[rolltidef32]

There is a nice debate going on in the Wheel and Tire section about changes in the precision and handling that can occur when switching from the BMW standard Run Flat tires, to Go Flat tires.

The Track Packages that are now offered on several models come standard with Michelin Pilot Super Sport Go Flat tires. ///M models also run this set up.

Is anyone aware of any suspension part or calibration set up changes that come from the factory once the change is made to non-RFTs? I've taken the RFTs off of my BMWs for about 10 years now, but don't feel this modification changes the dynamics of the car in a way that is negative and noticeable.

We all know the gains of going non-RFT (ride comfort, etc), so that is not the subject of the thread.

If anyone has made any chassis or suspension changes themselves following the tire switch, what changes did you make? What prompted the changes? What do you experience that is different, better/worse with these changes?

[xlover]

I doubt it because if you select track pack and 19s the build goes goes back to run flats.

[Blubaron79]

I don't think. They only choices you really have are the M Sport suspension which is lower and firmer, or the adaptive suspension (the way to go). Plus the new generation run flats are really starting to get a lot better compared to my E92's run flats.

[HighlandPete]

Originally Posted by rolltidef32

There is a nice debate going on in the Wheel and Tire section about changes in the precision and handling that can occur when switching from the BMW standard Run Flat tires, to Go Flat tires.

The Track Packages that are now offered on several models come standard with Michelin Pilot Super Sport Go Flat tires. ///M models also run this set up.

Is anyone aware of any suspension part or calibration set up changes that come from the factory once the change is made to non-RFTs? I've taken the RFTs off of my BMWs for about 10 years now, but don't feel this modification changes the dynamics of the car in a way that is negative and noticeable.

We all know the gains of going non-RFT (ride comfort, etc), so that is not the subject of the thread.

If anyone has made any chassis or suspension changes themselves following the tire switch, what changes did you make? What prompted the changes? What do you experience that is different, better/worse with these changes?

Interesting topic and has applied from years back, when BMW used the "designed for run-flat" comments for the RFT fitted models.

There has to be some change to the chassis dynamics whenever we move from the wheel/tire combination of the 'standard' build, assuming the build is the 'sweet spot' for the model/engine/chassis. BMW follow "the best compromise of all relevant criteria" development process. We change wheel size or tire types, something gives.

I know from experience when changing to go-flats on my 2006 E91 wagon, the suspension was no longer matched with the tires, without changing the damping. Was clear the OE damping was softened to try and work with stiff sidewall tires. With same wheel size go-flats, the car was under-damped, too much float and bumps were not thumped out with the 'one thud' we expect from decent compression/rebound control. I fitted Koni FSD dampers to improve the body control, got that good old solid BMW feel back to the suspension.

What has changed? Run-flat tire Vertical Stiffness is now much closer to a similar high performance go-flat equivalent, we are not in the same place as 10-years ago. Swapping tires on the latest models will not have such a dramatic change to the dynamics as the early days of RFTs.

Personally I see the changes to vertical stiffness, giving BMW more scope again, for wheel/tire combinations without moving the envelope too much, or requiring suspension mods. Saying that, there are still changes, but the compromises are not as obvious and are less dramatic.

[ynguldyn]

There are no part number differences that would depend on the choice of the tire.

[XKxRome0ox]

Originally Posted by HighlandPete

Interesting topic and has applied from years back, when BMW used the "designed for run-flat" comments for the RFT fitted models.

BMW's are now "designed for run-flat" ... in that they don't give you a spare tire anymore

i wish they would at least give us the space to put a spare in the trunk if we chose to have one

[HighlandPete]

Originally Posted by ynguldyn

There are no part number differences that would depend on the choice of the tire.

It is this anomaly which has applied for years (models in Europe with or without run-flats) that has really undermined the statement that the suspension is designed particularly for run-flats. I've (with my cynical head on) seen it more as "compromised for run-flats".

[HighlandPete]

Originally Posted by XKxRome0ox

BMW's are now "designed for run-flat" ... in that they don't give you a spare tire anymore

i wish they would at least give us the space to put a spare in the trunk if we chose to have one

Perhaps it is more a situation that go-flats are designed out!

Agree on the option for a spare, but a bit of wishful thinking I'd say. When you see the size of our current full sized wheels, requires a big 'wheel well' for a full sized spare. I'm not too sure about space savers myself.

