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From: fowler@uw-beaver (Rob Fowler)
Newsgroups: net.auto
Subject: Re: tire inflation pressures
Message-ID: <1412@uw-beaver>
Date: Sat, 20-Jul-85 15:16:12 EDT
Article-I.D.: uw-beave.1412
Posted: Sat Jul 20 15:16:12 1985
Date-Received: Mon, 22-Jul-85 08:36:05 EDT
References: <32@zeus.UUCP>
Reply-To: fowler@uw-beaver.UUCP (Rob fowler)
Organization: U of Washington Computer Science
Lines: 23
Summary: 

About the guy that got killed inflating a truck tire:  Truck wheels
and tires are different from what you get on light vehicles.

The tires are so heavy and stiff that you cannot mount them by putting part
of the bead in the center well of the wheel and pulling the rest over the
rim.  In fact, large truck wheels do not have center wells at all.  This is
to improve the strength/weight ratio.  Heavy truck wheels have detachable
rims.  To mount a tire you remove one rim put the tire on, and put the rim
back on.  Some rims are held on with lots of bolts and "dogs" while others
fit together like a puzzle under a shorter rim that the tire can fit over.
The air pressure in the tire serves to lock the pieces together and to the
wheel.  When you inflate a truck tire for the first time there is a danger
that the latter type of rim will not lock properly and and will be blown
off.  This throws several pounds of steel pieces outward at several hundred
feet per second.  This can occur with just normal inflation pressures (75
lbs/in^2 and more).  Because of this danger it is standard procedure in
truck shops to put the wheel and tire in a cage that will contain the
shrapnel if the rim blows when the tire is first inflated.  The guy that got
killed in Seattle was taking a shortcut and was not using a cage.

Safety first!

-- Rob Fowler (uw-beaver!fowler or fowler@washington.arpa)