Does anyone have a 120 series tire on there front rim?  Any change in handling?  I'm looking to get a bigger front tire to match the 160 I put on the back with the Katana swap, do I need a Katana front rim as well or will the stock gs rim fit a 120? What do you guys think?

you personally will not notice a difference. Nothing bad about it besides more rotating mass. Why are you so concerned about matching tire size?

Pre '98 Katana rims (maybe post as well) are the same as the gs rim. You can put a 120 on the front plenty of people have done it.

http://gstwins.com/gsboard/index.php?topic=40609.0

I'm running 160 rear(on Kat rim) and 120 front(on stock rim) with no problems. Not sure about handling differences as these where on the bike when I got it.

All years of Katana wheels will work on the front.I have confirmed this by way of the German GS wiki.120 will work on the GS wheel.

I've run only 110/70 and 110/80 fronts on my GS's, I have a 110/80 at present.  A 110/80 is sized for a 2.5" preferred rim width so putting it on our 3.0 rims makes it about 115 mm wide.  A 120 front tire is sized for a 3.5" rim so putting it on our 3.0 rim makes it about 115 mm wide same as a the 110/80.  A tire is about 5 mm or .2" wider or narrower when put on a rim that is 1/2" wider or narrower than the preferred rim width.  I see no point in putting a 120 on that will be only 5 mm at best wider than a 110/70 oem size tire since the 110/70 will have the better shape on it's preferred rim width, racers may disagree.

I've run 130/70, 130/80, 130/90, 140/80, and 150/70 rears on my standard 3.5" rims on my GS's with 110 fronts.  I really haven't noticed any difference in handling that I'd attribute to differences in tire widths, but have noticed differences in steering quickness due to differences in tire diameters changing the rake.  I've noticed more differences due to type of tire, bias or radial and hard touring types or sticky sport types.  Just my opinions.

http://img.photobucket.com/albums/v443/jcp8832/GS500tirelog.jpg

Thanks guys, this forum is full of knowledgable fellow gs lovers!