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[asus389]

Originally Posted by cgpublic

Pre-LCI E90s suffer from a combination of older generation run-flats and a new control arm bushings design.

LCI E90s improve the situation with newer gen run-flats and revised bushings.

I previously owned an 08 E90, and it's night and day compared to the 11.

Third gen RFTs are supposedly even better; I've driven E90s with regular tires, and my driving style is accustomed to the tighter turn-in.

Horses for courses.

Do you have any more info about the revised control arm parts your refer to? ie which ones (or all) of them were updated? Also, what did they do to update them?

[Bamaben]

Originally Posted by markinva

run flats have better steering feel and turn-in response than most non-rfts.

agreed. which non-RFT has equal turn in reponse as RFT ? I've not heard of one. I know there are other benefits of non-RFT. I don't think there are any non-RFT on the market that have equal turn-in. I'm guessing the PSS is the closing thing you can get. which is why I'm considering that on my next set. I went from the RE-050 to the rft-PS2 last time.

[335BBS]

Originally Posted by Ricer X

correct me if I am wrong but if you get a nail in an rft it cannot be repaired but with a non-rft it may be repaired? something to do with the membrane on an rft?

At any rate, I run hankook non-rft's and it rides so much better. I also carry a conti-comfort kit that I (knock on wood) have never had to use.

You can almost always find someone to repair an RFT if nail is in tread. Once you drive the car after tire has gone down you are now driving on sidewall which makes the tire irepairable. Once the sidewall has been compromised the tire is garbage.

[Wires]

I've had my RFT's plugged lots, with no issues. Its the heat that kills them when they are flat. Theya re spec'd for something like 100 miles at 50MPH (or something like that). Faster/longer you go, hotter the tire gets, and the sidewall ribbing breaks down. Be smart about the flat, and you have no issues with them getting fixed.

I did have non-RFT on my Acura, and took a nail through the tread, it hit the rim, and curled through the sidewall. The tire was screwed, no amount of tire sealant would help it. I had a spare, otherwise I'd had to call a tow truck to haul it away.

[chromisdesigns]

Originally Posted by Leaker

You can almost always find someone to repair an RFT if nail is in tread. Once you drive the car after tire has gone down you are now driving on sidewall which makes the tire irepairable. Once the sidewall has been compromised the tire is garbage.

Yeah, the problem is, if you get the car towed by BMW roadside service, they will only take you to the nearest BMW dealer. And the dealer will NEVER plug a runflat. Then you have to get the car towed again to another location, or else find a spare wheel and tire somewhere while you go get the bum one fixed.

[bkrM3]

RFTs are horrible.

The ONLY possible perceived handling benefit is the turn-in, which feels crisp as a result of a non-compliant sidewall. Even though the super-stiff sidewall feels like a good thing, it isn't. As was already mentioned, the back end skips around on rough surfaces, etc...it's pretty frightening.

Also, the weight of those tires is shocking.

I run Hankook V12s for my summer tires (as do a lot of people I know with E92s) and they're wildly superior to any RFT I've experienced, not to mention half the price.

Get a mobility kit (or a compact spare if you really live in the boonies) and enjoy.

[RoundelM3]

Runflats are for helpless people, in my opinion. Both of my cars were equipped with runflats when new and both now ride on non-runflats, each with a mobility kit in the trunk. That and my cell phone are all I need to cope with a flat tire - which I've not had in a very long time. The extra expense, harsh ride, and the fact that most tire shops won't try to repair a runflat because of fear of liability are more than enough to make the decision for me. I'm running Conti Extreme Contact DWs on the 335 and Bridgestone RE760s on the 128 with zero complaints and zero flats.

[cgpublic]

Originally Posted by asus389

Do you have any more info about the revised control arm parts your refer to? ie which ones (or all) of them were updated? Also, what did they do to update them?

'bushings'

There are a number of threads that refer to the ongoing E9x suspension changes independent of the LCI. If you're considering swapping out your own, a number of members have done exactly that with varied results.

There has been so much conversation about RFTs, but it seems to me it boils down not to ride, but the tendency to be rough/loud over bumps, and more importantly, price.

Yes, they weigh more, but then, not as much as a spare.

Mobility kit? Sometimes they work. Sometimes they don't.

