11-09-2012, 03:48 PM | #1 |
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Run Flats quieter than Standard Tyres?
Very Old Auto Express Run Flat Tyre Review:
http://www.autoexpress.co.uk/accesso...-test-run-flat Very interesting to learn run flats are not as noisy as generally assumed and are less noisy than standard tyres.
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Present: Red Tornado Golf 7R 5 Dr, DSG + Toys Last edited by F30AM; 11-09-2012 at 03:59 PM.. |
11-10-2012, 01:56 AM | #3 | |
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The M Sport versions come with lower profile and wider rear tyres for both 18" and 19" wheels. More bump thump + tyre roar is probably a given.
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11-10-2012, 05:30 AM | #4 | |
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11-10-2012, 05:48 AM | #5 |
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11-10-2012, 06:05 AM | #6 |
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Interior noise as stated in the table is comparison between 3 run flats on same car. If they tried a non RFT as a comparison then a valid test, but as tested not valid at all.
They made a comment about comparisons between a Golf with Non RFT and a BMW with RFT, this would have to be a drive by. If it was done in cabin, that would be a meaningless test as you can't seperate out wind noise, engine noise, etc..... |
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11-10-2012, 06:18 AM | #7 | |
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All the tests here are in cabin. And they only claim that RTF tires isn't as noisy as people believe since the BMW is so much quieter even on RFT. |
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11-10-2012, 06:34 AM | #8 | |
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All european tyres by law have to have noise ratings listed, and tyres above a certain level are banned. These are drive-by tests and RFT score no higher in these, however, as the connection between tread block and alloy wheel is significantly stiffer on a RFT (I'm using self supporting RFT as that is what BMW use), there is no scientific reason for them to transmit less noise. RFT bump and thump more than a regular tyre for exactly the same reason, and low profile regular tyres are noiser than high profile again for exactly the same reason, you can't beat the laws of physics. It is also why they are trying to develop 'auxillary supported' RFT technology as that will enable normal low stiffness sidewalls, giving a quieter/softer ride. |
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11-10-2012, 06:39 AM | #9 | |
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As said, typically the stiffer tyre does come though with more NVH to the cabin. The Golf can't be a comparison, as there is no benchmark for NVH, against the BMW. So meaningless, other than a 'drive by' sound level. HighlandPete |
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11-10-2012, 06:47 AM | #10 | ||
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11-10-2012, 07:51 AM | #11 | ||
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11-10-2012, 07:58 AM | #12 | |
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11-10-2012, 08:14 AM | #13 |
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Quote from the article:
'And those who believe run-flats are excessively loud should think again. The BMW run-flat package was significantly quieter than the Volkswagen Golfs we tested on regular rubber at the same time. The quietest tyres on the VWs registered 70 decibels (dB), while the BMW was around 67dB. And remember, a drop of 3dB is around half the noise'. Must admit it's a bit of substandard journalism. They don't understand dB SPL, dB or the difference between loudness and power. The decibel scale is a Logarithmic scale. Subtracting dBL SPL levels is arithmetic. Adding them is lograthmic. dB SPL levels are a measurement of acoustic power using a Sound Level Meter (SLM) and therfore are an 'objective' measure. Loudness is a 'subjective' measure. Therefore:- Addition: 60dB SPL + 60dB SPL = 63dB SPL. The 3dB increase signifies 2 x power. Subtraction: 63dB SPL - 60dB SPL = 3dB which measures acoustic gain. This means the acoustic power is reduced by half but not the loudness. For a sound to appear twice as loud, a level increase of 10dB is needed. To achieve this, approximately 10 times the power is required. Therefore, a 70 Watt RMS power amplifier will produce half the loudness (-10 dB) from the same loudspeaker compared to a 700 Watt RMS amplifier. (RMS = Root Mean Square). A 3dB reduction does not mean that the subjective noise level is halved, but is detectable by the human ear as only a small reduction in noise level. Thus endeth the lesson.
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Present: Red Tornado Golf 7R 5 Dr, DSG + Toys Last edited by F30AM; 11-10-2012 at 02:20 PM.. |
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11-10-2012, 08:22 AM | #14 | |
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But I'll finish by saying your assumption that they are referring to interior noise levels, is most probably right. Good job auto express didn't use the same test to work out how noisy the concorde's tyres were |
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11-10-2012, 08:29 AM | #15 | |
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