Tyre noise

[SAC1]

How do tyre manufacturers compare the Db level of their tyres, because as we have all said it totally depends on the road surface?

EU Tyre Label: How the tyres are tested:

Since June 2012, tyre manufacturers have been required to provide data in relation to the performance of their tyres through testing.

Due to the sheer vast number of tyre models, it was decided that a centralised EU tyre testing facility would be unmanageable and unproductive. Therefore, tyre label testing is self-certified using specific EU standardised methods that every test must adhere to.

Testing Rolling Resistance
A tyre is mounted to a specially designed two-metre drum. It is then rotated with a defined load and pressure.

The test engineers have the torque required to rotate the drum before the tyre is fitted, so they are able to calculate the torque of the tyre by subtracting the new level required when the tyre is mounted against the level when it is not.

It is through calculating the difference of the drum's torque with or without the tyre that they can record what is known as the 'Rolling Resistance Coefficient'. This is what is used to work out the correct grading for the new tyre label.

Testing Wet Grip
There are two tests that engineers are required to carry out to come up with the wet grip rating.

First of all they need to carry out a wet braking test. This measures the performance of a tyre when a vehicle is braking on a wet surface. The distance that the car travels when slowing from 50mph to 12mph is recorded.

They also carry out what is known as a skid trailer test. This calculates the friction between the tyre and the road surface. For the tests to be valid, it must take place when the vehicle is travelling at 40mph.

Once they have both results, they combine them to create the Wet Grip Index (WGI) - this shows the percentage of improved ability compared with an independent reference tyre.

Testing Noise Emission
This test is done to find out the external noise of a tyre in decibels (dB).

The actual test consists of a microphone being set up on the edge of a track to measure the sound level of a test vehicle - the mircophone is required to be 7.5m from the centre of the track at sit at 1.2m above the ground. When passing, the vehicle must be travelling at 50 mph with the engine turned off for the test to be valid.

[happy days]

So not open to any form of mis-use then...

[Paul]

....see my not so tongue in cheek comment in page 1 of the thread.....

....manufacturers self-certifying using specific EU standards......

[SAC1]

The surface is an ISO surface and the test vehicle requirements are strictly controlled. Atmospheric conditions such as temperature, ambient noise and wind are monitored. In the UK days at MIRA waiting for the correct conditions or testing usually goes to Spain if lots of tyre noise testing to do.
Testing is conducted by the tyre maker and monitored by the VCA. http://www.dft.gov.uk/vca/

[Deleted User 1874]

It's another case of bling choices having downsides that people don't appreciate when ticking the boxes. It's well known that 21's are noisier, give a harsher ride and are more subject to damage due to potholes than tyres with greater sidewalls. The wheels are more prone to damage too. The perceived handling improvement is irrelevant for road use. But the fact so many will pay large sums of money for large wheels demonstrates the power of bling.

I agree with this. Marketing always talks of improved handling, but actually that's very questionable too. When I was working for the Vauxhall BTCC team in the mid 90s we were asked by Dunlop and Michelin to evaluate 18" vs 19" rims for performance. The tyre manufacturers wanted to push the 19s for marketing reasons, but which do you guys think were actually quickest around a track?


Well it was the 18s by quite some margin. But we still had to switch to 19s for marketing reasons. Obviously since that time a lot of development has gone into ultra-low profile tyres, but they are certainly not inherently superior to slightly higher profile tyres and since we are talking about public road use with patchy surfaces, bumps, potholes etc then a bit of extra sidewall certainly trumps any marginal improvement in max lateral load capability.

Personally I would never go for 21" wheels on a car like the Macan. I'd actually go with 19s out of choice as I can't see the wheels when I'm driving, but I can feel the potholes and hear the road noise!

[Tom 2000]

It's another case of bling choices having downsides that people don't appreciate when ticking the boxes. It's well known that 21's are noisier, give a harsher ride and are more subject to damage due to potholes than tyres with greater sidewalls. The wheels are more prone to damage too. The perceived handling improvement is irrelevant for road use. But the fact so many will pay large sums of money for large wheels demonstrates the power of bling.

I agree with this. Marketing always talks of improved handling, but actually that's very questionable too. When I was working for the Vauxhall BTCC team in the mid 90s we were asked by Dunlop and Michelin to evaluate 18" vs 19" rims for performance. The tyre manufacturers wanted to push the 19s for marketing reasons, but which do you guys think were actually quickest around a track?


Well it was the 18s by quite some margin. But we still had to switch to 19s for marketing reasons. Obviously since that time a lot of development has gone into ultra-low profile tyres, but they are certainly not inherently superior to slightly higher profile tyres and since we are talking about public road use with patchy surfaces, bumps, potholes etc then a bit of extra sidewall certainly trumps any marginal improvement in max lateral load capability.

