Bike fit advice and reduced power in aero position?

To start off with, your seat is too high. Look at the toeing at the bottom of the pedal stroke and even more so, the rocking of the hips.

15% power drop is quite a bit more then I would expect to see. Yes, you will produce slightly less power in aero, but the whole point is to find the compromise between aerodynamics, efficiency and comfort. The longer the race/ride distance, the more important comfort will be, the shorter the distance, the more important aerodynamics will be.

As asked, are you using the same device to measure power? If so, what is it? It's not crank bases (from the video), nor does it look like a power tap… How long have you been riding your road bike and how long have you been riding your tri bike? It's VERY common that you see a quite significant drop from a position you are very used to compared to a new position…. muscles are forced to fire differently and it simply takes time and miles to get the power back up.

And you have nothing to worry about riding your bike on the trainer! You put more torsional forces on it on the road that you do on a trainer. The two things to think about though… you need to use a steel skewer (the aluminum skewer will deform almost instantly…) and you want to use a trainer tire… the compound is specifically designed to withstand the higher temperatures without disintegrating, plus it offers superior grip, make the trainer ride much more like being on the road (expect the boredom of the trainer…)

Thanks for the advice - I'll have a look with a lower saddle (though strangely I'd actually put it up because it felt more comfortable there!).

The bike is sadly as large as I could easily get - I'm 6'4" with unreasonably long legs (37" inside leg) so figured (hoped!) the short torso would make it less of an issue. I've had it a couple of years, though have been guilty of not really spending much time training in aero on it (it doesn't help I live in a very hilly area and am terrified of descending aero) - and I do quite a lot of my bike training in a group with pure cyclists so end up on a road bike for that.

I'm measuring power with a powertap (it's in some of the RALtech wheel covers - highly recommended), though when training I mostly use the turbo's virtual power which is fairly accurate once it's warmed up.

Edited by thigger 2014-06-19 4:34 AM

The seat is too high by at least a cm, and a bit too far forward, maybe as much as 2cm. That will help some, but I can't help bit notice you're pulling on those bars up front. What's going on there? Balance issues? Too much gear? I'd like to see the video after the adjustments, but at a much higher cadence, somewhere in the 100-110 region. Then we can spot things easier.

And seriously, that garage is filthy. What the heck?

At first, I saw going to disagree with the seat position being too far forward, but then I paused the video at the bottom of the pedal stroke. Your medial malleolus (the boney protrusion where your fibula/tibia ends and your foot begins) is quite a bit behind your femur hip joint. When you ride really steep, these are aligned in a vertical line, but you shouldn't be ahead of that line, or you will lose power.

Also, the observation is correct that you seem to pull on your bars, but I think that is because your seat is significantly too high. I'm not even sure 2cm is enough… it may very well be more. Yes, it's that off.

There's something going on with your left leg as well… at the very bottom of the extension, you seem to rock to your left. This is symptomatic of three issues, leg length discrepancy, muscular imbalance or limitations in range of motion. This is commonly combined with a fourth, improper pedal technique…

If you are going to compare the power, you can't use an actual measured and a virtual… the virtual will be off, but what makes it useful as a training tool is that it's a fairly constant delta, i.e. you are always off, but at least it's off by the same amount. In this case, you really need to use the PowerTap and the trainer to compare power. Once you're on the road, you can compare functional power (basically, what can you sustain)

Thanks again for all the advice - some really useful ideas

I had the seat forward because I noticed I was tending to ride right on the front; the bracket is at the 80 degree position marked on the seatpost, though there's slightly more rail in front than behind at the moment. It's an Adamo (I'm told they're a little different regarding positioning).

Power - whilst I mostly use virtual power for turbo sessions (so I can keep an outdoor tyre on the powertap), the comparison was made using the powertap and shows a good 15% drop. As I mentioned earlier, the road bike (where I produce more power) has its saddle 1cm higher than the TT bike - hence my confusion about heights! I'd even raised the TT saddle recently to try to match the road more closely.

I've tried some changes: (videoed away from garage/bike store to limit comments )

Original revideoed: http://youtu.be/cZnqlPD-gz8

Saddle down by 2cm: http://youtu.be/xHeWdTC18Cg

Saddle down by 2cm, base bar up by 2cm: http://youtu.be/AKKwgFWUXx0

I tried to put some stickers on for measuring but the only one you can really see is the hip one (greater trochanter)
The moving back and forth on the extensions is not me being uncomfortable, I was just looking to see if I need to lengthen the extensions.

Thanks again!

I can't quite picture this description, could you provide a reference with an actual picture? I'm curious to know myself.

when you say 'base bar up 2cm', it *looks* like you threw a couple more spacers under the base bar, am I correct?

You're on the right track I think. Seat height looks a lot better, but you can still come down with it even another cm. You're still extending too far on the down stroke. However, you are better positioned over the bottom bracket now. If you drop the seat I think the bar height will sort itself out if you leave it where it is (with the max spacers).

Ultimately, this bike isn't a great fit for you, but you knew that already. this is just to get what you can out of it. I have the same bike fwiw, and it's really designed for a much steeper angle than you can get into from what it looks like. It sucks how few options there are for tall guys, it really does.

green line is the femur, red line on medial malleolus. this is off the second video, so it's getting better, but it's still too high and too far forward



Edited by fisherman76 2014-06-19 10:21 AM






Attachments
----------------
fitpic.jpg (407KB - 9 downloads)

The only thing that I could add to this discussion is from my own personal observations. What I learned from myself and subsequently read on physiology is that the hamstrings will tighten as you bend over at the hip joints... I had to do several static tests, but my torso angle on the road bike is 105 degrees, and my angle on the TT is around 92 degrees, but I can't keep the same saddle height on the 2 bikes, my hamstrings would be too tight... so my saddle height is about .5 cm lower on the TT. Oddly, my knee angle is more open on the TT at about 145 degrees with a lower saddle height than on the road bike, which is about 142 degrees. I like to go by knee angles myself than static formulas, but I start at the static formulas and adjust from there.

