Joined: Nov 2015
From: So Cal
I Ride: 1990 ZX-7 H2, 1992 ZX-7R K2, 1992 ZX-7/9, 2002 Ducati 900ie Supersport, etc...
Hi and welcome man, got one myself and they're great handling bikes if you set them up right.
Yup, a 170/60 was the original rear size as Zed stated above. That was kind of a big deal back in the day that a 170 came on the bike stock.
If you do want to go wider, a 180/55 will work also but you then may want to raise the forks up in the triples to drop the front, or raise the rear ride height a bit to quicken up the steering. This is in order to make up for the change in resistance and profile of the wider rear tire.
Definitely DO NOT go to a 190 rear tire... the tire will mushroom around the rim and when you corner hard it can just "drop off the edge" of the tire without the usual warning because it is being compressed to fit on a 5.0" rear rim.
For a 190, you need to have at least a 5.5" (a la the later J/K/L/M) or ideally a 6.0 There's really no point in doing that for an H as the handling and power delivery works just fine with the original 170.