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  1. #1
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    Road vs. Mtn efficiency

    So some random thoughts have been banging around in my head lately as to the roadie vs. mtb "debate" (for lack of a better word).

    Why is it that most people think road bikes are more efficient than mt. bikes?
    My personal vote is that they are not.

    Lets take an example, or situation, to explain my line of thinking:

    Lugged steel road bike with 105 components, bare wheels (no tires/tubes) in a repair stand.

    Lugged steel rigid mtb with XT components, bare wheels in a repair stand.

    Both bikes are highly tuned, meaning the hubs are properly lubed/adjusted, chain is in good nick and properly oiled, brake pads are not rubbing, derailleurs are finely tuned and adjusted.

    Should not the drivelines (hubs, gears, derailleurs and BB) all deliver about the same drag due to whatever accumulated friciton from seals or whatever?

    Now then, wouldn't the mtb with (probably) larger diameter tubing deliver the power from the crank to the rear wheel more effectively than the road bike with smaller diameter tubing?
    If so, this may only be a percent of a percentage point, right?

    So then, you put a 26 x 1.2 slick on the mtb, pumped up to 90 psi, and hit the road.

    You put an equal sized tire on the road bike, pumped up to 90 psi, and hit the road.

    Wouldn't the mtb deliver the power from the hub to the ground more efficiently than the road bike due to its shorter, and therefore stiffer (or more resistant to deflection, anyway), spokes?

    I've never been really comfortable on a road bike in spite of doing the Serotta fitcycle fitting exercises.
    I've always been more comfortable on a mtb. Don't know if its the longer top tube, or the more upright seating position, or what it is, but there it is.
    I know seating and positioning are paramount to comfort and therefore efficiency, so this point probably is moot in my argument.....

    At any rate, the drivetrain can't possibly offer up much difference between road and mountain.
    The wheels maybe but the only real difference I see is the diameter. Seems to me that the smaller diameter wheel would be more efficient, but then I'm no rocket scientist engineer type.

    The frame may account for some negligible difference as well, but, really, they're both about the same (at least when comparing apples to apples, i.e., steel to steel or carbon to carbon). Right?

    Any thoughts / comments?

  2. #2
    Single-serving poster electrik's Avatar
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    Two huge things going for road bikes.

    Aerodynamic position
    Seat further forward for better muscle recruitment.

    Both increase efficiency.

    On a mountain bike neither are recommended, aero positions are unstable and having your hips forward results in unstable handling.

  3. #3
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    Also, things are not ever equal like wheel diameter and size.

    The "road bike" we're talking about has a larger diameter and thinner tires. that means less effort to keep the wheel rolling by way of bigger tires, less drag both friction-wise and aerodynamically from the tire width.

    Also, i'm not riding a bike without tires. Road tires and made to roll faster, by way of compound used and lack of knobby tread. Mountainbike tires are made to be more grippy offroad, with "stickier" compounds and knobs.

    I would've just said troll right at first, but your post seems thought out, even if incorrectly.
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    I learned this the hard way. They say that experience is the best teacher, but I would have been preferred to just read about it on the internet.

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    The bike itself, in terms of the mechanics are equally as efficient. As you have mentioned the drivechain are very similar.

    However, you fail to take into account the motor and and what the bike is doing while travelling.

    The body position of a person on a bike allows greater pedal efficiency on a road bike. Road bikes are also generally lighter because they don't have to be made to withstand jumps and bumps.
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  5. #5
    Senior Member Nermal's Avatar
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    Quote Originally Posted by electrik View Post
    Two huge things going for road bikes.

    Aerodynamic position
    Seat further forward for better muscle recruitment.

    Both increase efficiency.

    On a mountain bike neither are recommended, aero positions are unstable and having your hips forward results in unstable handling.
    Thanks for confirming my own thoughts. I ride a hybrid that is nearly perfect for me, but that's just me.
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  6. #6
    Senior Member bigvegan's Avatar
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    "Why is it that most people think road bikes are more efficient than mt. bikes? My personal vote is that they are not."

    Because they are. You can rationalize your choices any way you want to, and come up with arguments that sound good, but very few people are winning road races on MTBs.

    "Wouldn't the mtb deliver the power from the hub to the ground more efficiently than the road bike due to its shorter, and therefore stiffer (or more resistant to deflection, anyway), spokes?"

