# what makes the mountain bike much slower than a road bike?



## cannondalejohn (Jul 4, 2009)

hi guys, i know this is a really simple qn. cos my nephew who is in school has been instructed to write an essay on this topic and to compare how they are built different and what makes the mountain bike much slower.

Thus he asked me, and i replied him these;

1. the tires are bigger?

2. the geometry is more slack, thus not so aerodynamic

3. they are heavier

4. the chain ring has fewer teeth

er..

is there anything else i missed out?

thks guys!


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## Dictatorsaurus (Sep 11, 2009)

tire thread pattern


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## Punkeyboozter (Mar 31, 2009)

beer belly's


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## Flystagg (Nov 14, 2006)

The rider, and....


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## emptybe_er (Jan 15, 2006)

...terrain.


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## CaveGiant (Aug 21, 2007)

Don't forget the softer tyre compounds.

The air drag only comes into effect at higher speed.

Geometry generally isn't slacker, slack geometry makes a bike more stable at high speeds.
weight only affects acceleration, not top speed.

I Ride a Niner WFO on Schwalbe big apples, I can take most road riders without trying.

Don't forget suspension taking power out of the hard stokes.

oh and tyre pressure.

Riding stouts I literally knock 10mph off my top speed from the apple


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## CaveGiant (Aug 21, 2007)

rotating weight of wheels for acceleration too.


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## emtnate (Feb 9, 2008)

The gear ratios are the main reason road bikes are faster.


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## dnlwthrn (Jan 26, 2006)

Physics.....

Less mass, larger gear ratios, smaller contact patch (less rolling resistance), and a more aero position all lend to road bikes being "faster" than mtbs.

And CaveGiant, the point isn't about road "riders" being faster than mountain "riders," its about road BIKES needing less effort to go fast than mountain BIKES. If you were on a 16lb road bike, you'd be able to dust those "road riders" that you pass on your Niner even more easily...


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## C Dunlop (Sep 26, 2008)

Any decent roadie on the flat could easily spin a 53-14/15 gear at 90+ cadence (pretty cruisy). This is about 43km/h. This is on the equivalent of a 26 inch MTB is about 105 cadence (a lot) in your 42/11 gear. In other words, in order to keep up with a roadie (who is just riding tempo) you would have to spin the f*#k out of your highest gear. The roadie can hold a conversation at this point, the MTB rider is into oxygen debt (ie cannot sustain this pace).

The reasons why you can't get to this speed are a combination of (a) not high enough gearing, (b) high rolling resistance on wide and knobby tyres and (c) wind resistance. Weight is a minor factor that only really comes into play on climbs. For example, on a 1 hour hillclimb assuming uniform power output (260w or so) at 8% gradient there is a loss of about 1.2 seconds per oz (28g).

For example, if a road and moutain bike arre climbing an 8% paved road, and start together, climb for one hour, and the road bike weighs 7kg and the mtb (hardtail to remove suspension bob losses) weighs 10kg, plus 2kg of camelback and water, plus say 1kg of heavier equiptment that MTB riders carry the road rider will end ~257 seconds ahead of the MTB rider(assuming 250w at 17km/h). This is a rough and ready set of calculations, but it gives a general outline of the weight factor.

I call BS on the guy who 'can easily take most roadies'. The fact is that on the road, road bikes are 15-20 km/h (+) faster for similar effort. Sure, that doesn't mean you can't burn your legs up and overtake an old guy or two, but a typical road ride lasts about 2 1/2 hours. Road riding is mostly about sitting back and riding tempo. I used to think I 'could take roadies' until I actually started counting. You tend not to notice the ones that zip by you, and make it some kind of personal victory when you do overtake somone who in truth is probably warming up or spinning down. You also don't even see the vast majority who start ahead of you and stay ahead. That is to say, it doesn't count if they are not racing. If they were, then they would call an early end to their warm up, put it into the big dog and ride away into the sunset, leaving the MTB rider to wallow in a heap of lactic acid.

weight only comes into play in acceleration and up hills, not maximum speed. Maximum speed on the flat is determined by wind resistance, power, gearing and rolling resistance.

