Every bike I remember owning had 27 x 1.25 inch tires. When my old
Shwinn Continental frame broke almost 5 years ago I bought another used
road bike -- a Miyata, not a high end bike, but a pretty good quality
mass-production bike. It has a triple-butted frame of Chrome-Moly, fair
components but nothing special. The best thing is that it isn't
particularly thief bait and I don't have to be too nervous locking it up
outside in my town (Berkeley, CA).

Lately I've taken up daily 12 mile rides with about a 1000 foot mostly
gradual climb. The descent, however, is pretty steep. I've seen guys
blow by me at probably 35 miles/hour on the steepest part ( !! ) but it
makes me shudder to think what would happen to them if they had a flat
or a blowout. I read a story of a guy who's a quadrapalegic now who had
just such an accident in my vicinity.

Well, that story stuck with me and I don't want it happening to me. Of
course, there's just no being really safe on a bike, but I figure I can
start here by paying attention to my tires and not screaming down that
hill.

I had a blowout a couple days ago. I was at elevation and noticed some
bumping and saw a z-jag in my back tire and took it REAL slow down the
descent. I got to pretty flat elevation before the tire unexpectedly
blew out with what sounded like a gun shot. I just hopped off the bike,
locked it, and walked the rest of the way and came back and got it with
my car later.

That tire was not on that bike more than about a month. It was one of
several cheap tires I bought a few years ago and they seem to have all
gotten stiff, somewhat brittle and even crumbly just sitting around.
Does this always happen with bike tires? You can't buy them and store
them without them going bad? Is there something you can do to protect
them, like an application of Armor All? I also have many individual
packets of Turtle Wax Clear Guard protectant that I could try. I wonder
if anyone uses this stuff with either stored tires or tires that they
are riding in an effort to prolong their life.

I also have one not cheap new tire, a Michelin 27 x 1.38 inch tire, and
it too seems to have lost its suppleness and I'm afraid to try using it.
If I was just riding around the city I wouldn't be so afraid to just use
these new but apparently deteriorated tires and see what happens but
since I'm doing descents at sometimes pretty high speeds I don't want to
take unnecessary chances.

Another question I have is this: The place where I bought my used Miyata
said they could convert it to a 700cc bike to use the now common tire. I
assume that there's a whole lot more available in the 700 size, right?
I've been finding it hard to find anything in a 27 x 1.25. I bought a
couple at Orchard Supply yesterday, made in China I guess. They are
nothing special but at least the rubber seems fresh and vibrant.

Additional note: I use urethane tire liners (oversized), which I glue
into the tires with contact cement. I've been doing that for a number of
years and they seem to have reduced my flats by a factor of at least 3.

Thanks for your help, suggestions, etc.

Dan