How much power is required to go 23.8mph?

tim cronk

I just do not believe todays power file yet again.  I just got my Quarq back (3rd one) and today was my 3rd ride with it.   The first 2 rides where last weekends 4 hrs with intervals and 3 hrs ABP rides and the power seemed right on and all was well.  The problem I was having with last Quarq was it would be fine and then all of a sudden go off on tangent 50 watts or more  up or down ans stay there until zeroing by back peddling again.  This did not happen today but having the past issues have put alot of doubt into the numbers I see.

My OS numbers where 210, 224 , 231, 224.... the last one dropped off due to training for Boston but I have just kept my FTP at 230 for training but have yet to re-confirm due to faulty PM...also of note last years peak FTP was 222  a 4.1 w/kg ratio...

Todays ride was suposed to be 90min and alot of FTP work but I adjusted down in prep for Bullmoose weekend coming up and was planning to do wu ,  1x20 @ ; 90-100%,  cd  and done.... Well the loop planned for the 20 minute section is part of an up coming sprint  and I have been training on it.... I have done this loop without HR or Power 4 times but RPE 10  and my speeds were 22.4 , 22.4 , 23 , and 22.6....Naturally I wanted to beat my best time so I went for it... specially since I had the new PM again....

Todays loop  20:03 minutes  7.94miles  AP277 NP 277   23.8mph   HR 176 and Cad 100.... Pretty much crushing my best average speed ... So very much faster than any other previous loop,  effort was 10+,  HR after it settled was legit and @ LTHR,  the warm up power and subsequent power seemed right but the 1x20 just still seems out of whack.  The course is easy and a full loop so there is no advantage of hills or wind.  Last year I did a few all out 20 min efforts to judge FTP and was around 23mph at 235watts....

So again the question is how much power is needed to propel a body and a bike 23.8mph?  Or how much additional power is needed to propel one from 23mph to 23.8mph?    I know there are variables, weight, wind, aero , etc,,,,  This is by far the fastest TT loop I have ever done but the power is just too high?

If it were correct at 277 and I took a conservative 90% that would be 249.... ON top of that I checked in on the scale this am a bit dehydrated and weighing 120lbs for the first time this year (my race weight but not thinking I am really quite there yet)  anyway that would give my a 4.9 w/kg ratio for the 20 min ride and a 4.6 w/kg ratio for the FTP..... Dont think so!  Thats like Jeff Brandenburg numbers...

http://connect.garmin.com/activity/184038340

Here is the garmin file and fwiw the joule is the same.

So here I am again a few days before the BullMoose weekend and I dont trust my PM .

Anybody have some comparisons or possible explanations?

Thanks Tim,

 

 

jhbinsc

As you pointed out, too many variables to say X watts + y speed but the bigger issue is trusting the #'s for racing and training. I'd like to see if the #'s are repeatable. As long as they are consistent, that's the main issue. Watts/kg or absolute wattage is good for bragging, but it all boils down to how fast you can go efficiently.
If you have a good fit and at your weight, I certainly think you are going to be ripping the bike leg!
I am concerned about the need to constantly re zero your PM. Hopefully that is now resolved.
I have a friend who has a Quarq that I believe reads pretty high (as compared to his speed for his FTP) and another who has a Quarq that seems right on and yet another w/ a SRM wireless who seems to read low. The main thing is repeatability. That and going fast w/ the watts you can make! My wireless SRM seems a bit pessimistic to me but it gives me the exact same readings time after time and that's what really matters.
Still, congrats for smoking your local course!

Scott Alexander

What stands out to me is "AP277 NP 277". That's a VI = 1.00. That's some awesome steady riding for an outside ride!

robin sarner

I now have my third replacement Quarq.       Finally seems to work.     Has the SRAM label on it.   

Quarq service is good but so what if their product is faulty, which seems to be pretty common.     

Hopefully your new replacment Quarq and my new replacement Quarq are going to do what they are supposed to do.           

congrats on the power and the speed.

zildgen

Tim nothing much to add as far as the power question. I do think JB nailed it. The numbers are the numbers as long as they are repeatable. What that number is is not so important as long as you can use the numbers to plan your race. And Oh yea that is smoking fast.