This is a table of road tyres in rolling resistance tests. As you can see there is even quite a difference between road tyres. Tubes even make a small difference!

MTB tyres are even more diverse, but I cannot see any one MTB tyre being more efficient that any one road tyre. Wide and grippy tyres = slow. Small wheels also have some impact as bearing resistance comes into play (small wheels have to turn more times per metre travelled and bearing resistance increases exponentially with the number of revolutions per minute).

aerodynamics is a very big factor. to demonstrate this, get a road bike and a mountain bike and put the two on a trainer and do standing start to, say, 40km/h accelerations. The results will be about the same.

However, for the sake of a child's science assignment I would keep it simple. Stress the following: Power output - wind resistance - weight - rolling resistance. Then a breif explanation of gearing ratios. Just for reference, a typical geared MTB setup is 22-32-42 chainrings with something like a 12-28 cassette. A typical road setup is 39-53 with an 11-25 cassette. A conclusion to the report/presentation could be along the lines of design specificity. While on flat, straight road conditions a road bike will perform better, off road, with poor traction, over uneven terrain, a moutain bike will be faster than a road bike.

The question of what is faster in a straight line is not relevant. Neither bike is designed for that purpose (that is a time trial bike). Rather, it is a matter of designers assessing the needs for a product, applying physics and making two different products to meet different conditions.


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## CaveGiant (Aug 21, 2007)

Calling BS on me?

Just because you cannot do it doesn't mean others can.
Don't forget I am on road tyres.


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## PscyclePath (Aug 29, 2007)

First and foremost -- It ain't the bike, it's the motor ;-)

Mechanically, the extra weight of the MTB, lower gearing, and the increased rolling resistance of the wheels (wider, knobby tires as well as lower tire pressure) will make the bike slower than a road bike for the same amount of pedaling effort.


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## deftones156 (Sep 12, 2008)

PscyclePath said:


> First and foremost -- It ain't the bike, it's the motor ;-)


Very true. However, I have seen a LOT of people on this site claim that they can smoke roadies on their MTBs even with knobbies on. I'm sure some can, and I KNOW some are full of BS.

And as C Dunlop stated, you often don't really know if that person you "smoked" was warming up, cooling down, or had already ridden for 50 miles. Or maybe they are doing intervals...

It's like being able to bench press "more" than that big guy in the gym who might have already done 5 sets before you came in.


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## dnlwthrn (Jan 26, 2006)

CaveGiant said:


> Calling BS on me?
> 
> Just because you cannot do it doesn't mean others can.
> Don't forget I am on road tyres.


If this was pointed at me, the answer is no. I was merely stating that you, on a true road bike, with road gearing (50/34 or 53/39 chainring) are going to be able to go faster than you already can on your 29er mtb with 44T chainring. Its simple physics. Also, your "road" tires are what, 1.5" width? Throw a true road tire (23cm wide) on a true road rim, and you'll be able to go even faster. You'll see an instant increase in speed relative to power (or a instant decrease in power needed to go the same speed) by swapping to a road wheelset.


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## nachomc (Apr 26, 2006)

Can we define the context of "faster" for the purposes of the essay? Put a mountain bike and a road bike on a rocky downhill, and the road bike isn't so fast . Put a mountain bike and a road bike on a flat paved road, and my money is on the road bike, given equal rider strength/fitness.


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## louisssss (Jun 24, 2009)

you're comparing two different beasts, the road bike is faster on THE ROAD, the mountain bike is faster on THE MOUNTAIN. you're comparing apples to oranges. Why not ask why the road bike is slower than a mountain bike (when taken on a trail)

they both have their purposes and are aces at that.

pretty simple concept


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## CHUM (Aug 30, 2004)

what about 'cross' bikes?....best of both worlds?...or the worst?


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## BumpityBump (Mar 9, 2008)

CaveGiant said:


> I Ride a Niner WFO on Schwalbe big apples, I can take most road riders without trying.


Noobs inter-braggin' on the beginner forum.

Every time I check this forum, I get to chuckle. Thanks

Now where's a phone and BS's number. I have to make a call....


