I've always owned a mountain bike mainly cause they are CHEAP and I used to ride my bike rarely.

Nowadays I've gotten very addicted to the sport and still ride my mountain bike. My brother tried a road-bike the other day and said it is SOOO much easier to pedal, the efficiency is much better. I figured that is from lower resistance from the thinner width of the tires, correct? Or is it because the bike is lighter? I never understood how the bike being, let's say 10 pounds lighter would be the greatest cause of the greater speed and efficiency considering people like me weigh 170 pounds.

So is it the wheel width that is contributing to the road bikes efficiency the most? Is it the actual TYPE of tire that has a lower rolling resistance? Is there even a big difference between tires?

I'm just wondering because if 700 is more efficient than 26" MTB wheels, then wouldn't our range be a lot better on our electric bikes if we use those wheels instead?

Anyway, just a lot of thoughts going through my head... thanks in advance. :thumb:

It is the lower rolling resistance of the narrow profile higher pressure tire. I have never understood the popularity of the fat mountain bike tire for folks who ride on pavement. if offload sure. I don't like the riding position of a road bike but that is easily fixed with a new seat and mountain style handlebars. The mountain tires do ride smoother, but at a considerable cost in efficiency! You will likely experience more flats with the 700c bike though. Lately I have built recumbent bikes with 700c wheels for the most in efficiency and comfort! You can buy high pressure mountain type wheels and tires but they still haven't got the low rolling resistance of a good 700c road wheel!
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It is the lower rolling resistance of the narrow profile higher pressure tire. I have never understood the popularity of the fat mountain bike tire for folks who ride on pavement. if offload sure. I don't like the riding position of a road bike but that is easily fixed with a new seat and mountain style handlebars. The mountain tires do ride smoother, but at a considerable cost in efficiency! You will likely experience more flats with the 700c bike though. Lately I have built recumbent bikes with 700c wheels for the most in efficiency and comfort! You can buy high pressure mountain type wheels and tires but they still haven't got the low rolling resistance of a good 700c road wheel!
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I understand.

I've heard that the 700c wheels get more flats as well. Would that be solved if you add the slime-product (or anything similar) to the inner tubes? I figure it would be worth it rather than spending $5 to replace a tube every couple weeks or so.

The flats are primarily due to the fact that those high pressure tires typically feature thin sidewalls, an absence of puncture protection, and that the low volume makes them easy to pinch flat. Nothing comes free, and that speed has its price in durability - much the same story with the wheels themselves (between two comparable wheels in quality, the 26" version will be stronger than the 700c version)

Touring tires are a nice compromise. Definitely treaded for road, but with the added durability for heavier use, which is nice on an e-bike where flats can be a real pain to repair.

I don't know why stores sell mountain bikes with knobby tires in an urban area, in fact many stores only sell bikes with knobby tires, very sad. I have a mountain bike and can barely make it up a small incline in the road. I need to put it in 1st gear and pedal about 3 MPH. When I get on my 27" road bike, I don't even know that hill is there. In fact I don't even have to down shift, it's like= what hill? I just bought a Schwinn Izip, still waiting on the battery though, but it has 26"x2" slick/semi slick road tires. I took it up the same road without any power assist and it went up almost as easily as my 27" road bike. When I got 75% up the little hill, that is when I noticed it is a hill and it started slowing a bit, but still did very good. The Schwinn Izip weighs about twice as much as my 27" road bike.
This leads me to believe that the biggest problem with mountain bikes is the knobby tires. The width might affect it a bit but not very much. I just ordered (2) 26"x1.75 slick road tires to replace the 26"x1.95" knobby tires. I will know more about this soon. I believe this should be a major improvement in my mountain bike.

wheel size alone does not affect efficiency to any significant degree, if you are riding on-road.

wheel+tire weight does matter some, though.

20" wheels and tires are not a bad choice, simply because their small size makes them lighter. the rolling-resistance is almost exactly the same for 20" tires and comparable-width-and-pressure 26" or 700C tires.

A 700C will draw a less current at the same voltage output to achieve the same speed that would be achieved with the same set-up with a 26" tire, assuming same tire/tread/tube, corrected for diameter.

Everyone has given you good answers. but to summarize

size of rim does not matter, having the right gearing for the size of rim you have does.

a heavier frame is not a big deal the improvements are insignificant. (a lighter frame will feel different though)

the parts that move are the most important for performance meaning wheels, crank, and choice of pedals (flat, clipless, toeclips) in that order.

thinner wheels go faster. smaller wheels go faster. lighter rims go faster, smaller rims go faster. oiled hubs go faster than greased hubs. "an once of the wheels is worth 10 off the frame"

20" wheels are not used because the size of chainring necessary to race on these would not fit on a bicycle, thats all.

IF YOU LIKE YOUR MTB if you can try putting 700c rims on your mountain bike and if dont already have one an aluminum crank set. Buy high pressure tires and you will see how "efficent" you bike becomes. Its just that a mtb position is comfortable and not too efficient. if you like it though you will see performance thats close to a "road" bike.

A 700C will draw a less current at the same voltage output to achieve the same speed that would be achieved with the same set-up with a 26" tire, assuming same tire/tread/tube, corrected for diameter.

To achieve the same amount of effective torque, (for a given motor, amount of current will determine how much torque) a 700C wheel will actually require MORE current. Which is really not a useful measure, because percentage-efficiency depends on voltage and current, not current alone.

With the same motor, a 700C wheel will have higher top speed than a 26" wheel, but the 26" wheel will usually have better range, especially if any steep uphills are required (where the 26" wheel's 4% higher torque/4% lower speed trade-off is an advantage).

The speed where you achieve peak-efficiency and peak-power for the 26" wheel is 4% slower.

cerewa you make this all sound so logical. Nice explanation! I guess this stuff has to be logical since Mother Nature gave birth to the concept of logic.

"an once of the wheels is worth 10 off the frame"

Dead wrong. This is a matter of simple (and very predictable) physics, but people treat it (and wheel size) like it's a matter of opinion and "feel".

An ounce off the tire or rim is worth 2 ounces off the frame in acceleration/braking and an ounce off the tire or rim is worth exactly the same as an ounce off the frame in terms of the effort required to move the bike uphill at constant speed.

If you don't believe me, consider this. You ride a bike on a trainer. You accelerate the rear wheel until the speed the rim/tire are moving is 20mph. 20mph in a circle, but 20mph nonetheless. Turns out that the energy that you have put in accelerating the rim and tire (after drivetrain-losses, air resistance, etc) is exactly the amount of energy you would have put in getting the rim and tire going 20mph in a straight line without rotating (like if you had a device that would throw them through the air).

When you accelerate a bicycle 0-20mph, you put in the amount of energy required to rotate the wheels and tires up to 20mph at the same time as you put in the amount of energy that would be required to move those wheels&tires the same speed without rotating them. In addition, you must of course put in the energy required to accelerate yourself and the not-wheels parts of the bike. And the energy required to rotate the cranks (and the rotating portion of your lower leg) up to a couple miles per hour (the gearing allows the cranks to not rotate fast even though the rims are). And overcome losses to various kinds of friction / air resistance.