All time personal best achieved tonight

67 replies [Last post]
Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012

I am proud to announce an all time personal best in my chosen standard: a one hour time trial.
Tonight I went 42km in 59:25.
I allow myself a flying start, straight out, a safe turn around with another flying start back in. Start line is the finish line.
Factors in my favor: Cruzbike Vendetta, self-made tail box, V3.0(pic to follow, it may be upside down), self-made rear wheel cover, weather: fairly calm but not absolutely so, road: quite straight (I did hit a light), terrain: surface-paved, 9/10 quality, low rolling hills with about 1/3 flat.
Great bike, John.
Thanks for the customer support, Jim/Maria.
I think I could still go a little faster. If I hit all conditions right on, 44, maybe 45km/hr?
My next big goal is 55km in one hour, pulling out all the aero stops, that is, fully faired.
Why 55? Next year that will be my age.
Jim

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
Loaded for bear, uh-air

marshall2389's picture
marshall2389
Offline
Joined: 1 Aug 2010
Share
WOW that's FAST!!  Well done,

WOW that's FAST!!  Well done, both on the athletic performance and sweet aero outfitting!

__________________

Elliot

KiwiGuy's picture
KiwiGuy
Offline
Joined: 9 Dec 2012
Share
SWEET!

Well done Jim. Impressive time.

I'm curious about the hand position you used for this TT. Did you spend most of the time in the 'drops' as per your photograph here, or did you hold a higher hand position on the 'hoods'??

I'm interested because John has mentioned that his experience is that higher is faster.

Kind regards...

__________________

Blair
Auckland, New Zealand

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
In the drops

KG, I spend close to 100% of my time in the drops. I find that a pistol grip on the hoods leaves my thumbs in a position to scratch my outer thighs close to the knee. Optimally, I would like some kind of aero-bar set up as seen in John's skunk works. That sort of set up would not have been good to learn on but as I add time on the Vendetta I'm finding I can mix up my grips and even use hand signals.
Thanks for asking and the kind remarks,
Jim

Eric Winn's picture
Eric Winn
Offline
Joined: 31 Jul 2012
Share
Jim, hands up on the hoods

Jim, hands up on the hoods seems faster to me too but I haven't captured actual performance data to validate yet. I had 3 rides in with my new Stages power meter before my accident and hoods vs drops was one of the things I was going to compare on my typical 20+ mile (32+ km) out and back ride.

I'm leaning toward getting a set of John's bullhorns because riding the hoods also felt more comfortable and I seemed to have better control but I was going to try and compare multiple rides before I made up my mind.

Since you have a basis to compare against, you might want to try again staying close to 100% on the hoods. I can shift the brifters from there too but it is a little tricky.

Interesting about your thumbs and knees. We look to be similar in size but I don't recall getting close to my knees. When I get the bike where I can check I'll see how close I get.

Here are how my hoods are aligned with my bars. When on the hoods, I'm wrapping my thumb around up high on the apex, almost cupping them.
 
Brifter and hood alignment to handlebars

-Eric
 

yakmurph's picture
yakmurph
Offline
Joined: 6 Mar 2008
Share
Aero!

Here's an idea I stole from a record-breaking European custom
carbonfibre low rider....

You guys -people with working/normal memories-
may remember that it set a record indoors, in a velodrome, was unfaired and that
the rider was male.
The controversy about the record was due to the rider using fairings on his pedals!
The rules had nothing specifically to say about faired foot-soles....

Think about fairing the flat soles of your shoes, in other words.

I like your tail fairing!

Keep it up!

-Steve

__________________

"Me, we."
-Muhammad Ali

marshall2389's picture
marshall2389
Offline
Joined: 1 Aug 2010
Share
your feet do move quite

your feet do move quite fast.  Every time you pedal forward that foot is going even faster than the rest of the bike (excluding the tops of the tires) and your leading foot is the first thing that meets the oncoming air.  I'm curious how he made a shoe/pedal fairing, though.

__________________

Elliot

marshall2389's picture
marshall2389
Offline
Joined: 1 Aug 2010
Share
pretty cool story about

pretty cool story about recumbents and pedal fairings.  read the following forum thread:

http://recumbents.com/forums/topic.asp?TOPIC_ID=4512&whichpage=4

__________________

Elliot

Jim Parker's picture
Jim Parker
Offline
Joined: 2 Oct 2009
Share
Over 26 mph for an hour is

Over 26 mph for an hour is MOVING!