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## siwilliams (Jul 23, 2009)

CaveGiant said:


> Calling BS on me?
> 
> Just because you cannot do it doesn't mean others can.
> Don't forget I am on road tyres.


mmmm, my P.O.S., (and heavy Apollo MTB with slicks blows away my Scale with knobblies on the road. My undersized, unloved, elderly Peugot road bike leaves them both for dead. Same rider, different bikes. The tires are definitely the main difference - the Apollo has low level, well worn components and is heavier than the brand new, well fitting Scale but still rolls much faster.


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## Dugg-E (Jul 9, 2009)

you're assisting your nephew in cheating....:nono: lol


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## BigSharks (Oct 4, 2009)

I always thought it was all the spandex that made them faster...


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## louisssss (Jun 24, 2009)

CaveGiant said:


> Don't forget the softer tyre compounds.
> 
> The air drag only comes into effect at higher speed.
> 
> ...


this isn't an epenis contest, we're talking about why road bikes are faster than mtbs on the road.

it doesn't matter what you ride, how fast you are, how how big your dick is, a road bike is faster than a mountain bike on the road.


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## osmarandsara (Jun 26, 2006)

C Dunlop said:


> Any decent roadie on the flat could easily spin a 53-14/15 gear at 90+ cadence (pretty cruisy). This is about 43km/h. This is on the equivalent of a 26 inch MTB is about 105 cadence (a lot) in your 42/11 gear. In other words, in order to keep up with a roadie (who is just riding tempo) you would have to spin the f*#k out of your highest gear. The roadie can hold a conversation at this point, the MTB rider is into oxygen debt (ie cannot sustain this pace).
> 
> The reasons why you can't get to this speed are a combination of (a) not high enough gearing, (b) high rolling resistance on wide and knobby tyres and (c) wind resistance. Weight is a minor factor that only really comes into play on climbs. For example, on a 1 hour hillclimb assuming uniform power output (260w or so) at 8% gradient there is a loss of about 1.2 seconds per oz (28g).
> 
> ...


Hey cannondaleJohn, get your nephew to just cut and paste this and his paper is done :thumbsup:


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## Brodino (Sep 15, 2008)

My opinion is that cross bikes are the worst of both worlds. Built to operate in both but excel at none...


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## CHUM (Aug 30, 2004)

Hill_Lover said:


> My opinion is that cross bikes are the worst of both worlds. Built to operate in both but excel at none...


well 'hrmph' to you sir...rft:


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## CroMoHo (Oct 20, 2009)

I think it must be because mountain bikes are *cooler*. Have you ever noticed how all the super *cool* cars on the street are just cruisin' along all chill-like? You know, like those old hot rod roadsters that have the flames painted on them and stuff. Then you got the cocky chumps that drive around in the tuner cars and they're always flying around corners and racing side by side with their mufflers fartin'. I don't know, something about them kind of reminds me of road bikes, and well....roadies. Deffinately *NOT* cool.
After all, this is MTBR Forums, not roadbike forums right? So if you're a roadie and now you're all mad because you just read this, just remember, I'm allowed to say it because this forum was created for mountain bikers, not roadies! 
Anyways, *cooler *things just have to move *slower*. It's like some kind of law or something.


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## jalopy jockey (Jun 7, 2007)

CaveGiant said:


> Calling BS on me?
> 
> Just because you cannot do it doesn't mean others can.
> Don't forget I am on road tyres.


Dude you just don't get it do you. I once smoked a dude on a Madone while towing my 2 kids on my 1st mountain bike a 15 year old . We chatted as I passed. he was in for a 30 mile ride I was doing 40 or so on a rail trail, so out and back. I passed him a couple miles in saw him again after I turned around still heading out. I sure smoked than ancient roadie.

A strong cyclist is a strong cyclist, and will smoke a weak one. But the bike will play a role.


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## CaveGiant (Aug 21, 2007)

Hi,

My point was the main factor above and beyond anything else is tyre drag.
With road tyres I can overtake roadies even though on a 6 inch FS. With mtb tyres, I get left for dead.

