help needed with tires

hello everybody i need some help deciding what brand and what size is best for my 1978 kz1000 Z1R being the japanese version i have 18 front and rear wheels, ive made a lot of research and the best 2 options i have are bridgestone battlax bt45 ar metzelers lasertec. Now the big decision i face is do i go for the metz in 100/90/18(F);120/90/18(R) OR
the bridgestones 100/80/18(F);120/80/18(R) I read an article from a rider thats says the 80s instead of the 90s improved in a great way the handling, cornering and total feeling of the bike he affirms that with the 90s the front wheel wobbles more is this true? wich tires are better quality, and will be better to lean hard in curves etc..
DONT KNOW WHAT TO DO PLEASE ADVICE A.S.A.P.THANKS RIDERS

Don't know about the difference between the 80 and 90 profile tires but you will probably get many different opinions on this. Mine is that the Metzeler tires are better while I've never had any luck with Bridgestones.

I thought the 80 and 90 referred to the aspect ratio, that is the ratio of height to width. I am running 90s front and rear on my KZ750 and have no problem but I don't hot rod. I run the 100-90-19 front and 110-90-18 rear. Stock tires were 3.25-19/4.00-18 front/rear.

Tire profile should have zero effect on wobble. If your bike has a wobble check for problem with 1. tires/wheels; 2. swing arm bushings/bearings; 3. steering stem bearings; 4. shocks; 5. wheel bearings; 6. frame/fork damage.

Regarding tires; I like these:

Pirelli Sport Demon

The first tires I put on my Z1R were Avon "Roadrunners" in 1979. Since than I have never bought another tire besides Avon because of their all-around performance. I use Avons to this day.

www.avon-tyres.co.uk/motorcycle/

This is me in February of 1979

Awesome picture! Do you still have that same Z1-R? The bike was practically new in that photo. Didn't take you long to custom paint it! :laugh:

I've also had good luck with Avons. It's getting harder to find the correct sizes as the years go by. There might be more for the 78 Z1-R since the front is an 18". The lower profile tires look nice but the rim usually has to be wider. Just check the permissible rim widths for whatever tires you choose. 2.15" front and rear on the Z1-R I think??

Yes I do still have that same bike. I bought it painted with that Mural on the side from the dealer (Cycle City, Honolulu) new. I also have a second one which is like new with only 500Mi on it. That I also bought new. That is tits one with the really nice back rest. If you take a look on the Avon link that I provided you will find they have ALL the sizes for all of these bikes. They even have Vintage pattern tires if you want them.

This second one I bought New at Southwest Kawasaki In Burr Ridge IL (Exactly 20 years before I moved to the town)Matter of fact, in this picture it still has the temporary dealer plate on it.

In the Avons I like the Am-20/21 "Roadrunner" But they are being discontinued. The AM-26 "Roadrider" is replacing it. I also like the "Venom" AM-41/42. Between just those two all the sizes are covered for our bikes.

I got a set of the roadriders and put them on last summer. I can't say I feel any difference in ride or handling, but one great thing going for them is you are not forced to use metric sizes. They come in 3.25 and 4.00 inch sizing as well as the newer 120/90 stuff. For sure the 4.00-18 is wearing much better than my previous 120/90-18 because it fits the 2.15" rim spec. 110/90-18 doesn't fit at all, too wimpy looking being lower profile and narrow, so you can go 120 and be too wide for the wheel whether it a 90 or 80 aspect ratio doesn't matter, or go the factory size 4.00-18 and fit and wear correctly. Sure 99% of the guys want the widest tire you can fit, but wide on a narrow wheel is a waste and doesn't work.

One thing that must be realized is that all the original tires on these pre-1980 bikes were bias-ply tires and all these new tires we are putting on are radial. This makes the radials look much smaller because they wrap more than the bias tires. To compensate for this you should go 10-20mm wider with the radial than the original inch tires. Because the original tires were all 90% profile in the rear and 90-100% profile in the front, if you go with a 20mm wider tire you should go with a 80% profile to compensate for the difference in diameter.

What radial tires can mount on the 2.15" rims? I couldn't find any when I looked a couple of years ago. Are they Avon also?

First of all, ALL of the high performance tires today are radial. a 2.15" rim can take anything from a 90 to a 120. If you go to the 120 than you should go with a 80% profile. However the 100-90-** is the best fit for a 2.15" rim.