Jim

 

currystomper's picture
currystomper
Offline
Joined: 12 Apr 2008
Share
Way Fast!!!

Wow - that's fast. 

How fast do you think you would be on standard diamond road bike??

CS

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
Last year

Last year I went over 40km/hr for one hour, 15 times. My best effort was 41.6km/hr on a diamond framed bike with aero bars. In these efforts though, I was experiencing a lot of numbness in my crotch and left arm. Of course, this was concerning. When I switched to the Vendetta, I also got a new cycle computer (Bontrager, wireless) and I noticed that it measured my regular course as being shorter than on my previous computer set up by about 250m over 20 k. Crotch problem gone, still get a little numbness in my arm.
So there was (is) a learning curve to get the most out of the V, probably a slightly higher measure of distance (making last year's timings slightly higher, and this year's gains harder to achieve. And my favorite road was 'fixed' making the shoulders bumpy or, in places, too dangerous for me (and I am admittedly slack on 'dangerous' but I have my limits). I've got a new road that I can live with      (And there's one under construction nearby that, when finished, is going to be promising) and a few more inexpensive aero add-ons to try.
That said I'm really happy with the 42.4km/hr clocking and I think I can beat it.
That's more info than you asked for but thanks for asking,
Jim

currystomper's picture
currystomper
Offline
Joined: 12 Apr 2008
Share
10 mile TTs

I'm interested in the detail as I plan to do some timetrials in the UK and compare a stand diamond road bike with a Silivio rev 2, They will be 10 mile TTs  - on a good day I'm a 20mph (32.2km/h) kind of guy so I'm interested to see how much faster I can go on the Silivio. Note my diamond times are done without tribars. 

Please keep posting your times as I'm really interested to see your progress.

CS

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
New PB

42km in 58:49 for an average speed of 42.8km/hr.
Calm winds, lots of traffic-especially 5th wheel and semis(they provide a significant albeit brief buffet and useable 'draft' when they're going my direction. I added a wheel well in anticipation of adding a trailing body fairing. I was not expecting any benefit but a 46 second improvement on my previous PB  is significant. AND I had to stop twice: once on the outbound leg for a light, once on the inbound leg for a train. I don't shut off my computer so I have to suffer a timing penalty for the deceleration and the acceleration back up to speed. When I'm stopped, the clock stops. All this to say that it only encourages me because I know there's more speed to get out of this current set up which is being cobbled together, evolving one might say.
I'll see if I can get a pic up.
ps, my paper aero hat(a newer, improved version from the one first pictured)sustained rain and hail damage on a previous outing but I'm going to use it a couple of more times before a rebuild.
Jim
 

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
Pics

yakmurph's picture
yakmurph
Offline
Joined: 6 Mar 2008
Share
Looking Better and Better!

You're thinking of adding wheel covers, right?

If not, you ought to....

I used to bake for a living and I still bake our bread.
We're having pizza tonight, for example, with scratch-made dough.

To make the starter, I use my wire whisk to whip together the water, the flour, the yeast and stuff.

A wire whisk is made of wire.
Sort of like the spokes of a bike wheel: wire spokes.
Right?

So, if you have a whisk handy, try whipping it around through the air and listen to all that
air you're whipping up!

Compare that to whipping a spatula through the air, edge-on.

After you have your wheel covers figured out, think about adding a little bikini
fairing, mounted out in front of your feet!

-Steve

 

__________________

"Me, we."
-Muhammad Ali

John Tolhurst's picture
John Tolhurst
Offline
Joined: 27 Feb 2008
Share
I am interesting in

I am interesting in understanding if added elements below this line are worthwhile.

hamishbarker's picture
hamishbarker
Offline
Joined: 6 May 2013
Share
He already covered the rear

He already covered the rear wheel with plastic film because he has a disc brake and can there fore stick the film to the rim walls.

Eric Winn's picture
Eric Winn
Offline
Joined: 31 Jul 2012
Share
Turbulent air flow from

Turbulent air flow from pedaling being funneled by the seat bottom and back over the rear aero wheel disc returning laminar flow as it leaves the rear of the bike reducing drag?