The entire BMW ecosystem is built around RFTs. Why? Simply, and this is personal experience, they work. You can get a flat, and drive 50 miles to your home or to the dealer.

No, they cannot be repaired. Guess what? I'm not driving a BMW in excess of 90 miles per hour down 95 on a tire that's been repaired.

If you are speaking of handling, in my opinion turn-in is superior with RFTs.

End of story. Your BMW will not handle better on non-RFTs.

If you are speaking of ride, as defined what does it feel like when traversing a bump, in my opinion it was more or less fixed with the bushing change.

Does it ride like a Lexus? No. Want a ride like a Lexus, buy a Lexus.

If you are speaking of price, well non-RFTs are cheaper than RFTs. It gets old spending in excess of $1200 on Summer tires that need to be replaced every 10K.

Perfectly understandable. Money is not cheap.

To me, the type and quality of the tire you choose is of the utmost importance. Keep in mind that there are people on the board spending 4K on rims and seeking to save $500 on tires.

That's fine, but I'm not one of them.

[Myriad]

Originally Posted by bkr335

RFTs are horrible.

The ONLY possible perceived handling benefit is the turn-in, which feels crisp as a result of a non-compliant sidewall. Even though the super-stiff sidewall feels like a good thing, it isn't. As was already mentioned, the back end skips around on rough surfaces, etc...it's pretty frightening.

Also, the weight of those tires is shocking.

I run Hankook V12s for my summer tires (as do a lot of people I know with E92s) and they're wildly superior to any RFT I've experienced, not to mention half the price.

Get a mobility kit (or a compact spare if you really live in the boonies) and enjoy.

This.

Runflats are terrifying when you hit bumps with any sort of speed (like on the highway). I have Nitto's non RFT on my car now and a mobility kit in the trunk. Most places have cell service now-a-days anyway so I figure I'll be okay.

[Gripster]

The first problem that I have with run flats is that they are uncomfortable.

By uncomfortable, I mean that they are are extremely stiff by design. They transmit every road surface imperfection into the cabin. Road noise is terrible. Tramlining worse, and they don't handle well either. Search for "pothole explosions" and you will see how others feel. I would put up with all this if the tire was fail safe, but it is not. Which brings me to the next problem I have with run-flats. They are not infallible.

By not infallible, I mean that I have had one fail on me, where the tread peeled away. To be fair, it was overdue for replacement - I just lost track of it (it was my wife's DD then). The reason that I did not change that old tire with the other tires was because of the other problem that run-flats have. They are fragile.

By fragile, I have replaced 3 of them due to sidewall bubble formation. This is when the tire hits a pothole (it doesn't have to be a bad one) and a sidewall bubble is created. The tire starts to lose pressure over time and this cannot be repaired. See this video from another member - http://www.youtube.com/watch?v=k3R43qPZvGw. What is worse - it will fail on you if you ignore it so you have to replace it. Which brings me to the next problem run-flats have. They are expensive.

By expensive, I mean that I've paid $400 to have one installed in the past. You can get them cheaper, but I was stranded. By contrast, I had a set of 4 staggered Nitto Invo's put on for around $500-600.

Let's recap - uncomfortable, not infallible, fragile, expensive. I hate them. Moving to non-RFTs has transformed my car.

Catastrophic punctures are rare these days. Yes - it is a risk riding non-RFTs in a car without a spare wheel, but I got my M mobility kit and bought AAA roadside assistance. If you look after your tires, keep them properly inflated and check regularly for issues, they should last you well.

[CWS335]

It's refreshing to see a good two-sided debate about RFTs.

[M340i Pride]

in my books, run flats are no-no.

i still have them on but too many minus verses plus.

mobility kits usually can patch up simple nails on most tires. when mine is due for replacement, i will go for some hankooks.

[JDLM]

http://www.e90post.com/forums/forumdisplay.php?f=12

[BlackSheep343]

Originally Posted by korr

just put some continental extremecontact dws on. threw the rfts in my garage ；x

+1 DWS

I have installed a set of the DWS's and I will NEVER look back to the RFT's... The RFT's were so rock hard,
I constantly had to look out for pot holes and such, too many bubbles on the side walls...

[derrick603]

Originally Posted by cgpublic

If you are speaking of handling, in my opinion turn-in is superior with RFTs.

