A tyring subject ... ratings and quietness

[Dave2002]

I took my car to the garage yesterday, and it was pointed out to me that the front tyres really are now getting near the end of their useful life, so I should replace them very soon.

I was given a sheet which now shows that tyres are given a rating (since when?) for energy efficiency and braking efficiency, and also an indication of road noise level. Most of the suggested tyres are in fact in roughly the same price range, even though some are described as premum and others as mid-range. One tyre - from Michelin had an A-A rating, but a noise level of 70dB. Some of the others have a noise level of 67dB. Would that extra 3dBs of noise really be such a problem? Should I buy tyres with slightly worse measured performance regards road handling and efficiency in order to get lower road noise?

I think the tyre ratings are potentially a useful and helpful development, though they may not turn out to be quite so useful in practice because of compromises and the way one evaluates these things.

[Dave2002]

Follow up to msg 1 - this page (aimed at US readers) is interesting - http://www.hybridcars.com/low-rollin...e-primer-50256

There's an interesting observation that tyres which may be useless in wet conditions may be really good in the dry, and vice-versa!
Very significant differences in performance can be observed, and in critical conditions that might be important.

[rauschwerk]

Apparently an increase of 10 dB is subjectively a doubling in loudness, such is the pecularity of the human ear. I imagine that 3 dB won't sound like much difference at all once engine and wind noise are accounted for.

[Dave2002]

Apparently an increase of 10 dB is subjectively a doubling in loudness, such is the pecularity of the human ear. I imagine that 3 dB won't sound like much difference at all once engine and wind noise are accounted for.

The 67dB and 70dB measurements are also a bit meaningless without knowing more, such as at what road speeds these levels occur, and also the frequency characteristics, and perhaps how they depend on road surface. It is very noticeable that some road surfaces sound very noisy - others less so.

[Eine Alpensinfonie]

It's the noise of cars from the outside that bothers me - noisy engines, selfishly loud music with the windows wide open, etc.

[johnb]

I think that the overwhelmingly dominant factor is the design of the car rather than the brand of tyre. My current car, a Focus Xetec Estate, is by far the noisiest car I have ever owned - you hear and feel the road surface very clearly - dreadful. Changing tyres makes minimal difference though all tyres get noisier as they wear down.

[Nick Armstrong]

... One tyre - from Michelin had an A-A rating, but a noise level of 70dB. Some of the others have a noise level of 67dB. Would that extra 3dBs of noise really be such a problem? Should I buy tyres with slightly worse measured performance regards road handling and efficiency in order to get lower road noise?

I got a new car 2 months ago and have been thinking about this. I have noticed that the road noise is significantly higher on some surfaces than the previous car, even though the new car is supposedly better and certainly 15 years newer! (Note: it's not a bloody Maserati... )

This post made me check the tyre rating - I have Goodyears and the type/size I have measures 70db. On noisy road surfaces (those horrible light-coloured motorway sections) they are noisier - but on good smooth surfaces (the dark asphalt - or almost all French roads!), they are nonetheless silent.

So I would say that the noise rating accentuates the differences between different surfaces.

I would also say that the performance should be the only thing you are guided by - noise is secondary !!

[Don Petter]

While we are discussing tyres, I was surprised at the difference that tyre widths can make to fuel economy.

I was fed up with having to buy two new alloy wheels (at £220 each) in as many months because of pothole rim damage. So I changed over to an alternative specification for the car using smaller steel wheels and higher profile tyres (225/40 to 205/55). Apart from making the car much more pleasant to drive, with less road noise and less tracking of road irregularities, the reduction in width, of just 20mm, has made an impressive improvement to the miles per gallon.

I have always kept a log of every fill, and the relevant average figures are:

47000 miles on original tyre size - 33.8 mpg
4500 miles on new size - 36.5 mpg

I can't put the difference down to any other factor. Tyre pressures are the same, as is the car usage. Eight per cent improvement was an unlooked-for bonus (and, touch wood, there has yet been no pothole damage to the steel wheels).

[Dave2002]

I am back to this topic, as trying to find tyres suiable for winter in a snowy part of these islands.

I found this web site which seems to have a very comprehensive list of available tyres - http://www.mytyres.co.uk/start.html?...&wt_mc=msn_pkw - there is a page where you can put in your car number, and it'll list available/suitable tyres. Also, to my surprise, the firm was able to recommend a dealer to fit the tyres within only a couple of miles of the target area.

Re Caliban's comment on tyre performance being the only thing that really matters, I agree with this very largely. Last time I ordered tyres for my own car I checked out the tyres from a few suggested by the garage where I have the car serviced, and then went for a more expensive one since it had good performance re grip etc., and also low fuel consumption - the latter information which I viewed somewhat with a pinch of salt. However, the fuel consumption has gone down, the grip has been good, and the noise inside the car has not been noticeably worse than before. The label figures for the new tyres in any case only refer to the external noise, not the internal noise.