It would be interesting to see a smoke wand in a wind tunnel applied to Jim's creation to actually see what it is doing.

Jim, have you covered the bottom span of the wheel stays to avoid creating an air brake? See photo below. wink

-Eric
 

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
Dear Eric

Yes,
JG

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
Not a PB, but. . .

So I added a 'storm-door' heat shrink plastic fairing to the seat back of my V AND I covered the front wheel in similar fashion. Tonight's weather was not conducive to an all out assault on my PB so I went out 20k at a sub optimal pace (against a quartering head wind, maybe a 7-8km/hr component head on. I decided to keep it fairly comfortable on the way back but that head wind was now a tail wind so I took what the road would give me. I hit my nemesis light at the 17 km mark and checked my average speed-it was over 45km/hr. What a hoot! Back in town I was going down a through street and decided to see how fast I could go (on a flat, @10km/hr wind behind me, I topped out at 58 point something (speed limit 60). I had an experience of being alive.
JG

marshall2389's picture
marshall2389
Offline
Joined: 1 Aug 2010
Share
oh my god you're fast. 

oh my god you're fast.  sooooo cool.  How do you deal with hydration?  Short enough rides that you don't need it?

__________________

Elliot

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
Hydration

Yeah, that's an issue. 
The bottle under the boom does not work for me.
I tried mounting a bracket on the back rest but it's not accessible at speed.
I tried placing a bottle in between the bottom rear stays but, again, not easily accessed.
I thought about a bottle behind the head rest, but that space is being used.
Then I filled in the space below the seat back for aerodynamic efficiency(?). At least I made it accessible when stopped.
So, on a one hour, time trial type ride, I take a drink before leaving home, I get about 150ml at the turn around (from a bottle hidden in the under seat space) then I can have a drink when I get home (if I want one). Oddly enough, it's not a high priority when I get back.
I would drink more if I had a better solution.
JG

marshall2389's picture
marshall2389
Offline
Joined: 1 Aug 2010
Share
A possibilityy would be a

A possibilityy would be a bladder behind your seat or headrest with the hose coming out of your aero housing and resting on your shoulder.

__________________

Elliot

cplager's picture
cplager
Offline
Joined: 22 Jan 2012
Share
A possibilityy would be a

A possibilityy would be a bladder behind your seat or headrest with the hose coming out of your aero housing and resting on your shoulder.

That's exactly what I would do.

Wait.... That is what I do (except that it's just strapped behind the seat and I'm not cool enough for an aerobox. Laughing out loud

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
A day at the track

Edmonton, a city adjacent to my home, has an outdoor velodrome. It was made in 1977 for the 1978 Commonwealth games and has since been maintained on a shoestring budget. It's surface is concrete and through the years has been patched and shaved to retain a semblance of surface credibility. I've been on it before and recently decided to have a go with my aero V. They normally prefer track bikes only but Monday mornings are not too busy (read-virtually abandoned) and the controlling body was desparate for my $5.
I took a walk around the perimeter of the 333.3m track and it looked pretty good so out came the bike.
As I took the bike out of the van a pedestrian comes by, oogles my bike and asks if it hurts my neck, to which I reply, 'does reclining on a couch hurt your neck?'
The track is well designed with banked corners but I stay on the flat apron during my warm-up. That was not too bad and as I got up some speed I started to climb up the banks. There is a black line around the oval that defines the track proper. I assumed that if I were to follow this line around once I would travel 333.3m. Great. So I get up to speed, outside the black line and there are more bumps than smooth spots. I was less concerned for my amalgam fillings than I was for my bike to rattle to pieces. I dropped back onto the apron and was thinking about giving it up when I thought, 'what the heck, I'm here so why not tool around on the apron for a bit. After 4 or 5 laps I found my speed getting up, I found a relatively flat orbit that included some of the bank. The upshoot being, I thought I might as well give it a 15 minute trial.
It was a fairly warm, calm, humid morning. After 15 minutes my computer tallied 10.9km for an average speed of 43.6km/hr. Pretty good, I thought as I looked around for that smart aleck pedestrian and rubbed my neck.
I must admit that I don't think I could maintain that pace for an hour but after a short break that included  my ration of water I set out again. I decided on a slightly less aggressive pace and finished with 10.8km in 15:07 which I think is just slightly under 43km/hr. 
The attendant told me that she knew of no standing track records but recalled  a group ride of 150 laps taking  an hour and 20 minutes. That's37.5 km/hr so comparatively I'm pleased with this showing.
JG

