tires: how much does size matter?
 

I posted this question on the commuting forum, but am curious to have road cyclists weigh in. I ride a fairly lightweight, custom, Reynolds steel touring/hybrid bike with 26" wheels. I use it whenever I can instead of my car, for 40-60 mile fitness rides, for touring. I ride primarily on the road, but I live on a dirt road, so to get to pavement I have to travel on dirt, which makes a bike with very skinny tires impractical.
I've been riding on a 26x1" which did pretty well on the dirt and just fine on the pavement, but last week one of them was destroyed during a ride and the lbs only had a 1.5" to replace it. At some point I'm either going to buy it's mate, or buy a new pair of tires, and so I want to know if it will make a difference to my overall efficiency which size tire I ride on, and which style, and if I should care that some tires are 200 g heavier than others. I do a lot of serious hill-climbing (and descents), if that matters, and am also hoping to extend distance of the fitness rides. Thanks.

Between 1" and 1.5" you'll see a difference. But bigger difference may come also from the thread pattern and flexibility of the tire. 200g heavier it's a lot in my opinion if you do serious hill-climbing. I would recommend that you choose the smallest size you can. If 1" is well suited for you type of road don't go for bigger size.

You're joking right. What are you, a uphill time trial specialist?

To the OP: I'd get the 1" if you can ride those fine on the dirt section. The rolling resistance between the 1.5's and 1's will be dramatic.

My Vittoria Rubino pro weight 210g, so 200g would be 95% weight increase. I understand that for 1" tire the weight increase is not as drastical but original poster mentioned "serious hill-climbing". Depends on what you call "serious" but for me 200g would be significant in this case.

Ummmmmmmmmmmmm 200g? So if you're LA putting out 450 watts on the Alpe D'huez TT, you'd beat Ullrich by 6 minutes instead of 5 minutes, 55 seconds?