For a while now I've been riding a 21-speed mountain bike. Climbing some of the hills around my area when tired is a no-go: I often end up walking up.

This is with a 24t small chainring and 28t large cog. On 26" tires that's about 22-23 GI.

A bit more about this bike: It is a 15" step-through frame, which due to my inseam, I've had to run the seatpost at it's limit. The handlebar is positioned so that I have to lean forward slightly. (I haven't bothered to adjust it). The tires do have knobs on the sides, but they are slick-centered.

That bike is now hung up for repairs that I can't afford at the moment.

So now I'm riding an old 10-speed road bike I picked up cheaply. If anything, the bars are actually lower relative to the seat than on the mountain bike. Typical of this style of bike, the small chainring is larger than the large cog, which while I haven't actually counted the teeth yet, I'm guessing puts 1st gear somewhere around 30 GI with 27" tires.

Tire pressure is about equal, as the old tires on the road bike have the same 35-65 PSI range as on the mountain bike, although the road bike tires are 1.25", and the mountain bike tires are 1.5" wide.

The weird part is, even when I'm tired, it seems like I can tackle more hill on this old bike, than on the mountain bike. I can only really chalk this up to some type of geometry difference, but what part, I don't know. Seat height is roughly out of the equation, as it's equal on both.

I'm planning on building a bike at some point for long distance traveling, and having experienced this major difference in hill climbing ability, I'm interested in measuring the bikes I have to determine what would be the best fit for me in building up a traveling bike.

Your input is appreciated.

I suspect the rolling resistance is the main difference both tires and aero position but mostly the tires. I had a mtn bike that I put a really good quality tire of the type you have slick in the middle and tread knobs to the side and when I later replaced it with a true slick it was a lot different. The one bike could just be freer rolling also. The test would be take them both to a hill and coast out till you stop. Mark where you stop on each bike should tell you.

Geometry could also play a part. Line the two bikes up side by side and take a photo straight on (from side). If you are doing your hills seated on both bikes look at bar position and seat to centerline of crank for a clue.

By "tackle more hill" you mean steeper? My steepness limitation on an mtb is keeping the front wheel on the ground and being able to go fast enough to not fall over. Is that what stops you on your mtb and are you saying the new bike is better at this?

It's definately faster climbing with a road bike. The geometry balnaces out the weight distribution more evenly and the shorter chain stays makes climbing more efficient

too small a frame, Poor fit. go test-ride some new bikes..

I have triple cranks on my touring and the Road Bike.. FWIW.

Not necessarily steeper, (the road bike will not take some of the hills I dared on the mountain bike, such as a short, 45-degree incline in the grass), but on pavement, hills which would force me to walk when tired on the mountain bike, I can continue to struggle up on the road bike. I seem to be able to maintain a higher cadence, and thus a higher speed, in spite of the gearing disadvantage on the road bike.

A road bike will go up hill better because it lighter, has less rolling resistance, and is stiffer in pedaling. Does your mountain bike have suspension? Suspension absorbs not only energy of impacts but also the energy of rider, especially rear suspension. Locking it out helps. Differing riding position between the two bikes can have an effect on your pedaling efficiency too. Saddle height and setback being the most important when your seated.

No suspension on the mountain bike, and the road bike is steel, whereas the former is aluminum.

Road bikes just make propulsion easier, that's why they can be geared higher than an MTB. If you want a great hillclimbing bike, start with a road bike and gear it like an MTB.