    It doesn't matter, assuming, for the purposes of the argument, that there is any difference in spoke stiffness for that extra inch. The lighter weight of the road bike frame / components / rims / spokes / etc. allow the road bike to accelerate more quickly than the MTB, and the larger diameter wheels allow it to maintain that speed more easily. (You can find Brompton [EDIT: MOULTON] enthusiasts that will claim that their small-wheeled bikes are only kept from TDF victory by the UCI led conspiracy, but that's a whole other issue.)

    "I've always been more comfortable on a mtb. Don't know if its the longer top tube, or the more upright seating position, or what it is, but there it is."

    It's the upright seating position.

    "I know seating and positioning are paramount to comfort and therefore efficiency, so this point probably is moot in my argument....."

    No, seating and positioning are paramount to comfort OR efficiency. Very few of us would be comfortable for any length of time in the positions road racers maintain. This is why randonneurs and touring bikes are set up very differently from racing and track bikes.

    "At any rate, the drivetrain can't possibly offer up much difference between road and mountain."

    Yes, it most certainly can. At the basic level, most road bikes have higher gearing than most MTBs, which makes them faster on the flats and down hills. Then there's bottom bracket height, crank length, component weight, etc., etc., etc.

    "The wheels maybe but the only real difference I see is the diameter. Seems to me that the smaller diameter wheel would be more efficient, but then I'm no rocket scientist engineer type."

    No, there are additional differences between MTB and road bike wheels.

    "The frame may account for some negligible difference as well, but, really, they're both about the same (at least when comparing apples to apples, i.e., steel to steel or carbon to carbon). Right?"

    No. There's a reason MTBs and road bikes are built differently. The frames are built for fundamentally different purposes and are fundamentally, not negligibly, different.

    If you're more comfortable on an upright MTB / townie style bike, awesome. So are many of us. But accept that it's a personal preference, and that these bikes, for road riding, are, generally speaking, in no way faster or more efficient than road bikes.
    Last edited by bigvegan; 02-02-10 at 01:03 AM.

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    You have Bromptons mixed up with Moultons .There aint no Brompton guys even think TDF is doable in competition with Brompton that i know of. Now Moultons is a different story. Moulton still has a speed record thats not been broken from years back. Read history of Moultons, theres some merit to what you call conspiracy.
    But as you say thats a whole other issue.

  8. #8
    Insane Bicycle Mechanic Jeff Wills's Avatar
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    Quote Originally Posted by ddez View Post
    You have Bromptons mixed up with Moultons .There aint no Brompton guys even think TDF is doable in competition with Brompton that i know of. Now Moultons is a different story. Moulton still has a speed record thats not been broken from years back. Read history of Moultons, theres some merit to what you call conspiracy.
    But as you say thats a whole other issue.
    The Moulton speed record used a fairing to improve aerodynamics:
    http://members.localnet.com/~milliken/liner/
    http://www.moultonbuzz.com/2007/07/a...eeled-bicycle/

    This is in the "conventional upright position". The record for the equivalent recumbent bicycle is more than 30 mph faster.
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  9. #9
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    You're comparing apples to oranges with this. I have a 3 steel bikes, the geared road bike which is a lugged bike, the track bike and my mtb aren't lugged. Also you can't compare them on a repair stand, you don't get the full effect. Go out and do a 40 mile road ride on a road bike properly setup and you are feeling pretty good, the next day or so go out on the same 40 mile ride on a mtb set up and I am pretty sure that you would be feeling a bit spent from the effort. There's also the rolling resistance of a 26x1.2 tire, the amount of rolling resistance in a 26x1.2 tire is significantly more than what can be had on a 700x23c or in my case with the geared road bike, a 28x22(sew-ups). A 1.2inch wide tire equates to 30mm wide.

    Wheel size has a huge factor with it.

    Also you have to remember though, that mountain bikes are designed to be efficient offroad, which is a completely different beast than road efficiency. All in total, if you want to be efficient on the road, get a road bike or a flatbar bike, like a trek fx.
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  10. #10
    Alfredo Contador |3iker's Avatar
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    If only Lance Armstrong rode a Kona Hei Hei at TDF, he'd snatch the yellow jersey from Contador last year!!!!

