I ride these old Specialized tires, made in Japan. I like the wear and feel, and am accomodated to the oversizeing, so that a 28 fits as a true 25. The raised central ribs on those I've handled wear away quickly on the rear wheel, after which the Turbo /R and Turbo /S are hard to distinguish.
I'm with Charles Petry's explanation for what GL feels -- tread separation, Too bad GL didn't get to use all the tread, but so many tires today suffer cuts and sidewall degradation,. After all, the OP has ridden these tires for 3 years.
We'd all do well to inspect tires before and after rides. But, that's the same caution included in the manuals for automobiles, too.
Harry Travis Washington, DC USA
On Wed, Dec 10, 2008 at 9:55 AM, Bob Freitas <firstname.lastname@example.org> wrote:
> I think the idea was that you could cut the rolling resistance
> by raising the center of the tread. The idea had been around for a while
> with Dunlop producing a tire (Road Speed?) which had a raised center section
> (but with a groove at the center) during the 60s it had a Japanese imitator
> branded ''Million'' .These were the first mixed tread pattern tires (there
> was a raised diamond pattern to the sides of the center ridge)I remember
> seeing.I recall the Dunlop casings as being prone to rim cutting.
> Under the ''old is new'' I see a current tire with this tread pattern being
> called a rain tire.
> During the mid 70s raised center tires were produced by Goodyear
> and the Japanese manufactuerers and sold not only by Specialized but
> Schwinn, Avocet and others.These I think were marketed as touring tires.
> It turned out to be a poor design as the edge of that center section
> would catch road irregularities and produce an unstable feel when
> transitioning from pavement types.They were particularly tricky if you
> slipped off the road edge and then tried to ride back onto the pavement.
> I suspect Garths ''Squishy'' sound is related to the
> rubbers thickness at the center of the tire.The treadless tires came after
> this period and signaled the ''We sell the lightest tire'' phase of the bike
> business also called the ''lets lie about the actual size of our tires''
> BOB FREITAS
> coffee kicking in here in MILL VALLEY, CA USA
> Dave Staub could have added more here and you could
> probably search for his input in the archives (Dave, we miss you)