Aerodynamics / Aerodynamic Cost / Aero parts

You already have a chainset so why not just buy a single large ring for these your fast TTs?

For 1/4 the cost of a DA chainset you could have a Fibrelyte 5xT ring made to suit whatever cranks you already own.

I think that's the conclusion I've come to - £172 at Evans for the DA chainrings with a bit of cashback action, seems like a lower stress option than the best price (£170) I can find from the German retailers...

If/when you sell your DA cranks let me know....

So can someone explain this Q factor thing to me please...

I've seen Xav posting stuff about the Limits PM where he seems to be saying that high Q leads to injury risk, but I also see lots of people mentioning Q in this thread which leads me to guess that there is an aero benefit. Perhaps narrow Q -> lower frontal area and less turbulent air between your legs and the frame, thus more aero?

I need new cranks for my TT bike... The cheapest option is to replace the chainrings on my existing Rival cranks (which are the correct length), but I also like the look of Rotor flow cranks, but then posts on the previous page appear to poo poo rotor for increasing Q...? Do I need to worry about Q and why?

You don't need to worry about it, low q might help you make more power and it might make you more aero but it's fairly marginal stuff.

Margarine gainz

It's another string to your psychological bow: "How much? No wonder you walk like a fuckin' cowboy!"

Or bragging rights: "Yeahboi. Got that sucker under won-fordy dawg."

New 3T aerobar

21st Century inverted North Road. I like it.

Since posting my question I have been led, via the wikipedia article on Q-Factor, to Disley and Li's interesting paper on self selected Q. In their study they found that SSQ leads to higher knee stability and higher mechanical efficiency, and also that SSQ could be reliably predicted using a simple suspension test.

Taking the advice to heart, I tried suspending myself between two office chairs while I was waiting for the kettle to boil. I eyeballed my inter-medial-malleoli-distance to be around 70mm, and that using Disley & Li's equation(1) my SSQ should therefore be approximately 154.57mm.

So now I have 2 new questions...
(a) @xavierdisley , It's not clear to me from my reading of your paper how I should translate my estimated SSQ into a real Q factor. In lay terms, Q seems to be measured as the distance between the outer faces of the crank arm (e.g. here), however this wouldn't account for differences in Q from different pedals or cleat positions (which varied between participants). When you were measuring Q, where were you measuring it from-to?

(b) Since my pedal Q is fixed (I'm committed to vector pedals) is there a useful database of Q factors for different cranks? It's a faff going through each manufacturers specification page individually...

(1) y = 0.569x + 114.74

It's a faff going through each manufacturers specification page individually...

Even if they actually bothered to publish them

I don't think non-round rings were ever "bunked"

Bugger

1 Attachment

How does front shifting work with these things?

How does front shifting work with these things?

Not as well as it does with circular ones

Not aware of a concise database, certainly not up-to-date for multiple manufacturers but a basic Shimano one is here and SRAM here

Wait, what: a "triple"?

I'll believe it when I see it.

Wait, what: a "triple"?

No, you're a Wankel

No,
Surely
U are.

Is this for real?

How can this relate to a "two-stroke" pedalling action?

Think tandem with the two cranksets set at 120° to one another

These guys should have visited this thread.

http://road.cc/content/news/178185-video-watch-riders-battle-100kph-headwind-without-success

Looks fun.

How are you getting on with your Gub helmet? I saw them on Aliexpress the other day and they seem to look quite good. How does it compare to the Air attack?

Unless I've fucked something up (almost certain), I should be able to swap my ~80mm/-6deg PRO LT stem

with an 80mm/-10deg PRO Missile stem, plus a 5mm spacer under it (which I have above the current one anyway). It puts the bars at the same height and pushes them out 4mm, which I hope my glutes can cope with.

HED and Specialized just sent out a press release regarding a recently-approved HED patent from 2009 that... http://fb.me/4KgpTC7pg

You need to do much better than an eyeball measurement. We used 13 infrared cameras with insane accuracy for that paper, and when I do it in the field for pro clients I use a highspeed camera and lots of repeats. Q Factor is measured at the crankarm, yes - moving your cleats out will increase the distance further. With our custom floating pedal setup (here's my PhD for night time snooze reading: http://etheses.bham.ac.uk/5523/1/Disley14PhD.pdf) we measured at the inside edge of the foot plate, so actually taking Q Factor and not the centre of the foot or anything.

You can see the custom erg that I built on page 40 and a diagram of the floating pedals on page 58.

Looks awfully similar to Steve Hed's patent which expired a few years go. In fact, at the moment I can see any major difference between them.