The owner's manual for my 1978 Toyota Corolla Liftback specified front to back rotation, stating that radial tires were required to continue to rotate in one direction only, due to warping that would occur if they were switched sides.  That was a decade or so after radial tires were becoming the norm in the U.S.  That car had a full sized spare, and the one that came new with the vehicle was identical to the four on the pavement.  I maintained the rotation pattern recommended in the book, got over 85K miles on the set, and just moved the spare onto the pavement, bought three new ones like it, and kept the best of the original four for a spare.  Still had some legal tread.  Those were Bridgestones, don't remember the label or size now, but they were 13 inch tires and wheels.  They were also a high profile tire, way higher than used on any modern vehicle today.  At that time, that set of tires sold me on Bridgestones.  I realized after a while that the brand varies across labels, like any brand.

mcneely

---- David Beierl <dbeierl@ATTGLOBAL.NET> wrote: 
> At 03:58 PM 3/6/2011, Karl Wolz wrote:
> >According to my brother-in-law, who is a Discount Tire manager, radial
> >tires, even the early ones, were not unidirectional; the whole thing was an
> >old wives' tale of sorts.  No one really knows where the rumor started, but
> 
> Could be.  I was one of the early adopters of the Michelin X (40,000
> miles on a tire?  Unheard of!), and I *think* I remember reading in
> Consumer Reports of the time about the front-to-back rotation.  I'm
> quite certain it was in Consumer Reports of a later time that I read
> it was no longer necessary.  Not that CR are always correct by any
> means, but they do have access to primary sources.  And it wasn't
> that they were unidirectional as such, but that once they'd been run
> in in one direction, wasn't good for them to switch.
> 
> Yours,
> d

--
David McNeely