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  1. #1
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    Brakes are the enemy, rolling mass inertia not so much

    Just a few thoughts here.

    During a crit, one of the biggest things to avoid is using the brakes. If the pack slows down, instead of braking to avoid running into the rider in front, go around them, maintain your momentum, and move through on the side (if possible). That way you carry your momentum and use less energy once they start moving again. In this crit scenario, let’s pretend we have large differences in wheel weight:
    -If you are coasting through and your wheels are light, you would slow down sooner and would have to regain more speed to keep up with the pack.
    -If your wheels are heavy, you would slow down less and wouldn't have to pick up as much speed, but it would still be hard to speed up since wheels are heavier.
    But in both scenarios, overall energy expenditure is about the same.


    In mountain biking, we always emphasize "rotating weight" so much , especially with the 29er vs 26er debate. But looking at the scenario above, I believe that it is our brakes that is the problem. If we could use our brakes less, then our MTB wheels would maintain more momentum and we would use less overall energy.

    But assuming big weight differences in wheels, if you are a poor bike handler, then you are probably better off racing with lighter wheels, since there is more braking and unneccessary regaining of speed. Speed has to be regained more often thus making the lighter wheels a better choice.

    In contrast, a good bike handler would be better served by heavier wheels since a good bike handler hardly ever brakes and would subsequently keep that momentum going.

    But there is probably not enough difference in weight between wheel type to warrant “wheel choice vs bike handling abilities.”

    But the main point here is that brakes are really the enemy.

    So does any company sell an electrical shock device on the brake levers yet?
    Last edited by Poncharelli; 07-12-2013 at 04:59 PM.
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  2. #2
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    While mtb racing, I find myself looking for places to coast into a corner, doing a little less hard braking just to give myself a short break, but also to have good exit speed. Late/hard braking can be detrimental. It's like in car racing, the old adage: the most important turn is the one leading to the longest (or fastest) straight, -the real answer is the most important turn is the one with the biggest penalty for coming in 'wrong' (too hot, wrong placement), and having to slow too much, paying a penalty after the turn. A now deceased pro car racer, Jerry Grant (first 200mph+ lap at indy), told me that at LeMans driving GT40s in the 60s, he figured out that if you lift the throttle a bit prior to the braking zone, the rear comes up ruining the aerodynamics, slowing the car quite a bit (rather than threshold braking later), which saved them at least one brake change in the 24 our race. I think about that, and trying to save my legs just a little during each turn by proper placement. On a bike, with relatively little hp, maintaining the speed through the corners can really add up, given all the possible un-necessary post turn accellerations. When I re-started cx last fall I was shocked at how badly many of the C4 racers go through corners, I've been doing Porsche club autocross for about 15 years, and we spend some time looking at cornering. Many lower level bike racers would be smart to read a decent racing book (bike or car) with a chapter on corners.

  3. #3
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    Re: Brakes are the enemy, rolling mass inertia not so much

    Do you have any specific book recommendations? I don't race but this sounds very interesting nonetheless

  4. #4
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    I learned this lesson riding behind a very fast XC racer on a local trail I'm very familiar with, as a cool-down lap after a race. Wow, I was pedal-pedal-pedal ~80+ RPM just to keep up with him, but he was barley turning the cranks .... OK, he was maybe 50 RPM. The difference was he never hit the brakes at all during the three mile loop ... OK maybe he hit them some. But you get the point.

    Want to race faster? Don't slow down. Wow, why didn't I think of that!?

  5. #5
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    Agreed. Nearly all your energy goes into...

    -Braking. (increase speed through tech sections)
    -Rolling resistance. (quality tires are worth every penny for racing)
    -Air resistance. (don't pedal over 18-20 mph, unless you just want to push air around for minimal gain)
    -Suspension damping. (take the smooth line and minimize travel or damping...all that heat in your shock came from somewhere, and unless you rode the lift up, it's you!)

    Minimize losses to each and you'll go faster for the energy expended. Some races are decided mostly by energy expenditure (long), some primarily by aerobic capacity (med length with no sustained rest), and some are primarily decided by anaerobic capacity (short to medium length, with periods of sustained rest).

    I've found that the last type of racing listed is the least critical for absolute energy conservation.

    Guess I got a little off topic there....
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  6. #6
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    So much of what is true for racing cars is also true for bikes.
    I liked Ross Bentley's book 'speed secrets', and it looks like he has a new one out called 'ultimate speed secrets'.
    It's been a long time since I've read it, but I remember enjoying Vic Elford's 'Porsche high performance driving handbook', He is a great storyteller and has driven so many great cars and tracks, if you like vintage and/or rally you'll like Vic Elford's book, he was a rally pioneer, and iirc he first developed rally notes.

    re brakes: I think it was Ross Bentley that talked about how Jackie Stewart said one of the reasons he was a champion is that he released his brakes more smoothly than his competition, -how smoothly do you release your brakes?
    Last edited by jimPacNW; 07-14-2013 at 11:12 PM. Reason: clearity

  7. #7
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    So in the future XC racing bikes will have flexy caliper rim brakes that barely work and 12 lb. wheels?

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