. So I like having the run flats for her knowing she doesn't need to be stopped in that neighborhood by a flat tire. So... really depends on your priorities and only you can answer that question.

[adrian206]

Thanks for the input, that's kind of what I was leaning towards. performance is definitely part of the equation and I'm single and not too worried about having to repair a tire and already have the spare. I'll look into those michelins, I've had good luck with michelin's in the past on motorcycles as well. I've had a couple of three series cars but I'm enjoying the hell out of this m235i so far. It's actually metal definitely more of a driving machine.

[4Hockey4]

Michelin PS4S esp. since you are in south. Not a good tire under 40 degrees.

But they are NOT a high mileage tire, you will love them otherwise.

[RoundelM3]

Both of my cars (2015 F80 M3 and 2016 F23 228i Convertible) have Continental Extreme Contact Sport non-runflats. Good balance between grip, treadwear, and cost. Been running these for years on various BMWs, never had any issues.

[adrian206]

A little bit on the same subject, I've noticed backing out of a stall and steering sharply I feel kind of a weird tire slippage that I'm assuming is mostly because the tires are wider than I've had on other cars? Second possibility is alignment way out of whack or something, steering sharply into a parking spot slowly does the same thing. Is this normal on an m235i? I guess I'm hijacking my own thread a little bit.......

[TrboMike]

I put snow tires on this winter. I was shocked how much better the car felt in ride and handling without the runflats, and that was with low grip snow tires. Now that its approaching spring the runflats will not be going back on.

Also, I had two sidewall blowouts from small pothole hits. It was nice to be able to drive home on a runflat, but IMO a non-runflat would not have blown out. The sidewalls are SO stiff on a runflat (which is how you can drive on it with no air) not only does it fuck up your ride and handling, but the sidewall with destroy itself on a pothole much more quickly than a nonrunflat would.

I'm not looking forward to a flatbed if I do get a flat now. I did look into getting a donut but for one to guaranteed to fit its expensive. And you have a huge donut sitting in your trunk ALL the time just in case you get a flat. Now that I have a set of summers and snows if I do get a flat, hopefully I can get someone from home to drive me out a jack and tire from the other set just so I can get home.

[albertw]

A recent Car & Driver track report described the Cadillac CT4V as having exceptional chassis dynamics and excellent steering feedback. Apparently it uses Continental summer runflat tires in the same sizes as our cars. This might be a good alternative for those who want better steering and handling while retaining runflat tires.

I have not been able to find out more about these tires from the Cadillac or Continental websites. Does anyone know the exact model designation?

[dradernh]

Originally Posted by albertw

A recent Car & Driver track report described the Cadillac CT4V as having exceptional chassis dynamics and excellent steering feedback. Apparently it uses Continental summer runflat tires in the same sizes as our cars. This might be a good alternative for those who want better steering and handling while retaining runflat tires.

I have not been able to find out more about these tires from the Cadillac or Continental websites. Does anyone know the exact model designation?

Continental SportContact 6 SSR, 235/40R-18 95Y TPC Spec 3150

Here it is at the Rack: https://www.tirerack.com/tires/tires...D&autoModClar=

Source: https://www.caranddriver.com/reviews...c-ct4-v-drive/

Note: it's possible that the Contis were developed specifically for the CT4-V, although if that's the case I don't think it would necessarily make them a bad match for our 6-cyl cars with their similar power and weight.

[albertw]

Originally Posted by dradernh

Continental SportContact 6 SSR, 235/40R-18 95Y TPC Spec 3150

Here it is at the Rack: https://www.tirerack.com/tires/tires...D&autoModClar=

Source: https://www.caranddriver.com/reviews...c-ct4-v-drive/

Note: it's possible that the Contis were developed specifically for the CT4-V, although if that's the case I don't think it would necessarily make them a bad match for our 6-cyl cars with their similar power and weight.

Thanks! I guess I need to start looking at the websites of my favorite car magazines.

That tire looks really interesting. Excellent braking distances on the CT4V, but a modest .91g so I could probe the cornering limits on the street without going ridiculously fast as one must with Michelins.

It didn't turn up in my searches because it is 235 rather than 225. If 225s are hard to find, I suspect 235s will fit our wheels.

[dradernh]

Originally Posted by albertw

That tire looks really interesting. Excellent braking distances on the CT4V, but a modest .91g...

Isn't it incredible how tires have advanced across the years? I'm too lazy to go back and look, but it doesn't seem all that long ago that numbers over .80 were quite impressive.

In that same context, we can always put Extreme Performance Summer tires on when we want max grip on the street. I don't want to listen to the racket those tires produce, but if I was 50 years younger I'm pretty sure I'd be rocking Bridgestone Potenza RE-71Rs on my car during the warmer months.