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
New Personal Best

40.7km in 56:10 for an average speed of 43.5km/hr. 
A) I was out this morning and missed the 43km/hr mark by 4 seconds.
B) tonight the weather was close to perfect with a slight push on the return leg.
C) my splits were 22k outbound in 30:03 for an average speed of 43.9km/hr and
                            18.7 inbound in 26:07 for an average speed of 43.0km/hr
D) my inbound leg should have been faster but I had to stop once to put my chain back on (!) remember, by my clocking, if I stop, the clock stops so the penalty is deceleration and acceleration time, not fix it time.
E) my inbound leg was shorter because I hit my nemesis light (but I anticipate this possibility by making my outbound leg longer.
F) I'm reporting this but I'd really like a clean run to 'own it'.
G) I carried on to my original starting point and still made +43km/hr. That light really gets in my way.
Grade besides the perfect weather, the newest addition to my equipment is the covering on my front wheel, the effects of which are noticeable.
Feeling good,
JG

marshall2389's picture
marshall2389
Offline
Joined: 1 Aug 2010
Share
show a pic of your front

show a pic of your front wheel cover!

__________________

Elliot

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
He owns it!

44km in 60:36 for an average speed of 43.6km/hr.
   Outbound leg: 22 km in 30:12, avg speed 43.7
   Inbound leg:    22 km in 30:24, avg speed 43.4
had to slow down but not stop for traffic light each way.
Inbound leg had the day's wind behind me but didn't help.
Hoorah!
JG

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
Pushing The Limit

A new personal best.
44.3km/hr average speed 
Outbound leg 19.5km in 25:21 for an average speed of 46.2km/hr
Inbound leg 19.5km in 27:25 for an average speed of  42.7km/hr
I started timing at the last set of lights heading out so that became my finish line inbound.
Unlike most of my time trials this summer, I had the day's wind behind me on the outbound leg which was less of a factor coming back. I'm also using the straight arm, hood grip more often suggested by the likes of John and Eric (and thanks, Eric, I angled the hoods out a bit so that my thumb nails don't scrape my outer thighs.
If anyone reading this saw my Facebook front fairing, I took it off and I'm working on an improved version. Everything needs an improved version but that is going to be a winter project.
For now, Yeehaw!
JG

Kenneth Jessett's picture
Kenneth Jessett
Offline
Joined: 12 Jun 2013
Share
Jim, do you have a plan to

Jim, do you have a plan to step up your distance riding, maybe some of the 12 and 24 hour events?

John Tolhurst's picture
John Tolhurst
Offline
Joined: 27 Feb 2008
Share
I'm interested in a

I'm interested in a comparison ride without the aero dressing ... to get a fix on how much its doing.

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
Two questions, Two answers

I don't foresee myself doing many rides much past an hour and a half. A metric and an imperial century could be possible but that's not in this year's or even next year's plan. My goal is to do a one hour time trial type ride without any 'governing body' dictating arbitrary limitations. (I will listen to reason but I don't always follow it.)
As for John's question, before the season is over, I plan to take all the aero extras off and have a few goes. I was on a site that features a power formula. It indicated that I would require about 290 watts to produce a speed of 44km/hr on a Vendetta type recumbent. Last winter (if you can believe a public gym stationary recumbent type bike's metrics) I could sustain about 230 watts.
So in the ball park of 25% improvement(?). We'll see. There are a lot of factors to take into account.
JG

Eric Winn's picture
Eric Winn
Offline
Joined: 31 Jul 2012
Share
Jim, here is one of the few

Jim, here is one of the few rides I completed on my Vendetta with my power meter before I got clobbered. I was starting to experiment with trying to keep my speed up without spiking my power too much on hills. 

