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      09-07-2010, 07:27 PM   #1
Cuz5150
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check this out: RFT

Flipping the pages on Oct issue Automobile Mag i come across.......
The Q&A section(page 66)
They asked 5 questions to Chassis development engineer Heinz Krusche.

The last question:
Why does BMW favor run-flat tires?

Answer:
They provide several advantages, including [B]more precise steering[B]andhandling
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      09-07-2010, 08:25 PM   #2
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Quote:
Why does BMW favor run-flat tires?

Answer:
They provide several advantages, including significant financial considerations for BMW.
There. Fixed that for him
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      09-07-2010, 08:27 PM   #3
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I thought stiffer sidewall does provide more precise steering. Just that the compound used on run crap is too hard to provide descent traction.
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      09-07-2010, 08:38 PM   #4
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Achtung, Achtung, Heinz Krusche, You know nothing, you see nothing.
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      09-08-2010, 12:01 AM   #5
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I guess I'm in the minority, but I really do believe the RFT's had much better steering feel and response. After I switched the the Hankook's, it lost some of the instant response that the RFT's had. There is better overall grip, but the steering response is much more delayed.
Just my opinion!

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      09-08-2010, 12:54 AM   #6
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Interesting, the topic pops up again and again. Over two years ago when I owned Z4 people were ready to kill each other arguing why RFT good or bad. My opinion that RFT are good, comfortable ride (same or even better than regular tires), precise handling, great grip for acceleration, but what is most important outstanding safety. Yes, here is some financial drawback for owners, like these tires not reparable, so you got nail, you got $500 out of your pocket.
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      09-08-2010, 01:14 AM   #7
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Quote:
Originally Posted by akak1997 View Post
I thought stiffer sidewall does provide more precise steering. Just that the compound used on run crap is too hard to provide descent traction.
This, and the compound on the 3rd gen Bridgestone RFTs are now supposedly the same as the non-RFT variants. I love my RFTs, both on the road and for competition. They've treated me well so far.

I've read quite a few threads now where people are disappointed after making the switch to non-RFTs because of the "sluggish" feeling of the tires, even though grip is possibly improved. That's why I haven't bothered to swap out the RFTs for autocross even though everyone there is saying "those are run flats? Man, I feel sorry for you" when talking in grid waiting for our runs. At the end of the day though, they always end up saying "Man, you're fast on those run flats!"

I ran faster than several experienced drivers in modified cars with supposedly stickier tires, including a very seasoned driver in an RX-8 with Hoosiers and all STU class cars last event and I've only done 7 events total, 3 with the 135, so I don't consider myself a great driver either. I even left the day thinking I could have gone faster, I even knocked 1 full second off my time on my last run.

The Bridgestone RFTs on the 2011s (possibly 2010s too) are great tires. Maybe on a track day with extended periods at high speeds/temperatures, the RFTs may not be so great... but for the majority, the RFTs are great.
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Last edited by MarkR171; 09-08-2010 at 01:25 AM..
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      09-08-2010, 07:02 AM   #8
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Quote:
Originally Posted by MOCKBA View Post
Yes, here is some financial drawback for owners, like these tires not reparable, so you got nail, you got $500 out of your pocket.
run flats are repairable
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      09-08-2010, 07:11 AM   #9
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Quote:
Originally Posted by joeo View Post
I guess I'm in the minority, but I really do believe the RFT's had much better steering feel and response. After I switched the the Hankook's, it lost some of the instant response that the RFT's had. There is better overall grip, but the steering response is much more delayed.
Just my opinion!

-Joe
Agree - drastically reduced tram-lining with stiffer sidewalls is one of the biggest advantages I have seen with RFTs.
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      09-08-2010, 07:12 AM   #10
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Quote:
Originally Posted by Taymaishu View Post
Agree - drastically reduced tram-lining with stiffer sidewalls is one of the biggest advantages I have seen with RFTs.
I disagree with this, I drive the same road every day, on day one with star spec's I noticed how much less tram lining i had to deal with

