Mountain Biking - Mountain bike speed vs road bike

Ok,

question:

With a rider who lets say avg's 25km/h up hill on his mountain bike and say about 35km/h down hill (bigger hill = faster just picking on avg here) on a entry level race bike (2KCDN 1500$USD) Approx how fast would he go on a road bike of approx value. Again same rider.


So basically for someone who rides both I want to see a comparison. Basically want to see if Im just a slow arse because I haven't ridden hard enough due to my riding partners being a little slow. Or if my bike is holding me back.

I am getting a road bike but atm I dont want to settle so I am waiting till I can get the one I want.


Anyway for what its worth I have a Michellin windgripper in back and a tioga knobby tire up front (cant remember name)


Thanks guys,
CK

I would love to be able to help you but there are trails 6km long that take me a full 3 hours to finish. Thats less than 2km/hr. When I turn around I make it down in 20min or so. maybe 30. Thats still not as fast as you go.

I will assume you are talking knobbies on road since your times seem rather consistent for offroading.

You really can't just ask for speed variations it depends on your terrain. Compare yourself to the people in your area. My times ma seem slow but I am not an overly slow rider at all. Or better yet travel. Find other spots to ride to measure yourself against others in that area. That will give you a better measurement of your speed. I know I can move and travel a lot farther and faster in Ontario than out here as the terrain isn't overly technical (except in certain spots) and is 'pretty' flat.

All of that said. Road bikes on the road being ridden by the same rider who just road that same spot on a knobbie will go signifigantly faster. Esepcially if you wear the lycra ;):D

Now I was wearing lycra when I did this :-)


And I was on the road, I was doing the Niagara Falls - Niagara On the lake.


My avg speed ended up being 18.0km/h for a 65KM ride which while I'm not overly happy with isn't that bad considering the ride up the escarment.

I talked to some of the guys at the bike shop around here but they tell me they avg 35km/h without a problem on road bikes and dont touch their mountain bikes anymore cuz they are roadie converts.

Other thing is ya I was on the road doing it, off road varies. (I go less then 10km/h when clearing logs that are taller then my front tire =0


any rough ideas are appreciated,

CK

35km/hr is a good speed for well trained roadies. You probably won't be able to maintain that speed on a road bike off the bat. Average speed on the road...25 to 30 ish until your conditioning is pure road. But this seems like a better question asked to a roadie not a mtber :)

If I understand your question correctly, you're curious to know if -- for example -- a $700 road bike would be a more efficient machine than a $1400 road bike. The simple answer is NO. It's all about the motor that drives the bike.

The more complex answer is a more expensive bike would likely have a lighter weight frame and components which would obviously be an advantage if you were functioning at peak performance. Light weight wheel sets -- which are sometimes featured on more expensive bikes -- are certainly easier to climb with than heavier ones given the nature of rotating weight.

Regardless, simply switching to a slick and more narrow tire -- even on your mountain bike -- will significantly improve your riding efficiency and speeds in all aspects.

I appreciate the answer but I dont think anyone is quite understanding what i am asking.


Rather.


If the same rider. (ME for instance) can maintain 25km/h on his 1500$mtn bike (per say Kona Caldera) on a bike path. APPROX how fast can the same guy maintain on a road bike (same value for instance R-600 canondale) doing the exact same ride.

Will I go only 1-2km/h faster, or more about 5-10km/h faster?


Again I'm just looking for approx and hopefully everyone understands what i mean by this.

I asked here and not in roadie form because alot of roadies are just roadies whereas I find more mtn bikers ride road on the side.

CK

Like I said...in my last post. I think the speed difference would be signifigant...maybe 5 to 10...maybe more...but you would definately notice a difference.

Originally posted by chad
Will I go only 1-2km/h faster, or more about 5-10km/h faster?


Again I'm just looking for approx and hopefully everyone understands what i mean by this.

Uh let me bust out my mountain bike to road bike speed calculator formula. Ohhhh WAIT, i don't have one, and no one else does either. THere is nothing approximate, you won't know until you try. Have fun

If you're comparing the performance of your mountain bike with knobby tires to a road bike with high pressure racing tires assume about a 8 - 10% increase speed / reduced effort at at 25 kph and the power required to overcome friction will continue to rise linearly with speed.

Of course, if you put 26" slicks inflated to 100 psi on your mountain bike you'd also get about a 9% increase in your speed / reduced effort.

The biggest issue you're dealing with regard to the loss of efficiency is friction from the knobby tires, secondarily the contact patch size and thirdly the width of the tire. A high pressure slick tire will resolve most of the surface friction and the more narrow the tire is the more aerodynamic it becomes. Also, the higher the speed the greater the hit on riding efficiency, i.e., the faster you try to go the harder it becomes on the mountain bike vs a road bike.

Obviously, at some point your available gear inches will become a limiting factor depending on how efficient your cadence is. And of course there is the aerodynamics associated with your body position which will also be a factor as would the bike's weight if you're climbing, acceleration hits due to the heavy off-road tires and wheels, inefficiencies associated with any suspension, etc...

The price of the bikes is a non-issue - see above.

Originally posted by livngood
If you're comparing the performance of your mountain bike with knobby tires to a road bike with high pressure racing tires assume about a 8 - 10% increase speed / reduced effort at at 25 kph and the power required to overcome friction will continue to rise linearly with speed.

Of course, if you put 26" slicks inflated to 100 psi on your mountain bike you'd also get about a 9% increase in your speed / reduced effort.

The biggest issue you're dealing with regard to the loss of efficiency is friction from the knobby tires, secondarily the contact patch size and thirdly the width of the tire. A high pressure slick tire will resolve most of the surface friction and the more narrow the tire is the more aerodynamic it becomes. Also, the higher the speed the greater the hit on riding efficiency, i.e., the faster you try to go the harder it becomes on the mountain bike vs a road bike.

Obviously, at some point your available gear inches will become a limiting factor depending on how efficient your cadence is. And of course there is the aerodynamics associated with your body position which will also be a factor as would the bike's weight if you're climbing, acceleration hits due to the heavy off-road tires and wheels, inefficiencies associated with any suspension, etc...

The price of the bikes is a non-issue - see above.



THANK YOU!!!!!


Now one more question: In relation to aerodynamics of the upright position of a mtn bike as opposed to that of a road bike is this where the 8-10% difference comes in?

That and the high pressure racing tire vs my semi-knobby mtn bike tires was what I was looking for.


Thanks to those who provided useful info. (Maelstorm your info was helpful but I was looking for a little more detail)


CK

Originally posted by DrGonzo
Uh let me bust out my mountain bike to road bike speed calculator formula. Ohhhh WAIT, i don't have one, and no one else does either. THere is nothing approximate, you won't know until you try. Have fun

I'm pretty sure that someone who uses a computer on both bikes and OWNS both bikes can give me a rough estimate (as others have)

Thanks for being unhelpful. Always not appreciated.

Ck

Originally posted by chad
THANK YOU!!!!!


Now one more question: In relation to aerodynamics of the upright position of a mtn bike as opposed to that of a road bike is this where the 8-10% difference comes in?

That and the high pressure racing tire vs my semi-knobby mtn bike tires was what I was looking for.


Thanks to those who provided useful info. (Maelstorm your info was helpful but I was looking for a little more detail)


CK

Hey no prob. I am just always surprised when people are THIS worried about the nuances of speed. To me it take away the fun. I even removed the computer from my bike as it got in the way and interfered with my riding. If you are this concerned with speed and energy expended you should consider being a roadie ;):D

hey chad,

well, i'd have to go back through all my logs to be able to exactly tell you, but i've gotten myself all confused b/c most of my road biking was back in the US in mph and now i've been using km/h so i'm can't pull numbers out of my head, and i ride almost only MTB.

but here is what i can come up with:

the faster you are and the higher the speed the greater the difference.

yes, the high pressure tire make the biggest difference. and the higher the speed the more difference. and the aero body postion makes a difference. and i _feel_ like for some reason that i can crank more efficiently at high speed on the road bike, but i don't really know.

anyway, i would say where it REALLY makes a difference is if you are pack riding and riding extra high speeds -- many criteriums and pack races the group rides speed in the 40-50km/h or even higher. if not on a decent road bike even a VERY fit rider can probably not stay up.

but riding solo, breaking your own wind, i would say the difference is not so great - unless you're racing or near the pro level. for me on flat road by myself on the MTB it is pretty hard work to maintain 30km/h (i.e. high pulse and i can for only an hour or so unless i'm really pushing/racing) and on the road bike i think i can maintain a 32km/hr pace for a longer ride with less effort... as i said, i forgot my old TT numbers, but if i remember right i was averaging 22mph in 20 mile TTs so that would be 35km/h ----- so for solo riding, i would guess for me a difference of 30km/h to 35km/h ---- and if you're riding higher speed, especially drafting more like 35km/h to 45km/h. next time i get out on the road bike i'll try and take notice... hope that helps a little

Well when i was riding for a team...some 10 years ago....we did a time trial on flat road...13km stage run in under 13minutes ...that is a sustained average speed of 60km/h on flat road (almost no wind at all) ridden on a road bike. At the same time road downhill speed was max at 95km/h and off road downhill speed at 60km/h.

The aerodynamics of MTB vs road bike are not fixed. Many cx style MTBs have very aero positions, with the bars 6" below the saddle and quite narrow bars. There is nothing magic about drop bars or road bikes, you can ride them in a deep aero crouch or in a more upright touring style according to taste.
At higher speeds, aerodynamic resistance is the limiting factor, and is far more important than weight or rolling resistance, but you need slick tyres to achieve these speeds.

Originally posted by chad
Now one more question: In relation to aerodynamics of the upright position of a mtn bike as opposed to that of a road bike is this where the 8-10% difference comes in?

Most of the efficiency is lost through surface friction between the tire and the road -- note my comments on fitting high pressure road slicks to your mountain bike.

Depending on how fat your front tire is and if you have a front shock, that's probably robbing you of more aero efficiency than the differences between upper body position** but it's still pretty minimal in the big scheme of things.

**The riding position efficiency assumes you're comparing a pretty efficient mountain bike riding position to a road riding position on the tops of the hoods or bars and not in the drops or aero bars. Obviously the latter -- such as used in time trials or by Tri-Geeks -- yields a pretty significant aero improvement that would further boost average speeds up several ticks.

ok maelstrom dude 6 kms in three hours sounds horrable but think if you took a 2000 dollar road bike down that trail that guy would be like 20 hours caus his bike would fall apart on our trails! Now i cant get all scientific or even prove my point with a post but to sum up road bikes are faster, mnt bikes are slower, road bikes are not really that much fun and dont look cool covered in mud and mnt bikes are and do, you can huck a 10 foot drop on a mnt bike @ 15 kms an hour mabey 20 with good wind, and you cant on a road bike

Auger....

The trail described was Forplay...I am sure you remember it. 3 hours up...it is only a 6k trail according to the trail head...

I wonder if they have connected it to Wedge yet. It is suppost to be dh return trip from kill me thrill me by the middle of summer...

I ride both mtb and road. When I ride my mtb on the road and push it I can average 16mph on average. On my road bike on the same route I can do 18mph without really pushing it. This is over 25 miles in Florida so there are no hills.
I have found my top speed on the mtb in a sprint on the road to be about 25mph. The road bike does 30mph with a lot less effort.
I'm 48 years old so your results could be more dramatic.

Thanks for the reply george.

I topped my mtn bike out on the road at 60km/h (40mph?) And haven't ridden a road bike hard enough to give a good comparison.

I appreciate teh answer and its about what I seem to be getting from everyone.

Thanks again

Not sure if this helps or not but aero position does seem to help quite a bit. I added aero bars on my road bike and when I go from riding on the hoods to using the aero bar, I immediately see my speed go up 1 - 1.5 mph.