Can Position affect FTP (TT question)

wilmar13

OK, I estimate my FTP to be about 370-380 watts... but this is on my road bike. I cannot seem to create this power on my TT bike, even for a shorter duration.

Last time I did a 10mile TT, I avged 340 watts, for a 21min effort and it hurt. This would be nothing on my road bike... for example today I was off the front on a 55 mile road race from the beginning and I avgd 333 watts for 2hr 10m (360NP)... if I can do this on my road bike, for over two hours without going all out... why would I have trouble doing this on TT bike for 20min? I have no problem putting out a 20MP of 400 watts on my road bike FWIW.

Is it a question of acclimatization to the TT position, and I have a lot of low hanging fruit to harvest by just riding the TT bike more, or is this an indication my position on the TT bike is whack? Something else at play here?

Thanks for you help!

Oh , I use SRM Pro D/A crank... the same one on both bikes.

mullerrj

Something is wrong!!!! If your FTP is 340 watts (20 min TT x .95 computed via A. Coggan) there is NO WAY you'd be able to average 333 for over 2 hrs. I'm guessing that your FTP value (340 watts) is correct and that your road race value (333 watts) is in error. BTW, don't forget to multiply your 340 watts x 95% for a true FTP value..which is 323 watts. Have you had both SRM cranks calibrated lately? As I said, somethings not right.

wilmar13

I don't think you read my post before you replied ... my FTP is at least 370 watts probably higher... and I have lots of race and ride data where I was able to hold over 330 watts for more than 2 hrs... my point is that I can't come close to matching this on the TT bike and am wondering if this indicates I need to adapt to the position, or if it indicates something else is wrong... also is this big of a difference normal?

mullerrj

Sorry, my bad..if your FTP is 370 watts or higher..and you have race data to support 330 watts over 2 hrs..then something is up with positioin/bike setup/etc. I still wouldn't rule out a difference in Power Meter data though. BTW, that's impressive..330 watts average over 2 hrs..that's BIG BOY Power.

patrick_

Both are certainly possible. Unfortunatly I don't know a quick way to tell what it might be.

I'd try to avoid riding positions different enough to require acclimatization, it might hurt your performance on both positions.

Bruce Diesel

I have experienced the same thing. My ftp is aroung 330-340 (last race I did was 340NP for 2h40, VI ~1.1). I have just started training on my TT bike and I struggle to maintain 300watts for 20 minutes.

We have had the same experience with another rider we coach. After 6 weeks of regular riding on his TT bike he is only now able to do 30 minutes at just below his road bike FTP.

tigermilk

What you describe can be completely normal. I've used 3 different TT setups trying to get the best balance of speed and power:

1. Hooker time trial frame (700c version), VisionTech integrated bars - a hefty drop that gets me in a very aerodynamic position. I can go fast, but it costs me. I can sustain about 90% of my road bike hour power on it.
2. Converted road bike - this option opened up my chest more allowing me to breath easier. The drop wasn't as big despite using an adjustable stem to drop the integrated A700 bars lower. I could ride right around 100% of my road bike hour power, but speed really wasn't much different than 1) above.
3. One size small tri frame - late last summer I bought a dirt cheap Leader 730TT frame to try that out (didn't want to spend big bucks on an experiment). I ride a 56cm road bike and went with a 53cm frame. Combined with the 78 degree seat tube angle I'm really forward. Despite a big drop, the smaller frame is allowing me to open up a little more to the point I'm hitting around 95% of my road hour power.

The other thing that has helped has been going with shorter cranks. In my aggressive position the crank length I usually ride were causing my thighs to come awfully close to my torso.

ovalmaster

I have exactly the same problem only a little more complex and it's all to do with the femur/trunk angle and arm position. I've been about 70W down on my TT bike Vs my road bike but also found a big difference between sitting upright, hands on the hoods and on the drops. I found that I produce the most power on the drops therefore I've tried to mimic my road position as close as possible on the TT bike and found I could get back the 70W (a lot of the pros do this). I've ended up moving the aero bars out very wide (just under hip width) and the armrests slightly lower. I noticed that David Miller has moved his bars wider as has Brad Wiggins.

If you look at some of the track guys like Chris Hoy you can see that big powerful riders are better with a wider arm position.

I reckon if you get your position right and train in it your FTP on your road and TT bikes should be very similar (say within 10W).

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Philsybob

I am having the same problem. FTP on road bike is 310. Current TT FTP, is 250 (I have had it up to 300), but I have changed my position in recent weeks. I am going to try and train in this position to see if it comes down.

Is it about position, or is it about getting used to the position?

Not sure yet.

jmocallaghan

Wilmar, 55 mile race the other day. Sounds like you were in the Cat 3/4 with me at Tour De Moore possibly over here in Southern Pines. Yes, position can effect your FTP, in my case, a change of position resulted in a 40 watt gain. What I'd recommend if you've got the time and interest is contact Dr. Greg Combs at www.velosmart.com and tell him Joe O'Callaghan sent you. Greg does a lot of work with fitting in the area from Greensboro to Charlotte to Ft. Bragg. Give him a call or email and he'll probably be able to help you the best.

rr9876

You might want to do a static torque test with the cranks on each bike and make sure that they are reading the same. I think I've read that some people's SRMs have different slope values when switching the cranks from bike to bike.

rmur17

interesting question. So roughly speaking your 20MP is around 340W on the TT bike but some 400+ W on the road bike. That's a 15% drop.

(1) How much have your ridden the TT bike. Hard or easy?
(2) Any pics up of your TT position?
(3) Possible zero-offset or slope issue with the SRM?

IME, it IS possible to go too low or if your saddle position is limited - get too cramped in the TT position. I've been there, done that and ain't ashamed of the T-shirt. IMHO, you should explore your limits.

In my case, I tried this (for me) large drop over several training TT's and two official TT's before realizing I could not sustain nearly enough power to balance the (probably) reduced drag. This was over a six-week time period riding the TT position twice weekly. IOW, I was consistently slower and ultimately that's what counts.

I'd dropped the bars about 5cm but found that raising then only 1.5cm brought my power right up to the expected level (FTP-10W or better) and I haven't messed with it since.

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rmur

wilmar13

If "with me", you mean riding with the peloton that was racing for 3rd place while myself and another strong man were off the front from the start line to the finish... yeah that was me .


So it sounds like everyone is saying this power loss is normal and is just because I am using a position I am not used to.

I did a 10 mile TT last year in 20:46 with 400 watt avg... but it was a different PM (Polar), which while accurate, may have a bloated avg since it doesn't count 0 watt data points (but I use CP now)... unfortunantly I don't have the power file anymore... my position was less aero and more upright then.

My time with the 340 watts was just over 21min… which I calculate my CdA to be about .26… if I can get my power up to 400 again without reducing my CdA I will go under 20M… I think this is more realistic than reducing my CdA more as I am a larger rider.

Didn’t realize you would have different slope using same cranks on different bike with SRM… I don’t understand how that could be… are you sure you aren’t thinking of Ergomo? Either way, based on the fact that my legs scream in pain and my HR will not go up, it is probably that I don’t have the muscle adaptation and riding the TT bike more will help out. I am glad to hear this is normal, and will just need to spend some time on the TT bike in order to pump out the power closer to the road bike.

jmocallaghan

Yeah, that was us coming in for 3d. of course no marshalls on the course and it was a real cluster..... We re-rode the last 2 miles. Who knows what Judy gave us.

There are a lot of things that will differ that position will change inclusive to pedal stroke. Talk to Greg Combs or read his papers, should help you.