Right. Some of the energy that was used to accelerate/maintain speed ends up being used to wear down your brake pads and rims/rotors along with producing waste heat.

Think about how many times a typical commuter hits their brakes on the way to work.

Hybrid in one market is Cross bike in another.. 700c 35ish tires is the commonality.

Drop bars are not required ? then thats fine.. I like Figure 8 bend Trekking bars,
in place of straight ones.

Weight of the bike is the last thing that's going to impact me because I'm a built like a whale with arms and legs. It isn't pretty once that all gets squeezed into lycra cycling attire, trust me. Still, I suggested wheels and pedals as a place to save weight rather than other components because as I remember my physics class (long time ago so I'm prepared to be wrong) the weight's distance from the centerline(axle) increased the energy requirement by the square of the distance. Changing the weight at the location only adjusts the energy proportinally though, so it might all be a wash. Still, it is not a net zero impact because of the need to brake as mentioned by others. Pedal weight has to be lifted every revolution of the pedals, so the weight difference again adds up. I think the thing to remember here is that while all that is true, the rider is by far the biggest influence on the performance of the bike, followed by aerodynamic position (also mostly determined by the rider and geometry, not weight) of the bike. Put a peleton rider on a hybrid and they'd still destroy the typical commuter even if they were on a time trial bike with all the goodies.

Long winded way of saying, the math is irrelevant to most of us, use what feels good to you, and don't worry about justifying it.

That is a good point and to maybe take it a step further, a different bike might help some but ultimately better physical conditioning is what will make the biggest difference. Over time you will get used to the hills and the added distance.

OP, I think the most important question is: on your current commute with the MTB, are you running out of gears in either direction? I.e. going up hills do you get down to the granny combination (chain all the way to the left) and still can't pedal at smooth, brisk cadence of, say 80+rpm? Going down hills, do you get into the high combination (chain all the way to the right) and still spin out? (And if you do spin out, do you care, or are you content to roll downhill plenty fast?)

If your existing gear range is working for you (and will continue to work on the new commute) then I"d say you do not need a new bike, you are fine as is. (Of course, new bikes are fun! So if you have money to buy one, buy one! Maybe do you have cyclist friends that could loan you bikes to try out and see what you like?)

The other consideration mentioned above is about suspension fork. If you have to stand on the pedals going uphill you will bounce like crazy and lose tons of energy. And even if you don't stand up, you will bounce some, and lose some energy. So if your fork has "lockout", use it. If not, you might consider a new bike, or at least a rigid fork or a fork with lockout.

As many have recommended above, "cyclocross" is the keyword to look for in a road bike. Essentially, it is a kind of road bike, and among the many types of road bikes it is the most robust for commuting while still offering some performance. I commute on a Crosscheck (like some of those above), and I love it; but there are other models that would work as well. Also somebody mentioned carrying their bike up and down stairs; one peculiarty of cyclocross bikes is they are designed with the rear brake cable is routed along the top of the top tube, so it can be more comfortably carried on your shoulder.

Another option would be a "touring" bike, but that design is oriented towards carrying heavy loads long distances at low speeds (think bike-camping). Get a tourer if you want to feel like you're driving a bus.

Stay away from "hybrids" as well, unless you want to feel like you're a bear riding a bike in a circus.

I didn't write that weight doesn't matter, weight matters a lot.

What doesn't matter is where the weight is located. Weight in the wheel, weight in the cranks, weight on the rider. All the same.

I inflate my tires to the pressure that I figure is ideal for their width, so about 100 for 25mm width and about 70 for 32mm width. I've overinflated the tires on my 3-speed to 60, and that didn't make it faster, for sure. It made the ride pretty harsh, though. It's a slow bike, no matter what.

Recorded times on the different bikes is quite different. Maybe there's a psychological reason that rewards me for going faster on a light bike, but whatever.

Another interesting datum is that I had a Surly Cross Check, a heavy steel frame, and I put very light racing wheels on it. Overall, it felt like a light bike. Then I put heavy wheels on it with 37mm tires on it. It rode like a dog. So, draw your own conclusions. Mine is that I'm pretty sensitive to a bike's weight, especially at the wheels.

