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fsrftc said:
what are you specifically looking for? I have probably 30-40 from the last 9 months or so
I would like to see a normal XC race and a hard group ride. See how they compare.

And with that, time in Zones. (aerobic, tempo, threshold, AC, etc. if possible).

Also, TSS, and IF. That way it gets normalized to your power level. (Which is a lot higher than the rest of us;) )
 

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Poncharelli said:
I would like to see a normal XC race and a hard group ride. See how they compare.

And with that, time in Zones. (aerobic, tempo, threshold, AC, etc. if possible).

Also, TSS, and IF. That way it gets normalized to your power level. (Which is a lot higher than the rest of us;) )
hah, well I'm a bigger guy so its all relative? ;)

I don't really do group rides, maybe 1 or 2 a year. I do almost all my long training rides solo, so my data may be a bit off from what you are looking for.

this was my best recorded "tempo-ish" ride of last season: http://www.trainingpeaks.com/sw/KOWHWTP6HZ3FQWC45OFNA2FR5E and one of the few rides I did last year chasing a particular number, in this case 300 watts.

and this was the only "short" XC race I had recorded with power for last season, I placed 3rd in Expert, less than 11 seconds from 1st. http://www.trainingpeaks.com/sw/OV5WU4INEDOYXLH47QEENBFBS4 (interval 2 is the race)

The XC race was King of the Rockies in Winter Park, CO which is nearly all between 9-11,000 feet elevation (probably a 5-6% power loss from me at my normal 5000ish foot rides) and my 1st good race after my late summer crack (I got completely overtrained/tired/whatever you want to call it). I was about 182 pounds for both of these files and my 20 minute interval power was at least 400 watts, hope that helps.
 

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Training Peaks doesn't display the recorded information that well if there's lots of stopping and starting. I might rewrite this post with some WKO+ pictures instead.:)

This is the power data from the mountain bike ride I did today. It's fairly representative of what mountain bike rides are like if you're not very good.;)

http://www.trainingpeaks.com/sw/ZSEB4ZMQBHR4NZVJ5BRTU5CLNQ

Today's ride had 20.7 miles of offroad in a 48 mile ride which is typical. A ride in the hills involves sections of bridleway, byway and unmarked tracks linked by country lanes. It's quite dry at the moment so less muddy than normal making it quicker. The surface is mostly hardpack mud, gravel and rocks.

There's unavoidably lots of stopping and starting. The time gaps aren't data drop outs. They're where I had to stop for gates, crossings etc. One section was a complete disaster as it was deep ruts left by motocross bikes and I hardly managed to ride any of it which added 30 minutes on.:madman:
 

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I've been thinking about getting a powermeter for my MTB, so this thread is interesting to me. Its difficult to go from having power on the road to me and not having it on the MTB.

For those that have road and mtb power, do you find a 100TSS road ride feels like a 100TSS MTB ride?

How about NP compared to AP, I find on the road, my NP is generally within 20W of AP, is there a bigger gap due the the coasting thats neccessary on the MTB?
 

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Poncharelli said:
Man!! And I thought I was OCD!! :D

How did you label all those intervals? (road, byway, track, etc.). Did you just start an new interval real time, and rename later?
I'm using a Powertap hub with a Cycle Ops Joule 2.0 head unit.

The interval markers are from manually pressing the "interval" button on the head unit during the ride. I add the notes in afterwards.

What you can't see on a graph is whether there were bumps, mud, rocks etc. Whilst you can usually be fairly sure that a road ride on tarmac is similar wherever you are along the route the differences in surface type and terrain offroad have to be taken into account. Riding across a muddy bridleway isn't equal to a rocky byway for example. It isn't simply about power output as bike handling and traction become increasingly important. If my bike handling was better then the power output over many of the offroad sections of yesterday's ride could have been much higher. It's one of the things that looking at your offroad power data can show up very clearly. :)

Without adding lots of markers it's difficult to work out where you are on a ride like this one when you're switching between on and offroad every few minutes and turning at lots of junctions. It needs the detail to add any meaning to the information. That file is the shortened version of the original WKO+ file. The original file has much longer notes for each interval (place names, surface type etc) along with a 157 word summary of the route.:eekster:

This is a 3.5 hour ride from last Thursday, using the same Specialized Epic mountain bike with the same knobbly tyres fitted, but all on tarmac for comparison. The equipment differences were that the rear suspension was set to full firm and the tyres were at 60psi instead of 35psi for the road ride. You can see how the overall average power and average speed was much higher on road, along with much less stationary time and also less of a difference between the average and normalized power. Last Thursday's ride was a harder ride from an intensity perspective. What you do get with riding offroad is more of a general fatigue from riding on rougher surfaces though.

