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CB750FOUR TIRES     Subject: New Dunlop GT501 Tires By rider and roadracer Mark Newby   Recently, I wore out the last of several sets of Dunlop K591 tires that I ran on my 1978 CB750K8 model, and when I called my favorite tire dealer, Sport Tire Services (800-776-8473), I found out that the model was no longer being manufactured.  I was perturbed at this, as that was the best tire I had ever found for this motorcycle, both in terms of handling and tire wear.  It turns out that Dunlop did not let us down, and manufactures a new series called the GT501 in virtually every size needed to fit any vintage motorcycle ever made.    My motorcycle is completely restored and completely stock except for the custom steel braided brake line on the front (a definite improvement over stock).  The front rim dimensions are 1.85x19 and takes a 100/90VB-19 GT501 (Dunlop Part Number 3004-25) and the rear rim is a 2.50x17 and takes a 140/80VB17 (Dunlop Part Number 3006-87).     An interesting note:  The K591 tires required me to adjust the front end such that the front fork tubes were set 10mm down in the triple clamps in an effort to maintain ride height and good stable cornering performance.  I am pretty handy at the calculations involved in this adjustment from racing experience.  The new GT501s made the bike turn in so quickly that I ran the calculations again and determined that the stock fork height position was necessary.  This means that the fork tubes are set back to exactly even with the top of the triple clamp to maintain ride height.  I recommend that this be used as the fork tube position when you change to these tires.  You can drop it if it seems too slow for your riding style.     I cannot break these tires loose in cornering - I touch metal on both sides before getting to that point and it feels stable as a rock in any type of maneuver.  Dunlop did a great job on this design, and I rode them 1500 miles from Denver to Sturgis and the Black Hills this year to develop that opinion.   We hit rain for the last 150 miles on the return trip, and they are even better than K591s in wet conditions - I had to run 70mph in the wet to keep up with my buddies on their big cruisers and had no planing problems whatsoever.  Note also that I run a National Cycle Plexistar 2 windshield on the bike for long rides.     This information might help someone who needs new rubber.   Ride Safe!     Mark Newby Thank you Mark for the contribution.