I like the concept of the run-flat, (I've kept with them on my current BMW), but not necessarily how the application is executed. A spare is a comfort, even if do have to carry it around all the time, without need to use it.

[rolltidef32]

Ok, check out this post from thakid22 in the wheel and tire forum. I don't feel a difference, but he does and quoted several who seem to confirm that there could be issues with a RFT swap to Go Flats. Seems to argue that configuration changes should be made with the suspension. Thoughts?

Originally Posted by thakid22

So. There you have it. From multiple sources...
You will easily find more on your own if so inclined. But EVERYTHING I have said is well documented by those who actually make the switch.
As for rft vs non rft, you just have to know the right questions to ask.
I (initially) did not. Most conversations revolve around ride quality and NVH. You'll also hear about how non rfts handle better. And they do! In certain situations. The extra compliance increases grip and stability greatly on less than perfect roads. But the down side is that the steering will be less direct, slower, and on center feel and effort ramp up can weaken.

Think about it. For a moment, forget spring rate, shock valving, etc. Think of each corner as an assembly. Each corner has its own wheel rate, the rate at which the bushings/mounts/tires/springs/rim/shocks, etc all cumulatively operate. A rft can be up to 35 % stiffer than a conventional tire. Swapping it with a softer tire is somewhat similar to swapping in softer shocks/bushings/springs etc. The overall wheel rate drops.

Lower wheel rate can produce a smoother and quiet ride, but can and will also reduce control and response.

E90s were designed around early runflats that were stiffer than todays models. Adding non rfts to those cars evoked a night and day difference. They took on a smoother, more civilized, but almost underdamped demeanor on non rfts. Today's F-Series BMW makes less concessions owed to its new generation, softer (but still stiff) rfts.

Again, I'm not advocating runflats. I wish BMW had left them off of the spec sheet. The rfts are now an integral part of the BMW chassis. Those rfts do impart a sense of sportiness. BMW knows they are stiff. Consequently, stiffness has been removed and added from/to various other chassis parts to accommodate that. Throw away the rft stiffness and the car is left without a bit of stiffness that it once used.

The steering is a perfect example. With reduced sidewall flex it literally takes less steering angle (especially initially) to turn the car. Go flats increase flex and also the required steering angle for a given turn. It is very obvious when you are looking for it, especially if you can drive to cars back to back (rft vs nrft).

All that being said, go flats are not gonna destroy the handling precision of these cars. They will dull it every so slightly. Some may never even notice.
In the end it can argued that go flats give MORE in traction and nvh, than they take away from precision.

I hope I have been able to help and perhaps save someone the shock I experienced.

On another note, uh - I know I'm getting long winded, the current crop of RFT are much less of a NVH compromise than they used to be.

The Michelin PS2 ZP runflat was nearly as civilized as the PSS nonrft I replaced them with. In fact, they felt like a sportier version of the same tire, around town. Quiet, firm, and responsive. I do feel that the PSS did have better ultimate grip though. Anyway, I've strayed from the original topic...

[JamRWS6]

While I can appreciate the effort in the comparison the biggest factor here isn't mentioned. Are we talking all-season RFTs vs all-season non-RFT? Or max performance summer RFT vs an equivalent max performance summer non-RFT? I can tell you in comparing the latter that the Pilot Super Sports I changed to were superior in all aspects. There's too many variables when not naming exact tires being compared.

[Polo08816]

Originally Posted by rolltidef32

There is a nice debate going on in the Wheel and Tire section about changes in the precision and handling that can occur when switching from the BMW standard Run Flat tires, to Go Flat tires.

The Track Packages that are now offered on several models come standard with Michelin Pilot Super Sport Go Flat tires. ///M models also run this set up.

Is anyone aware of any suspension part or calibration set up changes that come from the factory once the change is made to non-RFTs? I've taken the RFTs off of my BMWs for about 10 years now, but don't feel this modification changes the dynamics of the car in a way that is negative and noticeable.

We all know the gains of going non-RFT (ride comfort, etc), so that is not the subject of the thread.

If anyone has made any chassis or suspension changes themselves following the tire switch, what changes did you make? What prompted the changes? What do you experience that is different, better/worse with these changes?

You know there doesn't seem to be any differences as far as alignment goes between a 335i RWD Sport Suspension and a 340i RWD Sport Suspension. They seem to point to the same place as far as ISTA+ goes.

[thakid22]

Originally Posted by rolltidef32

There is a nice debate going on in the Wheel and Tire section about changes in the precision and handling that can occur when switching from the BMW standard Run Flat tires, to Go Flat tires.