Personally I would never go for 21" wheels on a car like the Macan. I'd actually go with 19s out of choice as I can't see the wheels when I'm driving, but I can feel the potholes and hear the road noise!

Good post.

[Bigboyrolo]

It's another case of bling choices having downsides that people don't appreciate when ticking the boxes. It's well known that 21's are noisier, give a harsher ride and are more subject to damage due to potholes than tyres with greater sidewalls. The wheels are more prone to damage too. The perceived handling improvement is irrelevant for road use. But the fact so many will pay large sums of money for large wheels demonstrates the power of bling.

I agree with this. Marketing always talks of improved handling, but actually that's very questionable too. When I was working for the Vauxhall BTCC team in the mid 90s we were asked by Dunlop and Michelin to evaluate 18" vs 19" rims for performance. The tyre manufacturers wanted to push the 19s for marketing reasons, but which do you guys think were actually quickest around a track?


Well it was the 18s by quite some margin. But we still had to switch to 19s for marketing reasons. Obviously since that time a lot of development has gone into ultra-low profile tyres, but they are certainly not inherently superior to slightly higher profile tyres and since we are talking about public road use with patchy surfaces, bumps, potholes etc then a bit of extra sidewall certainly trumps any marginal improvement in max lateral load capability.

Personally I would never go for 21" wheels on a car like the Macan. I'd actually go with 19s out of choice as I can't see the wheels when I'm driving, but I can feel the potholes and hear the road noise!

I agree as well and with the beneft of personal experience. My first test drive was on 21s from Silverstone OPC. We thought the tyre noise was so significant that we took the car back early, lost interest, called it a day and drove away in my XF on 20" 35 profile tyres, which was so much better. 20's have the same width, so similar noise level I presume. The Dealer replaced the 21" classics for 19" turbos, all much more pleasant, and we bought the car. Macan No2 has 19" classics and Air, the best combination in my experience and approprate for us.
I am looking at Turbos for sale and notice that the majority have 21" 911 Turbo Design fitted. I doubt that so many Turbo buyers had these wheels from new and suspect that OPCs fit them for looks and marketing.

[Zinzan]

It's another case of bling choices having downsides that people don't appreciate when ticking the boxes. It's well known that 21's are noisier, give a harsher ride and are more subject to damage due to potholes than tyres with greater sidewalls. The wheels are more prone to damage too. The perceived handling improvement is irrelevant for road use. But the fact so many will pay large sums of money for large wheels demonstrates the power of bling.

I agree with this. Marketing always talks of improved handling, but actually that's very questionable too. When I was working for the Vauxhall BTCC team in the mid 90s we were asked by Dunlop and Michelin to evaluate 18" vs 19" rims for performance. The tyre manufacturers wanted to push the 19s for marketing reasons, but which do you guys think were actually quickest around a track?


Well it was the 18s by quite some margin. But we still had to switch to 19s for marketing reasons. Obviously since that time a lot of development has gone into ultra-low profile tyres, but they are certainly not inherently superior to slightly higher profile tyres and since we are talking about public road use with patchy surfaces, bumps, potholes etc then a bit of extra sidewall certainly trumps any marginal improvement in max lateral load capability.

Personally I would never go for 21" wheels on a car like the Macan. I'd actually go with 19s out of choice as I can't see the wheels when I'm driving, but I can feel the potholes and hear the road noise!

Very interesting post. The other thing about the big wheels is that they are usually heavier - so increase unsprung weight which is generally considered to be detrimental to handling - and they require more power to accelerate (though I suspect the effect is not noticeable in normal use if at all). Wet weather grip may also not be as good.

It's really all about bling.

[Deleted User 1874]

Yes, it's all about the look. No question the big wheels do look great in the showroom, but especially on an SUV slightly smaller rims with more chunky looking tyres can look pretty good too. When you weigh up all the pros and cons, for me 19" is a great compromise on the Macan. You are giving up pretty much zero "track" performance and of course a bit of bling for quite a few real world advantages.

[Custard]

19" classics and Air, the best combination in my experience and approprate for us.

+1

Porsche are pretty good about encouraging you to test drive a range of demo and used cars to make sure you get the right extras. Driving half a dozen Macans made me change my option choices significantly within my budget. For the audio books and radio broadcasts that I mainly listen to I couldn't hear any difference between the standard audio and the premium set ups, so out that went. But in terms of drive quality air suspension plus 19" or 20" wheels was noticeably better, so that came in.

I guess every driver will have their own priorities, but it's always worth taking advantage of Porsche's willingness to let you put those priorities to the test. I went into the showroom with the usual set of opinions about what I thought I wanted, but once behind the wheel in differently configured vehicles I was surprised at how much I changed my mind.