Different tire types?

[Kypper]

I have Dunlop K591 tires on the front and rear now and need a new rear tire. It looks like Dunlop discontinued the 130/80 size for the K591's. Is it safe to leave the K591 on the front and get a different rear tire? Is it safe to have a 130/80 on the front and a 130/70 on the rear?

[Wagoneer]

Something tells me you don't have 130/80 on the front... stock size is 110/70/17 on the front and 130/70/17 on the rear.

Put a 140/70 on the rear and call it a day. I was planning on uppin to a 140 in the rear when I shopped for tires but if you're staying with a 130 on the rear, the choice is slim.

[RossLH]

Building on what Wagoneer said, you should be fine so long as you don't mix bias ply with radial ply.

[gsJack]

Radial rear with bias front can be ok but radial front with bias rear is not. 

Are you sure that's a 130/80-17 you have on the front?  Wouldn't fit inside a stock GS front fender, a 120/70 almost touches on the width and a 110/80 almost touches on the OD.  Most of the K591 were belted tires as I recall and a belted front with a bias rear can be as bad as the radial front/bias rear combo.

With all the different brands, types, and sizes of tires I've run on the GSs a GT501 belted front with a Z2 radial rear was the only bad mix I ever had, felt like the bike was falling out from under me in spirited corners.

http://www.gs500.net/gallery/data/500/GS500tirelogs.jpg