You can hover your mouse over the graph at the bottom and move left to right to see my progress (or hit the play button in the bottom right)

If you ever get a power meter I'd like to see what your data looks like.

http://ridewithgps.com/trips/1484929

Metric

  • Max Watts: 769
  • Avg. Watts: 170 (160 with 0s)
  • Normalized Power 190
  • Work 810 kJ
  • Max Speed: 56.6 kph
  • Avg. Speed: 29.4 kph

Imperial

  • Max Watts: 769
  • Avg. Watts: 170 (160 with 0s)
  • Normalized Power 190
  • Work 810 kJ
  • Max Speed: 35.2 mph
  • Avg. Speed: 18.3 mph

-Eric
 

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
iPhone, ridewithGPS, Stages power meter

I'm going to get all the above: iPhone soon, the rest before next riding season begins.
I notice the Imperial summary still reads watts(metric) not horsepower(imperial). I know it's a simple equation but can it be programmed to display both or either?
JG

Eric Winn's picture
Eric Winn
Offline
Joined: 31 Jul 2012
Share
For RWGPS there is just a

For RWGPS there is just a toggle switch that redisplays values one way or the other but doesn't do anything with watts. Maybe because the numbers are "bigger" with watts? 

e.g. easier or more comfortable comparing:

  • 170 watts to 200 watts

Rather than comparing:

  • 0.227973755 horsepower to 0.268204418 horsepower

170 watts = 0.227973755 horsepower
200 watts = 0.268204418 horsepower

I think I would have a harder time trying to hold a particular power level if the display was in horsepower. Or maybe not - but 170 watts sounds more impressive than 0.228 horsepower   Laughing out loud
 
-Eric

 

cplager's picture
cplager
Offline
Joined: 22 Jan 2012
Share
I think I would have a harder

I think I would have a harder time trying to hold a particular power level if the display was in horsepower. Or maybe not - but 170 watts sounds more impressive than 0.228 horsepower   [Laughing out loud]

So now you're a quarter-horse? Laughing out loud

Eric Winn's picture
Eric Winn
Offline
Joined: 31 Jul 2012
Share
Neigh Charles, I'm not.    

Neigh Charles, I'm not.   Laughing out loud
 

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
And yet. . .

At your max you're more than a little hoarse.

Eric Winn's picture
Eric Winn
Offline
Joined: 31 Jul 2012
Share
Here is what horsing around

Here is what horsing around cyclists is all about:

cheeky

Someone recently posted this on BROL and it just seemed appropo at this point..

-Eric
 

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
All time low

I crashed.
A combination of factors took me down: a three yard long, 3X3" gash in the pavement that I hadn't noticed on my first pass was the major contributor, speed(+40km/hr), reaction time, incorrect response (in retrospect, maybe I shouldn't have tried to get back on the pavement having been jolted off of it).
Injuries: sprained left pinky, sore left shoulder, skinned pinky, road rash on inside of left arm, deeper road rash on left trochanter about the size of a dessert plate, road rash on right gluteal(I can't figure out how that got there). Bones, head and neck not involved.
Bike: The left handle bar on the bike got pinched(saved from worse damage by my pinky, hooray) and, of course, the tape was torn and the bar end came off but I found it. I don't know yet how much the handle bar is bent. I had to ride the bike home and everything seemed to be working but I was not too concerned about a smoothly operating bike. The fairing  on the left side was messed up but I have a new idea for improvements.
Consideration: as this project grows in complexity, I'll have to give serious thought to parameters like where and how this thing can be ridden with a fair shot at safety. Obviously, pushing limits (even personal limits) has a degree of danger. I realize and accept this.
It will probably be two weeks for healing and repair if all is as described above.
It could have been way worse.. . .
down but not out,
JG

cplager's picture
cplager
Offline
Joined: 22 Jan 2012
Share
I'm glad that you and the

I'm glad that you and the bike are (mostly) o.k.  Stay with us.... Laughing out loud

Eric Winn's picture
Eric Winn
Offline
Joined: 31 Jul 2012
Share
Sorry to hear about the crash

Sorry to hear about the crash Jim but glad to hear you are mostly OK. Sounds like the Vendetta cockpit mostly protected you as you went down - that was my experience anyway. 

The base of my right ring finger and pinky got gouged and scraped pretty good on my smackdown. In retrospect, I think I got "bitten" by the shift paddle under the brake lever of my brifters.