End of story. Your BMW will not handle better on non-RFTs.

So superior turn-in is the only requisite for good handling?

[Neill7]

thanks for all of your comments and advice.

I guess most of you are saying the Run flats make the car ride more spongy? and so turns are going to be a little more bouncy?

[asus389]

What about the issue of uneven wear on the edges? What is the verdict on this? Its been 6 years of e90 with RFTs. In 2006 and 2007 people complained that their tires were wearing unevenly "cupping" and got extremely noisy and started to vibrate well before they were legitimately worn out. BMW even had a program to pay for all or half of the cost of new bridgestone turanza RFTs for people who complained enough. As far as I know, the Potenza RFTs weren't covered, but there are many posts with the same complaints about them. A similar program existed for the e60 and the Dunlop RFTs in 2004-on.

Reasons given by BMW were cars were out of alignment, or the compound on certain batches of tires was bad, etc.. Were these really the root cause, or did BMW just tell people that at the time? A lot of people got new tires (including non RFT), but did this really solve the problem? Or were those tires noisy again after 5k? Did anyone actually have this problem, get an alignment back to spec, and not have the issue on subsequent RFTs? Or does switching to non-RFT really solve this issue? Other brands of RFT? If so, which tires fare better? Is this exclusive to pre-lci?

[Reznick]

When its time, I personally, would ditch the run flats. You can buy a small electronic pump that runs off the power outlet for about $30 at Lowes or Home Depot and its small enough to fit under the front passenger seat. Then buy a good tire repair kit at Pep Boys for $15. Plugging a nail puncture is an easy job.You'll be much happier with the ride and feel of a Non RFT , as long as you spend the money to buy a good performance or all-season tire.

[bkrM3]

Originally Posted by Neill7

thanks for all of your comments and advice.

I guess most of you are saying the Run flats make the car ride more spongy? and so turns are going to be a little more bouncy?

sigh.

[CamelBiscuit]

Originally Posted by Neill7

thanks for all of your comments and advice.

I guess most of you are saying the Run flats make the car ride more spongy? and so turns are going to be a little more bouncy?

That's a big hairy negative! Run flats are going to make the ride stiffer and not bouncy in turns. The sidewalls are stiff so it is going to make the tire slip more in the corners. So it will kinda feel like you are riding on a slightly wet surface in the corners. But if you are not tracking your car you will not notice the difference unless you are racing on the street and in that case then there is no hope for you. There are a lot of pro's and con's on this one but in the long run it is up to you. I raced superbikes for a while so I know the difference between great tires and race tires. The RFT's are not that bad to me I have driven all over Europe and had no problems. Then maybe I am just lucky.

[captainaudio]

The runflats do not make the ride mor "spongey" they make it more harsh. There is a common misconception that the stiffer the suspension the better a car will handle. This may be true up to a point but there is a point at which making the suspension stiffer will make the car handle worse. If the 'stiffer the suspension the better the handing" was the case it would follow that for ultimate handling you would not need a suspension at all and could just attach the wheels to the frame of the car.

The so called "Crisp Turn In" of RFTs may give the illusion of good handling but in my experience the RFTs, or at least the ones that my 07 335i came with were not good handling tires. They were OK on smooth roads but the real world does not consist of exclusively smooth roads. I found that as soon as the road surface was anything less than pristine the car would start bouncing all over the place. A car that can not keep its contact patches on the road (the are called contact patches for a reason) is not a good handling car and neither is a car that is easily upset by irregular road surfaces. The RFTs were especially bad on bumpy curves. They would bounce around and the rear end would start to step out. I named this "CTO" for Crappy Tire Oversteer". I also found that they were unpredictable one you reached the limits of adhesion. They tended to break loose with very little warning.