As the original garage wasn't able to source the somewhat specialised tyres I wanted, I opted to use a mobile tyre fitting service which was able to supply and fit them on my drive. It seemed a much easier way to buy and fit the tyres than having to go to a garage some miles away, and I'd recommend mobile tyre fitting services again.

[pastoralguy]

I am back to this topic, as trying to find tyres suiable for winter in a snowy part of these islands.

I found this web site which seems to have a very comprehensive list of available tyres - http://www.mytyres.co.uk/start.html?...&wt_mc=msn_pkw - there is a page where you can put in your car number, and it'll list available/suitable tyres. Also, to my surprise, the firm was able to recommend a dealer to fit the tyres within only a couple of miles of the target area.

Re Caliban's comment on tyre performance being the only thing that really matters, I agree with this very largely. Last time I ordered tyres for my own car I checked out the tyres from a few suggested by the garage where I have the car serviced, and then went for a more expensive one since it had good performance re grip etc., and also low fuel consumption - the latter information which I viewed somewhat with a pinch of salt. However, the fuel consumption has gone down, the grip has been good, and the noise inside the car has not been noticeably worse than before. The label figures for the new tyres in any case only refer to the external noise, not the internal noise.

As the original garage wasn't able to source the somewhat specialised tyres I wanted, I opted to use a mobile tyre fitting service which was able to supply and fit them on my drive. It seemed a much easier way to buy and fit the tyres than having to go to a garage some miles away, and I'd recommend mobile tyre fitting services again.

This is spooky, Dave, since I only discovered this site last night. I thought about the mobile service but since the usual place I go to is near some great charity shops, I just did what I always do - order the tyres, hand over my bank card and try not to think too hard about the great wedge of cash being removed from my bank account.

I couldn't easily get premium winter tyres so I plumped for the medium quality ones on the premise that we might be changing our car next year.

[Dave2002]

I couldn't easily get premium winter tyres so I plumped for the medium quality ones on the premise that we might be changing our car next year.

Seems reasonable. We live a long way south of you - though we have had problems with snow in some recent years. However, my researches are for a car considerably further north than you are - so it may make sense to pay out for better tyres. I'm guessing that Edinburgh and Glasgow aren't too bad for snow most years - though I might be wrong. I have even driven on studded tyres, though not in the UK, and at what would probably be considered ludicrously high speeds here (about 60mph) - though on sheet ice even the studded tyres don't hold - even at 20mph!

[pastoralguy]

The problem in Edinburgh is that are lots of hills so even a small amount of snow can cause chaos! Thinking about it, all the bumps I've been involved in (mercifully, not many), have usually been weather Releted. No, I've never driven on studs but would like too.

[Dave2002]

I did chicken out of driving across a frozen lake - though from a nearby vantage point then saw a much larger car go straight across the line I would have taken.
OTOH sometimes people drowned by trying this either too early or late in the season!

[pastoralguy]

I did chicken out of driving across a frozen lake - though from a nearby vantage point then saw a much larger car go straight across the line I would have taken.
OTOH sometimes people drowned by trying this either too early or late in the season!

Well, that's our car re-shod for another few thousand miles. It wasn't until I saw the new tyres I realised how worn the previous ones were!

[Gordon]

Subjectively and as experienced inside the car noise levels vary a lot on the road as has been pointed out and are also accompanied by all the other noises a car makes. However according to this:

http://www.bksv.co.uk/doc/bo0452.pdf only for the stout hearted

the official tyre noise is not measured INSIDE but outside and is done with a moving vehicle, not on a rolling road. It is notoriously difficult to do absolutely and to omit any other noise like the engine but ratios are a bit easier because the reference and subject are measured the same way. Take the noise rating with a pinch of salt.

Oh and BTW: +10dB is 10 times more powerful a sound [than some reference] and 3dB is twice so. The relative power of two sounds [subject to some defined characteristics like how long the sounds last as well as how loud they are and what the spectrum distribution is] as perceived is expressed in decibels. A Bel [after Alexander Graham whose wife was deaf and so he studied hearing very closely as well as inventing the telephone] is the logarithm to base 10 of the ratio of two sound powers, one of which may be a standard reference. There are 10 deciBels in a Bel.

A power ratio of 10 therefore has a log of 1 and so is 1 Bel; but multiplying that by 10 gets you to 10dB. A power ratio of 2 has a log of 0.3 and so is 3dB. IOW doubling the perceived power of a sound requires a 3dB increase in its power. Thus a tyre with a 3dB lower noise rating than another emits half the noise power - but not necessarily inside the car.