What is your rim size and what is the widest tire you have run?
What do think the widest tire is that you could run without problems?
I'm hoping to get at least a 160 on the back and I'm not sure about how wide I can go in the front...any thoughts?
If you are putting your on the road as a motard I think you will find this site usefull.
http://www.supermotech.co.uk/when you get on it Scroll down the bit on the left untill you see TECH, Click on that and read the bit called "Tyre sizes the truth"
I am going to fit a 4.25 rim on mine and I have a few 150 tyres that measure 152 mm at the widest point when fitted to a 4.25 rim.
I think I measured that more than 157 mm and it would push the chain to the side so I think the rim would need offsetting..
Anyway, the people I have spoken to say that 160 tyres cause the bike to turn slower and 150s can cope with the power OK