To generate maxium grip and hense maximum cornering force a tire needs to have a certain amount to slip angle. There is a sweet spot for slip angle and too much or too little will have a negative effect on handling. IMO the OEM RFTs that BMW put on my 335i had too little slip angel due to the stiff sidewalls. You can google "slip angle" and find a lot of info but here is a brief description,

===============================================

Slip Angle

Return to the tracking page

Slip angle is the angular difference between the direction the tyre contact patch with the road is pointing and the direction of the wheel (figure 1, below). This sounds odd - you might expect that the tyre tread would point in the same direction as the wheel wouldn't you? It doesn't because being made of rubber, the tyre sidewalls deform, and the tread pattern itself can 'squirm' when the wheel is turned from the straight-ahead.
In fact, modest slip angles are 'good' as tyres generate progressively more grip with increasing slip angles (figure 2, opposite), albeit up to definable limit where after no further grip is generated. Thereafter, increasing slip angles are 'bad', and the tyre will tend to loose grip.
Therefore, it should be apparent that if the slip angles for the front and rear tyres are the same (the tyres front and rear are generating similar levels of grip), the car will steer essentially as if there was no slip angle at all (neutral cornering).

Figure 1. Definition of slip angle. Note how the contact patch of the tyre need not be in the same orientation as the whole wheel, often lagging a few degrees behind.

Now let us consider what happens when the slip angles exceed our optimal grip generation limits. If the rear slip angle is larger than the front one you have a condition known as over-steer while if the front slip angle is larger, the condition known as under-steer results (also see the explanation on the tracking page). You will recall that a slip angle results from a combination of tyre sidewall flex and tyre traction. Note that if there is no traction (on ice, for example), then the slip angle will become essentially zero. On the other hand, if a wheel travels in a direction other than the one its contact patch is pointing, then you have a SLIDE angle rather than a slip angle.
Slide angles and slip angles are VERY DIFFERENT. Inertia determines the direction the car will travel if it slides (centripetal force). If you lose traction you will slide in the direction you were travelling at the time the slide starts. So long as you have traction you will travel in the direction the contact patch points, not the tyre. Slide angle is the angular difference between the direction inertia sends you and the direction your tyres are pointing while slip angle is the angular difference between the direction your contact patch is pointed (thus, the direction the tyre moves) and the direction the tyre is pointed.
Decreased traction reduces slip angles and increases slide angles!
Figure 2. Lateral force versus slip angle. Note that lateral force progressively increases from 0 degrees slip to a peak at about 8 degrees. Thereafter, the adhesion is lost, and the lateral force that the tyre is capable of generation progressively deteriorates.
What else affects slip angles? Acceleration and braking, tyre profile size and tyre camber. Acceleration and braking affect traction primarily because of weight transfer and toe-angle changes.
The greater camber, the greater the camber thrust. Camber thrust attempts to turn your wheel into a turn in the direction of lean. Thus, greater camber thrust yields smaller slip angles.
Given that the rear camber of the MGF is greater than the front, you should expect that the rear tyres are almost always operating with a lower slip angle than the front tyres. (I.e., your car tends to under-steer.)
What changes a slip angle into a slide angle? Excessive slip angles!!! That is, a slip angle is so called because the part of the contact patch that is to the outside of your turn is moving faster than the wheel itself is in the direction it (the contact patch) is pointing while the part on the inside is moving more slowly. (Exactly like camber thrust.) Since the outside part is moving faster than the tyre it must be slipping. The inside part is gripping better than it would if moving in a straight line. For this reason the contact patch 'walks' itself into the turn.
The greater the slip angle, the larger portion of the contact patch that is slipping. At some point there is so little part of the contact patch that is not slipping that traction is lost and the tyre begins to slide. Until shortly before then, slide traction increases. Note, however, that traction is generally not lost all at once. Rather than an abrupt loss of traction, it tends to be lost gradually. (Thankfully!!!)

[cgpublic]

Originally Posted by derrick603

So superior turn-in is the only requisite for good handling?

I'd define handling as responsiveness to driver input, and for me, a RFT tire is more responsive to steering input than a non-RFT.

In fact, when I drive a BMW without RFTs, my impression is not that the car doesn't handle well, but the car does not drive like a BMW.

If you want to say that you prefer the feel of non-RFTs to RFTs, that's OK.

But to say that non-RFTs are superior in 'handling' is misleading. They're not using the definition above.

If you want to say the ride with a RFT over bumps is harsher/louder, that's also OK, but based on owning an 08 and an 11, it's more than simply a better RFT, it's also the bushings that has improved that aspect of the ride.

My point is simply this. RFT tech and how BMW tunes the suspension accordingly has improved immensely since the E90 was introduced 7 years ago.

Based on the latest reviews of RFTs, the same old same old repeated over and over again just doesn't drive the story as it did back in 2006.