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      01-20-2014, 10:47 AM   #1
Qunadry
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Switching From Run-flat tires

I am considering switching from the Dunlop run-flats that came with my 135i M Sport package to Michelin PSS in the spring when I have my winter wheels/tires removed. I have two friends that own BMWs and they both said that when they switched to regular tires the car's handling, in particular cornering was adversely affected. I find this hard to believe based on all the positive comments I have read regarding switching to regular tires. Your input would be appreciated.
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      01-20-2014, 11:01 AM   #2
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Definitely recommend it. Benefits from switching to non run-flats are:
1. Smoother ride
2. Better handling
3. No need to buy a new tire if one gets punctured
4. Lighter tire for better acceleration, braking and MPG
5. More grip

I'm sure there is even more I am missing.
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      01-20-2014, 11:54 AM   #3
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I can see how cornering would be affected. Run-flat tires' sidewalls are really stiff, especially compared to a regular tire. Stiffer sidewalls = better cornering. Softer sidewalls = better ride comfort.

My 135i is a daily driver and I still plan to get non-run-flats when my run-flats wear out. I'll take ride comfort over the slight loss of handling.
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      01-20-2014, 12:50 PM   #4
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Seriously do it and don't look back. It has been the best money spent on my car to date. You will get alittle more sidewall flex but that's to be expected. Best part is the ride quality VASTLY improves!
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      01-21-2014, 11:19 AM   #5
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Saying that the tires adversely impacted the car is to miss the real problem. When you switch from an all season run flat to a max performance summer, you are seriously bumping the level of grip. That new grip creates additional load for the suspension, which will essentially fall on its face as it is not designed for such use. This is when upgrading bushings and struts becomes essential to restore balance.
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      01-21-2014, 01:21 PM   #6
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Quote:
Originally Posted by TheSt|G View Post
Saying that the tires adversely impacted the car is to miss the real problem. When you switch from an all season run flat to a max performance summer, you are seriously bumping the level of grip.
Absolutely....run flats are great for women, not for performance....hey, BMW did it for liability reasons....a blowout with a run flat probably won't cause a roll-over, killing all aboard...but hey, putting stiff, heavy, no-grip, all-season (except spring, summer, fall & winter), expensive-but-worthless tires on the "ultimate driving machine" does seem like an oxymoron....
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      01-21-2014, 02:51 PM   #7
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Quote:
Originally Posted by TheSt|G View Post
Saying that the tires adversely impacted the car is to miss the real problem. When you switch from an all season run flat to a max performance summer, you are seriously bumping the level of grip. That new grip creates additional load for the suspension, which will essentially fall on its face as it is not designed for such use. This is when upgrading bushings and struts becomes essential to restore balance.
The Dunlop's that come with the 135i M Sport Package are not all-season; they are summer tires.
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      01-21-2014, 06:22 PM   #8
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I recommend to stay with the OEM set-up, the RFT's are recommended by BMW AG, and always, "drive it like you stole it."
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Last edited by sixburgh; 01-21-2014 at 07:19 PM..
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      01-21-2014, 09:08 PM   #9
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Quote:
Originally Posted by Qunadry View Post
The Dunlop's that come with the 135i M Sport Package are not all-season; they are summer tires.
Which, in the grand scheme of things, are closer to all seasons than max performance summers.

Quote:
Originally Posted by sixburgh View Post
I recommend to stay with the OEM set-up, the RFT's are recommended by BMW AG, and always, "drive it like you stole it."
You do know you posted two cars that did not ship with RFTs right?
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      01-22-2014, 08:24 AM   #10
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Quote:
Originally Posted by TheSt|G View Post
Saying that the tires adversely impacted the car is to miss the real problem. When you switch from an all season run flat to a max performance summer, you are seriously bumping the level of grip. That new grip creates additional load for the suspension, which will essentially fall on its face as it is not designed for such use. This is when upgrading bushings and struts becomes essential to restore balance.
Switching to non run flat performance tires is a benefit, but like the STIG said above that switch will further expose the weak link in the car which is the stock suspension, especially the dampers. Going with non run flat tires and upgrading the suspension (new dampers/springs or coil overs and some M3 suspension pieces) will transform the car.
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      01-22-2014, 12:50 PM   #11
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Quote:
Originally Posted by TheSt|G View Post
the extremely limited tool kit in the trunk
You got a tool kit with yours?
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      01-23-2014, 08:53 AM   #12
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Quote:
Originally Posted by Suprgnat View Post
You got a tool kit with yours?
Screwdriver and tow hook in a pouch.
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      01-23-2014, 09:06 AM   #13
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Quote:
Originally Posted by TheSt|G View Post
Screwdriver and tow hook in a pouch.
I don't even consider the tow hook much of a tool, so we're down to one lowly screwdriver. What's that for? Think I can get to all the bulbs, fuses and tow hook mounts without tools...
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      01-23-2014, 09:49 AM   #14
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My assumption was that the RFT's are very harsh. Thus BMW went with much softer bushings to reduce NVH.

