TT bike adaptation?

mikeyp123

How long does it take you guys to start seeing similiar power on your TT bike as your road bike? Do you ride your TT bike regularly? Can you achieve the same 20 min power?

I finally got the TT bike built and ready to go. Just started training on it, once a week, 2x20. Getting good results. Managed to beat my personal best 20 min just this morning. I honestly thought I would never achieve similiar power numbers on the bike... but once I got the legs ticking over at the same cadence as my roadbike bike it all magically came together. But damn that thing is uncomfortable, esp for my boys.

Alex Simmons

Some never do but persist anyway as the speed improvement of better aero often overrides the power loss.

Try changing the tilt of your saddle a little and see if that helps.

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swampy1970

I still think that most people do the time trial bike thing ass-about-tit. Instead of accepting power loss, spend alot of time working on a position that works and allows you to pedal in reasonable comfort whilst allowing you to unleash your hard earned watts.

I spent 3 months working on a time trial bike position before I got a "trial" frame made from 531. Thankfully I had a BCF/ABCC senior coach who had a fully adjustable ergometer and worked in an engineering department. Talk about being in the right place at the right time. LOL

The damn thing worked so well that I never did get a frame made from a fancier material. I carted the frame across the atlantic when I moved to the US a while back - but with it's rather steep seat angle and uber long top tube I'm not sure of it's legality in events here right now. The old 8 speed Campag Shamals are gathering dust right next to it....

daveryanwyoming

If that gives you the best overall watts/CdA then great, but if you can sacrifice a few watts for a substantial CdA drop then you come out ahead in flat time trials. That's why folks pay big bucks for wind tunnel time.

Power alone doesn't win flat time trials. It's basically the same as a guy who can sustain 400 watts for an hour but weighs 100 kilos, all that power doesn't get the job done while climbing if you've gotta carry that weight up the hill. Where's the best tradeoff? That's what folks try to figure out when it comes to fitting a TT bike or targeting an ideal race weight, no simple answers and peak watts may or may not be the right solution.

-Dave

swampy1970

I'm well aware of that and have been ever since reading all the good stuff from Chester Kyle and his Cycling Science magazines back in the late 80's and early 90's. Yes, I come from the pre-tri bar era.

With a lot of work, trial and error you can design something that lets you have your cake and eat it too but most often that doesn't come in the shape of an off-the-peg frame even though stuff like the P3's look so-so-sexy... Of course if the governing body forces you to adopt UCI rules and regs then you might as well just go that route.

You shouldnt have to worry about "your boys" going numb in a race - it's just too distracting!

daveryanwyoming

Can't argue with that

mikeyp123

Ya seriously, it's that damn tip of the saddle 5cm behind BB UCI regulation. Which has me sitting on the very front part of the saddle to open up the hip-angle. I even purchased a triahtlon saddle, with the over-padded front portion, it helps some. If I sit proper on the saddle I need to raise the aero-bars.. then I lose the flat back. I have a couple TT events later this year where they will probably measure. If you look at most of the pros these days, they are doing much the same thing. Sitting on the very front of the saddle, low bars, flat back, open hip-angle.

Good thing I won't have to spend more than an hour racing in that position.. and I only train on the bike once a week, no more than 2 hours.

peterpen

You might want to look into an Adamo saddle by ISM. Silly looking thing that take a bit of getting used to, but quite helpful if you're having trouble getting far enough forward. Also, I've seen comments recently from people working in wind tunnels that a flat back is not *necessarily* ideal. I think it's all about frontal area - if a rounded back allows you to have a lower head, narrower shoulders, or better transition from helmet tip to back, it might be faster.

My power on the TT bike is 5 - 7% less than on the road bike but the position is worth it. Mentally it can be difficult when struggling to hit numbers that are lower than what I'm used to, but TT's are scored based on time, not watts.

Be mindful that your power in the TT position can follow something of a 'U' shape over the course of a few weeks. A new position may initially feel great and high wattages may be possible as new, less-fatigued muscles are called upon. Next those muscles reach a similar state of long-term fatigue and power drops. Finally you adapt to the new position, train those muscles, and power comes back up.

mikeyp123

There's an interesting aero test spreadsheet at the google wattage group... Alex recently posted it. I believe he reworked a spreadsheet originally done by Robert Chung. Anyway, I have a regular loop I ride.. I took my PT data and worked it in the spreadsheet. I got a CdA of 0.249 m^2, which I suspect isn't bad.. given I was using a regular helmet, wheel-cover, and no water bottles.

Anyone have any ideas about what a good CdA is.. or the ranges of those numbers?

rmur17

a range of 0.20 to 0.30 covers a wide range of riders, body mass, body types in an aero position of course and with typical gear. Road bike on the tops with 32-spoke wheels and you're into a different realm altogether.

0.25 is firmly midrange - whether it's good, bad or average depends on your mass mostly I would judge. Of course speed on a typical TT course is pretty much dominated by W/CdA so that's the ratio which needs to be maximized.

Re your Cda test, was it windy on the day?

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PSUcycling

2nd on the ISM. I've switched even on my road bike. Hardly any numbness ever.

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mikeyp123

I weight in at 149 lbs (67.6 kg) at 5' 10.75".

Very little wind during the CdA test. One aspect of the spreadsheet I'm having issues is with, is figuring out an appropriate rolling resistance. For the .249 CdA number I used a CRR of .00650.. I would think that number is a little inflated. Michelin Pro Race 2 are supposed to have a pretty low CRR.

mikeyp123

Ordered it today. It took my privates almost 24 hours to completely lose the numbness, after the 40k TT this weekend.

rmur17

low wind = Good Chung

For Crr, with good tires on good roads with normal temperatures, the range of 0.004 to 0.006 should about cover it. Chipseal -> who knows!!! Gravel or trails? dont' even think about it.

My approach lately is to run it across five Crr cases: 0.004, 0.0045, 0.005, 0.0055, 0.006. It's pretty quick to do that as you know by now.

One test isn't going to give you a 'confident' estimate anyway but do enough across a reasonable Crr range and the data should converge.

For the Pr2, on good roads and say ~20C temps or higher, 0.0045 would be my single best estimate.

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