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MTB to Road Conversion Ratio


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I was riding home yesterday from my local dirt paradise, when a roadie passed me by. Tried jumping his wheel, but within a few hundred meters, my HR was outside of my training zone, which lead me to thinking: "How many road km's = 1 MTB km?"

 

We all know that riding a MTB takes more effort, as there's increased rolling resistance, more weight and different gearing applicable BUT, would it be possible to calculate a conversion ratio.

 

Maybe the roadtainbikers on the hub could do an experiment:

 

1. Ride a known route on your MTB at a set pace and note average HR, min and max HR and energy (Kcal) consumption

2. Ride the same route a day later on your road bike, at the same pace, and note the same stats, then publish the stats and let's see what the results look like.

 

I know there are many variables, including time of day, weather, wind, diet, etc. but given enough results, some kind of average could still be calculated.

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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.

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Interesting topic. No scientific reports on offer here, but I believe the difference is not that great.

 

At higher speeds, the difference increases due to the exponential effect of wind resistance, particularly on the knobs of the tyres. Remember that when you travel at say 50km/hr, the uppermost portion of your tyre is moving at 100km/hr (relevant to the ground or 50km/hr relevant to you). The resistance of knobbies due to the "friction" on the road is thus far less that the wind resistance it creates.

 

My fastest tt time on a 20km round route is only 2min faster on the road bike. (roughly 5%)

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Yea, I would agree with that to an extent - I have always worked on 1.6

 

BUT

 

It depends on the route, when I was starting out racing last year I hit it off with the Tru-Cape MTB 20km, the went on to Die Burger 30km - my TIME in the 30km was better than the 20km (complete with the traffic jams at every single track) simply because that was a drag race through farm roads rather than long climbs and technical singletrack. Not to mention that by average speed for the Knysna 50km was better than my Argus ave spd (mind you, there weren't any massages in Knysna to slow me down)

 

1.6km Road -> 1km MTB is a good starting point but don't use it as a hard rule. I have a roadie friend whose first MTB race was the Tru-cape 50km this year, he believes it is way more than 2km road per 1km mtb after that - and I wasn't far off from agreeing with him!

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Interesting topic. No scientific reports on offer here, but I believe the difference is not that great.

 

At higher speeds, the difference increases due to the exponential effect of wind resistance, particularly on the knobs of the tyres. Remember that when you travel at say 50km/hr, the uppermost portion of your tyre is moving at 100km/hr (relevant to the ground or 50km/hr relevant to you). The resistance of knobbies due to the "friction" on the road is thus far less that the wind resistance it creates.

 

My fastest tt time on a 20km round route is only 2min faster on the road bike. (roughly 5%)

 

Please explain the bolded bit to me like I'm a sperm cell. If you're travelling at 50kph, then the surface of your tire is moving along the ground at 50kph. The air (assuming there's no headwind) is hitting the surface of that tire at the same speed - 50kph, which will be the same speed it would hit you. How can you just double that number?

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Simple Equasion - Did my first Argus on a very entry level MTB - 4h20. One year later, after many hours in the saddle, being alot fitter, good seeding and a reasonable road bike I did it in 3h20. If I was at the same fitness level the year before, I could have broken 4h. Therefor the equasion would be 240/200 and come out at 1.2 km mtb per 1 km road. Conditions were near perfect on both rides (2007 and 2008)

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Okay, someone must know this...

 

What is the average speed of the TdF top 10 riders for the entire tour? And last 10 riders? Taking into account they are all professionals.

 

What is the average speed of the top 10 riders of the Cape Epic? And last 10 of the sponsored riders?

 

Maybe this will give us an indication?

 

Time trial averages between TdF and Epic?

 

Will be interesting to see.

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ask an epic rider... they will tell you exactly how big the difference is.

many moons ago witha rigid fork was around 3:1 but bikes had no sus and were heavy chromo things, so i reckon more like 2:1 h/t or 3:2 for full sussers

would luv to see the science

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Okay, someone must know this...

 

What is the average speed of the TdF top 10 riders for the entire tour? And last 10 riders? Taking into account they are all professionals.

 

What is the average speed of the top 10 riders of the Cape Epic? And last 10 of the sponsored riders?

 

Maybe this will give us an indication?

 

Time trial averages between TdF and Epic?

 

Will be interesting to see.

Too many variables. I'd like to see what the difference the bike ALONE makes. Same route, same conditions and same rider will provide a simple, but accurate answer.

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Too many variables. I'd like to see what the difference the bike ALONE makes. Same route, same conditions and same rider will provide a simple, but accurate answer.

