It is tire size vs rim size- you should have a 4.5in rear rim. I would run a 160/60- with a rim that wide the 150 size tire is really opened up- that is why it does not look rounded. The exact opposite happens when too wide of a tire is placed on a narrow rim . The tire will not fully open up and all of the side tread will not be useable. Suzuki put a 150/70 on the 89-96 Kat's with the narrower stock 3.5in rim. I know the sizes as I just converted my 1983 GS750 to Katana wheels. I would run radials 120/70 front and 160/60 rear. This is the setup I am going to run on my GS750. The later model Kat's (98 and up) had very nice wide wheels that will accept radials nicely.The Dunlop 208ZR's are excellent- I have them on my 2001 TL1000S. Good Luck, Ed.
http://groups.msn.com/SuzukiGSGarage/gs750edbacktolife.msnw?action=ShowPhoto&PhotoID=3334
http://groups.msn.com/SuzukiGSGarage/gs750edbacktolife.msnw?action=ShowPhoto&PhotoID=3334
