Re: [A/S] Michelin or Bridgestone , Bias vs. Radials

["Carol and Oliver Filippi" <ofilippi@xxxxxxxxxxxxx>]

I don't understand this desire to go with a bias ply tire because it is
stiffer sideways over a radial.  Sounds to me like a lot of misinformation
or coming to a conclusion based on faulty data.

A good ROUND well made radial tire will roll STRAIGHT, if the tire is made
round and symmetrical and all the components are CENTERED properly.  It is
true that domestic tire makers have had a hard time making round radial
tires.  The real reason is that the tolerances in a radial tire are a lot
more critical than those of a bias constructed tire.  Thus, American tire
manufacturers used their sloppy tolerances (which they could get away with
on a bias ply tire) when they went to radials and got into a lot of trouble.

For this very reason, I am very reluctant to buy radial tires made by
domestic tire manufacturers - with a few special exceptions.  On the other
hand, Michelin (who invented the radial tire) and Pirelli consistently turn
out very good radial tires.

In the early days of passenger car radial tires, I had an experience which
confirms my contention that a good radial tire will  track STRAIGHT.  I
bought a set of Michelin XAS tires for my wife's '69 Mercedes (this was
1971).  I had the tires mounted and then balanced on the best balancer
available at the time (a German Hoffman - which still is the best and is now
available as FMC or Hunter and perhaps others which use Hoffman's
technology) and then took the car to the Mercedes dealer for an alignment.
After the alignment(?) the car pulled to one side with the new Michelin
radial tires.  So, I went back to the dealer, where the service manager had
the alignment mechanic put the car back on the alignment machine.  At this
point the mechanic (who would have to correct any bad work of his on his own
time) proudly pointed out that the alignment was "within specifications"
(but not at the factory nominal values).  The service manager looked and
spotted the Michelin radials and then told the mechanic, "these are radials
and within tolerance is not good enough, the car must be aligned to the
nominal value factory specs with ZERO tolerance." So, the mechanic realigned
the car to the nominal values, at which point the car went absolutely
straight and required minimal effort to drive and DID NOT WANDER.

Yes, radial tires intentionally have very flexible sidewalls, (compared to
bias ply tires) which are necessary because the belt is very rigid and the
sidewall has to flex or the tire will self destruct.  If the radial is made
round, it won't wobble and roll cockeyed.  If you want to reduce the flex in
the sidewall of a radial simply increase the air pressure (within the
operating range of the tire).

Some of you may recall the abortive attempt of domestic tire manufacturers
to compete with the radial tire with a belted bias tire in the mid '60s.
They put a belt on a conventional bias constructed carcass.  Naturally, they
self destructed since the squirm of the bias plies (when the tire rolled)
caused internal stresses and ultimately,  separation of the belt from the
bias carcass.  You don't see any bias belted tires any more.

I would much rather spend my money on a tire that is less likely to fail,
than buy an inferior design which might do less damage when it fails (but
which is likely to fail).

I think we must differentiate between comparing a good bias ply tire to a
poor radial, and to comparing high quality radials to high quality bias
tires.  In the latter case, the radial wins hands down.  Also, the radial
has a lot less rolling resistance (and longer life) which translates into
noticeably superior fuel economy and lower life cycle cost. Plus, the radial
will be stable as well.  Any side stability attributed to the bias tire
(over the radial) comes from undesirable internal friction within the tire
which generates heat and other negative internal stresses WHICH ARE NOT
GOOD!

The only legitimate reason I can think of for choosing a bias tire over a
radial is if you have an affinity for hitting and scuffing curbs.  The
highly flexible radial sidewall is not happy scraping curbs on a regular
basis.

Oliver Filippi