I want a bigger rear tire for my Bob, but dont want to compromise for handling, which size should I go for? 170 or 180? Any difference in riding characteristics?

 

you probably won't be able to tell a difference between those two sizes. I went from 160 to 170 and the bike handles better, butI think that is due to the quality of tire. I went with a metz. As long as you get a good quality tire it definitely won't handle any worse than the stock dunlop.

 

The Dunlop tire had a flat place in the center of the tire, it caused me concern when going over uneven places in the road, especially when they was paving it and one lane was higher than the other side. When I went to Metzler 880 tires, the tire is more rounded and rides better. I went from a 160/70 17 dunlop to a 170/60 17 and it was 1/4 inch wider. Nest I'm going to a 180/55 17 and try it.
Realize this only about 1" of yer tire rides on the road at one time.
YOu have to look at where it will run yer fender or brake lines.
The Streaming Eagle Dyna which is a superglide has a 170/60 17 tire on it. Go to the dealer and look at the wheel on the SE dyna.

 

I agree -

You will notice a difference betweena Screamin Eagle 180 vs a Metz 170 - considerable width difference. I really liked my SE 180 but it is a very soft compound. The 170 Metz ME 880isn't noticably wider than the stock Dung-crap, but the ride quality is much improved.