Shinko 230 Tour Master
$131.30/pair
*100/90-19 front
*120/90-18 rear
+awesome grip, I've ridden these A LOT in conjunction with a similar Shinko SR741 in a wider rear to fit my wider aftermarket rims, wife had 130/90 rear in the 230, same carcass and compound on SR741 & 230 Tour Master
+149mph V-rated carcass
+Lightest tires of all these choices
+good tread performance in rain
--rear will wear down fastest of all, ~4,000mi rear max, but front @ 9,000mi+ is excellent at least
--more frequent rear tire changing labor
Avon AM26 Road Rider
$181.76/pair
*90/90-19 front
(closest to original size 3.25-19 but shorter for quicker steering, best fit on GS rim)
(Avon runs bigger than competitors so I wouldn't run the 100/90-19, plus they're the only ones who offer a 90/90-19)
*4.00-18 rear
(OEM stock size, best fit on 1.85 GS rim, taller look vs 110 for aesthetics+quicker steering)
+Best tread wear of all these performance gripping choices, best for lots of city riding and long highway road trip miles 8,000mi+ on rear, 12,000mi front
+best fit on stock GS 2.15x18 & 1.85x19 rims, means the ideal profile curvature for slightly smoother lean-in feel when you lean over into a turn
+best grip of all higher mileage / longer tread life tires
+good wet weather performance
+/-Sane riders rave about their grip vs treadwear, but those who push it hard into corners leaning over substantially and riding very twisty roads in the hills will be running Bridgestone Battlax, Pirelli Sport Demon, or Shinko tires
--I got mine used 2 yrs old less than 100mi on them but had issues with cornering traction from the start. Some tell me it's because they were older, but it's a known fact the others I list grip better for aggressive cornering. I won't run these again unless I am planning many long road trips - may run rear only at that point.
--it's best to keep tires fresh - replace 'em by 3yrs old, front tread outlasts the rubber's good gripping lifespan if you don't rack up tons of miles to wear them out in 2 seasons or less
***(110/90-18 is similar rear to the 4.00-18 but not as tall & very slightly narrower - taller rear looks more appropriate and quickens steering but slows acceleration slightly due to gear ratio changing from height increase - that goes for all these in 120 rears - swap on 1T bigger rear sprocket next time you put on new chain. Slightly more sidewall flex on taller tire also)
Bridgestone Battlax BT45V
$221.76/pair
*100/90-19 front
*120/90-18 rear
+AWESOME cornering grip, used on older sport bikes @ racetracks often, grips 96% as good as the Pirelli Sport Demon but wears substantially better
+front tires run the shortest height for each size vs all other brands, which helps quicken the steering more to make it ride more sporty and fun
+2nd fastest lap times on race track test comparison
+rear tires use Bridgestone Sport SACT technology so has super soft grippy rubber on sides for intense cornering grip, but harder / better wearing rubber strip in middle for slightly longer treadlife on city/highway miles
-/+still wears down pretty quickly for a dual compound rear tread, but outlasts all other super grippy soft compound tires, 5,000mi+ on rear 10,000mi front, rear wears better than Shinko or Pirelli
-front tire not as good in wet weather, some bikes notice uneven front treadwear but others are fine
***(cheaper H rated rear is available in 110/90-18 but I opted to recommend the V-rated 120 as the 100 and 120 both are at the same maximum manufacturer recommended size fitment for stock 1.85"/2.15" GS rims so they'll both have same tread profile curvature ft vs rr & taller rear quickens the steering but will sidewall will flex slightly more)
Bridgestone Battlax BT45 H-rated
$199.76
100/90-19 ft
110/90-18 rr
*same as above except carcass only H-rated for continuous use up to 112mph, less sizes available - these are the sizes to fit GS 1.85x19 & 2.15x18 rims
Pirelli Sport Demon
$195.76/pair
100/90-19 ft
110/90-18 rr
**---Pirelli doesn't rate these size tires as a recommended fit for stock early GS 1.85/2.15 width rims even though Avon and Bridgestone do, but people still run them on GS rims with very excellent praise
+*BEST CORNERING TIRES OF ALL GS TIRES
+best lap times of the top tires in a race track test comparison
*Best wet weather performance of all
-rear will show lots of wear by 2,500mi but will last ~4,300mi or so
I recommended the most raved about options here. There are a few other slifhtly less popular "good" choices, Metzler makes a couple of popular tires but some models are ancient technology and some are newer, good reviews on the newer but against a Battlax or Sport Demon, those 2 always beat the Metzler.
Continental makes a Conti-Go and Classic Attack (radial I think, made for vintage sizes) but they are pricey and wear down as fast as the budget priced Shinko or faster even.
Dunlop makes one tire that I have heard a few people say real good things about, but the Avon/Pirelli/Battlax tires have a wealth of excellent reviews on the GS Forums and all over the Internet so you can be very assured of well experienced aggressive riding reviewers' feedback.