TT - Roll down test - first time go, any advice please?
willbevan
Posts: 1,241
Hi all,
Well I'm going to be doing some roll down tests to adjust my position and attempt to get more aero, any helpful tips for a newbie would be helpful? (I have a garmin 705 that I will record speed etc on for each run)
From what I understand
1. Always start at the same point on the hill
2. If a car goes past up or down, scrap the run.
3. Only ever adjust one item (e.g. handlebar height), never more than that
4. Do at least 5 valid runs with each setup (If possible doing them interleved, so original position on 1,3,5 etc, and the new position on 2,4,6 etc)
Presuming the position is an improvement you need to:
5. Check the position isn't negatively affecting your power output, e.g. doing 5-10 min efforts at a set power to gauge your HR response, with enough rest in between (Power reading from a powertap on a turbo in my case with massive fans to ensure no over heating)
What I will be doing is bascially
1. Deciding which is a faster front wheel - quad spoke xentis TT or 82mm planet X (both with the same size and brand and model of tub)
2. Lowering/raising my bar length
3. Deciding if straight, s bend or J bends give me a better speed
A lot to do, that is going to take a while.
Anyone got some advice please? =
Also has anyone done any roll down tests with S bends or J bends to see which was better for them?
Cheers
Will
2.
Well I'm going to be doing some roll down tests to adjust my position and attempt to get more aero, any helpful tips for a newbie would be helpful? (I have a garmin 705 that I will record speed etc on for each run)
From what I understand
1. Always start at the same point on the hill
2. If a car goes past up or down, scrap the run.
3. Only ever adjust one item (e.g. handlebar height), never more than that
4. Do at least 5 valid runs with each setup (If possible doing them interleved, so original position on 1,3,5 etc, and the new position on 2,4,6 etc)
Presuming the position is an improvement you need to:
5. Check the position isn't negatively affecting your power output, e.g. doing 5-10 min efforts at a set power to gauge your HR response, with enough rest in between (Power reading from a powertap on a turbo in my case with massive fans to ensure no over heating)
What I will be doing is bascially
1. Deciding which is a faster front wheel - quad spoke xentis TT or 82mm planet X (both with the same size and brand and model of tub)
2. Lowering/raising my bar length
3. Deciding if straight, s bend or J bends give me a better speed
A lot to do, that is going to take a while.
Anyone got some advice please? =
Also has anyone done any roll down tests with S bends or J bends to see which was better for them?
Cheers
Will
2.
0
Comments
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IMO, way too many variables involved to get any decent data out of it.
If you are looking at aerodynamics, do it properly and pay for a tunnel session, not cheap, but at least it'll be accurate.0 -
Just get a mirror and a tubro trainer simple and cheap!!!!!!!!!0
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I do already have two cameras setup I use to ensure I'm staying in positon when on the turbo, keeping the knees in, shoulders close together etc etc.
Yes it does make you look aero but I have seen before from aero testing, that once you go past a certain 'low' you actually become less aero hence the testing.
Well I have done two tests in less than ideal conditions
The first on my road bike one the hoods then on the drops, I could easily see the difference.
Then on the TT bike I changed the angle of the stem (adjustable stem with angle markers) and did a run for each setting. I did them out of order while writting down which angle i did in which set of runs(.e..g not doing -10 degrees, 0 degrees, 10 degrees, 20 degrees etc).
By some miracle (I think luck) when I worked out the cda and put them back in order.
I don't expect I will be able to tell the difference though between different bends, oh and im not paying 500+ for a wind tunnel, not this season anyway
What it did though was let me appriciate the comfort aspect and how small changes in actual bar heights (e.g. -10 to 0 degrees) can make the differece between being very comfortable and not at all!0
