Aero Deep Dive in The Specialized Win Tunnel – Ask a Cycling a Coach 188



Whats the difference between lightweight butyl tube vs latex tubes.


Seeing a Win Tunnel of no bag vs seat post vs behind the stem would be nice. Most of use don’t have a support car.

What is the ‘correct’ QR placement?


For everybody that was wondering if the aerodynamic measurements are relevant for slower athletes:

Their Youtube Channel “Win Tunnel”, has many videos about aerodynamics including the following one that targets this specific question:




This podcast is going to make me ridiculously OCD about my cable routing for my Mtb now


For those that missed it, here is a video that adds more context to @Superdave’s comment about cables:

In terms of tidying up cables, I don’t know enough to opine on shrink wrapping multiple cables together vs. separated cables, but I do know that I see excessive amounts of cable on most bikes on a showroom floor. Chances are you can shorten things up and save some watts.

When I build my bikes, cable routing and organization takes almost as much time as the rest of the build. I find that I run less cable length than most, and the length of each cable is relative to the other cable it runs parallel to. IOW, the shift and brake cable from my left shifter will be cut at such lengths to allow them to run perfectly parallel, allowing me to use small zip ties or shrink wrap to tidy them up.


Yes. Which means the power savings from various aero improvements are overstated for mere mortals, and/for cyclocross, or MTB.

If they are anchoring everything on 30mph, then the % of the quoted gain at different speeds will be as follows:

  • 30 mph: 100%
  • 25 mph: 58%
  • 20 mph: 30%
  • 15 mph: 13%
  • 10 mph: 4%

So for a MTB race averaging 12mph, the 20 watt gain from that aero road helmet becomes 1.3 watts.


This is true, but you have to consider time out on course as well. You may be getting less aero benefit as a percentage at 20mph, but you’re getting the benefits for a lot longer time period. The slower you are the more time you actually save in real numbers:


Don’t undervalue the benefit of getting a gap on competitors going into a flat section after a downhill though.

In MTB there are regularly times where you are opening up the throttle on a fireroad downhill and are spun out, which means that could be the difference of more than a few feet which makes it much harder for the person behind you to get back on your wheel at the bottom.


For sure. And for the times when you’re at 20mph, the aero benefit grows a lot more than it shrinks at 8mph relative to a 12mph average - meaning the aero gain in a race with a lot of speed fluctuations will be more than if it’s a steady 12mph.

The main reason I’ve been looking at this is to decide how much I want to spend on aero equipment for Leadville. Between shoes, helmet, skin suit that could be a lot. Then I’d ruin it all by wearing a camelbak :grin:


IMO for Leadville:

  • Strategic cable reroute/shrinkwrap
  • Bolt on through axles front and rear
  • Aero helmet
  • Ready to go waxed chain for race day
  • If you have the cash for the skin suit, go for it

That’s what I’ll do the next time.

I think you could easily save 10-15 minutes between Pipeline and Twin Lakes (and the reverse)


I’m thinking camelbak under my skinsuit for my gravel races this upcoming season. I know it’ll be sweaty and uncomfortable but I’ll live with it if it means an extra 20 watts.


Especially on the way back into that headwind. Plus by then, many riders are too zoned out to form a coherent pace line.


I’d prioritize a skin suit in my purchases. It’s a huge gain and can be used in any discipline and on any bike.

They last a long time if you only use them in races too (as long as you don’t crash).




Whilst those percentages of baseline watts saved are correct for the different speeds, the required watts also go down at the same rate, so it’s important to remember that the advantages of those saving are all exactly the same, no matter what speed you’re doing.



These are the more relevant calculations that should be done vs looking at watts savings at a given reference speed. Harder to explain in a single sentance tho!


A better way to explain the aero benefit is probably just to say what the reduction in Cd is. This removes the effect of speed from the quoted aero benefit, and allows for an easier calculation on impact on times e.g. in best bike split, or, or the like.


If you all are looking for a speedsuit check out Velotec. They tested very well against Castelli among others. Super reasonable price at $113 USD/100 EU + Shipping.