My second point was the big willy.


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## perttime (Aug 26, 2005)

If you want performance, pick the right tool for the job.

Same difference:
http://www.scotoffroad.co.uk/pictures.html
vs.
http://www.porsche.com/usa/models/boxster/boxster-s/webspecial/


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## CaveGiant (Aug 21, 2007)

perttime said:


> If you want performance, pick the right tool for the job.
> 
> Same difference:
> http://www.scotoffroad.co.uk/pictures.html
> ...


Cyclocross =-) can't do anything well

http://www.porsche.com/microsite/cayenne-transsyberia/usa.aspx


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## perttime (Aug 26, 2005)

Oh, a cyclocross bike does some things quite well.

Just like my 1998 Audi A3 does some things quite well 
(no good for off-road or racing on a track for sure...)


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## Ken in KC (Jan 12, 2004)

*I disagree...*



CaveGiant said:


> Hi,
> 
> My point was the main factor above and beyond anything else is tyre drag.
> With road tyres I can overtake roadies even though on a 6 inch FS. With mtb tyres, I get left for dead.
> ...


It is a factor but not the main factor....


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## Punkeyboozter (Mar 31, 2009)

blumarvel said:


> I think it must be because mountain bikes are *cooler*. Have you ever noticed how all the super *cool* cars on the street are just cruisin' along all chill-like? You know, like those old hot rod roadsters that have the flames painted on them and stuff. Then you got the cocky chumps that drive around in the tuner cars and they're always flying around corners and racing side by side with their mufflers fartin'. I don't know, something about them kind of reminds me of road bikes, and well....roadies. Deffinately *NOT* cool.
> After all, this is MTBR Forums, not roadbike forums right? So if you're a roadie and now you're all mad because you just read this, just remember, I'm allowed to say it because this forum was created for mountain bikers, not roadies!
> Anyways, *cooler *things just have to move *slower*. It's like some kind of law or something.


You meen like this?








and this? 








I know what id rather have?


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## Punkeyboozter (Mar 31, 2009)

CaveGiant said:


> Cyclocross =-) can't do anything well
> 
> https://www.porsche.com/microsite/cayenne-transsyberia/usa.aspx


how is this for a cyclocross in comparison?


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## Punkeyboozter (Mar 31, 2009)

perttime said:


> Oh, a cyclocross bike does some things quite well.
> 
> Just like my 1998 Audi A3 does some things quite well
> (no good for off-road or racing on a track for sure...)


ok so i like cars as well, but this one is to make pertime happy..im sure with the right gear it will work just fine on the track.


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## perttime (Aug 26, 2005)

Punkeyboozter said:


> im sure with the right gear it will work just fine on the track.


But then it wouldn't be quite so handy around town, quite so comfortable driving all day, or quite so steady on a dirt road.

And M/S rated tires would look weird on it (that is what mine has now, waiting for the snow)


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## emtnate (Feb 9, 2008)

CaveGiant said:


> Cyclocross =-) can't do anything well
> 
> http://www.porsche.com/microsite/cayenne-transsyberia/usa.aspx


Have you ridden a cross bike? I disagree.

Also you have missed the point of this thread. Assuming you can blow by any roadie on your 6" bike, try something.

Make a course on the road and warm up. Assuming you can but identical effort 2 laps in a row. Run a lap on the 6" bike and run a lap on a road bike.

For equal effort, the road bike will be faster every time. It is all about the gear ratios.


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## Flystagg (Nov 14, 2006)

Gearing is definitly not the main factor, who can honestly say that for the majority of a ride they are spinning out a 44 11 on flat ground? My nobby tires keep me in about 44 13-15. put road geaing on a mountain bike it will still be slower.


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## JPark (Aug 12, 2009)

Flystagg said:


> Gearing is definitly not the main factor, who can honestly say that for the majority of a ride they are spinning out a 44 11 on flat ground? My nobby tires keep me in about 44 13-15. put road geaing on a mountain bike it will still be slower.


