Subject: Re: Metric system in the USA? Re: Metric system in the USA? > I got used to having two sets of wrenches > years ago when I had a British car and a Japanese bike, neither of which ran terribly > well..... Sorry, Pete, but the bikes aren't fully metric in the continental Europe either. Not only in most European countries - except France, the birthplace of the metric system - are the wheel sizes given in inch. A full size bike is 28" in the metric world too.Peter Brooks wrote: > I got used to having two sets of wrenches > years ago when I had a British car and a Japanese bike, neither of which ra

From: Louis JOURDAN <[email-masked]>
Date: Tue, 24 Sep 1996 09:49:12 +0200

Peter Brooks wrote:

>>I got used to having two sets of wrenches years ago when I had a British car and >>a Japanese bike, neither of which ran terribly well.....

>Sorry, Pete, but the bikes aren't fully metric in the continental Europe either.
>Not only in most European countries - except France, the birthplace of the metric 
>system - are the wheel sizes given in inch. A full size bike is 28" in the metric >world too.

Well, even in France, the birthplace of the metric system, bike wheel
sizes are given in inches. My Mercier mountain bike has 26 inches
wheels.

Even more curious indeed is the system used for car wheels and tyres. My
SAAB has 5.5 J 15 " wheels, which I interpret as
		diameter 15 inches
		Width 5.5 inches
and is fitted with 185/65 R15H tyres, which, I guess, means
		inner diameter 15 inches
		tyre width 185 mm
		ratio width/height 0.65

Questions :
	-	why using the british system to measure bike and car wheels ?
	-	are wheel diameter a round figure in inches or a round figure in
metric expressed in inches (like the computer diskettes : a 3 1/2
diskette is actually 90 mm wide) ?
	-	what system is used in USA to measure tyres ? Also a mix of metric
and english units ?

---

From: [email-masked] (Honor� de Gronckel)
Date: Wed, 25 Sep 1996 17:14:56 GMT

>sizes are given in inches. My Mercier mountain bike has 26 inches

That's because mountain biking drifted to europe from the US. The
bikes became the fashion and with it its US terminology. That's the
way to make a standard! Officially there is a different ('metric')
size naming convention in europe.
The problem with the inch tyre size system is that it's inconvenient.
A 27" tyre has a larger outside diameter than a 28", also different
28" tyres need not to fit onto the same rim. That's why years ago bike
manufacturers (at least the european and I believe also the japanese)
went over to the ERTRO system, in which the tyre is designated by its
'inner' diameter, its width and height. No more confusion which tyre
fits which rim. These dimensions are printed on the side of each tyre
(admittedly, the size in the inch system is also still printed there).

IMHO the type of standard is irrelevant as long as it's uniquely
defined, measurable (and related to the important dimensions of the
product) and the same around the world. Preferable is that it's also
easy to use, so errors will be rare (that's why I like the SI/metric
system).

Honoré.

---

From: "Tony P." <[email-masked]>
Date: Wed, 25 Sep 1996 21:30:58 -0700

I agree.  Chauvinism about that kind of thing gets really stale after 
puddling around with the inconvenience of dual standards long enough.  
_Any_ uniform standard is usually better than _two_ coexisting ones.

					Tony