kz1000st tire question

I just bought this bike and the tires are rotten. The bridgestone website says that the best match for stock tire sizes is 100/90-19 (front) and 120/90-17 (rear). The tires that are on the bike are stock (I assume) and look a bit skinny. I was thinking of going up a bit in width but keeping the diameter close to the same, so instead of a 100/90-19, maybe a 110/80-19, and instead of a 120/90-17 maybe a 130/80-17. A search on this site showed a lot of opinions, and it seems some people opt for a wider tire but keep the same aspect ratio (i.e. 90). Opinions? Thanks.

-Doug

Careful with the width....when I put Bridgestones on mine (77 kz1000a), I wanted to go 110/90-19 on the front instead of 100/90. Mistake!!!! The tire would mount ok on the rim, but the friggin' front fender wouldnt clear the added width. CURSES!....Foiled again!
Just a heads-up.......

Was it just the width, or was the tire too tall as well? What if you had gone with a 110/80-19?

I'm sure most of y'all already know this, but in a 100/90-19 tire the section height ( see here for definitions ) is 90% of the section width (100mm), thus 100/90. A 110/90 will be both wider and taller, whereas a 110/80 will be wider but about the same height.

So I'm just wondering what size tires you guys are using. Should I stick with the Bridgestone recommendations (I'm thinking of using Battlax BT-45s, by the way) or are those recommendations outdated because of "modern tire technology" or whatever? Thanks again.

rckz wrote:...

Was it just the width, or was the tire too tall as well? What if you had gone with a 110/80-19? ... So I'm just wondering what size tires you guys are using. Should I stick with the Bridgestone recommendations (I'm thinking of using Battlax BT-45s, by the way) or are those recommendations outdated because of "modern tire technology" or whatever? Thanks again.

Physical measurement of supposedly same size tires does actually vary between manufacturers, so probably safest to follow the particular tire manufacturer's recommendations.

When replacing the front wheel with new tire mounted, sometimes deflating the tire eases getting it into place between forks with dual brake calipers.

Admittedly paranoid about speed wobble, am gunshy about tampering with front tire size. Perhaps unfounded, but prefer the stock appearance anyhow.

Believe one size larger rear tire would be okay, maybe even better, but any larger might exceed the safest stock rim width capability. At some point, a wider rim obviously becomes nescessary. A larger diameter tire results in a slightly higher overall gear ratio throughout the range.

Opinions differ on whether to have the mounted tires balanced. Some folks don't bother and have never have a problem. Mine get balanced.


Just my .02

I have a couple STs... I use a 100/90-19 on the front and a 130/90-17 on the rear. I currently have a set of Dunlop 404s on my "daily ride" which is the 79 pictured in the projects folder (look for wiredgeorge). They ride nice and have good grip. Next set, I will put tubes in the tires, even though ST rims are marked tubeless as mine leak just bit of air... likely around the valve stem. I have to check the air every few rides.