100% correct. In order to go faster on the road you must overcome one thing only, friction.
Friction from the air, the contact with the ground(tires), wheel bearings, and drivetrain.
A road bike is more efficient in all these areas, and because of this, the higher gears are needed.


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## louisssss (Jun 24, 2009)

CaveGiant said:


> Hi,
> 
> My point was the main factor above and beyond anything else is tyre drag.
> With road tyres I can overtake roadies even though on a 6 inch FS. With mtb tyres, I get left for dead.
> ...


get over yourself... nobodys asking anyone here if they're faster than a road biker. 
epenis + 1 for you being so fast


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## tkerr (Oct 12, 2009)

"Anyways, cooler things just have to move slower. It's like some kind of law or something"

you just might have a point there blumarvel. Damned if I ain't cool then 'cause I'm sure slow


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## Ken in KC (Jan 12, 2004)

*I disagree...*



JPark said:


> 100% correct. In order to go faster on the road you must overcome one thing only, friction.
> Friction from the air, the contact with the ground(tires), wheel bearings, and drivetrain.
> A road bike is more efficient in all these areas, and because of this, the higher gears are needed.


A transmission trumps tires.

A 6 cyl sports car with a transmission geared for upper end speed will go faster than a 6 cyl truck, regardless of tires.

A bike with a larger upper end gear ration will go faster than a bike with a fewer upper end gears, regardless of tires.


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## JPark (Aug 12, 2009)

*??????????????????*



Ken in KC said:


> A transmission trumps tires.
> 
> A 6 cyl sports car with a transmission geared for upper end speed will go faster than a 6 cyl truck, regardless of tires.
> 
> A bike with a larger upper end gear ration will go faster than a bike with a fewer upper end gears, regardless of tires.


Can you honestly say that you can consistently spin out a 42x11 on a mtb with knobby tires?
If so, maybe you are in the wrong line of work. You should move to Europe and race pro road.
Yes, if you can push a larger gear at the same cadence, you will go faster.
But, for those of us mere mortals, the only way to be able to do this we need all the help we can get.
Road bikes are much more efficient at overcoming friction and therefore can justify a larger gear combo.
With your logic, pro roadies would be using chainrings that would only be limited by actual size(as not to scrape the ground)
In reality most never go beyond 53t.


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## siwilliams (Jul 23, 2009)

Ken in KC said:


> A transmission trumps tires.
> 
> A 6 cyl sports car with a transmission geared for upper end speed will go faster than a 6 cyl truck, regardless of tires.
> 
> A bike with a larger upper end gear ration will go faster than a bike with a fewer upper end gears, regardless of tires.


I think there's some other reasons why a sports car will go faster than the truck!

At some point on a bike you will be limited by fiction, yes higher gears will stop you spinning out but ultimately friction will limit your speed. Most of the friction is from air and tires. Running slicks mean more of your power can be aimed at air friction.


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## 006_007 (Jan 12, 2004)

siwilliams said:


> I think there's some other reasons why a sports car will go faster than the truck!
> 
> At some point on a bike you will be limited by fiction, yes higher gears will stop you spinning out but ultimately friction will limit your speed. Most of the friction is from air and tires. Running slicks mean more of your power can be aimed at air friction.


Here is a truck that does a 10sec 1/4..............


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## tduro (Jan 2, 2007)

Ken in KC said:


> A transmission trumps tires.
> 
> A 6 cyl sports car with a transmission geared for upper end speed will go faster than a 6 cyl truck, regardless of tires.
> 
> A bike with a larger upper end gear ration will go faster than a bike with a fewer upper end gears, regardless of tires.


Ken, I know you know better than that. Neither of your statements is universally true, as you make them sound.

What if the truck had greater displacement and horsepower? That could easily trump transmission. Number of cylinders means nothing.

What if a bike had such high gear ratios that it couldn't be pedaled efficiently? The other bike would win. What if the gear ratios were the same? Then tires would matter.


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## dysfunction (Aug 15, 2009)

JPark said:


> 100% correct. In order to go faster on the road you must overcome one thing only, friction.
> Friction from the air, the contact with the ground(tires), wheel bearings, and drivetrain.
> A road bike is more efficient in all these areas, and because of this, the higher gears are needed.


