Like one of the earlier posts said, it's primarily due to the aspect ratio of the side wall on the low profile tires. These have several adavantages: looks, larger contact patch, reduced rolling resistance (better milage) You might spend a lot of time and effort swapping tires and find nothing is as good (ride-wise) as changing to a smaller wheel with more sidewall.
But, I'm sure there's a better riding tire out there than the Goodyear tires that are OE....I just need to hear from a few folks that have replaced theirs and can state that there was a definite improvement.
Michelin LTX M/S2 are probably one of the best highway tires you can get. my dad just replaced his 1st set of these Michelin's on his 04 silverado, they last almost 90,000 miles! that is what i'll be putting on my 2010 silverado once the original tires wear out. here's a link for them:
Grab a copy of CONSUMER REPORTS (or subscribe to http://www.consumerreports.org -- the online edition). I bought the GENERAL GRABBER HTS to replace my OE tires (16" stock rims), because they were rated best overall for highway driving. I do NOT regret my purchase (bought them online from http://discounttires.com/ -- as they had the best price, by far, at the time). Here are the most recent TIRE RATINGS, from my consumer reports online subscription:
Tire Brand & Name - Avg. Price - Rating (100 being best)
General Grabber HTS - $105 - 80
Continental CrossContact LX - $108 - 73
Kumho Road Venture APT KL51 - $104 - 72
Cooper Discoverer CTS - $159 - 68
Michelin LTX M/S - $165 - 67
Yokohama Geolandar H/T-S G051 - $111 - 67
Firestone Destination LE - $106 - 66
Bridgestone Dueler H/L Alenza - $154 - 66
Dayton Timberline HT II - $99 - 66
Pirelli Scorpion STR A - $128 - 65
Goodyear Wrangler SR-A - $133 - 64
Dunlop Radial Rover A/T - $118 - 63
Hankook DynaPro AS RH03 - $98 - 63
Goodyear Fortera TripleTred - $162 - 63
Toyo Open Country H/T - $108 - 62
Nitto Dura Grappler Highway Terrain - $148 - 61
Dunlop Grandtrek AT20 - $119 - 58
Uniroyal Laredo Cross Country - $103 - 55
BFGoodrich Rugged Trail T/A - $127 - 53
Falken Ziex S/TZ-04 - $102 - 50
YMMV - karl
...just adding the following for general FYI as to "tires and their makers"
* goto: http://www.neilkline.com/Tech%20Tips/whoownswho.htm
* scroll to the last section on that page, entitled:
Tire Manufacturer Web Sites
* just above that section heading is an interesting note regarding "who owns who" as to tire manufacturers.
NOTE that "Continental" owns "General" (and both brand names are #1 and #2 on the Consumer Reports list which I posted above). And, of course, below that TITLED section is a list of links to a plethora of tire makers' websites.
FWIW - karl