It depends on the rim size as to what size tire it can take. Check the rim for something like 622x14 or something like that. Then look here http://sheldonbrown.com/tire-sizing.html. I have no problem with 700x23 and you'd probably get used to it, but I did just switch to 700x28 for a much smoother ride and I'd guess they'd give you the feel of more stability especially on rough roads, loose dirt, gravel, or debris. Buy some cheapies and use them for a while and then if you decide you like the size upgrade to some quality tires keeping the cheap ones for spares. Probably use the same tubes.