[F30AM]

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.

[matt@stratford]

I didn't notice any difference between the two.

Does the M sport still come with run flats (18")?

[F30AM]

Originally Posted by matt@stratford

I didn't notice any difference between the two.

Does the M sport still come with run flats (18")?

All F30s, except for the 320d Efficient Dynamics with 16" wheels, come with run flats.

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.

[NISFAN]

Originally Posted by F30AM

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.

Nope, that test is a drive by noise level. Doesn't mean anything about the tyre noise in the cabin which will be higher on stiff sidewalled run flats.

[Rossifumi]

Originally Posted by NISFAN

Nope, that test is a drive by noise level. Doesn't mean anything about the tyre noise in the cabin which will be higher on stiff sidewalled run flats.

Auto Express table says "Interior noise".

[NISFAN]

Originally Posted by Rossifumi

Auto Express table says "Interior noise".

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.....

[Rossifumi]

Originally Posted by NISFAN

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.....

There is no mentioning of a drive by test. They just say that the Golf was 70db and the BMW 67db (on RFT). I agree that comparing tires on two different cars isn't a valid test. But I have no idea of what you are getting at with the "drive by" remarks.

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.

[NISFAN]

Originally Posted by Rossifumi

There is no mentioning of a drive by test. They just say that the Golf was 70db and the BMW 67db (on RFT). I agree that comparing tires on two different cars isn't a valid test. But I have no idea of what you are getting at with the "drive by" remarks.

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.

So how does a non valid test have any relevance to how quiet or noisy a RFT is in cabin?

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.

[HighlandPete]

Originally Posted by Rossifumi

There is no mentioning of a drive by test. They just say that the Golf was 70db and the BMW 67db (on RFT). I agree that comparing tires on two different cars isn't a valid test. But I have no idea of what you are getting at with the "drive by" remarks.

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.

Change the RFT on the BMW, to the same brand 'non RFT' specification and users have found the non RFT version is much quieter.

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

[Rossifumi]

Originally Posted by NISFAN

So how does a non valid test have any relevance to how quiet or noisy a RFT is in cabin?

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.

All I was saying was that this wasn't a drive by test. NOTHING else.

Originally Posted by HighlandPete

Change the RFT on the BMW, to the same brand 'non RFT' specification and users have found the non RFT version is much quieter.

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

As I stated above. I never said anything else. I just said that this wasn't a drive by test since it clearly states that it is measured in the cabin.

[NISFAN]

Originally Posted by Rossifumi

All I was saying was that this wasn't a drive by test. NOTHING else.



As I stated above. I never said anything else. I just said that this wasn't a drive by test since it clearly states that it is measured in the cabin.

Below is the extract that compared RFT with Non RFT, (which is absolutely diabolical to compare one car with another). Nowhere does it state where the noise was measured from, so if being absolutely correct, neither one of us can catogorically state it was internal or external.

How noisy?
Early run-flats earned a reputation for being noisy and uncomfortable, thanks to their stiff sidewalls – the technology behind the rubber is explained in our panel. But constant development has reduced this drastically, and all three brands have made similar progress. There was nothing between the Bridgestone and Michelin, with the Conti a fraction behind in terms of noise.

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.

[Rossifumi]

Originally Posted by NISFAN

Below is the extract that compared RFT with Non RFT, (which is absolutely diabolical to compare one car with another). Nowhere does it state where the noise was measured from, so if being absolutely correct, neither one of us can catogorically state it was internal or external.

They say "around 67db" and that is what is says in the table under "Interior noise".

[F30AM]

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.

[NISFAN]

Originally Posted by Rossifumi

They say "around 67db" and that is what is says in the table under "Interior noise".

Look on any tyre selling site that lists tyre noise in drive by's.....guess what? ......also around the late 60's to early 70's, so also fits the "around 67db".

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

[Rossifumi]

Originally Posted by NISFAN

Look on any tyre selling site that lists tyre noise in drive by's.....guess what? ......also around the late 60's to early 70's, so also fits the "around 67db".

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

And I agree about your statement that it pointless to compare a Golf on non-RFT with a BMW with RFT!