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RinkWorks Stupid Emails

426.    Synching the Wheels

To:  sam@rinkworks.com
Subject:  Comment on the site and a particular story...
Date:  Sun, 26 Mar 2006 21:26:44 -0700

Hi!

Loving all the various little stories on your website. One in particular, in
the Anecdotes of Stupidity, did catch my attention though, primarily because
I don't think it was stupid...

" With his car up on a lift in the garage where my father worked, the owner
of a 1970s Cadillac (with the extra wheel well fenders that covered a fair
portion of the tires) asked that all four wheels be rotated such that the
valve stems were "pointing up" (and therefore not obstructed by the fender
extensions). This was to ensure that the next time he pulled into a service
station to put air into the tires, all four valve stems would be accessible
without needing to move the car several times to get access."

That was not stupid on this man's part, it was actually quite brilliant. If
all the valve stems are indeed "pointing up" when the rotation in finished,
then logically, when the man stops the Caddy somewhere, they will all be
pointing in the same direction. So when he pulls into a station to get air,
he just needs to position the car once, because if one stem is avalible,
they all will be.

Anyhow... thanks for maintaining such an entertaining site!

This letter was a rarity: a stupid email that made me think. He's wrong, of course. If the valves on each wheel of a car are oriented the same way, all four will get out of synch with each other the second the car turns a corner. But in composing a reply, I thought about it some more and stumbled upon other ways they might get out of alignment. If, for example, you drive along a road that has a dip on one side and not on the other, the wheels that go through the dip will cover a little bit more ground than the wheels that do not and therefore have to spin a little bit further. The effect is slight, but I bet there's a substantial cumulative effect when you drive on bad roads: usually, when old roads degrade, the wear and tear hits the outside worse than the inside. So (in countries where you drive on the right), the right wheels are, in general, going to travel over more bumps and divots than the left wheels.