  11. #11
    Share The Road bent eagle's Avatar
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    Interesting thought experiment, but what does the theoretical mountain bike weigh compared to the road bike? Like 10 lbs. more?
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    Didn't think I was a troll, thanks for not labeling me one. I spent 7 years as a mechaninc in bike shops from Colorado to California, so have some experience with bikes. Just not a lot of experience with road bikes.
    You all have brought up many points I did not (obviously) consider.
    Yeah, if mtbs were as efficient as road bikes, then I suppose you'd see a lot more at the TdeF (damn UCI conspiracy is right!).

    I guess my main train of thought was that the drivetrain, (chain, hubs, cranks) more than anything, would be more or less equal road vs. mtn.

  13. #13
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    I ride both on a regular basis. For every pedal stroke, the road bike travels further them the mt bike due to bigger wheels.

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    Quote Originally Posted by Smokinapankake View Post
    Why is it that most people think road bikes are more efficient than mt. bikes?
    Assuming one is using similar tires and both have similar weights, the efficiency (energy required to move it at a particular speed) is probably fairly close at low speeds.

    At higher speeds, aerodynamics becomes much, much more of an issue (it overwhelms drive train losses). MTBs either don't have to worry about aeodynamics OR their design trades-off aeodynamics for other reasons (eg, control).

    Quote Originally Posted by Leebo View Post
    I ride both on a regular basis. For every pedal stroke, the road bike travels further them the mt bike due to bigger wheels.
    This is a gearing issue: you are not using equivalent gears.
    Last edited by njkayaker; 02-02-10 at 10:49 AM.

  15. #15
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    Vehicle:
    Speed at 100 watts of power
    Speed at 150 watts of power
    Speed at 200 watts of power
    Critical Power speedbike
    45 kph (28 mph)
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    Aerodynamics plays a big part in bicycle efficiency. Weight is also a factor as is power loss due to suspension. But this chart shows how position, weight and aerodynamics effect efficiency in the real world of cycling.

  16. #16
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    My Mountain bikes are efficient- so are my road bikes. Same motor so not a great deal of variance there unless you want to say so.

    I will not ride my Road bikes offroad because they do not work in that situation. I can change the gearing- tyres and put on stronger wheels but they will not be efficient.

    I do ride my MTB's on the road but that is only to get to the offroad. Lower gearing- heavier overral weight- suspension that saps energy and smaller wheels with chunky tyres mean that they are hard work on the road- in comarison to a road bike.

    Before I went road- I used to do 100milers on the road (And Offroad) on the MTB's. Lower the bars- fit narrower slick tyres and possibly change the cassette to give me closer ratios gears. Never had a problem. These bikes worked on the road. Then I got a road bike at about 1/5th the value of my MTB and sorry---- Mtb's do not work on the road.
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  17. #17
    Bike ≠ Car ≠ Ped. BarracksSi's Avatar
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    Quote Originally Posted by Smokinapankake View Post
    Didn't think I was a troll, thanks for not labeling me one. I spent 7 years as a mechaninc in bike shops from Colorado to California, so have some experience with bikes. Just not a lot of experience with road bikes.
    Get a road bike that fits you (bet you could just borrow one of the shop's, if you still work at one) and go on a road ride, then do the same ride using your MTB.

    As they say, "All will become clear."

    I've gone the same routes on a Cannondale Bad Boy (MTB frame with skinny slicks) and a CAAD8 road bike. Because I'm not strong enough to spin out the top gear ratio of each bike while on the flats, I can say that the primary difference was body position.

    Compared to the Bad Boy, I can go faster for the same effort, or the same speed with less effort, on the road bike. Because of that efficiency (and because of the variety of hand positions available), I always take the road bike if I'm planning a longer ride.

  18. #18
    Senior Member DieselDan's Avatar
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    Quote Originally Posted by Leebo View Post
    I ride both on a regular basis. For every pedal stroke, the road bike travels further them the mt bike due to bigger wheels.
    Right on the money Leebo. The OP failed to recognize the wheels itself as a gear. MTBs usually cannot get close the same gear as a road bike, even the 29"(622mm rim) wheels, as the frame of an MTB may restrict the chainring to 48 teeth.
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  19. #19
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    I've ridden my cyclocross bike with mountain bikers before on fire trails. And even with 32mm dirt tires, my bike was much faster: and by this I mean that downhills, when everyone was just coasting and no one used their brakes at all, I'd pass many mountain bikers. And this is with me on the hoods - if I was to get into the drops, I'd have been even faster. In other words, the aerodynamic advantage makes a huge difference.

