On straight track I typically use 2" centers. For curved track it really depends on several factors: 1. What radius of curve are you using? 2. How long are the cars you will be running? 3. How large are the locomotives you will be running and what type? The tighter the radius the more overhang that cars and locomotives have. The longer the cars and locomotives are the more overhang they have. Certain locomotives like Mallets have a lot of overhang as do full length passenger cars and freight cars. Take a look at: http://www.nmra.org/standards/s-8.html That will give you some idea as to the minimums you should use. David
