Z1 Tire Sizes

I have a 1974 Z1 900 and I have purchased a set of polished Sun rims with stainless spokes size 185 x 19 rim in the front and a 250 x 18 in the rear. Should I use a 90/90-19 and a 120/90-18 with a stock swingarm. Thanks in advance SMV

The front sounds small to me. These bikes wobble with small front tires. I would do the 100/90

etbike3135 wrote: The front sounds small to me. These bikes wobble with small front tires. I would do the 100/90

Correct, that 90/90-19 is too small. Use 100/90-19

OK so its a 100/90-19 on the front. For the rear will a 130/90-18 work OK with the 2.5 rear rim and stock swingarm or do I need to stay with the 120/90-18? SMV

I could be wrong, but I thought the stock rear wheel on the '74 Z1 was the same as that on the KZ650 - 2.15" wide. If so, the 130 tire will work, but you would be better off to use the 120/90-18. I used 130/90-18 tires on my bike for many years, but I now use 120/90-18. The problem is that bead on the 130 must be squeezed so much to fit on the 2.15 rim that the cross-section of the tire ends up deformed. As a result, even though the 130 tire is wider there is no more tread on the ground (maybe less) than there is when a 120/90-18 is used. Also, the 130 is a real bear to mount on the rim, but it can be done. Other than that, the only problem I had using the 130 was that it rubbed the stock chain guard. Ed

Yes the stock rear is 2.15 but when I ordered the rims I got a 2.50 for the rear, With that being said will a 130/80-18 work or should I stay with the 120? SMV

I've never used a 2.50 rim, but I took a quick look online to see what I could find on the subject. In the last table in the link it shows rim width and permissible tire sizes. According to the chart a 130 should work on a 2.50 rim. I recommend you do some more research to verify because sometimes one reference will disagree with others. Ed

www.denniskirk.com/help_center/tire-sizes.jsp

2.5" wheel is fine for a 130 tire, but like Ed mentioned it most likely won't work with the stock plastic chainguard. If you've removed the guard :sick: or added an aftermarket chrome part it will most likely fit just fine.