  20. #20
    Bike ≠ Car ≠ Ped. BarracksSi's Avatar
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    Quote Originally Posted by DieselDan View Post
    Right on the money Leebo. The OP failed to recognize the wheels itself as a gear. MTBs usually cannot get close the same gear as a road bike, even the 29"(622mm rim) wheels, as the frame of an MTB may restrict the chainring to 48 teeth.
    Nah, I don't buy it. But, I also don't count downhill speeds as an indicator of pedaling efficiency, either.

    If a rider takes a MTB, puts it on the big ring and small cog, and can spin his legs well past 100-120 rpm on flat ground to get near 30 mph, then he's maxing out the possible human-powered speed of the bike-and-rider combination. IMO, that's the point where taller gearing makes a difference -- not in efficiency, but in top speed capability.

    Use the equivalent ratio on a road bike, and it'll be easier for the rider to spin the same cadence and/or maintain the same speed. That's a certain indicator of efficiency.

    26" vs. 700c wheel diameters don't matter as much as people seem to think, either. At least not when big, fat MTB tires are being used -- my MTB's 2.whatever" tires are nearly as tall as my road bike's 23mm tires.

  21. #21
    Senior Member DieselDan's Avatar
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    Quote Originally Posted by BarracksSi View Post
    Nah, I don't buy it. But, I also don't count downhill speeds as an indicator of pedaling efficiency, either.

    26" vs. 700c wheel diameters don't matter as much as people seem to think, either. At least not when big, fat MTB tires are being used -- my MTB's 2.whatever" tires are nearly as tall as my road bike's 23mm tires.
    Really? You sure? Your big beefy MTB tires may seem to be as bike as my skinny road bike tires, but your have tons more rolling resistance ripping your precieved efficiency away.

    If you think the difference in wheel diameters isn't much, learn to use pi.
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  22. #22
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    Wow

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    Bike ≠ Car ≠ Ped. BarracksSi's Avatar
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    Quote Originally Posted by DieselDan View Post
    Really? You sure? Your big beefy MTB tires may seem to be as bike as my skinny road bike tires, but your have tons more rolling resistance ripping your precieved efficiency away.

    If you think the difference in wheel diameters isn't much, learn to use pi.
    Stand your road bike wheel and tire next to your mountain bike wheel and tire (assuming it's got knobbies) and then tell me that they're not close to the same height.

    Do I need to take pics of mine, or what?

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    He was talking about slicks, not wide knobbies, but for the record:

    tire size ISO # Circumference
    26 X 1.25 32-559 1953mm
    26 X 2.125 54-559 2070mm
    700 X 23 23-622 2097mm

    But this isn't nearly the whole story when it comes to rolling resistance, aerodynamics, etc.

  25. #25
    Banned. Mr. Beanz's Avatar
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    Quote Originally Posted by Leebo View Post
    I ride both on a regular basis. For every pedal stroke, the road bike travels further them the mt bike due to bigger wheels.
    Not true! I ride the 39 ring on my roadie a large percentage of the time. I can't count the times I have met riders in the 53 ring that can't kep up while I spin a smaller gear.

    I once encountered a guy on an mtb that made a comment as I rolled by, "I could keep up with you if I had big gears like your roadie"...I had to slow down for that one to show that it had nothing to do with the fact that I had bigger gears, because I wasn't using them. He was pounding his MTB 42/13 while I was spinning in my 39/14. Had nothing to do with the gear and the amount of travel with each a pedal stroke.

    I agree with stapfam, MTB's are designed for offoad and roadies for road riding. Each has it's own use. I'm really surprised there aren't more reversed comparison thereads "Is a roadie just as efficient as an mtb while climbing in mud, sand, dirt and rock at 26 % inclines" That would be about as silly as these mtb efficient as roadies on the road threads.
    Last edited by Mr. Beanz; 02-06-10 at 12:32 PM.

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