the grip/handling on star specs vs stock runflats is an amazing improvement
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      09-08-2010, 07:31 AM   #11
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Quote:
Originally Posted by MOCKBA View Post
Interesting, the topic pops up again and again. Over two years ago when I owned Z4 people were ready to kill each other arguing why RFT good or bad. My opinion that RFT are good, comfortable ride (same or even better than regular tires), precise handling, great grip for acceleration, but what is most important outstanding safety. Yes, here is some financial drawback for owners, like these tires not reparable, so you got nail, you got $500 out of your pocket.
Can you dig a bigger hole?
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      09-08-2010, 07:42 AM   #12
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Quote:
Originally Posted by MarkR171 View Post
This, and the compound on the 3rd gen Bridgestone RFTs are now supposedly the same as the non-RFT variants. I love my RFTs, both on the road and for competition. They've treated me well so far.

I've read quite a few threads now where people are disappointed after making the switch to non-RFTs because of the "sluggish" feeling of the tires, even though grip is possibly improved. That's why I haven't bothered to swap out the RFTs for autocross even though everyone there is saying "those are run flats? Man, I feel sorry for you" when talking in grid waiting for our runs. At the end of the day though, they always end up saying "Man, you're fast on those run flats!"

I ran faster than several experienced drivers in modified cars with supposedly stickier tires, including a very seasoned driver in an RX-8 with Hoosiers and all STU class cars last event and I've only done 7 events total, 3 with the 135, so I don't consider myself a great driver either. I even left the day thinking I could have gone faster, I even knocked 1 full second off my time on my last run.

The Bridgestone RFTs on the 2011s (possibly 2010s too) are great tires. Maybe on a track day with extended periods at high speeds/temperatures, the RFTs may not be so great... but for the majority, the RFTs are great.
They should be asking if you have DCT. RFT compliance can't deal with a bumpy road surface and have tendency to skip off the road and unsettle the car.
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      09-08-2010, 10:10 AM   #13
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Quote:
Originally Posted by maxnix View Post
Once again, one would have to run the same tire in RFT and non RFT back to back to obtain a valid inference.
I need new tires, and don't care what anyone says about RFT, I will not be replacing them with more RFT's (I also don't believe that anyone has 3rd Gen RFT's either). I have briefly considered trying the RE-050a non RFT, but don't really find them to be very good tires for any purpose, so will likely change to something else, but it's still tempting just to see what the change to the same tire, just non RFT would be. Unfortunately, they only make the RE-050a in 335i sizes (and non XL load rating), not the OE 135i sizes, so this idea seems dead in the water.
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      09-08-2010, 10:26 AM   #14
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Quote:
Originally Posted by MOCKBA View Post
comfortable ride (same or even better than regular tires)
I hated the ride in my wife's e90 from day 1 (and if it wasn't for the e30 we picked up I would still hate BMW to this day) as it was just way too jarring and uncomfortable, yet it didn't have the crisp feel of a performance car to make up for it. Originally I thought the ride issues were the sport seats, but when she had a sidewall blow out she replaced them with PS1s and everything changed for the better. It now has a better steering feel and a much more comfortable ride (though still uncomfortable for trips over an hour or so for me).

Her's is an Xi, so she doesn't have the sport suspension and I could believe that there is a feel difference between the all weather and performance variant.

I have been hearing good reports on the 3rd gen RFTs so I will give them a chance as I drive all over Europe, but I'm still going to be prepared to re-shoe it after it gets home.
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      09-08-2010, 10:49 AM   #15
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One funny thing I found about the BMW chassis engineers comments. If indeed BMW feels the RFT are the better choice for handling and steering then why do they fit non RFT on the M3? I believe it comes with Michelin non RFT. Seeing as that is their top car for steering/handling I would say they believe the non-RFT are the choice for the best handling/steering...wouldn't you say???
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      09-08-2010, 12:27 PM   #16
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^^ Yes. M3 and 1M have non-RFTs.

As for advantages, RFTs are excellent when terrorists try to shoot out your tires.
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      09-08-2010, 12:29 PM   #17
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Quote:
Originally Posted by GaryS View Post
^^ Yes. M3 and 1M have non-RFTs.

As for advantages, RFTs are excellent when terrorists try to shoot out your tires.
Provided those terrorists are driving a Tesla, a Leaf or a Mini-E and only have a 49 mile range.
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