Well, this morning on way to work I seen something that convinced me of what everyone here has been saying about the efficiency of a road bike,
I was going up a reasonable incline and one cyclist appeared out of nowhere, he did not look fit, looked a bit out of shape, possibly about another 70 pounds heavier than me, He flew past me as if i was the out of shape one and that we had swapped bikes! It was very impressive, I thought that if he could fly past me on that bike going up a hill, either my cycling of 12 miles a day for 3 years has made no impact on my fitness, or it had to do with the bike.
One person asked about my gears, I have 24, usually on the straight, I can run out, due to the tires being 1.5 inch, on hills I still stay on the larger cog and 1st/2nd gear.

How much more efficient do you think that road bike is? I bet you that guy wouldn't slow down by more than 2mph if he swapped bikes with you, unless you were battling a 20mph+ headwind as well as the incline.

Cycling 12 miles a day is very healthy. This kind of exercise reduces many health risks by a ton. But unless you push yourself on every ride, it doesn't make you that much stronger. It's like going to the gym five days a week but never increasing the weight; you'll hit a plateau very quickly and stop getting stronger. That guy who flew past you may be a fat bastard but he has more muscle for sure.

Ouch that hurt!

Most table that tell you what pressure for what width tire are giving you a pressure for "comfort." 37mm tires pumped up to the recommended pressure are going to roll a lot slower than skinny race tires.

If you don't care, then leave it alone. If you want to see, put the same tire/tube and same pressure on different wheels and it will be much harder to tell the difference.

Cheers,
Charles

Should you decide to try a road bike--something I strongly encourage--have a good look at the Ribble Winter/Audax bike.

It comes available fully pre-configured from £659.95
The bikebuilder version where you specify each individual component from £579.95
Or as the bare frame-only for £103.96

The price softened the £50 shipping to the US, but it ships post-free in the UK, and they participate in the UK's Bike to Work voucher scheme.

I chose it because I wanted a road frame, in fairly conservative geometry (for comfort and stability with a load in the panniers), made from aluminum (it will see salt and I don't want it rusting) having rack and fender mounts, and the ability to fit full fenders (mudguards to you lot) over 28mm tires.

Disregard the 23mm tyre size bit on the web site. It's no doubt a typo. Mine's sitting in the living room now with 28mm tires under SKS P35 fenders. I suspect that using other fenders you could stuff 32mm tires in there.

My frame was delivered over the past weekend and I'm building it up now. The forecast is for studded tires through the weekend, so don't expect a ride report until next week sometime.

Nice website, I will save this for later, thnks.

Sorry, I didn't mean it as an insult, more like a fair warning that buying that guy's bike won't give you that guy's speed

You say 2 mph as if that's small. It's a very big difference in my view. And it might be the margin of speed at which the fat guy passed.

I said, ALL terrain commuter, you say terrain commuter. Thats the difference.

No, I was only joking!! you actually have a valid point, although every time i have had someone in front of me it has been a road bike, and others I see on a mountain bike I either keep the pace or overtake, I also don't just cycle to work, I also train with weights 3 times a week too, So I am reasonably fit.
I think on a sprint if we were both on the same bike, i would be slightly embarrassed if this heavy lad whipped me!!!
As was said 2mph faster would have been a reasonable figure that he passed me on a hill.

Once upon a time, I did a long climb twice: once on a road bike, then on a mountain bike. I kept my heart rate in the same range to maintain the same level of effort, and I did the two climbs on different days. The mountain bike was 15% slower, even though the MT bike+rider mass was only 3% more than the road bike+rider mass.

FYI, the route was Big Pine, CA to the Schulman Grove. The profile:



Mountain bikes are slow.

I'm assuming you didn't have knobby tires on the mountain bike. Same tire pressure? Same type of tires?
It's certainly true that mountain bikes put riders in a less aerodynamic position for road bikes, but for climbing, this should matter less than for flats.

One of the main benefits of a road bike is that it puts you in a position to better output power.

As far as wheel weight making a big difference, I don't doubt that it could, but I would imagine that the tires that are run on each wheelset are making the largest difference. Not related to the tire pressure or the size of tire itself, but how supple the tires casing is. Most larger diameter tires are made with much heavier duty casing than skinny tires which are almost always produced for racing-ish purposes and not durability.

Different tires on the road and MTB, which explains the bulk of the difference in climbing speed between the road and mountain bike. It's not the difference in mass or riding position, as the mass difference was small and the riding positions were similar.

I wrote above that mountain bikes are slow, which is true. The main reason for the slowness is their tires.