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Discussion Starter #1
Tomorrow is my first time trial of the season in Tampa, FL at the Squiggy Classic. The time trial is on a closed course loop and is 7 miles long. Should be a great race and I'm hoping to put up a decent time for my Cat 5 self. Any tips for doing well? I'm feeling pretty strong and have a solid base and the bike is pretty aero. The big thing for tomorrow is that it is expected to be a little windy. The majority of the course runs West to East in a counter-clockwise circle. I will be running a HED3 up front and a disc in the back. With the extra wind, should I go with a HED3 in the back as well? Any other tips to squeeze a few more seconds out?

Thanks!

the Flash
 

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Too late now

So, you've already run the TT by now, but there are a whole bunch of little points which, when added together can both improve your time and make the TT a more "enjoyable" ride. Be well fed and well hydrated, with a good carbo intake the day before and the day of the event. If its an evening ride, snack & sip through the afternoon. Some caffeine 30-60 minutes before the ride doesn't hurt. Be well warmed up - the saying is the shorter the TT, the longer you should warm up. A 10 mile ride to warm up for a 10 mile TT is good. Shortly before your start, do a couple of "jumps" up to maximum effort for 1/4-1/2 mile to get your body ready for a fast start. Arrive at the line sweating, but not out of breath, and ready for a rapid acceleration up to TT speed. Try to get to your maximum sustainable effort ASAP (remember, you're already warmed up). If your legs seem like they are the limit to going faster, shift to a lower gear. If your lungs seem like your limit, shift to a higher gear. Get into your best aero position and stay there. For the turnaround, hold your speed as long as possible, jam the brakes and bank the turn faster than you think you can go. Forget this business about sprinting for the finish - you should have nothing left to sprint with. Around here, the finish of a TT is described as "notfarfrompukin" if you get my point.
 

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Kerry Irons said:
So, you've already run the TT by now, but there are a whole bunch of little points which, when added together can both improve your time and make the TT a more "enjoyable" ride. Be well fed and well hydrated, with a good carbo intake the day before and the day of the event. If its an evening ride, snack & sip through the afternoon. Some caffeine 30-60 minutes before the ride doesn't hurt. Be well warmed up - the saying is the shorter the TT, the longer you should warm up. A 10 mile ride to warm up for a 10 mile TT is good. Shortly before your start, do a couple of "jumps" up to maximum effort for 1/4-1/2 mile to get your body ready for a fast start. Arrive at the line sweating, but not out of breath, and ready for a rapid acceleration up to TT speed. Try to get to your maximum sustainable effort ASAP (remember, you're already warmed up). If your legs seem like they are the limit to going faster, shift to a lower gear. If your lungs seem like your limit, shift to a higher gear. Get into your best aero position and stay there. For the turnaround, hold your speed as long as possible, jam the brakes and bank the turn faster than you think you can go. Forget this business about sprinting for the finish - you should have nothing left to sprint with. Around here, the finish of a TT is described as "notfarfrompukin" if you get my point.
All good stuff, I would add to note the time that the first rider goes off. I have rarely seen a TT start on time and your time will shift. Showing up to the line all ready to go just to find out that you have another five minutes will throw you off, especially in a short time trial. I wear my watch during my warmup with the stop watch running counting up to my start time. I start it off of the first rider. As far as a cycling computer, start the clock on the guy in front of you if it is a one minute interval. That way you don't mess with it when you start.
 

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Discussion Starter #4
So the race went pretty well....

I took off at 8:34:30 from the start ramp and got up to a speed of 25-26mph pretty quickly. once I made the turn going west, I noticed a little bit of a tailwind, so I picked it up a bit and ended up averaging around 24mph for the first 3.5 miles. Then the turn to go back East....massive headwind! I buckled down, but kept my speed about 21mph and slowly climbed back up in speed. I ended up finishing exactly at 19 minutes with an average of 22.1mph. Put me in the middle of the pack for cat 5, and a minute below my goal of 20 minutes. Overall, a real good race and I was near puking at the end. I did real well cutting all of the apexes, and didn't get passed by anyone even with the 30 second intervals. The only thing I wish I could have changed was my cassette. I was running an 11-23 and I started getting to close to the 2 cog jumps in the headwind. I probably should have switched to the 14-25. The other big difference is that I ran a HED3 in the front and disc in the back. I did a faster lap with my AC 350's later in the day as those wheels are almost 2lbs. lighter!