http://www.trainingpeaks.com/sw/63HJXDUJZYYNXQDC66M6IC74K4

On some surfaces there's hardly any difference between tarmac and riding offroad. On others it's a lot. The two graphs below show 8 minute sections of last Thursday and last Monday's rides. The average power and altitude ascended are very similar between the two sections. One is riding offroad along a narrow and twisty rocky track which was giving the bike's suspension a good workout. It was bumpy but not difficult enough that I had to start backing off. The other is riding on smooth tarmac. I've adjusted the graph scales so that power and speed are in the same place on each graph. The difference in speed between very marked and you can see that the power delivery is more variable offroad where I'm riding over rocks.

What's really interesting is when you compare the same section of rocky track in opposite directions. On the way out it was downhill and uphill on the way back so would be much faster downhill you'd think. It's actually a very good example of how my poor bike handling rapidly becomes the limiting factor. Rather than going faster I ended up going roughly the same speed each way and pedalling gently instead. Average 11.9mph, 82 watts and 79rpm downhill compared to average 11.0mph, 174 watts and 89rpm going back up the same track.

It doesn't take a power meter to show up these weaknesses but what it can do is allow you to see if you're improving or not. It helps explain why a rider with reasonable fitness but poor bike handling can be much slower offroad than a rider who's unfit but a good bike handler. If you're only able to use a small percentage of your available power output then it's possible for the fitter rider to actually be producing less power offroad than a unfit rider who is able to ride harder over the same terrain.:)

Pictured below: Power Output along a rocky track uphill and downhill in the same ride.
Power output and speed on tarmac using same bike.
 

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wetpaint said:
For those that have road and mtb power, do you find a 100TSS road ride feels like a 100TSS MTB ride?
No TSS seems to be always much lower on a MTB ride for a given effort.

When mountain biking you do a lot of work is done that that power meter doesn't count.

A good example is on a pump track, I can have my heart rate at threshold without ever turning the pedals.
 

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I'm sure you've seen this study of the rolling resistance of different Schwalbe tyres offroad before.:)

http://www.mtbonline.co.za/downloads/Rolling_Resistance_Eng_illustrated.pdf

The study was originally carried out by Peter Nilges, for his graduate dissertation at the German College of Physical Education, Cologne.

He used a SRM power meter to try and evaluate how power varies offroad depending upon factors such as surface, tyre pressure and tyre tread.

It's a good demonstration of how you can use a power meter on the mountain bike to help with decisions such as tyre choice.:)

(The graph on Page 7 of the study is mislabelled. I've corrected the key of the graph posted below.)

Pictured below: Extract from rolling resistance study.
 

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Bumping this thread because I ended up ordering a powertap. TSS and IF end up feeling about the same as the road, but the power distribution is different. I'm quite happy to be getting power data from road and mountain now.

My road power files end up being fairly smooth and the power distribution is mostly Z2, Z3 for an easy ride. The mountain bike data is really spikey, lots of time in Z1 and then threshold or above.

Here's a lap from a smooth flowing single track
Duration: 31:23
Work: 371 kJ
TSS: 27.6 (intensity factor 0.726)
Norm Power: 214
VI: 1.09
Pw:HR: 5.77%
Pa:HR: -8.62%
Distance: 6.545 mi
Elevation Gain: 517 ft
Elevation Loss: 521 ft
Grade: -0.0 % (-6 ft)
Min Max Avg
Power: 0 637 197 watts
Heart Rate: 80 161 137 bpm
Cadence: 30 212 88 rpm
Speed: 0 35.5 12.5 mph
Pace 1:41 0:00 4:49 min/mi
Altitude: 732 774 754 ft
Crank Torque: 0 800 191 lb-in
 

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wetpaint said:
Here's a lap from a smooth flowing single track

Duration: 31:23
Work: 371 kJ
TSS: 27.6 (intensity factor 0.726)
Norm Power: 214
VI: 1.09
Pw:HR: 5.77%
Pa:HR: -8.62%
Distance: 6.545 mi
Elevation Gain: 517 ft
Elevation Loss: 521 ft
Grade: -0.0 % (-6 ft)
Min Max Avg
Power: 0 637 197 watts
Heart Rate: 80 161 137 bpm
Cadence: 30 212 88 rpm
Speed: 0 35.5 12.5 mph
Pace 1:41 0:00 4:49 min/mi
Altitude: 732 774 754 ft
Crank Torque: 0 800 191 lb-in
How does that power output compare to your road data and FTP figures? Was it constantly up and down or a climb followed by a descent?

