Simple answer: There is no way to tell, without performing a numerical simulation, or wind tunnel tests, each of which will cost you very serious money. Note also that it is not at all clear whether such a modification will decrease, or actually increase aerodynamic drag.Old Junker said:i have 1 inch spacers under my aerobar, if i remove these asuuming all things constant ie,power,comfort etc how much time is it worth at 40kph on a 40k itt???
i cant find any info/data or website on this
Do a field test with a powermeter and see if you get differences in speed for a given constant power - people who use suitable roads and testing methodology can find differences that are repeatable and have been verified by others for changes in equipment.Old Junker said:
What do you mean by a "real response"?Old Junker said:
Correct. In this particular case, the one thing that is clear is that the effect of the proposed modification will be below the experimental noise of the methods you suggested. Not to be misunderstood, those methods are perfectly fine, in principle, but they are not sensitive enough to decide this question.Woofer said:
Dietmar said:
Really? People actually pay money for this kind of nonsense? How much? We could perform much more sophisticated analyses in our group, for a comparably reasonable amount of money, so I am genuinely interested in whether there is a market for such capabilities.Woofer said:
P.S.: The way I understood this poster, he was going to eliminate the spacers, but then raise the stem such that everything else, including rider position, remains equal.Woofer said:
Dietmar said:
I think we all know the question you are asking, however the way you posed the question you seem to have "fixed" the speed at 40kph over the length of the distance traversed which would mean that there would be NO time differential; but, you will have hopefully expended less energy in doing so!Old Junker said:i have 1 inch spacers under my aerobar, if i remove these asuuming all things constant ie,power,comfort etc how much time is it worth at 40kph on a 40k itt???
that's slow in a car, but for some people it is fast on a bike) or coasting on a particular false flat (~15 MPH vs. ~18 MPH) ... move to the tops, the speed would drop by about 3 MPH, move down, and the speed would resume toward the higher end of the particular range. Your results may (make that will) vary, and it was probably more coincidental than not (or, just my memory) that the differential in both cases was about 3 MPH since one would think that there would be more wind resistance as the speed increases ... you may coast at 5 MPH faster when in the drops because your body position is more aggressive OR possibly only 2 MPH because your higher body position is more efficient than mine.
Hmmm.... that wouldn't make much sense, but now I see why you said there was a chance that drag could increase. I read that he was wanting to lower his torso by 1".Dietmar said:
I hate it when people respond to my posts and don't tell me what I want to hear too!Old Junker said:
you read it right 1 inch torso lower and i beleive its worth about 2 minutes in a 40k at same power/weather/coursefrenchyge said:Hmmm.... that wouldn't make much sense, but now I see why you said there was a chance that drag could increase. I read that he was wanting to lower his torso by 1".
Either way, your answer was correct -- there's no way at all to know. In addition to the uncertainty of the aerodynamics (which should improve, although it's impossible to guess by how much) there's also the question of whether he would be able to generate as much power in the lower, more cramped riding position (again, impossible to know based on the post).
I guess there just aren't any easy answers.
i will try a feild test thanks alfengalfeng said:Having said that, as noted, rather than a wind tunnel test, you could do a "field test" of sorts ... if you have either a RELATIVELY LONG descent OR LONGER false flat you can simply change your body position and see how much more slowly you COAST when you are catching the additional bit of air than when you are 1" lower ...
As one very imprecise benchmark, from the tops to the drops on a road bar is between 2-to-3 MPH as I recall from making the CASUAL observation whether coasting on a particular descent (~35 MPH vs. ~38 MPH ...
There is obviously more than a 1" difference in body position when moving from the tops to the drops with a road bar (and, not all road bars have the same drop) than the 1" adjustment you plan to make; AND similarly, we don't know how efficient your current body position is ...
So, before doing your field test, I would be greatly surprised if your gain wasn't well less than 1 KPH -- is that the type of answer you were looking for? Well, seconds ARE seconds in any time trial ...
Alright, my fault, but I was confused by your reference to other things being equal.Old Junker said:
Well, obviously that depends on your position before you lowered your bar, and you need to take into account that the efficiency of your power output is affected by your position, too. But, yes, with the scenario as I understand it now, your best affordable bet is to do test runs as described by several people above.Old Junker said:
Depending on how flexible the OP is, this could have a much bigger effect than the aerodynamic savings. You can spend all you want on complicated testing and analysis, but the only way to really find out if it works is to get out on the road and try it.frenchyge said:
