MTB to Road Conversion Ratio

[Minion]

What we need is someone with a power meter on their mountain bike and road bike. Ride the same piece of road on both bikes at the same power and note the difference in speed.

 

Edit: it seems the original question was regarding the difference between road bike and MTB when both are on tar.

[Lounge Lizard]

To just compare the Road bike and MTB on tar road does not give enough data

 

A Road wheel is also larger that mtb so rolling resistance is further reduced.

 

And regarding the speed of the upper part of the wheel to the lower part - that is why the bottom of the wheel stands still when you are not riding even if the wind speed is 80km/h (i.e. if it did not stand still and the road stands still - it would drag ! right) So at 80 km/h the bottom of the wheel must stand still, but the top part of the wheel must catch up so it will turn at 160 in the opposite direction.

 

Mathematically -

if the top of the wheel speed is 'x' and the bottom of the wheel is 'y', the hub speed is 'r' and the road speed is 'z'.

then given that y = z and e=mc2 (where r/^y*x)

Where the wind is 'q' then (x/y - q2)(8^2/7@3)

 

That is why in a 50km/h head wind you have to do 50 km/h just to stand still !!

 

I will do Majik forest and Hillcrest this weekend with my road scotty and let you know if this also works off road.

[Stretched@Birth]

Edit: it seems the original question was regarding the difference between road bike and MTB when both are on tar.

What I am really trying to determine is the difference in work rate, yes, there are multiple variables, like terrain, that's why I'm trying to eliminate the variables by saying do the experiment on the road, as the roadie bikes will not do well offroad...

 

Bottom line is, how much harder does one work on a mountain bike to achieve the same result as you would on a roadbike? Seems like the general consensus is between 1.4 and 1.6 to 1...

[DirtyFrank]

I'm going with 1.65rkm = 1mtbkm

 

 

But there are to many variables to really have a solid number...

I'd say terrain is the biggest factor between the two.

 

I agree this is also roughly (1,68) the same figure I get to when comparing energy spent/time/distance.

The whole debate is pointless though as the variables in gearing/terrain/weight are simply too great to make a proper comparison.

[Caerus]

So whos taking there nice expensive road bike offroad this weekened?

[Minion]

There was some dude doing it in another thread...

[Shebeen]

I know a story of someone contesting the argus sprint in the invitation group.on his full susser with knobblies.

 

Remember weight of the bike doesn't really affect anything apart from loading it onto the bikerack. Biggest difference between the two is tyres and tyres

[gongmech]

And what about the size of the wheel? Changed to 26" MTB slicks for the ARGUS losing about 1 inch on the diameter and my cateye noted that i did an extra 4kms.