Do you mean 100km or 160km? I don't work in miles...

If you're talking about 100km it takes me about 4hrs & a smidgen bit. It's not that hard as long as you think about how much you're drinking & eating per hour.

I've never actually done just a 160km ride. I did do a 100km off road ride this year & a 200km ride a few weeks ago though. The 100km off road ride is all uphill & it's all in your head!

My suggestion would be to pick up a copy of Nancy Clark [U]Guide to Sports Nutrition as it gives great examples of foods that give you the 50g of carbs/hr you need to keep going.

I guess what i'm trying to say through all my babble is think about what you're eating & drinking, pace yourself & don't worry about time. Just go out there and ride.

If you can do 100km you can do 200km. I'm still pondering the idea of doing another 200km soon but on easy off road trails. I do have the urge to do a 300km ride..
C