I am going to get a more street oriented tire to try out.

It seems like a 90/90-21 and a 120/80-18 is pretty common. 120/90-18 is pretty limited but I have also found a decent tire in the stock 4.6.

I like the 90/90 as it will be a little taller than a 3.0 and my speedo will be more accurate. However the 90/90 in the rear is about 8% shorter than the 4.6 and that is going to change my gear ratio. This is greater reduction than going to a 13t front sprocket.

Any one have any thoughts on this?

Edit: I was looking at an IRC tire and noticed that the 120/80-18 is taller than their 4.6. Go figure!
BTW what does the M/C stand for after the size?

http://www.irc-tire.com/mce/tires/spec/gp-110.gif

 

No idea what the M/C means.
Tire sizing conversion is some sort of voodoo! Especially going from inch to metric. 4.60 is supposedly 120/80 but it usually doesn't really measure out that way. The only way to be sure is to measure the tires mounted on the same width rim,inflated to the same pressure, which is hard to accomplish. Even measuring them unmounted leads to some surprises, all depending on how they've been stored they change a little or a lot once mounted.

 

I fitted a Michelin Sirac to my front wheel. It's great on ashphalt & okay off road after I let out some air.


When I went from a 3.00 x 21 to a 90/90x21, my speedo error was worse. However mine is a MY09 bike with the digital speedo so it could be different to your 2006. The specs for a 2012 Aust spec bike lists a 80/100x21 for the front & 110/100x18 for the rear.

 

I will check out the Sirac. I wonder how mine speedo will react? If it is a simple gear on the hub then a lager tire has fewer rotations and SHOULD register a slower speed. My guess with the 3.0 and 90/90 you used the overall circumference was such that the 3.0 was taller. The "on paper" number is that the 3.0 is a cm shorter but the real world tire may not have been.

A 3.00 tire as I understand it is a 3.00/3.00-21 or the metric equivalent 76.2/76.2 -21. But looking at the load index it is a lot closer to a 90/90-21.
The 80/100 sidewall height is basically the same as the 90/90 which is 81mm. An 80/100 may be a better rim fit. However the load index is usually less.

On the rear the USA spec'd bike is a 4.6 with a load of 63. I think that is because we are fat. The rim width is 2.15mm and that is pretty narrow. I think a 4.1 tire is a better fit for width. The load rating is less typically. I am not going two up so this may be fine for my needs. If I were going two up or loaded touring I would "load index" up.

I think it is as suggested just a bit of vodoo

 

I installed a 120/80x18 Heidenau K60 rear tyre to replace the original Dunlop D605. Probably would not go wider than this on a 2.15" rim. Should have listened to my mate & brought a Bridgestone TW42. Better value for money as the K60 hasn't really impressed me.

 

I posted some info somewhere but as I reduced the width of the rear tire a little with my recent change the bike seems to be better mannered near the higher end of the speed range.

found it - https://www.kawasakiforums.com/forum...80-18-a-37621/

 

I am right there with you guys. From the research it looks like a 110/xxx or a 4.1 or maybe a narrow 120 is the way to go. Having a wide tire adds to unsprung weight as well. A 2.15 rim will hold a larger tire but handling will be less precise with the rounder side wall. I am well within the load rating so I am not worried about it.

An 80/100-21 is good but it looks like most 90/90-21's will work but borderline on a 1.6 riim. The 3.0 may be the best fit if available.

 

From my recent experience when looking for new tyres, I found there was inconsistency with different brands. You could put two tyres labelled the same size side by side and they could have differing widths or diameters.

 

No doubt. Its even worse. Take a look at his IRC chart. The 3.5, 4.0, 4.1 and 4.6 don't have a lot of consistency. I think some tires like perhaps the 4.0 are made for a specific bike or market and they just fall into the line up.
http://www.irc-tire.com/mce/tires/spec/gp-1.gif

I am not buying any tires without all the specs first.

I may do this IRC GP-1 in a 2.75-21 and 4.1-18 rear. Smaller with less load than my stock bike but a good fit for the rims and I bet they will rider better too.

 

You want really odd - that 4.60 does NOT mean it is 4.60" it means it is a 4.00 with a lower aspect ratio. Stupid inch codes.

For the OP if you want a good buy on a tire that works well in both areas - street and most dirt - get the Duro Median HF903/904. About $120 for the pair! I've done about 30,000 miles on them, getting 4000 miles a set before I toss them. They aren't bald or anything, the rear is squared off and shallow enough the don't perform on gravel very well and the front is cupped, but 4000 miles is better than most sportbike tires. I ride it hard on pavement and the tires stick extremely well when chasing my friends on their supermotos. In the dirt they work great for a 60/40 tire, but not like a DOT knobby of course. Try them if you want a bargain - a diamond for the price of coal.