I'll take is as a good first race of the season. TT series doesn't start here until May, so I have time to work on it!

The Flash
 

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The Flash said:
The other big difference is that I ran a HED3 in the front and disc in the back. I did a faster lap with my AC 350's later in the day as those wheels are almost 2lbs. lighter!
If you're saying you think you should have used the AC350's instead of the HED3's for the TT, I wouldn't have. Aero beats light weight in a flat TT. For hills or crits, the lighter weight would help because you're accellerating constantly. For a TT, you want Aero, at the weight expense.
 

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Discussion Starter #6
So the question is, "Does it take more energy to keep heavier, aero wheels moving than lighter, less aero wheels?". It did seem a lot easier to keep the speed up on my road bike with the lighter wheels than on my TT bike with aero wheels. The only thing I can guess is that because I was sitting more upright, I was catching more of the gusting tailwind. At least 25mph gusts the last 2 days....

I'm going to try the Zipps on the next one and see if I feel any difference...

The Flash
 

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sometimes its better to chose the less areo wheel depending on conditions...
look at the last TT of the TDF last july. Most guys ran a rear disk, Lance didn't and won...
 

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The Flash said:
So the question is, "Does it take more energy to keep heavier, aero wheels moving than lighter, less aero wheels?". It did seem a lot easier to keep the speed up on my road bike with the lighter wheels than on my TT bike with aero wheels.
People usually say the opposite -- that heavier wheels take more energy to spin up, but they take less energy to keep spinning because of their intertia. Given a constant force of aerodynamic drag (i.e. all else being equal) the heavier wheels will decelerate less because of their higher mass.

One quick thought: were you using similar gearing/cadence on both runs? Perhaps you were riding a higher cadence on the road bike, which made it feel that your wheels were spinning up faster vs. mashing on the TT bike?

Cheers,
Ari
 

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Nope, sort of

ari said:
People usually say the opposite -- that heavier wheels take more energy to spin up, but they take less energy to keep spinning because of their intertia. Given a constant force of aerodynamic drag (i.e. all else being equal) the heavier wheels will decelerate less because of their higher mass.
This is a mix of truth and nonsense. Taken in order: 1) heavier wheels DO take more energy to spin up, 2) once things are up to speed, it makes NO significant difference what the wheel weight is, 3) heavier wheels will decelerate slower. So I guess you're batting .666 - 2 out of 3 ain't bad.
 

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Nope

The Flash said:
So the question is, "Does it take more energy to keep heavier, aero wheels moving than lighter, less aero wheels?". It did seem a lot easier to keep the speed up on my road bike with the lighter wheels than on my TT bike with aero wheels. The only thing I can guess is that because I was sitting more upright, I was catching more of the gusting tailwind. At least 25mph gusts the last 2 days....

I'm going to try the Zipps on the next one and see if I feel any difference...

The Flash
A heavier wheel(weight at the rim not center) has more momentum than a lighter wheel so once you get up to speed then the heavier wheel is easier to maintain speed with plus it is more aero. A technical course needs a lighter wheel if you are having to accelerate alot.
 

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kinda agree with that Kerry

heavier wheels don't decelerate slower. They just take more pressure from the breaks thus more pad wear. But really, your weight and momentum is what determines most of that. You will only break as fast as you feel comfortable.

Heavier wheels will want to stay spinning better. I sure noticed when i switched from 26" MTB to 29" (they are a bit heavier for similar build)

i think the greatest diffrence is just the weight you carry up the hills and the spin up into a sprint.
 