There's also wind resistance, the riding position is not as efficient at that on a mtb as it is on a road bike. Ride both on a windy day and *this* is what I notice the most. Even with the 700cx30 road tires. I notice gearing differences through hills.


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## gumbymark (May 25, 2007)

Ken in KC said:


> A transmission trumps tires.
> 
> A 6 cyl sports car with a transmission geared for upper end speed will go faster than a 6 cyl truck, regardless of tires.
> 
> A bike with a larger upper end gear ration will go faster than a bike with a fewer upper end gears, regardless of tires.


I disagree with your disagreement.

Using Sheldon Browns' (RIP) fancy gear inch calculator (found here) at a cadence of 100 rpm a bicycle with 26 X 2.125 tires and 175mm cranks will be doing 49.7 kmph (30.9 mph) in the 44 - 11.

Lower mtb gearing will NOT limit your speed you until you run out of gears (on the flat obviously). BTW most experienced should be able to hold (for a short period) 120 rpm which maxes the bike out at 59kmph.

In summing up - unless you are riding along a flat road at 60 kmph (37 mph) and are trying to shift into the next gear (that you don't have) your gearing is not slowing you down.


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## carrot_top (Aug 22, 2007)

Ken in KC said:


> A transmission trumps tires.
> 
> A 6 cyl sports car with a transmission geared for upper end speed will go faster than a 6 cyl truck, regardless of tires.
> 
> A bike with a larger upper end gear ration will go faster than a bike with a fewer upper end gears, regardless of tires.


dont forget to take into account that the engine of a truck and a car arent the same...the truck's engine will have more low end torque than the 6cyl car engine....also, trucks will generally have larger engines as well....you could have a 5 liter truck engine, and a car will have something more like a 3.2 or something like that....so comparing the two based only on the gear ratios wouldnt be very accurate.....(then theirs weight, wind resistance, and all those other things to take into account)

as for the bike gears....back before i replaced my 3rd ring with a bash guard, i tried to see if i could spin out while on the top gear of my bike....i couldnt....wind resistance and friction wouldnt allow me.....so what if i had a road bikes gear ratios?.....if i couldnt pedal out in the top gear of my MTB gears, what makes you think having a couple more to go means i could go so much more faster? It would be the equivalent of (if your in a car, trying to go as fast as possible) shifting to 6th gear before your 1/2 way through 1st...(although since car engines dont get tired, it eventually would reach top speed, but it would take a hell of a long time)

besides..dont you think if we could go faster w/ road gears, wouldnt all us MTB'ers be spinning 53 tooth chainrings w/ road cassettes by now?


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## cannondalejohn (Jul 4, 2009)

*thks!!*

thanks guys for all the help and input given in here..

i am just wondering with all the physics behind it,

how did this guy win a road race on his mountain bike?? it just seems really impossible

http://www.bikeradar.com/news/article/mountain-biker-wins-road-race-on-his-hardtail-22736


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## CaveGiant (Aug 21, 2007)

cannondalejohn said:


> thanks guys for all the help and input given in here..
> 
> i am just wondering with all the physics behind it,
> 
> ...


Guess the engine has a lot to do with it as well =-)


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## CaveGiant (Aug 21, 2007)

louisssss said:


> get over yourself... nobodys asking anyone here if they're faster than a road biker.
> epenis + 1 for you being so fast


I am trying to work out if people really are this stupid, or if he is attempting sarcasm?

I am guessing the former, but one can never tell


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## Flystagg (Nov 14, 2006)

cannondalejohn said:


> thanks guys for all the help and input given in here..
> 
> i am just wondering with all the physics behind it,
> 
> ...


Have you ever watched a competative road race with more than say 20 riders? They don't spread out and try and out sprint each other the whole race, the bunch up and all draft each other, thats how the mountain bike can compete, if you can lock onto a roadies wheel you will be able to keep up even on a nobby tired all mountain bike. The guy on the mountain bike just let the roadies pull him the whole race, then out sprintied them at the very end. Still damn impressive though, but if it was a time trial there would be no chance in hell to pull off a win.