The Track Packages that are now offered on several models come standard with Michelin Pilot Super Sport Go Flat tires. ///M models also run this set up.

Is anyone aware of any suspension part or calibration set up changes that come from the factory once the change is made to non-RFTs? I've taken the RFTs off of my BMWs for about 10 years now, but don't feel this modification changes the dynamics of the car in a way that is negative and noticeable.

We all know the gains of going non-RFT (ride comfort, etc), so that is not the subject of the thread.

If anyone has made any chassis or suspension changes themselves following the tire switch, what changes did you make? What prompted the changes? What do you experience that is different, better/worse with these changes?

Hmmm... I see where you are going here. Good thinking!
Right off the bat, the Track & Handling Package automatically includes VSS (Variable Sport Steering). VSS is supposed to have "increased agility on winding roads and more safety at high speeds (Bmwusa.com website). To me, this says that the steering ratio is quicker overall, while also having a more relaxed ratio near on center. In addition, VSS is a completely different steering rack, than the regular unit. VSS steering ratio is 14.5:1 while the standard rack ratio is 15:1, if I remember correctly.

In addition all BMWs with electric steering also incorporate Servotronic. We know that Servotronic varies steering assist based upon speed. I mention this here because, in the past, different models had different Servotronic Settings. Looking at the Servotronic coding for my 535i, I saw that the M5, 550i, 528i, as well as different regions (usa, europe, etc) all had different steering assist values. BMW literally tailored each vehicle to have its own assist profile. The part # for the Servotronic computer is the same for all those models, but the actual programming changed its operating behavior based upon coding.

Could BMW be doing something similar with the F30? Most likely they are. I'll have to dig around a bit and see if I can find the actual values. Once the Track & Handling Package is added to the VO (vehicle equipment list), every module in the car is privy to the fact that the car has the option, and can (but not all do) run different parameters based upon that option.

Furthermore, all Track Package cars include Adaptive M Suspension.
Again, I would be willing to bet the Track Package has its own coding settings here too.

Looking at this, Is the Track and Handling Package optimized for the track?
Or is it just the best of what BMW already had available, paired with PSS and sold together? I won't be sure until I see the actual differences in programming (if there are any), because the hardware between track and non track is eerily similar.

[dc503]

Originally Posted by rolltidef32

Ok, check out this post from thakid22 in the hell and tire forum. I don't feel a difference, but he does and quoted several who seem to confirm that there could be issues with a RFT swap to Go Flats. Seems to argue that configuration changes should be made with the suspension. Thoughts?

This is pretty spot on from a fundamental perspective, obviously. The answer is yes, compensation should probably be made to optimize the tire change. However, my over-simplified guess is BMW has likely just found an acceptable operating window that they're happy with utilizing existing hardware and setup for the ZTR package - spring rates, bushings, shock valving, alignment, etc.

Steering and Adaptive dampers could be the one thing that could most impacted by factors that we can't see due to the electronics though.

[bimmercar]

Originally Posted by thakid22

Hmmm... I see where you are going here. Good thinking!
Right off the bat, the Track & Handling Package automatically includes VSS (Variable Sport Steering). VSS is supposed to have "increased agility on winding roads and more safety at high speeds (Bmwusa.com website). To me, this says that the steering ratio is quicker at low speeds, and more relaxed at higher speeds. In addition, VSS is a completely different steering rack, than the regular unit. VSS steering ratio is 14.5:1 while the standard rack ratio is 15:1, if I remember correctly.

In addition all BMWs with electric steering also incorporate Servotronic. We know that Servotronic varies steering assist based upon speed. I mention this here because, in the past, different models had different Servotronic Settings. Looking at the Servotronic coding for my 535i, I saw that the M5, 550i, 528i, as well as different regions (usa, europe, etc) all had different steering assist values. BMW literally tailored each vehicle to have its own assist profile. The part # for the Servotronic computer is the same for all those models, but the actual programming changed its operating behavior based upon coding.

Could BMW be doing something similar with the F30? Most likely they are. I'll have to dig around a bit and see if I can find the actual values. Once the Track & Handling Package is added to the VO (vehicle equipment list), every module in the car is privy to the fact that the car has the option, and can (but not all do) run different parameters based upon that option.

Furthermore, all Track Package cars include Adaptive M Suspension.
Again, I would be willing to bet the Track Package has its own coding settings here too.