Your data shows how big a difference there can be between mountain bike rides depending upon where you're riding. On a typical mountain bike ride around here you can't do a non stop 31 minutes offroad without having to stop for some reason. Well you could, but it would be riding up and down the same short section repeatedly. A ride setting off from home unavoidably involves lots of gates and short sections of offroad joined by tarmac.

Up in the hills the riding is mostly farm tracks and bridleway through fields which is very stop - start. The stationary time really adds up quickly. It breaks up the flow of the ride as well which is probably one reason why my average power outputs end up being so much lower for offroad. It's hard to stay focused on a hard ride when you're forced to stop so often.

My current FTP is about 233 watts at 154 lbs. (best 20 min 245 watts, best 5 min 290 watts) so I'm quite slow. A mountain bike ride like last Tuesday's with an average power of 137 watts and Normalized Power of 174 watts is still much lower than the power for a road ride of the same duration would be though.:(

The graph below from last Tuesday's ride is an example of what a mountain bike ride in the Cotswolds looks like overall. The grey sections are tarmac and the black sections are offroad. You can see why the data ends up needing lots of splits added to make sense because you're constantly switching between on and offroad. 14 miles offroad (41% of the total) is actually quite good for a 2h38 ride.:)

The other graph is an extract from the same ride. It's a climb that starts off on tarmac (5.3% gradient) but part way up you turn off onto a steeper bridleway (11.9% gradient) on loose rocks and roots. The power and cadence are quite smooth on the road but as soon as I get onto the looser surface it takes a big effort to keep going. You can see the drop in speed and big spike in power as I change down into bottom gear. The spikes in power output and changes in cadence become more pronounced as I'm struggling to get up the bridleway. The average power (212 watts on road) jumping up to an average of 298 watts shows how much harder it becomes on the bridleway.:)

Pictured below: Split between on and offroad for a typical Cotswolds ride.

Changes in power and cadence between climbing a hill on tarmac and then turning off onto a bridleway.
 

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Average power doesn't include stopped time, just coasting time, so the time you spend stopped won't affect your average, only the time coasting to a stop. There were some small rollers in that course, but it is fairly flat. The entire ride ended up having an IF of ~.7, it felt similar to what a .7 road ride would feel like, except the graph showed alot of spikes in power and coasting. On my typical road files, there is virtually no coasting and the power is quite constant.
 

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wetpaint said:
Average power doesn't include stopped time, just coasting time, so the time you spend stopped won't affect your average, only the time coasting to a stop. There were some small rollers in that course, but it is fairly flat. The entire ride ended up having an IF of ~.7, it felt similar to what a .7 road ride would feel like, except the graph showed alot of spikes in power and coasting. On my typical road files, there is virtually no coasting and the power is quite constant.
The constant breaks and interruptions in my rides don't affect the average power directly. The issue is that when you're only doing a few minutes between stops there isn't much incentive to try that hard so I end up taking it easy all the time instead. It's a bad habit on my part. In that ride on Tuesday for example I counted 24 stops.:madman: That included riding around someone's garden trying to work out where the restricted byway sign was pointing to, lots of gates and a few junctions in woods where I wasn't sure which turning to take.

That's the point of having a power meter though - to be able to take a hard look at what you actually did during a ride, as opposed to what you thought you did. My riding has got plenty of room for improvement. Keeping track of stationary time and trying to reduce it is one area that I'm working on.:)

When you see other people's offroad power data it's very reliant on the terrain. Direct comparisons between different riders in different areas can be quite difficult. You can learn a lot of useful lessons from your own data though. After looking at the power data going down the rocky track in Post #10 for example it was obvious that I should be able to pedal harder down it than I had been previously. As a result of that I managed to get down it at average 110 watts and average speed of 14.7mph subsequently. Still slow but better than before.:)

Pictured below: A short 30 minute extract from my ride on 19 April 2011 with time as the X-Axis to demonstrate how often I ended up stopping. The gaps in the trace are all times where I was stopped, rather than data drop outs.
 

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I rode a different route today that consists of tracks in woodland, rather than farmland.

3h54 ride time (plus 9 min stationary)
47 miles in total (13.3 miles offroad)
3834ft of climbing
141 watts average power, (181 watts Normalized Power)

I know these tracks much better and there are fewer gates. The offroad woodland sections were far more up and down than riding across farmland with some fun descents and steep climbs.