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Kerry Irons said:
This is a mix of truth and nonsense. Taken in order: 1) heavier wheels DO take more energy to spin up, 2) once things are up to speed, it makes NO significant difference what the wheel weight is, 3) heavier wheels will decelerate slower. So I guess you're batting .666 - 2 out of 3 ain't bad.
Ouch! I have a lot of respect for you, Kerry, so I feel the need to defend point 2 -- in fact, I think it's the same as point 3. The energy to keep wheels spinning is precisely energy spent fighting deceleration, mostly due to wind resistance. Because lighter wheels will want to decelerate faster, it requires more power to keep them going. Do I think this power is "significant", though? Probably not; I doubt it would make almost any performance difference. However, if I were trying for the unrestricted hour record, for example, where the goal is maintaining a constant speed with virtually no acceleration, I'd want some heavy wheels on my bike.

Cheers,
Ari
 

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Clear thinking

The problem here is that people are not thinking of the separate issues in a clear fashion. So let's take it step by step:

1) Lighter wheels will require less energy to accelerate, and once you stop applying power, they will decelerate faster. It's all about storing and recovering kinetic energy, which is 1/2xMxV^2 (one half mass times the square of velocity). Heavier wheels DO decelerate slower, all else equal.

2. Once the wheel is up to speed, the energy required to keep it going is almost entirely due to aero drag and friction and has virtually nothing to do with weight. Heavier wheels are not easier or harder to keep moving - more momentum does NOT mean it is easier (required less power) to keep it going.

3. IF a heavier wheel is more aero, then surely it will take less power to keep it moving, but this is NOT due to the fact that it weighs more. A lighter aero wheel (like a Campy Bora) would take less energy to move at a steady speed than a heavier non-aero wheel. That's all about aerodynamics and friction, not weight.

4. You don't expend energy "fighting deceleration," you expend energy to overcome friction and aerodynamic drag. A bike/bike wheel in motion decelerates when the power input is less than the power required to overcome that friction and aerodynamic drag.
 

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Whoops ... you're absolutely right, Kerry. Heavier wheels lose less velocity, which was my initial point -- but because of their increased mass, they still lose the same amount of momentum as lighter wheels with the same aero profile. Mathematically, this is because F = dp/dt (force = momentum/time), and drag force is independent of mass The subtle velocity vs. momentum point is what tripped me up. But logically, it makes complete sense -- every watt (force * velocity) lost to drag is a watt that has to be put back into the pedals, whether the wheels are light or heavy.

Now, for the love of God, don't tell my PhD advisor at Caltech that I said that -- I'm writing my thesis in classical mechanics, for crying out loud. ;)

Cheers,
Ari
 

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Kerry Irons said:
The problem here is that people are not thinking of the separate issues in a clear fashion. So let's take it step by step:

1) Lighter wheels will require less energy to accelerate, and once you stop applying power, they will decelerate faster. It's all about storing and recovering kinetic energy, which is 1/2xMxV^2 (one half mass times the square of velocity). Heavier wheels DO decelerate slower, all else equal.

2. Once the wheel is up to speed, the energy required to keep it going is almost entirely due to aero drag and friction and has virtually nothing to do with weight. Heavier wheels are not easier or harder to keep moving - more momentum does NOT mean it is easier (required less power) to keep it going.

3. IF a heavier wheel is more aero, then surely it will take less power to keep it moving, but this is NOT due to the fact that it weighs more. A lighter aero wheel (like a Campy Bora) would take less energy to move at a steady speed than a heavier non-aero wheel. That's all about aerodynamics and friction, not weight.

4. You don't expend energy "fighting deceleration," you expend energy to overcome friction and aerodynamic drag. A bike/bike wheel in motion decelerates when the power input is less than the power required to overcome that friction and aerodynamic drag.
revenge of the nerds :p
congrats on a great race, flash! sounds like you enjoyed it, got some good results and learned something from it for the future- what more can ya ask for? happy riding!
 

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you hit the nail on the head kerry.
now i must go because i'm getting terrible flashbacks to my college physics courses
 

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Discussion Starter #17
It was a pretty good race, and I learned a lot. The next time trial begins our series here in Florida. I plan on racing one of them on my AC350's and another on the Hed3/disc combo. I'll see if I run into any difference.

Most of all, I learned to go back to Junior gearing...a 14-25 is way more useful than an 11-23. There is a much tighter spacing toothwise between the cogs that makes it easier to keep cadence in my normal 95-100 range....

Flash
 
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