Looking at this, Is the Track and Handling Package optimized for the track?
Or is it just the best of what BMW already had available, paired with PSS and sold together? I won't be sure until I see the actual differences in programming (if there are any), because the hardware between track and non track is eerily similar.

its interesting that you mention that the steering varies with speed. I noticed that the music volume and windshield wiper speed also increases at higher speed

[Michael Schott]

Originally Posted by rolltidef32

Ok, check out this post from thakid22 in the hell and tire forum. I don't feel a difference, but he does and quoted several who seem to confirm that there could be issues with a RFT swap to Go Flats. Seems to argue that configuration changes should be made with the suspension. Thoughts?

There are a lot of generalizations in that post. A lot depends on the type of go flat tires you use. Tread design and compound are all variables. The DWS06 go flat tires I now run changed the handling and ride for the better while making the steering lighter (a detriment). Overall a much improved experience.

The disadvantage of RFT's is mainly the harshness due to the stiff sidewalls. BMW certainly specified springs and shocks to account for this but without going to super soft springs, the impacts are still felt. The change to go flats eliminated this issue. To be fair, even the 704 suspension in my Sport Line RWD car on 18" RFT's was far more acceptable than the base suspension with RFT's on my 2011 E90 with 17" wheels which was better than my 2008 on 16" tires with RFT's.

[ynguldyn]

Originally Posted by bimmercar

its interesting that you mention that the steering varies with speed.

That was just the poster's conjecture. It is incorrect. The details of VSS operation can be found in the technical documents for F3x and F80/F82 posted elsewhere in this forum.

[thakid22]

Originally Posted by Michael Schott

There are a lot of generalizations in that post. A lot depends on the type of go flat tires you use. Tread design and compound are all variables. The DWS06 go flat tires I now run changed the handling and ride for the better while making the steering lighter (a detriment). Overall a much improved experience.

The disadvantage of RFT's is mainly the harshness due to the stiff sidewalls. BMW certainly specified springs and shocks to account for this but without going to super soft springs, the impacts are still felt. The change to go flats eliminated this issue. To be fair, even the 704 suspension in my Sport Line RWD car on 18" RFT's was far more acceptable than the base suspension with RFT's on my 2011 E90 with 17" wheels which was better than my 2008 on 16" tires with RFT's.

No. There are no generalizations there. I am stating what actually happens when you go from a rft to what would be its non rft equivalent. In that thread, I specifically discuss the switch from Michelin PS2 ZP run flats to Micheline PSS non rft.

I think your statement regarding the DWS06 changing the ride and handling "for the better" is much more "general". Do they improve the ride in alot of ways? I'm certain they do. Do they improve the ride and handling in EVERY single way possible. Absolutely not. In the real world, there are trade offs and compromised to be made. How do you define ride? How do you define handling? Does the ride get smoother with non rfts! Absolutely. Can grip go up with non rfts? Certainly. But ride and handling are very intricate topics that encompass hundreds of other attributes that collectively make up what we call " ride and handling." Be rest assured that while the ride is quieter, smoother, and grippier with non rfts, other areas have been compromised. Whether one is observant, open minded, knowledgeable, keen, or experienced enough to notice the compromise is a whole other issue. I say that with zero malice. Also, like the OP stated, the merits of rfts are not in question here. I think we all agree on rft benefits.

Once again, no generalizations... I am describing what happens in reality. Not only that, I have backed it up with my own personal experiences, those of experts (including BMW), and a few novices as well.

I agree with you, that the type of tires matter alot. But for the sake of conversations like these, I try to compare apples to apples. In fact the tirerack link I provided, tested the rft and non rft version of the SAME tire (re960as) and found results similar to my own experiences.

[Michael Schott]

Originally Posted by thakid22

No. There are no generalizations there. I am stating what actually happens when you go from a rft to what would be its non rft equivalent. In that thread, I specifically discuss the switch from Michelin PS2 ZP run flats to Micheline PSS non rft.

I think your statement regarding the DWS06 changing the ride and handling "for the better" is much more "general". Do they improve the ride in alot of ways? I'm certain they do. Do they improve the ride and handling in EVERY single way possible. Absolutely not. In the real world, there are trade offs and compromised to be made. How do you define ride? How do you define handling? Does the ride get smoother with non rfts! Absolutely. Can grip go up with non rfts? Certainly. But ride and handling are very intricate topics that encompass hundreds of other attributes that collectively make up what we call " ride and handling." Be rest assured that while the ride is quieter, smoother, and grippier with non rfts, other areas have been compromised. Whether one is observant, open minded, knowledgeable, keen, or experienced enough to notice the compromise is a whole other issue. I say that with zero malice. Also, like the OP stated, the merits of rfts are not in question here. I think we all agree on rft benefits.