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## LWright (Jan 29, 2006)

Tire grip and wheel size.
Low pressure knobbies roll slower than high pressure road tires.
700 (or 29) rolls faster than 26


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## louisssss (Jun 24, 2009)

CaveGiant said:


> I am trying to work out if people really are this stupid, or if he is attempting sarcasm?
> 
> I am guessing the former, but one can never tell


wait what? you're going so fast i can't hear you


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## jahfakin (Sep 26, 2009)

between hitting the trails, I run 700cx35 on my 29er. It's still slower than a road bike, because it only has a 42x11 gearing. but it makes running errands a bit more easier.


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## Ken in KC (Jan 12, 2004)

*Okay....*



JPark said:


> Can you honestly say that you can consistently spin out a 42x11 on a mtb with knobby tires?
> If so, maybe you are in the wrong line of work. You should move to Europe and race pro road.
> Yes, if you can push a larger gear at the same cadence, you will go faster.
> But, for those of us mere mortals, the only way to be able to do this we need all the help we can get.
> ...


First, let's be very clear: I'm in no way saying that I spin out on either a road or mountain bike.

I also agree with tires are important. What I disagree with is that tires on a road bike are the primary reason why mountain bikes are slower on the road than road bikes. There are multiple factors that impact. I still feel that the transmission is more important than tires.

With all things other than the gear set being equal, you'll go faster using less energy with a road cassette vs. a mountain cassette.

With all things being equal other than the tire width, you'll go faster using less energy with a thinner tire vs. a thicker tire.

Which is *most* important? I think it can be discussed both ways.


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## 4slomo (Jul 4, 2006)

Is there a concensus that a mountain bike is also slower than a road bike off-road?


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## louisssss (Jun 24, 2009)

4slomo said:


> Is there a concensus that a mountain bike is also slower than a road bike off-road?


yes, unless cavegiant rides it, lol


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## CaveGiant (Aug 21, 2007)

=-)


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## JPark (Aug 12, 2009)

Ken in KC said:


> First, let's be very clear: I'm in no way saying that I spin out on either a road or mountain bike.
> 
> I also agree with tires are important. What I disagree with is that tires on a road bike are the primary reason why mountain bikes are slower on the road than road bikes. There are multiple factors that impact. I still feel that the transmission is more important than tires.
> 
> ...


When you first brought up the point about higher gear ratios I did not agree, but I could understand where you were coming from. I still feel that a higher gear ratio on a mtb with knobby tires is not an advantage at all. Unless you are on a 100% downhill slope, or have superhuman strength and endurance, the 42x11 combo that most mtb's are equipt with is more than sufficient.
But now you're talking cassettes, you do realize the top gear ratios on road and mtb cassettes are identical...don't you


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## siwilliams (Jul 23, 2009)

Ken in KC said:


> First, let's be very clear: I'm in no way saying that I spin out on either a road or mountain bike.
> 
> I also agree with tires are important. What I disagree with is that tires on a road bike are the primary reason why mountain bikes are slower on the road than road bikes. There are multiple factors that impact. I still feel that the transmission is more important than tires.
> 
> ...


Lets be very clear, if you were to swap *one *part on any given bike, the part than can make the most difference to your speed is the tires!

Sure, you could make you gearing stupidly low and spin out thus limiting your speed but with standard MTB clusters you'll still be better changing the tire to get more speed.


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## s0ckeyeus (Jun 20, 2008)

...the mountain?


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## Uncle Six Pack (Aug 29, 2004)

Funny topic.... not once have I ever been passed by a guy on a road bike. Actually, come to think of it, I never even see a road bike when I am on my mountain bike.


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## alkemyst (Sep 30, 2009)

less spandex and more leg hair.


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## davidbeinct (Dec 6, 2007)

Uncle Six Pack said:


> Funny topic.... not once have I ever been passed by a guy on a road bike. Actually, come to think of it, I never even see a road bike when I am on my mountain bike.