 

Exactly, too many people are comparing mountain biking to road biking instead of comparing the Mountain Bike to the Road Bike. The MTB can ride on the road far better than the Road Bike can ride on an offroad trail, so a road route done once on an MTB and once on a Road Bike would be the measurement you're looking for.

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Firstly, we are talking two different things here:

a) comparing a road bike with a mountain bike on the same tar road, and

B) comparing a mtb race distance with a road race distance.

 

For a) a maintain a 5% difference and for b0 I agree that it can be as much as 2:1. It obviously depends on the terrain, it is like asking how many foreigners are living in SA.

 

Secondly, to answer Kingcompass: Think of it this way; if the patch of tyre on the ground is moving at 50km/hr relavant to the ground you would leave one hell of a skidmark! The top part is moving twice as fast as the hub relevant to the ground. If it was travelling the same speed relevant to the ground, it would not be turning. The outer part of the tyre will always move at 50km/hr relevant to the hub if you are riding at 50km/hr, but not relevant to the road. Make sence now?

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Secondly, to answer Kingcompass: Think of it this way; if the patch of tyre on the ground is moving at 50km/hr relavant to the ground you would leave one hell of a skidmark! The top part is moving twice as fast as the hub relevant to the ground. If it was travelling the same speed relevant to the ground, it would not be turning. The outer part of the tyre will always move at 50km/hr relevant to the hub if you are riding at 50km/hr, but not relevant to the road. Make sence now?

 

Of course it does, duh. Sorry, I've had an ultra boring day, and I'm sure it's turned my brain to jelly, that should have been obvious to me. Thanks for the explanation.

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Exactly, too many people are comparing mountain biking to road biking instead of comparing the Mountain Bike to the Road Bike. The MTB can ride on the road far better than the Road Bike can ride on an offroad trail, so a road route done once on an MTB and once on a Road Bike would be the measurement you're looking for.

 

The elephant in the room here is the nature of the ground that a MTB travels over, sometimes soft sandy tracks sometimes hard pack sometimes rocky trails sometimes gravel district roads.

 

Sandy paths sap much more energy than district gravel roads.

 

Sandy paths on an incline sap even more energy.

 

Too may variables to get anywhere close to an accurate equation.

 

My formula is: MTB = much tougher than road riding by a long way.

 

My Argus uses around 2800kcal of energy my 70km MTB marathon = 3500+ kcal.

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Too many variables. I'd like to see what the difference the bike ALONE makes. Same route, same conditions and same rider will provide a simple, but accurate answer.

Bike alone, refer to 1.2 rkm to 1 mkm for the guy that did the Argus in 2007 and 2008.

 

But I did not get a MTB to do road and I believe I have not yet seen a road bike at Groenkloof. I think the average speed at TdF and Cape Epic... wait, let me get it.

 

Please forgive me if I'm out with a few km :P

 

TdF 3641.9km average of top 10 was 98.82 hours = average speed 36.85

Cape Epic 800km average of top 10 was 30.98 hours = average speed 26.08

 

Thus a 1.41 rkm to 1 mtbkm

 

For the top guys at least taking into account the varied terrain.

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No harder place to test this out than at Suikerbosrand - I did it last year while training for the Sabie Experience.

 

Conditions - Sunny, hot, 10-15Km/h wind (according to the weather bureau)

Route - Start at the circus, ride to Kareekloof, ride the long loop, and then back to the circus.

Distance - 70.7Km

Time lapse between rides - 1 week, road ride done first.

The road ride happened to be a club ride, and I chose not to do the full lap that particular day.

The MTB ride was with my SabieX partner, so the objective was to ride together, as we had to at SabieX. I had to wait for him a few times, but probably no longer than 10 minutes in total.

 

Road bike - Full Carbon 7.4Kg

Time - 02:20

Speed - 30.3Km/h

KCal - 2520

Max speed - 89.4Km/h

 

MTB - HT 13.4Kg

Time - 03:25 (excludes 10 minutes of stopping)

Speed - 18.85Km/h

KCal - 3717

Max Speed: 70.1Km/h

 

Ratios

Time - 1:1.464

KCal - 1:1.475

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Ok,

Here are my Statistics from this weekend at Lost City, i think this gives a fairly good account of things:

 

Saturday= Road Race - 103km, 2h44 avg HR= 85% 2968kcal (back of the flu shaking off a cough, may be a bit high hr)

Sunday= MTB Race- 50km (actually 45), 2:05 avg HR= 81% 2042kcal

 

So what I can see here is, my exertion was about the same for a similar amount of time, but the mtb distance was about half

 

Consider the following

Both were fast, flatish routes, non technical

 

I think its fair in general very roughly to say its a 2:1 Average

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