Thus, if you go with the softer sidewalls of non-RFT tires, you're now going to get a sloppier handling car. The path most people are taking to get back that precision is to upgrade to M3 bushings and suspension bits.

Is this somewhat accurate? Thoughts?
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      01-23-2014, 11:54 AM   #15
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Quote:
Originally Posted by 135ivert View Post
My assumption was that the RFT's are very harsh. Thus BMW went with much softer bushings to reduce NVH.

Thus, if you go with the softer sidewalls of non-RFT tires, you're now going to get a sloppier handling car. The path most people are taking to get back that precision is to upgrade to M3 bushings and suspension bits.

Is this somewhat accurate? Thoughts?
Pretty accurate. Another part of it is that a lot of what people who do not drive fast call "worse handling" is simply a decrease of steering response due to softer sidewalls.
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      01-23-2014, 12:38 PM   #16
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Quote:
Originally Posted by Suprgnat View Post
I don't even consider the tow hook much of a tool, so we're down to one lowly screwdriver. What's that for? Think I can get to all the bulbs, fuses and tow hook mounts without tools...
For stabbing yourself in the chest when you see the proper toolkit BMWs used to come with, back when you were expected to be involved in the maintenance of your vehicle.


E28 M5:

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      01-23-2014, 01:24 PM   #17
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OP - Just keep in mind that the sidewall stiffness of a conventional tire is not the same as a run-flat tire. RFTs are known for have very stiff sidewalls, whereas it's not really needed on a standard conventional tire. Your steering response might be a bit different, and the way the car drives will be a bit different, but overall it's a worthy upgrade in my opinion. You have way more tire brand/model/size choices, ride comfort goes up, tire prices go down. Can't really complain too much about that!
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      01-23-2014, 04:17 PM   #18
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Why not do Bridgestone run flats?
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      01-24-2014, 12:25 PM   #19
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Any runflat will have the same problems. Heavy, very high NVH, very expensive, not as grippy as non-RFT summer tires even if you get the most expensive summer RFT, etc. It's not a problem that the RFTs suck even for RFTs, it is that they are RFTs at all.

I agree with the above posts. Harshness of ride, weight for performance, cost, mediocre grip.

And I also agree steering feel is a bit slower when you switch to a non-RFT, and getting better bushings or stiffening the car up a touch is in order after you switch. You are essentially moving some of the NVH "buffer" into the tire and away from bushings.

For what it's worth, I actually went to RFTs for my winter tires (Blizzak LM RFT). Getting a flat sucks much more in the winter, not so much in the summer, and I'm not autocrossing in the winter on winter tires. I do still think I lose a bit of performance compared to a non-RFT winter tire, but it's not as critical for me.
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      01-24-2014, 07:39 PM   #20
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Quote:
Originally Posted by BMWEpic View Post
Why not do Bridgestone run flats?
I have the Bridgestone runflats on my 135i. The wife has Conti runflats on her 328xi. It's really hard to make a comparison between the two, but I think they both suck.
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      01-25-2014, 08:26 AM   #21
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Run flats are awful, switch them out ASAP. I put up with them for 3k miles. I wish I would have only put up with them for 3 miles instead. Of the things I have done to the car this was the best thing so far. I no longer feel like I am driving a jackhammer, and while you do feel a bit more squishiness, replacing the bushings or adding inserts is no big deal. Although it is a bit cold here in Chicago, so I will be waiting til spring to do that.
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      01-27-2014, 02:36 PM   #22
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Quote:
Originally Posted by 135ivert View Post
I have the Bridgestone runflats on my 135i. The wife has Conti runflats on her 328xi. It's really hard to make a comparison between the two, but I think they both suck.
I can understand - Bridgestone runflats are what originally came with my car, and I loved them. Eventually switched out my back tires for some Pirelli's which were even better.

Wouldn't know about on a 3 series though.

Downside to runflats in my opinion is they are more prone to bubbles and what not.
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