Stay safe. Good to hear you are not too discouraged.

-Eric
 

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
Update

Well, I'm healing up. I've been on a stationary recumbent up at the local fitness centre for about two weeks.
It turned out that I had damaged the front rim beyond repair ( I had it trued but it had a bump in it) and because I slid on the left side of the bike, the rear brake was bent (Avid BB7 to be replaced with same).The left side of the handle bar got a crimp in it near the bar end - here I am going to try a set of clamp on aero bars with bar end shifters and Jtek aero brakes. If I can master the resulting configuration on rollers over the winter, I'll make some more essays into the esoteric world of aerodynamics.
This past season was a qualified success. Except for that one fall there is no way (in my advanced maturity)that I should be setting personal bests on a bike unless it was a pretty special bike (kudos here to the Cruzbike Vendetta)
On a side note: I did not suffer a single flat this year.
JG

Eric Winn's picture
Eric Winn
Offline
Joined: 31 Jul 2012
Share
Good to hear you are OK Jim.

Good to hear you are OK Jim. Let us know how you and the Vendetta work on rollers. I haven't bothered to try mine since I have a KICKR now.

 When you get your handlebar setup I'd like to see photos and get a report on how well the Jtek brakes work. I really like the hand placement of John's bullhorns and although the cabling is a PITA to accomplish it is really comfortable not to have cable runs under the bar tape.

What is your assessment of having disc brakes on your Vendetta? I haven't been caught in anything but a short, light shower on mine so my rim brakes haven't been used in real wet conditions. They work great for dry stuff.

-Eric
 

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
New personal record

Sorry I haven't been posting this season on this site (check out my Facebook page for more recent stuff). But I am pretty excited to announce a new personal best in a time trial type ride. I've changed my favorite road from last year. Anyway, 40 km in 52:14 for an average speed of 45.9km/hr. You've gotta see my newest aero innovation but my iPad does not play well with this site so, again, check out my FB page. And I've got Another great project on the go that surpasses last year's paper prototype. 
45.9km/hr-I'm 55 and this is the fastest average speed I have ever achieved.

Eric Winn's picture
Eric Winn
Offline
Joined: 31 Jul 2012
Share
He's baaaaaccckkk! Way to go

He's baaaaaccckkk!

Way to go Jim! I've seen your FB page, how much difference do the aero-feet make?

-Eric
 

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
The difference

I have shaved two minutes off of my best 40k pace of last year. I'd like to calculate how many watts would be required to go from 44.3km/hr (average speed) to 45.9 factoring out the aero-booties.
But I have discovered a significant meteorological factor that I have never before taken into account (and I've never heard any cycling specific commentary on the subject, either; that is, air density.
I first got an inkling of this, this year. On my first TT with my front wheel 'storm-doored' I was expecting an improvement of about 45 seconds. I got over two minutes which was just too good to be true. So I said to myself, WTF? I've been doing some flying and one consideration of take off performance is density altitude. I made the connection with my cycling. I retrieved the barometric readings from a couple of my best performances and, lo, the density altitudes were high (or you could say air density was relatively low).
All this to say, yeah, I'm reaping some aerodynamic benefits from these mods (the body position afforded by the Vendetta being a significant factor) but the picture is complicated.

cplager's picture
cplager
Offline
Joined: 22 Jan 2012
Share
Good online bike calculators

Good online bike calculators all take air density into account (some will even help you calculate it).

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
On the night in question

I should add that, on the day of my latest PB, the density pressure was relatively high. The elevation of my route is about 2,500ft. I calculated the density pressure for that ride to be 3700ft. dP is, of course not the necessary nor the sufficient condition of peak performance but there it is. The down side of dP (or air density) as any pilot or mountain climber will tell you is the debilitating effects of 'thin air' on respiration at high altitudes.

Jim Gerwing's picture
Jim Gerwing
Offline
Joined: 12 Sep 2012
Share
Raising the (personal) standard

On a near perfect evening (density altitude relatively high albeit the slight haze from distant forest fires), I set a new PB: 40k in 51:38 for an average speed of 46.5km/hr. Huzzah! Take a look at my FB page. The aero-booties are not shown in this pic and I made a slight mod to the tail box. Stay tuned for a radical departure from some of these tweaks I've been making.