# Naked Science Forum

## General Discussion & Feedback => Radio Show & Podcast Feedback => Topic started by: DoctorBeaver on 26/03/2006 22:17:33

Title: Car tyres
Post by: DoctorBeaver on 26/03/2006 22:17:33
Where the hell did you get that 1 from! It's quite an amazing statistic, but what on Earth gave you the idea for it?

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Title: Re: Car tyres
Post by: rosy on 26/03/2006 23:02:26
Hmm... I wasn't much convinced by the back-of-the-envelope calculation for the states. 2 cars for *every* family? And, um, 1m diameter car tyres seems a pretty big average... tho' granted it you were talking about the states and I hear cars are bigger over there...
Title: Re: Car tyres
Post by: daveshorts on 27/03/2006 01:05:29
I think the 1m was probably meant to be the circumference... would have to listen to the show again.

When I did the back of the envelope calculation:
area of a car tyre:
.5m x pi * .10cm = .15m^2

.15m^2 * .005m =.00075m^3

4 tyres => .003m^3 * 1200kg/m^3 = 3.6kg of rubber per car

.9kg per car per year

In the UK there are 26 million cars
=> 26 million kg of rubber per year
or 26 000tonnes

according to :

there are about 200 million cars and light vehicles in the US
so chris' guess was pretty good!

so about 200 000tonnes in the US

Of course all these numbers will probably be considerably increased by trucks which run through much larger tyres in a month or two...
Title: Re: Car tyres
Post by: chris on 27/03/2006 09:20:01
quote:
Originally posted by rosy

Hmm... I wasn't much convinced by the back-of-the-envelope calculation for the states. 2 cars for *every* family? And, um, 1m diameter car tyres seems a pretty big average... tho' granted it you were talking about the states and I hear cars are bigger over there...

mmm, but we also assumed that the width of the tyres was 10cm (to make the sums easy). Most tyres are actually 15-20 cm wide, so the slight over egging of the diameter is made up for by the reduction in width.

Either way, Dave and I still arrived at the same order of magnitude, so a factor of 1 or 2 either way doesn't sound too bad. Also, 2 cars per family is probably not so excessive - kids ahve cars too!

Chris

"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
Title: Re: Car tyres
Post by: DoctorBeaver on 27/03/2006 16:24:02
The only quibble I would have with your calculations is that most tyres are changed before all the tread has worn away. Not many people would drive round on tyres until they were completely bald.

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Title: Re: Car tyres
Post by: neilep on 27/03/2006 16:56:43
Dearest Wuverly peeps,

For those of us who had the misfortune to miss the radio show, can you please tell us what the heck you're all talking about !! ?...thanks

hug&smishes

xx
Title: Re: Car tyres
Post by: DoctorBeaver on 28/03/2006 11:54:10
quote:
Originally posted by neilep

Dearest Wuverly peeps,

For those of us who had the misfortune to miss the radio show, can you please tell us what the heck you're all talking about !! ?...thanks

hug&smishes

xx

Chris was calculating how many tons of rubber turn to dust in the U.S. each year due to tyre wear.

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Title: Re: Car tyres
Post by: neilep on 28/03/2006 13:34:01
Ahh...yes...we actually had quite a good thread going on about that ages ago....I'm upset I missed the show...I must have been changing a tyre or something...better check my podcasts now.
Title: Re: Car tyres
Post by: neilep on 28/03/2006 14:10:55
http://www.thenakedscientists.com/forum/topic.asp?TOPIC_ID=1306
Title: Re: Car tyres
Post by: DoctorBeaver on 28/03/2006 20:10:27
On next week's show - an estimate of the total weight of bogies flicked by the under-10s in Beluchistan [:D]

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