Sunday, May 16, 2010

The Quiet Car

This is another entry that could fit into my series of fairy tales that start "Once upon I time, when I was young, cars/motorcycles were....."

Today one of the most common complaints with new cars is noise. I take that as a sign that car makers have really got their act together, because the most common complaint when I was young was cars falling apart. You would buy a brand new car, drive it off the Dealer's lot, then notice a long oil slick in the middle of the road right behind your brand new car. Then you would look ahead and see dry road. Then you would check the rear view mirror again, but it had fallen off. So you would do a U-turn, hopefully before the steering wheel came disconnected, and return to the dealer. His response would be a variation of "What did you expect? No car is perfect."

The one thing the dealer got right was "No car is perfect." No matter how good cars become, there will always be complaints, because people are basically idiots. (readers of this blog excepted). "My Hyundai Pony is not as smooth and powerful as my neighbour's Mercedes Benz, how come????". Which, translated into English, means "Chicks don't dig me because I drive a this piece of crap car, what are you going to do about it?"

I was doing a bit of research on the Internet about quiet cars, and found that about half the computer users who are interested in quiet, spelled it "quite". And that could have been even higher if I had actually Googled "quite cars".

There is a good reason to think that cars are actually getting noisier. I often walk beside busy roads, and one thing I notice about the noise levels is that it is not usually caused by engine exhaust noise, it is mostly tire noise. I remember once an almost completely silent car passed me, and I was surprised to find that it was a model T Ford. Those cars had extremely large diameter tires, that were also very narrow, almost like a motorcycle tire. Speaking of which, I never hear much noise from motorcycle tires either as they pass by me on the street. The tires are either very quiet, or the exhaust is just masking the noise.

If you are inside the car, you will hear something different to pedestrians. You will hear more wind noise, and the noise effects will all be amplified because you are basically inside a huge drum that is being pounded quite hard (notice not "quiet hard").

These days car tires are getting lower and wider, which means that noise is basically going to be increasing, unless the tire makers can find ways to stop it. That is very difficult, because customers are also demanding tread patterns that are dramatic, to enhance the performance image of their cars. So now you have diagonal slashes in the tread patterns, or you have big tread blocks for off-road traction. While the quietest design is actually the old fashioned circumferential grooves.

The tread design itself is not the only problem, as the road surface causes at least half the noise. The tire noise is generated by the tire coming into contact with the road at the leading edge of the contact patch. This is happening at very high speed, and the faster the tires spin, and the smaller the diameter, the harder the two surfaces come together. Any irregularities in the surfaces will generate noise or vibration. Actually, noise is just vibration transmitted through air, it's basically the same thing. Some road surfaces are especially noisy, usually the rougher surfaces. Some road surfaces are supposed to create noise inside the car, for example rumble strips. Take a look at the grooves on those rumble strips, and you will get an idea why no car tread has grooves running across the tire. By the way, rumble strips are barely audible if you are riding a motorcycle.

I recently put a new set of tires on my car that seemed to me to be very quiet. The were Michelin Primacy MXV4's. But a few days ago, when we were out for a ride in the car, I asked Mary Ann if she could hear a difference, all she said was "What???" So maybe it's all in my imagination.

Picture 1926 Ford Model T. Quietest car I ever heard, from the outside anyway. Look at the tires. And no, I was not born when that car was made.


  1. Used to be, back in the 50s and 60s that Rolls-Royce cars were claimed to be so quiet that, 'You could hear the clock ticking.'

    Now that Rolls (like everyone else) has switched to digital clocks, are they so quiet that you can hear the quartz crystal oscillating?

  2. I found a web page that had some background and explanation of this ad.

    Ogilvy's famous Rolls Royce ad

    Apparently it was not completely original, a similar ad had been used by Pierce-Arrow many years earlier.