Tyre sizes

What's critical about tyre specs (profile, width etc)? I have been pricing
up new tyres for my lardy old cruiser, looking for tyres that match the
exact size of the oem ones that need replacing. Talked to someone who puts
different size tyres on his bike. Struck me that on my bike perhaps tyre
size is not as critical as perhaps on some big sports jobbie. So what
difference would it make putting on tyres of a different width etc.? And if
I was to deviate from the oem specs, within what margins should I keep? I
don't know how the width and height affects tyre performance or handling and
couldn't find anything on the net.

 

Well, I found that putting Avon Venom AM41/42s (standard sizes) onto the
Drifter was a big improvement over the crap OEM keep-the-rims-off-the-road
Bridgestone Excreta G702/3 things.

I'd say you should look at staying with the stock sizes and look for a
better quality tyre. This site:

http://www.foreven.com/motorcycles/Tyres/

should give you some idea of what you're looking at and why.