Once again, no generalizations... I am describing what happens in reality. Not only that, I have backed it up with my own personal experiences, those of experts (including BMW), and a few novices as well.

I agree with you, that the type of tires matter alot. But for the sake of conversations like these, I try to compare apples to apples. In fact the tirerack link I provided, tested the rft and non rft version of the SAME tire (re960as) and found results similar to my own experiences.

Apples to apples I agree with you. In reality, how many at least on an enthusiast forum like this are changing from all season RFT's to equivalent all season RFT's? I switched to the Conti's not solely due to the go flat construction but because I wanted the best handling all season tire I could find. The smoother ride (less harshness over bumps) is a side benefit.

Regarding handling specifics, it's a difficult comparison because the stock Pirelli P7 Cinturato all seasons are at a disadvantage compared to a (Tire Rack description) Ultra High Performance all season tire. Regarding my impressions of the handling, on center feel is much improved as is turn in (still lacking due to the EPS) and ultimate grip is undoubtedly higher.

[nicknaz]

Originally Posted by Michael Schott

Apples to apples I agree with you. In reality, how many at least on an enthusiast forum like this are changing from all season RFT's to equivalent all season RFT's?r.

+1

Why bother with that kind of switch, unless the goal is truly to soften the ride

As an aside, you guys should check out the discussion on autox specific forums. there is a lot of discussion there of sidewall stiffness and suspension setups, as well as which tires do better on heavier or camber challenged cars.

[rolltidef32]

Originally Posted by nicknaz

+1

Why bother with that kind of switch, unless the goal is truly to soften the ride

As an aside, you guys should check out the discussion on autox specific forums. there is a lot of discussion there of sidewall stiffness and suspension setups, as well as which tires do better on heavier or camber challenged cars.

These guys are providing a lot of education, which I expected they would.

I'm curious about the topic because I've started to have concerns on the so called "warnings" that BMW has given on making the switch, yet contradicting this by offering Go Flats due to demand. Where these warnings just BS fashioned to scare us into buying more RFTs? Or, should we really be tweaking our suspensions when making the change.

Guess I've never really given RFTs much of a chance. On my last F30, which I leased, I did run the Conti Contact 5 RFTs for 2 years. Did this because I actually felt that the tires were pretty good performance wise on the street.

Over the past 2 weeks, I've gotten 2 screws in each rear MPSS. These are soft tires, so it's started me to thinking. Both were patched for free and there was no threat of a full on blow out (tire construction is made to theoretically prevent this from occurring). An RFT would have likely needed to be replaced in both cases, but the effect of the hard as a rock tire vs. the softer tire has me wondering of the effects on suspension and driving dynamics.

I don't track my DD F32, so it's not a big deal, but I felt the subject would be interesting for those who do. Fastest I've taking the car so far was 115mph on a straight in zero traffic. Dumb I know, but just being honest. Also have a Tail of the Dragon run coming in a couple of weeks, so trying to figure out what I may need to work on. The last time, the car did feel a bit floaty, but I just blamed it on the car itself.

[nicknaz]

Originally Posted by rolltidef32

I'm curious about the topic because I've started to have concerns on the so called "warnings" that BMW has given on making the switch, yet contradicting this by offering Go Flats due to demand.

An RFT would have likely needed to be replaced in both cases, but the effect of the hard as a rock tire vs. the softer tire has me wondering of the effects on suspension and driving dynamics.

My take is the nonRFT to RFT and patching RFT caveats are to avoid getting sued / confusing non enthusiasts

Just get your RFT of choice and call it done. It's already been discussed above the suspension part numbers are the same for 18" with MPSS vs. 19" with rft

[thakid22]

Originally Posted by ynguldyn

That was just the poster's conjecture. It is incorrect. The details of VSS operation can be found in the technical documents for F3x and F80/F82 posted elsewhere in this forum.

Ynguldyn is correct. VSS, as incorporated by BMW, has a quicker rack ratio than conventional steering. In addition, the ratio is slower near on center whilst still being quicker overall. Quite Nifty.