Wednesday, October 29, 2014

The Devil is in the Details (pt2)

But you could also say God is in the details. So, depending on whether you are an optimist or a pessimist, this post is either going to be a pain in the butt or omnipotent. (ok... it probably won't be omnipotent, but I'll try.)

This week let's talk about the details in your equipment. There are LOTS of guys that are giving up free speed for no good reason other than laziness and/or some common misconceptions. So hold on to your Gatorskins, this is going to get hairy. Let's dive right in. (I'm going to blatantly take some info from the internet here... I'll try to give all credit due)

Coggan suggested this formula (to keep in mind)
0.1 lbs (50 g) of drag (at 30 mph) = 0.5 s/km = 5 W = 0.005 m^2 CdA = 0.0005 Crr

Tires and Tubes:
Somehow, despite all of the efforts put out by Biketechreview and Tom Anhalt (Bikeblather, an extremely good read.) there are still a plethora of "serious" cyclists / triathletes who don't pay any attention to what rubber hits the road.

Let's say you're riding a Pro4 Service Course Michelin (CRR .0043) and I'm riding Conti GP4000s' (CRR .0034) a difference of .001. Not such a big deal you might think. But what if I said it was eating up 9 more watts of your power output to go 25mph? Over a 40k... that's the kind of time differences that don't just win (or lose) races, but can separate the podium from "mid field." Now imagine if you were on a "bulletproof" tire like a Gatorskin... I shudder to think.

The argument of course is one of durability. It's going to (maybe...) be slower to change a flat than it is to ride on an indestructible tire. For the most part I think this is BS. Considering your race tire is in great shape (it should be, it IS your race tire, not your trainer) it should be able to stand up to most of what you're going to find on a tt/tri course. Tacks/Glass/Thorns/etc are going to flat most tires, race or not.

Some of those runs are using latex tubes as well. For the most part from what I've seen, switching from butyl to latex in both tires is worth about 5-7 watts.

---aside on latex installation---

A lot of people are turned off by latex tubes because they think they are more likely to flat. With proper installation I believe they would find this is actually the opposite. However, proper installation takes a little more effort than butyl tubes, and improper installation DOES lead to popped tubes, so this thought process lives on. Here's the steps I take when installing mine. (I prefer velox tape as opposed to an actual rim strip that can move for most rims. I use veloplugs with a layer of packing tape myself.)
- shake the latex tube in with some talc powder.
- bead it and the tire as normal (might help to have a few lbs of air in the tube)
- BEFORE YOU START AIRING run your hands along both sides of the tire pushing the tire back to see if any of the tube is caught under the lip. If it is, a couple of "flicks" of the tire should move it back under. Do this step on both sides and take your time. This is where probably 99% of the errors come from.
- Once you are satisfied that the tube is under the lip of the tire, start airing it up.
- Profit! (or get the crap scared out of you when you hit about 90psi if you did it wrong.)


It's also important to understand that certain tire widths match up better with certain rims. Especially the older aero wheels (non-dimpled zipps, similar era HED's, Trispokes) that were designed on the "narrow is aero" philosophy, you can go from a great wheel to a terrible one when you throw a 28mm tire on it. On that topic, generally a wider tire has better rolling resistance, but a worse aero profile. That's where things can get tricky in picking a tire... Trading RR for aerodynamics is often a profitable tradeoff on the front wheel, where the RR is usually positive on the rear (especially on a modern tri bike that will "hide" a lot of the tire.

TLDR; Tires and tubes... pick wisely.

Cable routing:
This is another one that is not only costing people some speed, but also just killing the aesthetics of the front end.

Here's the difference between my old Felt and the current Cervelo's front end. (Sorry the Felt isn't a head on shot, I didn't know I'd need a head on picture 5 years later... I also didn't know about clean front ends...)

Lots of stuff sticking out around the front. Oh the good old days.
Very little for the wind to see cable wise. 

Now if you believe this

Famous aero dork picture!

Then you can see that having a bunch of cables hanging out and about is NOT a good thing. I use Nokons and/or Alligator links to get the really tight bends, but you can certainly emulate 99% of that with some smart/creative routing of your own. As great as di2 is, I have seen some nightmarish setups (see Andy Potts before his Tririg makeover)

Oh so easily forgotten. Clothing choices can do a lot to help (or hurt) you in a race. If you've watched Kona this year it would be easy to wonder if Ryf couldn't have saved 2 minutes over her bike split if she had worn a little bit more aero top. (along with an aero lid) Not saying that even if she had gained the time she would have won, but it's something to wonder.

Did the wrinkles make the difference?

The last few years we've seen the shift to the "aero top." The Castelli and the PI really kicked it off, but now most places have their athletes with sleeves, or at least with the option. Jim Manton's recent ST thread is an excellent read. An easy takeaway for this quick read "Skin is slow, wrinkles are worse."

I've had my own experience with the Castelli T1, and I'm still with mixed feelings. Some things I'd suggest everyone consider.
- Are you going to swim in it? (if applicable... no sleeves allowed in a no-wetsuit swim)
- Is it restricting your stroke if so? (I felt like it definitely was)
- How fast can you get it on (wet) in T1 if you aren't wearing it for the swim.
- Are you going to wear a tri jersey underneath? 
- How much time will it save on the bike?
- Are you going to wear it on the run? (a lot of tri's require *some* top for men)

Besides the aero top, when I was in the tunnel I found a onesie to be a couple of watts faster than my two-piece kit. I expect a lot of that was both the "rising sun" of my exposed lower back and the bike jersey'ish pockets on the two piece. Those big pockets can also be a source of drag in the water.

You've almost certainly seen Specialized's Win Tunnel report on shaving your legs... and while other credible sources have NOT seen anything as impressive as 10+ watts... it's really a no-brainer to shave your legs unless you have a good reason not to.

That's a good place to stop this week. I really appreciate everyone taking the time to read through. Hopefully you've found something useful, or at least a little enjoyment. Thanks for reading!

- Christopher Morelock

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