That's good, because from threads I've read on this site, their reaction to seeing mountain bikes will be somewhere along the lines of either: a) not waving, or b) stealing your firstborn; both of which, again from threads I've read here, are about equally despicable.

David B.


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## AndrwSwitch (Nov 8, 2007)

siwilliams said:


> Lets be very clear, if you were to swap *one *part on any given bike, the part than can make the most difference to your speed is the tires!


Am I allowed to change my handlebars, or does it not count because I'd need to change out some other parts for compatibility?

I don't remember where I found the statistics, and obviously they're dependent on speed. However, the biggest source of resistance on a bike ridden on pavement or a smooth fire road is air. Most air resistance comes from the rider. Being able to get into a good aero tuck makes a huge difference. I think I start to notice it as low as 12mph, and certainly by 15. That's part of why pro time trialists can put a 55-tooth big ring on their TT bikes and actually use it - they're in an even better tuck than a guy down low in the drop bars.

Rolling resistance is certainly important too. If the bikes are competing on a fire road climb, I think the mountain bike would be faster than the road bike due to the improved grip letting the rider apply more power, stand up at times, etc. I think a 'cross bike would trump them both, though - enough grip for fire roads, but less rolling resistance and without extra weight from suspension. FWIW, they're not the worst of both worlds - on a 'cross course, most mountain bike knobbies are a lot fatter and heavier than they need to be, and the flats and descents aren't bumpy enough to make a suspension fork enough of an advantage to justify carrying it up run-ups and pushing extra air (to say nothing of power losses if it doesn't have a really nice damper.)


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## jahfakin (Sep 26, 2009)

Flystagg said:


> The rider, and....


too funny!!!


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## CaveGiant (Aug 21, 2007)

I think the top gear on a road bike is 50x11 with a 700c wheel. 
Most normal MTB is 44x11 on a 26".

With road tyres on the main drag effect at most speeds is air.
When you include proper MTB tyres like a WTB stout at 7PSI, you have to be going very fast to consider the wind to have an effect, the top speed is dramatically reduced.


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## IstongKowldPaRin (Apr 6, 2009)

bigger appendages...

http://forums.mtbr.com/showthread.php?t=561625


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## spazzy (Aug 15, 2004)

Ken in KC said:


> A transmission trumps tires.
> 
> A 6 cyl sports car with a transmission geared for upper end speed will go faster than a 6 cyl truck, regardless of tires.
> 
> A bike with a larger upper end gear ration will go faster than a bike with a fewer upper end gears, regardless of tires.


Faster off the line...Popsickles chance in hell of a 6 cyl sports car (geared for speed) beating a granny geared truck to 25ish Gobs of torque rule at the line... 

Anyway to the op I am very slow with knobbies on and just slow with slicks lol


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## civil (Feb 13, 2008)

CaveGiant said:


> I think the top gear on a road bike is 50x11 with a 700c wheel.


53x11

Compacts are for wussy. Dial up to 400W and drope the hamer.


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## davidbeinct (Dec 6, 2007)

civil said:


> 53x11
> 
> Compacts are for wussy. Dial up to 400W and drope the hamer.


For when you're ready to get serious:

http://www.coloradocyclist.com/product/item/SSBIKWMX



David B.


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## nachomc (Apr 26, 2006)

davidbeinct said:


> For when you're ready to get serious:
> 
> http://www.coloradocyclist.com/product/item/SSBIKWMX
> 
> ...


ow.


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## [email protected] (Oct 17, 2009)




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## civil (Feb 13, 2008)

davidbeinct said:


> For when you're ready to get serious:
> 
> 
> 
> David B.


Haha. That is a big one......

Note that they are all back-ordered.....I believe that cavegiant bought them all for his MTB.

The largest I used was a 55 on a TT, if it weren't flat I would have died


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## mrclortho (May 12, 2009)

It is what the bike is designed to do, plain and simple. It is a combination of all of the mechanical stuff, riding geometry, not loosing energy in the suspension, etc... 

When I am riding my XC at 15mph and sucking wind and two 60 year old ladies pass me on their road bikes talking of HDTV, it have to tell myself, "It's the bike...it has GOT to be the bike....definatly."


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