[raddoc]

I ditched the run-flats after both front & rear on passenger side went flat going through puddle disguising a pothole at 7 mph. The sidewalls are just too weak. Replaced with Pilot Sport AS4 XL all around. $643 for 4 at Tire Rack, plus they installed in my garage!

[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 don't doubt that there is some benefit to switching to goflats. But as mentioned, I think you have to be clear about what you're giving up in the process. And whether you couldn't get a significant imrovement in handling just by replacing with another, more effective brand of new runflat, while retaining the puncture resistance.

[Mogki]

I think a lot of people all seem to have the same idea of it depends, I travel to and though some shitty neighborhoods where i don't want to have to stop and get out sometimes so I plan to keep the runflats.

That being said getting the bill to have them replaced after hitting a pothole at speed has me deeply questioning that now.

[Sportstick]

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 don't doubt that there is some benefit to switching to goflats. But as mentioned, I think you have to be clear about what you're giving up in the process. And whether you couldn't get a significant imrovement in handling just by replacing with another, more effective brand of new runflat, while retaining the puncture resistance.

Excellent analysis and spot on!

In fact, the tires used for original equipment are different from those in the aftermarket, even for the same brand and model. I speak from years of experience at a major vehicle manufacturer responsible for product planning. My chassis engineering colleagues explained to me that their two primary motivations in developing the specifications for a tire, that the tire manufacturers meet on a program-by-program basis, are rolling resistance and cost. Rolling resistance most directly affects fuel economy ratings which can cost an OEM significant penalties if the corporate average fuel economy is not on target. However, to improve rolling resistance, compounds are harder than used by the same tire manufacturer for the same model tire sold in the aftermarket. The harder compound results in noisier, harsher tires with less relative performance. Therefore, even a direct swap of seemingly identical brand and model tire with aftermarket-sourced should produce some improvement.

I will reiterate that the Michelin Primacy3 ZP tires I found after reading many reviews are surprisingly smooth-riding and quiet for my use on a 3 Series intended as our "family car".

[albertw]

Originally Posted by dradernh

Continental SportContact 6 SSR, 235/40R-18 95Y TPC Spec 3150

Here it is at the Rack: https://www.tirerack.com/tires/tires...D&autoModClar=

Source: https://www.caranddriver.com/reviews...c-ct4-v-drive/

Note: it's possible that the Contis were developed specifically for the CT4-V, although if that's the case I don't think it would necessarily make them a bad match for our 6-cyl cars with their similar power and weight.

About 15 years ago I had access to have a table of acceptable tire widths for each wheel width, probably on the TireRack website but maybe on Michelin's. Typically there were two acceptable widths on each side of the optimum. Unfortunately I can no longer find the table. A TireRack representative told me that 235s will not fit on 7.5 inch wheels, so I guess this tire is off my list.

There doesn't seem to be a lot of choice in performance runflats. The Bridgestone Potenza RE050A RFT that is original equipment on many BMWs gets panned about as much as the Pirellis.

I need two new tires because the centres of my rear Pirellis wore out due to a much-too-high recommended pressure. Since I have two good Pirellis on the front, I'm now thinking I might switch them to the back and get a couple AS4s or Pirelli PZero All Season Plus (which probably fit my driving style better according to TireRack's testing) to see whether the fabled improvement in steering is really there. Then I'll decide whether I want to carry a compact spare and necessary tools all the time in order to use goflats on the rear (where most flats occur). If the improvement is minor, I'll probably ditch the goflats and go back to the Pirelli runflats and do the lower control arm mod to improve the steering.

msej449's post is, I think, perfect.

(It's probably worth noting that I live and do most of my driving where taxes are high enough that governments can afford to fix potholes, and traffic is light enough that seeing and avoiding the occasional pothole is not a problem.)

[adrian206]

Thanks for all the input on tires, I was leaning towards getting rid of the run flats and now I'm definitely going to get rid of them. I already have the spare and jack setup from my three series, I'm pretty sure the spare will fit.

[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.

[Unicorn123]

OP, good thread and a good question

Not much to add here as you have received a well balanced analysis and some very sound advice. Bottom line is to determine what is important to you; like most things, there are pro's and con's to both approaches to tires.

I wanted more performance as my M235 is my DD; I drive 100 miles a day minimum and typically go to our office every day. I decided to forgo the security of run-flats and run two sets of tires depending on the time of year (Conti DW Summer HP, Michelin Ice-X); mine currently is running the winter tires. I have road service through my insurance company and carry a tire repair kit. Since COVID, I take my car on long road trips with a spare tire, my 24" breaker bar with a 17mm deep socket, and my trusty aluminum jack if I am going any significant distance. I'm too cheap to buy the "factory spare kit"...

Good luck and happy motoring!