Friday, April 17, 2009

Saris PowerTap Disc Brake wheel

This year, Saris were able to help out with a few pieces of equipment through Paligap – the most interesting piece being the new PowerTap SL 2.4 Disc built by Cycleways onto a Stans NoTubes Olympic Rim with Sapim Race spokes which just so happens to talk wirelessly with my Garmin Edge 705. I have used power on the road bike for over a year now and have found it a great training tool – sometimes, I do admit to riding t o a number (which is good sometimes) but the advantages for training specificity, pacing and training/performance recording has been immeasurable. With all that in mind, I was always intrigued to see what the difference would be off-road versus on the road. With a few weeks of training and an offroad time trial on the wheel I can start making some initial observations.

Full built wheel including brake rotor and rim tape is 1,250 grams

Firstly, mountain bikings power profile is dramatically different from the road. Looking at a road power file, you see power rise and fall a lot, this is nothing in comparison to what you find on a mountain bike. The amount of time that you spend at Anaerobic power levels is astonishing with the time spent around Threshold power levels being dramatically lower (unless of course there are long steady climbs in the ride/race). My observation is that you are basically coasting (steep or technical descending), riding at endurance pace (fireroad descending) or are at VO2max/Anaerobic Power Zones (all climbs).

A muddy one

Throughout the winter I spent a great amount of time training for increased power at Threshold/Tempo and increasing the time I can spend at it – it works well for the road but the power requirements for off-road are quiet different and something that I will be altering my training for.

For instance, if you take two rides, one on the road and one off-road that you would consider equally hard on your body, the MTB ride would have a much lower average power, but with a lot higher peaks. Also, generating the same power off road is much more difficult than on a nice smooth road.

Secondly, the cadences at which the power is output is dramatically different. Road riding, unless very steep (and not enough gears available) you can basically decide the cadence you wish to ride at, again, it is so steady. In mountain biking, the cadences vary dramatically, with a large chunk of the high powered efforts at low cadences (50-70). I guess this is a lot of the out of the saddle steep climbs, but again, a thing that my road riding had not prepared myself for properly. On the road, I do train at the slower cadences, but not at that power level – my Anaerobic, VO2Max efforts tend to be at the 80-90 range.

So what am I changing, without going into too much detail, more high powered steep climbs (not necessarily technical, I seem to handle those well), more 3-5 minute climbs and, if you read anything about my Cyprus racing, more training in relation to fast starts – clearing lactate etc…

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