FREE Speed 101
Let's talk about the concept of “free speed.” If you’ve heard the term before, you might be a little confused. Often people will talk about a very expensive bike part, and then say it’s related to “free” speed. They’re obviously not talking about money. What they mean is free in terms of the physics involved. And to be more precise, the concept of “free speed” means that a given athlete will go faster for the same amount of power output.
That’s because how fast you go is determined by a balance of forces: first there’s your own legs powering the bicycle to go forward, then there’s gravity, rolling resistance, mechanical losses, and aerodynamic drag all working to slow you down. The concept of “free speed” means reducing something about those forces against you. And unfortunately we don’t have anything that can counteract gravity. But we CAN make careful equipment and positional choices in order to minimize the other three forces.
So let’s talk about the lowest-hanging fruit in that equation. Today I’m going to talk about three very easy ways to find free speed, and ways which are actually free – as in they don’t cost anything. And let’s do one for each of the categories mentioned above. If you like this concept of free speed, leave a comment and we can go into more detail about other ways to find it.
1. Rolling Resistance
This force enters your bike at the blob-shaped patch where your tires contact the ground. And you can very easily reduce your rolling resistance by simply optimizing your tire pressure. No need for a purchase, no need to set up anything new, just select the correct tire pressure for your given tire size and system weight (including you). There’s a fantastic chart made by the folks at Flo Cycling with detailed information on optimal pressures, which you can find right here.
For most triathletes, you’re going to land somewhere between 75-95psi of pressure. But one critical piece of information you want to know is that if you were to chart rolling resistance against tire pressure, it will NOT be symmetrically distributed around that optimal level. It goes up faster once you exceed optimal. So that means if you’re 10psi over optimal, you will be measurably slower than if you are 10psi under the optimal level. So when in doubt, let a little air OUT. I tend to ride around 85psi on my tri bike, 35-40psi on this hybrid gravel rig. Total potential savings from a bad tire pressure to an optimal one can be up to 15 Watts easily.
2. Mechanical Losses
Nowhere on the bike do riders see greater mechanical losses than with a dirty chain. It's so simple, so easy, and yet SO OFTEN overlooked. Look at the bikes of Ironman-winning triathletes, and you will almost always see a spotless, well-cleaned chain. Just cleaning your chain, and replacing it when it gets old and elongated, will save you an easy 8 Watts. If you do want to get fancy, you can reduce losses even further with optimized lubricants. We love Silca products, and we’ve partnered with them to make a specialized version of their chain lube that can squeeze out even more speed.
3. Aerodynamics
This is perhaps the deepest rabbit hole as a category, but we’re going to pick a pretty easy target for this one. If you’re going to do an endurance sport, you need fluids along the way. And where you place those fluids matters a lot. Typically, bottles are placed on the downtube of a bicycle, where they stick out in the wind and disrupt the carefully-shaped frame your bicycle manufacturer has (hopefully) designed with care for the lowest possible drag. There are a couple spots you can place a bottle where it is not only invisible to the wind, but can even make you faster than having no bottle at all.
The first of these is right between the arms, or BTA as we call it. No matter what your position is, there’s almost always a benefit to putting the bottle right between your arms, or, if your arms are basically touching, just right above them. The rule in general is that you want to avoid any gaps in the complex of your arm/head/torso structure. The more you can “close the bag” so to speak, the easier path the wind can take around you, and the less drag will work against you. So a good BTA bottle can actually reduce drag compared to no bottle at all, and is certainly much better than a downtube bottle. The second great place for a bottle is right behind your saddle, generally as close to centerline and close to the saddle as you can get it. Whether you use a dedicated mount like the TriRig Beta, or just zip-tie the cage to your saddle rails, this is a great spot for a bottle because it’s basically invisible to the wind. In total, good bottle placement for a pair of bottles can save you up to 5 Watts compared to bad ones.
So What's it All Worth?
So, a few simple tweaks, and we’re talking about nearly 30 Watts of savings, without having spent a dime. What does that mean in terms of time? Well a good rule of thumb is for every 5 Watts, or approximately 50 grams of drag, you can save about 0.5 seconds per kilometer. For an Ironman-length ride, 30 Watts faster means you get to the finish line 7 MINUTES earlier. All for doing nothing more than pumping your tires right, cleaning your chain, and putting your bottle in the right spot.
If you want us to do more of a deep dive on this topic, please let us know. We know there are lots of you out there from first-timers all the way up to Ironman-winning pros, and we want to hear from all of you. Where do you want some advice on refining your rig? Thanks for reading, and we'll see you next time.