MattAaronson

I'm going to go out on a limb and say no way you had NP 277. Based on your historical numbers that is very high. Also to the question of speed vs. power, that is tough due to all the environmental factors, but I'm 138lb, 4.1 watts/kg and usually end up around 23-24mph on z4 intervals of 250ish watts. You are lighter obviously so I'd expect 23 is achievable at a lower wattage than me.

Now all that said, I wholehartedly agree with everyone above who says that PM consistency is the absolute key factor. The thing could tell me 400 watts, but I'm cool with that as long as it's super consistent.

(well actually I wouldn't REALLY be cool with it, but you know what I'm saying!!)

tim cronk

@Matt I dont think you are going out on a limb I completely agree with you based on my past numbers and past experience with faulty Quarq's. However that is still the fastest I have ever gone on a 20min interval so I am guessing higher than other data I have (low 23's @ 235NP for 20 min) and lower than the 277 I got yesterday. I think your comparison is accurate as well , just thinking out loud using a watt a little lower than your 250 say 245 for an average speed of 23.8 and then take 95% of that puts me at 232.... which is realistically where I best tested in OS.

@Dewey and Jeff..... repeatability is very much understood but there in lies my problem with that stupid Quarq! At this point I will be racing 3 races in the next 2 weeks again without being able to really believe what I am seeing.... after I accumulate that data I can call Quarq again. We will see.... Damn thing seemed to be fine last weekend for the first 2 rides.

@Robin... well mine was replaced again but I do not have the SRAM logo on mine.... it is on a rotor3d crank dont know if that makes a difference or not... My early guess is that this one is not working any better than the others.... good luck with yours... If I had to do it over again I would opt for a wheel PM.... I find the crank a pain in the ass since , I have different bottom brackets, shortened chain do to compact gearing etc.... so when I send mine back I cant put in the old crank without changing bottom bracket and chain.

@Scott .... keep in mind that was a 20min interval.... I do find most outside intervals to have very close AP/NP numbers...

There are a bunch of power to speed calculators available on the net.... you punch in your weight, bike weight, temp, elevation, wind, etc and it calculates predicted speed etc... most of the numbers I got using 277watts were much faster than 23.8 (these same calculators also predicted higher speeds than known data I have as well) .... but I did find one that predicted 23.8 on the money... so pretty much useless.

dotcatlin

well, what is it, Tim? The site you found...?

tim cronk

http://bikecalculator.com/veloUS.html

http://www.kreuzotter.de/english/espeed.htm

http://www.gribble.org/cycling/power_v_speed.html

Here's a few.

tim cronk

A few days since Bullmoose and not fully recovered but repeated the 20 min loop with an all out effort. Today's file is much more believable and within the realm of what I am capable of and what I have done before . Using todays number X .95 would yield FTP of 225 which is probably accurate and maybe a touch low since not fully recovered. Hower, the speed discrepancy still can't be explained. Did I really average 40 more watts to get that extra .5 mph avg last week?

Today 20:05 min , 7.79 dist , AP 237, NP 237, 23.3 mph avg , 68 degrees
Last week 20:03min , 7.94 dist , AP 277, NP 277, 23.8 mph avg , 81 degrees

jhbinsc

I still think that single abnormal value is fishy and would not trust it until you can get another accurate test when u have good legs!

tim cronk

Well I have ruled the day and the data in question and aberration of somekind. I still havent been able to match the speed or the watts of that day.

Below is the data I accumulated on the same course doing at various watts in either one loop or two with similar conditions . BTW my PM seems to be working perfect which again doesnt explain the day in question. I believe I have enough data from this and last years efforts to safely say that at my current weight of 120lbs , FTP of 225-230 , on a flat course I will average in the 23mph at or around FTP.

20min one loop 277NP was 23.8mph (file and day in question)
20min one loop 237NP was 23.3mph
43min two loop 209NP was 22.1mph had to slow several times for traffic
41min two loop 225NP was 23.6mph This was the sprint RACE I was 12th wave out of 14 and had slingshot passing the whole ride!

Since I just got my PM back I have not been able to retest. Considering 237NP times 95% is 225 and todays effort of under 41 minutes was NP 225 at least I can call my FTP 225.

Al Truscott

 Just chalk it up to sunspots or black helicopters or something.