This is what I thought, thanks. QR bikes are steep to begin with.... Dan Empfield has his own fit philosophies, as described on ST.

Yep - just bunged some spacers in (the height on the aero bars I'm using isn't adjustable so I had to bring the whole basebar up)

I've tried with the seat down another cm ( http://youtu.be/UKycU2azN0M) but it's starting to feel really odd now!

What sort of bike do you think might fit better? Just larger all over, or longer? It surprises me that now (with the seat dropped 3cm) I'm near the end of the range of markings on the seatpost (It's marked from 1 to 7, where 7 is the lowest, and I'm now on 6 having started on 3).

Realistically I'm unlikely to be allowed to spend enough for a change (this one was a gift) though my local shop has talked about lending me a Felt.

Dan has nothing to do with QR anymore, he sold it years ago. The bike fits me because I have a slightly longer reach than most, but otherwise fit comfortably on most long and low frames (ala Felt, Cervelo, etc) in the 55-56 range. I'm also fairly flexible, so *getting* steep isn't an issue for me, I'm comfortable at 78 degrees for a good 3 hours. At 76 I'm good until I pass out. Basically, out of the box with the seat as low as an uncut post will allow, I don't need much adjustment or any spacers to get into my fit coordinates. That offers me a ton of flexibility in changing my fit for different saddles, different bars, moving things around if I'm tight or need a more slack position for some reason, etc. I bought the most bike I could get underneath me to maximize the aerodynamics it affords me. To that end, it could easily be ridden a lot less steep than I have it. All I meant was that the bike offers a lot of flexibility to get VERY steep, and if you look at the range of options it affords, most of the angles are going to be in the 'aggressive' category.

Actually, that looks a lot better. A LOT. Sorry it feels weird! How's the power? Despite being weird is it comfortable? Fit changes always take a while to get used to, a couple hundred miles in my experience. If it's wrong, though, you'll know pretty quickly, because you will either hurt, fatigue quickly, or both.

Most Felts are the same basic fit family as the CD01. Long legged short torsoed folks generally fit better on the Slice, Speed Concept, and a few others I can't remember right now. Without knowing your stack and reach, we're just shooting in the dark, please don't pick a bike like that. If you're comfortable on the QR, put it out of mind completely. A purist might sneer at the spacer count, but if you feel good and put out good power, that's a good fit.

You have no idea how tempting it is to put it back up by at least a cm! Thanks for all your advice.

In my fiddling with Kinovea it looks like my knee angle comes out around 145 - is that not quite low? (or at least, at the lower end of 'acceptable'. I'm now 4cm below my road bike position!

I've not had the garmin out to check the power; I'm due a turbo anyway so I'll try it on the TT bike and see what happens.

No idea what's going on with your road bike, so making comparisons doesn't seem like the smart thing to do. The geometry is different between road and tri bikes, so measuring 'height' (what are we talking about, saddle nose height above bottom bracket? which saddle? or are we talking stack? what seat tube angle?) is not apples and apples.

Knee angle alone doesn't say much of anything either, although using the last video you posted it looks like your knee angle is closer to 160 than 145 just using a protractor... I'm not familiar with Kinovea. I'm also looking at your toes, which are still pointing down a bit at the bottom of your pedal stroke. Whether that's bad habit from riding too high, or the saddle is too far back I can't tell, but the point is there is more knee extension to be had from not pointing your toes if that's a concern. We're not even getting into (because, quite frankly, we've gone really about as far as you could go just using a video!) cleat placement, saddle pitch, crank length, and myriad other factors.

Genius! It's difficult to tell as I was doing weights yesterday so my legs are quite sore - but a quick spin up to FTP for a few minutes feels like it's much more sustainable. I think you've found me about 20-30 watts! And it's pretty comfortable too. Hopefully without losing too much aero; though it feels like I could take the bars back down a half cm or so.

I'm certainly convinced enough to leave it like this for the next few weeks. There's a local TT I might have a play at to test it out.

Re the road bike, the measurement I made on both bikes was BB centre to the flat part of the adamo saddle. It certainly has a less steep seat angle, though I bought a foward-facing seatpost and slammed the saddle as far forward as it would go to try to get closer to a tri position for turbo purposes.

Thanks! I believe I owe you a pint.

Wonderful! Glad to hear it!

You'll have to be state side for that pint though

By the way, your missing 4 cm is right here:

assuming the fit on the roadie is solid, you could easily add 4 cm of height to the measurement given you changed the effective seat tube angle as you did. This type of confusion is one of the drivers behind Dan Empfield's definitions of stack and reach. You can rotate a body around the bottom brackets and get different measurements on different tube lengths, but if stack and reach are held constant, the bike will still fit.

In the 3rd video, your upper body is significantly more still than the previous ones, your hips are not rocking and you're not looking cramped. The goal should be to get the back as flat as possible, but NOT lower. You look pretty flat in the 3rd video…

Finding significant power in a bike fit is a clear indication of a sub-par fit (and overly aggressive commonly)… Finding speed without change of power, is a clear indication of aerodynamic improvements. Interestingly, the most common indicator of improved comfort is not necessarily on the bike, but shows up in a faster run split (nothing wrong with that though!)

Hey I found this video to be interesting relating position and power..http://goo.gl/K7Pzd4 Triathlon Research does a great job posting videos like this to answer your questions