[net.cycle] Blow-Outs and Riding on Flats

donch@teklabs.UUCP (Don Chitwood) (04/15/86)

Regarding how to handle a blow-out at speed, I had an "opportunity"
to test both my reactions and some theories recently.

I picked up a nail in my rear tire and first noticed a problem when I turned a
gentle corner at about 40 mph.  The bike didn't want to turn, and when I 
straightened up, it overcorrected and wanted to go the other way.
I made it to a stop (using the REAR brake:  application of FRONT brake
caused the rear-end to weave wildly from side to side.)

The tire was a Michelin M45 (?) which was designed for safety under just
such a condition.  Its sidewalls are incredibly stiff and thick.  I have
never before fought so hard to mount a tire on the rim.  Michelin claims
that the stiff sidewalls allow enough stability to keep a motorcycle
upright in the event of a flat.

Well.  No flat kit or tire pump or tube with me.  The nearest cycle
dealer was 2 miles away.  So I decided to test Michelin's claims
(the tire was about 80% gone anyway) and drove it after removing the nail 
to the dealer to buy a new tire and tube.

While driving on a dead flat tire, I learned several things.  The most
helpful lesson was learned when I tried to ride in a straight line while
sitting bolt upright.  The rear of the bike would flop and weave from side to
side as a result of minimal sidewall support to keep the centerline
of the rim  in line with the center line of the tire.  The two centerlines
can (and do) move freely from side-to-side by as much as four inches. 
There's no stable point, except at the extremes, and that was the 
lesson.  By sitting off to one side so that the tire was
biased to one side as much as possible, I was able to control the
cycle up to about 20 mph.  The natural crown of the road also 
provided a bias to the tire along with my sidesaddle technique.

The next rear flat I get, I'll try the sidesaddle technique even though
I am not running the Michelin.  Any comments are welcome, including
gently warming flames.

Don Chitwood
Tektronix, Inc.