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E90/E91/E92/E93 (2006 - 2013)
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  #1  
Old 11-24-2013, 07:16 AM
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Sportsdad Sportsdad is offline
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Wive's tale: run flats are not louder

Untrue statement. They are indeed louder and now I have visual proof.

My wife loved the fact that her bimmer has run flats and she didn't believe me when I told her that she was sacrificing comfort and noise for the security of run flats.

So, I decided to do a little test. Her run flats had 40k+ on them so it was time to get new tires.

I convinced her to get traditional tires and ditch the security of the run flats with a Conti Comfort kit. (We also have Coach Net which covers all the vehicles, similar to AAA)

I decided test the noise levels of the run flats compared to the new traditional tires with a mic on a stretch of road that is the type of road where they seal it every two years with gravel and oil (not smooth) en route to getting the new tires.

After the tire swap out with traditional tires, I did the same test in the same conditions (same stretch of road, same temperature, same car speed)

Below is the 'unscientific' visual proof that run flats are louder. I used a simple capture device and a Azden SGM-1000 Super-Cardioid Shotgun Microphone.

I'm sure I could measure comfort if I have the right motion detecting gear but I do not.

Wife didn't need to see the graph to understand the difference. It is a very noticeable audio difference as well as ride.

Brown is run flat. (OEM Bridgestone Potenza Run flats)

Blue are new non-run flat (Michelin Pilot Sport)

This is an overlap of the two. The spikes you see on the blue (new tires) are a couple of rain drops had JUST started to hit the windshield and the mic picked it up.
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Last edited by Sportsdad; 11-24-2013 at 07:19 AM.
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  #2  
Old 11-24-2013, 07:52 AM
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CALWATERBOY CALWATERBOY is offline
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Quote:
Originally Posted by Sportsdad View Post
Untrue statement. They are indeed louder and now I have visual proof.

Top down, pretty clear PS2/PSS is significantly lower volume than stock RFT's.

Can't fool the ol' ear drums.
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  #3  
Old 11-24-2013, 08:03 AM
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I felt like we had a new car when we replaced the OEM Bridgestones with go flat Toyos ....... Used the on board electronics (stereo) to verify that the old run flats had been obliterating the high notes on "Stairway to Heaven" ......
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  #4  
Old 11-24-2013, 08:19 AM
sunny5280 sunny5280 is offline
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Quote:
Originally Posted by Sportsdad View Post
Untrue statement. They are indeed louder and now I have visual proof.

My wife loved the fact that her bimmer has run flats and she didn't believe me when I told her that she was sacrificing comfort and noise for the security of run flats.

So, I decided to do a little test. Her run flats had 40k+ on them so it was time to get new tires.

I convinced her to get traditional tires and ditch the security of the run flats with a Conti Comfort kit. (We also have Coach Net which covers all the vehicles, similar to AAA)

I decided test the noise levels of the run flats compared to the new traditional tires with a mic on a stretch of road that is the type of road where they seal it every two years with gravel and oil (not smooth) en route to getting the new tires.

After the tire swap out with traditional tires, I did the same test in the same conditions (same stretch of road, same temperature, same car speed)

Below is the 'unscientific' visual proof that run flats are louder. I used a simple capture device and a Azden SGM-1000 Super-Cardioid Shotgun Microphone.

I'm sure I could measure comfort if I have the right motion detecting gear but I do not.

Wife didn't need to see the graph to understand the difference. It is a very noticeable audio difference as well as ride.

Brown is run flat. (OEM Bridgestone Potenza Run flats)

Blue are new non-run flat (Michelin Pilot Sport)

This is an overlap of the two. The spikes you see on the blue (new tires) are a couple of rain drops had JUST started to hit the windshield and the mic picked it up.
Different tires have different noise characteristics. You could probably achieve similar results using two different tires of the same type (non-RFT versus non-RFT / RFT versus RFT) tires as well. Furthermore you're comparing worn tires to new tires. Don't worn tires tend to be noisier than new tires?
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  #5  
Old 11-24-2013, 09:29 AM
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Quote:
Originally Posted by sunny5280 View Post
Different tires have different noise characteristics. You could probably achieve similar results using two different tires of the same type (non-RFT versus non-RFT / RFT versus RFT) tires as well. Furthermore you're comparing worn tires to new tires. Don't worn tires tend to be noisier than new tires?
Good points and good questions. Thus the reason I used "Unscientific"
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  #6  
Old 11-24-2013, 09:33 AM
Tom K. Tom K. is offline
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Quote:
Originally Posted by sunny5280 View Post
Different tires have different noise characteristics. You could probably achieve similar results using two different tires of the same type (non-RFT versus non-RFT / RFT versus RFT) tires as well. Furthermore you're comparing worn tires to new tires. Don't worn tires tend to be noisier than new tires?
Perhaps Tire Rack can be persuaded to test go-flat & RFT versions of the same tire (Bridgestone 050, Michelin SS & AS3, ContiSportContact, etc.) at varying mileages. That might provide a more scientific comparison of apples to apples.

