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Steep vs. Slam
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I tried to come up with a test this weekend to see which position is faster and perhapes more bearble.

The test was very crude. I used a 78degree TT bike with Syntace bars and a Road bike with Jammer GTs

I rode 3x3miles on the TT and 3x3miles on the road bike with 2-3min rest. Surprisingly I saw almost no difference in speed in avg. speed (I used different computers on each bike)

Anyone done similar tests? I initally thought that for the shorter distance, a steep set up would be faster.
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Re: Steep vs. Slam [Redemann] [ In reply to ]
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I did a longer test but on different days same route. I am considerably quicker with steeper set up, looking at some 2km/ph faster, I was so surprised. I have done it again and it was the same. Conditions were similiar and route was flat. Very crude test but I know the route well and the conditions were very similiar. Also found that I was using a bigger gear on the steep bike with same heart rate and lower perceived effort.



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Simple Simon
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Re: Steep vs. Slam [Redemann] [ In reply to ]
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I set up two bikes - one steep, the other slack. Rode both for about 6 weeks. Had a friend put me on his computrainer and we did a series of 5 minute efforts, holding a flat heart rate at the top of my aerobic zone and recording the wattage. We alternated the bikes, doing 5 minutes on one, 5 minutes on the other, three times. This allowed us to establish a trend line to account for any fatigue, indoor warmth, etc. The forward position for me was a tad faster, but not significantly so.

A month later, I did a similar test on a trainer with an ergometer. I pedaled a steady cadence for 5 minutes, and recorded wattage and heart rate, again rotating the bikes. Here, the slack position was a tad faster.

After all that, I continued to experiment - including seeing just how far forward I could go - to the point that I have now thoroughly toured the top tube. I finally settled down to where the saddle nose is 2 cm behind the bb - eaxactly where it was when all this started. Good luck!
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Re: Steep vs. Slam [Redemann] [ In reply to ]
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As I am new to tri's (2.5yrs) I have asked this same question of the Elite racers both cycle and tri. There seems to be standard answers.
For the Tri racers it is not so much what the bike speed is, but how the transition to the run feels. The tri's feel that with the steeper angle they can better conserve muscle groups which are primarily used for running without compromising bike speed.
The cycle racers it seems to be personal choice. Usually related to femur/tib,fib ratio, and if they like hilly or flat races.
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Re: Steep vs. Slam [flyebaby] [ In reply to ]
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One problem with this method is it doesn't take into consideration wind resistance....and the faster you are going, the more difference this makes.



Quid quid latine dictum sit altum videtur
(That which is said in Latin sounds profound)
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Re: Steep vs. Slam [yaquicarbo] [ In reply to ]
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You are correct on the absence of wind data in that test. The other point that you make, however, that the faster you go the more wind resistance matters, is often stated in the reverse on this very site by some of the better credentialed people. I have always thought as you do, but there are those who say that 50 watts saved on a position is a percentage gain on the wattage output regardless. A 250 watt racer gets a 20% boost, but a 500 watt racer gets only a 10% gain. This one always gives me a headache.
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Re: Steep vs. Slam [Redemann] [ In reply to ]
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I tried hard to make the slam work for me. It made sense at the time because then I wouldn't have to bother with the additional expense of a tri bike. Just couldn't get it to happen. Biggest problem was my hamstrings entering the run. I have short femurs so tend to ride better steep.

The slam works for some people but IMO the likely criteria are long femurs, lean bodies and good lower back flexibility.

BTW, go on John Cobb's website and he says that windtunnel testing demonstrates that the slam can be just as aero as a steep position.
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Re: Steep vs. Slam [flyebaby] [ In reply to ]
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I guess the thing you are leaving out of the 500 watt rider vs. the 250 watt rider is the effect of the speed on aerodynamics. I think I read that the aerodynamic resistance increases by the square of the speed. I don't claim to actually know exactly what the relationship is since I've never really studied the precise math behind the claims, but I do know it is not a linear relationship between speed and resistance.

Consider that guy putting out 250 watts in a non-optimal position that "costs" 50 watts, he is going somewhere around 25 mph. But, if you take the same SAME non-optimal position in a rider putting out 500 watts (what speed is this guy going...32 mph?...I'm just guessing)...NOW this same position "costs" the faster rider more than 50 watts, it costs him the square of the increase in speed....that multiplies in a hurry!

The faster rider does indeed get punished more for non-optimal position because the non-optimal position creates drag equal to a logrithmic total...because we are not just talking about the numerical value of 50 watts. Another way to say this is: a floppy shirt may cost a 250 watt rider 10 watts, but a floppy shirt may cost a 500 watt rider 60 watts.

The faster the speed, the more the cost of sub-optimal aerodynamics.



Quid quid latine dictum sit altum videtur
(That which is said in Latin sounds profound)
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Re: Steep vs. Slam [flyebaby] [ In reply to ]
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i did something similiar as well on a computrainer and found that I was marginally faster in the steep, but if I moved the seat even more forward than the original position I got a little bit faster still (.5-1km/hr), but I took that set up outside and it was hard to ride in a straight line and not very comfortable. The thing is the difference in speed between the CT and outside on the two bikes was greatest outside, so I figuring that some aero advantage was gained from the bike it self (or my position) Note this is very crude test!



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Re: Steep vs. Slam [cerveloguy] [ In reply to ]
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You might be right about the femur length, I have a short femur and find the biking and running off a steeper set up so much quicker and more comfortable where as for some of my taller training buddies the opposite is true



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Simple Simon
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