I went with the Continental ContiExtreme Contact on both of my C5s.
Literally I drove them coast to coast both north an south and east and
west. Rain, snow, heat, and cold with no problems what so ever. Only
had 3 issues, first was a mild flatting when you first start out for a
mile or two, second was the tire pressure had to run higher, 5 pounds,
to compensate for the lighter side walls of the non runflats. The last
issue was that they were not as good as the runflats for autocross so
I run 2 sets of wheels, one with the runflats.

The benefits were that they did not cup and were ghostly quiet,
smooth, soft ride, and they stuck like glue in the heavy rains in
Washington. They were cheaper for a set of 4 than 2 runflat tires,
actually $1,400 versus $610 from Tirerack. Like the kit included with
all the Z06s I carried an air compressor and a plug kit for any on the
road temporary repairs you might need.

A side note about how quiet they are. The couple that bought my '98
came to me and wanted to buy the Continentals, rims and all, which
they did. Now she is bitching at him because she can hear the fuel
pump in the drivers tank, but then some people would kick if the were
hung with a new rope.

They will soon be on my C6, the Supercar tires are great but the
Continentals fit my traveling needs of comfort on long drives better
that the harsh runflats. Planning another trip to the west coast this
year.

Just swapped the front runflats for Yoko AVS-db2-S2's and got a major
decrease in road noise. Due to the nylon belt in the tire, it's slow to
warm up particularly in winter--nice ride after 6-7 miles.  The agility
hit won't be too tough unless he wants to auto-x the car.

Problem: according to my local dealer Yoko doesn't make this tire for
the rear. I've still got at least 5K left on the rears and don't have to
make a decision right now. (First owner had replaced the rears a few
thousand miles before he sold it.) Other Yoko's (AVS Sport and ES-100)
fit the rear and are OK on asphalt but get noisy on concrete.  (I run
db2's on the front of my C4 and ES-100s on the rear).

If matching the front and rear is important, Dad's extra-air suggestion
for Conti's might offer the quietest solution.  If Yoko doesn't produce
an 18" db2 next year, I'll probably try Conti's on the rear.

My solution to the no-spare issue was to bump up my Auto-Club membership
for 100 miles of towing. I've not had a highway flat in over 20 years.
Have spent more time checking the air in the spare than ever using it!

Just swapped the front runflats for Yoko AVS-db2-S2's and got a major
decrease in road noise. Due to the nylon belt in the tire, it's slow to
warm up particularly in winter--nice ride after 6-7 miles.  The agility
hit won't be too tough unless he wants to auto-x the car.

Problem: according to my local dealer Yoko doesn't make this tire for
the rear. I've still got at least 5K left on the rears and don't have to
make a decision right now. (First owner had replaced the rears a few
thousand miles before he sold it.) Other Yoko's (AVS Sport and ES-100)
fit the rear and are OK on asphalt but get noisy on concrete.  (I run
db2's on the front of my C4 and ES-100s on the rear).

If matching the front and rear is important, Dad's extra-air suggestion
for Conti's might offer the quietest solution.  If Yoko doesn't produce
an 18" db2 next year, I'll probably try Conti's on the rear.

My solution to the no-spare issue was to bump up my Auto-Club membership
for 100 miles of towing. I've not had a highway flat in over 20 years.
Have spent more time checking the air in the spare than ever using it!

I put ContiExtreme Contacts on my 2001 Coupe 15K miles ago.  Great traction,
quiet and very good tread wear.  I also got them at tirerack.com.

Jason
2001 Pewter C5 Coupe

Just put a set of BFG GForce on my C4. I looked and researched and found
that, according to a few tire guys and corvette club members, that the
Yoko and Kumos have a tread design that doesn't really play well with the
inherent camber on C4s. I researched and found the GForce to be superior
or at least equal to the Yoko and GY at a better price. Put them on Fri
and the difference over my old GY was amazing. The ride was at least 75%
better, very quiet, and responsive. I can hear my pipes again! Don't have
a bunch of miles on them but my initial reaction was a "Wow." Check out
the ratings on tirerack.com and ask around. I'm very pleased after a week
of driving.