Tom
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  #7  
Old 11-24-2013, 09:34 AM
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fun2drive fun2drive is offline
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+1 Bogus test. Worn tires typically are always noisier than new tires and new tires also handle better.
I can't recall but one exception to this which was a set of Firestone tires on my SuperDuty which were 10 ply tires. All my Michelin Sports be it Pilots or Pilots A/S were always higher dB at the end of their life.
If you want an honest comparison try new run flats with new conventional tires...
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  #8  
Old 11-24-2013, 09:53 AM
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New RFT 1500 miles vs new GFT. Get flats were quieter. Agree it can vary tire to tire but the top summers rated at Tire Rack get good marks for low noise. For impact shock & noise its no contest in favor of GFT.
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  #9  
Old 11-24-2013, 11:29 AM
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Michelin PS2 ZP are (in my and my son's opinion) quieter than the Bridgestone RE050A RFT, so one might well expect this in going from Bridgestone --> Michelin.
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  #10  
Old 11-24-2013, 12:46 PM
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  #11  
Old 11-25-2013, 06:35 AM
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Re: Wive's tale: run flats are not louder

Quote:
Originally Posted by Sportsdad View Post
Below is the 'unscientific' visual proof that run flats are louder.

Brown is run flat. (OEM Bridgestone Potenza Run flats)

Blue are new non-run flat (Michelin Pilot Sport)
Sorry, no. All this demonstrates is that a worn-out Bridgestone run-flat tire is louder than a brand-new Michelin conventional tire. You changed three variables at once, thereby making the "test" pointless and proving nothing.

As someone else noted, tires are always louder when worn than they were when new. The other two changes may have had an effect but that was the largest contributing factor to the improvement.
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  #12  
Old 11-25-2013, 12:53 PM
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bocabimmer bocabimmer is offline
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Wive's tale: run flats are not louder

Quote:
Originally Posted by Sportsdad View Post
I'm sure I could measure comfort if I have the right motion detecting gear but I do not.
I do. It's a combination butt-dyno/butt-comfortomemeter. Not only can I assess how fast my car feels, it can also tell me how comfortable it is to me. Amazing thing is I inherited it for free from my parents.

Now some may argue that it's not scientific. I vehemently disagree as comfort is defined as, "whatever my butt says is more comfortable" (forgot which dictionary that came from).

Anyways, the results of my months of laborious studies as both a driver and passenger is that the car is.... more comfortable without the run flats.


That aside, OP, you've developed an interesting hypothesis and I'd love to see someone test it accounting for some of the variables mentioned.


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  #13  
Old 11-25-2013, 02:09 PM
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B/\/\W B/\/\W is offline
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Forget the noise, RFTs are complete crap in general. My experience is that the sidewalls are so stiff that there's absolutely no give in the tyre, and the car skips around over bumps while accelerating and the traction control keeps coming on. Traction control coming on in a straight line in 2nd gear at 60mph while accelerating to overtake two 18 wheelers, utter joke.

Fine for soccer mums, bollocks for anyone that wants to drive a car on a British road covered in potholes. Well they aren't even potholes, I'm talking drain covers here, or undulations.

I can't wait to burn out the rears and put some proper tyres on.
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Last edited by B/\/\W; 11-25-2013 at 02:16 PM.
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  #14  
Old 11-26-2013, 07:22 AM
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DSXMachina DSXMachina is offline
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Let me throw an anecdotal log on the fire. Two weeks ago I test drove a Mercedes CLA. Many impressions, but the takeaway was that the road noise was extremely offensive, and was a deal breaker. When I told the salesman that, he was shocked. He said he had driven a CLA on several occasions and found the tires quiet. I explained that at highway speed the noise was a background hum, not really offensive. But on secondary roads I heard every flaw in the road, and there are many. It was constant and intrusive noise. I assumed the chassis was not properly tuned, or that Mercedes had taken one cost cutting measure too many.
On further checking we found that the test car was equipped with run-flats. He insisted I drive another car with standard tires. On the same route there was a world of difference. I heard virtually no road noise whatsoever. Except for color and a 165 mile odometer difference the cars were the same.
This basically confirmed what I had found when I took the original equipment tires off the E92 at 1200 miles and installed conventionals. The tires are the first line of defense in the suspension system. It makes sense that when the sidewalls are constructed in such a way as to support the vehicle when uninflated, that they must be more rigid and transmit more noise, like the needle on a phonograph (remember them?)
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  #15  
Old 11-26-2013, 08:40 AM
Tom K. Tom K. is offline
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Quote:
Originally Posted by DSXMachina View Post
On further checking we found that the test car was equipped with run-flats. He insisted I drive another car with standard tires. On the same route there was a world of difference. I heard virtually no road noise whatsoever. Except for color and a 165 mile odometer difference the cars were the same.
Interesting, as Tire Rack lists ONLY RFTs as OEM for the CLA - either touring A/S Pirellis or summer performance Pirellis or Continentals.

Tom
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  #16  
Old 11-26-2013, 11:07 AM
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bear-avhistory bear-avhistory is offline
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Could be a tire swap for someone. My 335is was noticeably quieter when I switch. Wife asked what changed during her first ride. The 135is still has what I expect a current generation RFT. They are quieter than the 335is OEM but still noisier than the DW's on the 335is.

BTW the Boxer S PDK was on my bucket list for next summer, how do you like it? I was really impressed on a set of back to back test rides 6MT vs PDK when my daughter picked up her Cayenne.
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  #17  
Old 11-26-2013, 11:17 AM
Tom K. Tom K. is offline
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Originally Posted by bear-avhistory View Post
BTW the Boxer S PDK was on my bucket list for next summer, how do you like it? I was really impressed on a set of back to back test rides 6MT vs PDK when my daughter picked up her Cayenne.
I have the base 6MT Boxster, and after 17k+ miles in 10 months, I still love it. I drove a PDK equipped Cayman loaner and while it offers the high overdrive 7th gear and is a great transmission for an "auto", I wasn't about to shell out the $3,200 extra. Especially since my last AT car ('73 Plymouth Fury) went to my ex-wife in the divorce over 30 years ago and I still need the left leg exercise.

Tom
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