This is the Training Peaks link for the entire ride file. Click on the individual offroad sections and then tick the Zoom tick box to look at them in more detail. I'd suggest changing the theme to WKO+, setting the smoothing slider to Low and hiding the torque and rpm traces in order to make it clearer.:)

Training Peaks 26 April 2011 MTB Ride
http://www.trainingpeaks.com/sw/ANIYJEAVH5JEKHJWLBCYN7UG64

Descending Recorded Data
Recorded data isn't just about seeing how hard you pedal. It lets you look at other aspects of your riding such as descending also.

It isn't essential to have a power meter in order to look at your descending recorded data. All you need is a speed trace recorded at 1 second sample rate from any device such as a Garmin Edge or Polar to allow you to get an idea of how you're riding. You can use the recorded speed trace to look at things like your braking g force and apex corner speeds. These are some examples of looking at descending a series of road hairpins using data from a Polar RS800CX heart rate monitor: :)

http://forums.mtbr.com/showpost.php?p=6079230&postcount=277

http://forums.mtbr.com/showpost.php?p=7102905&postcount=370

http://forums.mtbr.com/showpost.php?p=7104875&postcount=371

Offroad it's much harder to work out where you are exactly on a descent. Using short sections and adding plenty of manual lap times is about the best you can do. Recorded data with nothing else to refer to isn't as easy to interpret as on the road, especially on flowing sections as you can't see exactly where the corners are. This is where overlaying the power data onto the recording from a GoPro HD camera would be useful to make it clearer.

You can still roughly identify key features from changes in speed alone though. A drop in speed is likely to be where you're braking and a sharp increase in speed may be a drop off. A sudden drop in speed may be where you hit an obstacle that momentarily affects wheel speed such as a log or small rise. These memorable areas are what you can use to try and identify key points for comparing between runs.

The graph below is a section of singletrack descent through woodland that I did today with the main features marked on it. The top section consists of twisting corners with roots across them. There is then a multiple drop off that opens up into a fast straight before a few corners and then a track that comes back towards the road.

The first thing to note is the power trace down this descent. There's no pedalling at all. The first few spikes of power are getting over some roots before the descent starts properly and then it's all freewheeling. This is important if you know the terrain as it immediately shows that I'm riding cautiously. A better rider would be doing at least some pedalling to accelerate on the top sections which aren't that steep.

The main information comes from the speed trace. Because there's no pedalling my speed down this descent is controlled by the brakes. Any sudden drops in the speed are where I'm braking before a corner or obstacle or rolling up a rise. The large acceleration in speed midway down is riding multiple steep drop offs as I let the brakes off and allow the bike to run free on the straight section before braking hard again for the lower corners.

Using this information you can compare lines to see whether one line is quicker than another one. If you have timed laps for different sections then you can do the same for descents as on climbs by looking at lap times from the same descent on different rides to see whether you're improving or not :)

Pictured below: Singletrack Woodland Descent from 26 April 2011
 

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My 23T Rotor granny chainring snapped on a climb today. It was riding up the horse trail climb through the woods which is loose rocks and dirt. Suddenly the bike lost drive and I couldn't pedal any more. I got both feet unclipped and down but my left leg isn't strong enough and gave way. That was that, another mechanical related fall. That's two falls in two weeks due to mechanical issues.:(

I've attached the power data just before the chainring broke as it provides some clues as to why it broke when it did. You can see from the power data that there was a heavy load on the chainring immediately before it failed. I'd been in bottom gear averaging 410 watts at 83rpm (virtual cadence) up the steepest 18.5% gradient section of the rocky track.

Being as low as 79rpm is quite a low cadence for me as I was really fighting the bike to keep going over the rocks. A comfortable climbing cadence for me is usually very close to my normal cadence of 90rpm+. On this particular climb I'd run out of gears so couldn't downshift anymore. Offroad I often tend to ride at lower cadences though. When it's very bumpy I often find that my cadence can drop significantly.

When climbing a track like this one at low speed with very little momentum there are short spikes of effort that don't appear on the recorded data as you have to try and get the wheels to roll over each individual rock in turn. You can tell it's happening at the time but it usually doesn't show on the graph.



Pictured below:

Power output up climb immediately before chainring broke. You can see how I had put in a short burst of hard effort to get up the steepest part of the climb immediately before the chainring broke. The sudden drop in speed and abrupt stop is when the chainring has broken and I'm trying to work out why I can't pedal anymore.

Rotor 23T granny chainring snapped on climb.
 

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I doubt it broke just because of that one effort. Granted, the torque is pretty high with a ring that small and I'd rather see your torque numbers than your watts for something like this but I'd venture to guess a manufacturing defect or defect in heat treatment made itself known at that time. Maybe a steel or ti inner ring would be a better choice?

Can you screenshot your WKO+ graph with the torque channel turned on and the rest of them turned off? View > Torque.
 
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