Track bike gearing – Mario's blog
More or less a year ago I was about to ride for the first time in a velodrome… and since then I lapped more than 2,000 times around Herne Hill Velodrome's 450m smooth tarmac.
It’s hard to express in words the emotions I felt during my very first few laps on a banked surface with a single, fixed speed, no freewheel & no brakes track bike. I recall an indistinct mix of screams of joy (“whoohoo!!”) and “wow this is insane”.
Advancing the clock to today, I’m still along a very steep learning curve as track riding is a beast on its own and differs greatly under many aspects from any of my previous experiences on bicycles (MTB / road / triathlon).
In this post I’ll cover what I think is a fundamental specificity of track riding: the gearing
Unless you ride a single speed bike, you are unlikely to think too hard about which gears you put on your bike. You may swap an 11-23 to an 11-28 or 11-30 cassette if you go climbing in the Alps, and you may have heard of compact vs traditional chainrings (ie 50/36 vs 52/39, usually), but that’s most likely about it.
Track bikes have a fixed drivetrain with only 1 speed. This means that you pick the chainring (in the front) and the cog (in the rear) and you are done. To brake, “invert” the force you apply to the pedals. Easy!
The tricky bit is when you realise that you have the wrong gearing…simply because you are spinning like a madman and the others are still breezing past you, or you feel like you are pulling 5 other cyclists on a leash with your legs barely spinning.
It’s important to touch base on one concept: when you are out on track riding a certain gearing ratio, the key variable that changes when you put more watts into the pedals is the *cadence*. Your speed is linked to your cadence – you are riding a fixie and cannot change gears!
For road cyclists who have never tried riding a fixed gear bike, this feels very, very odd. At first, the lack of freewheeling and brakes is scary as you feel you cannot stop and you lack control. Once you have mastered this bit, then comes the realisation that you simply cannot shift your gears and your “preferred” range of cadence (say, 75 through to 95) is extremely narrow if you want to go at different speeds (eg cruising vs sprinting).
One key take away from my 2,000 laps around Herne Hill Velodrome is that being able to pedal at extremely high cadence is a fundamental skill to have in order to be competitive. How high? Think past 130rpm. Personally my heart rate shoots to the stars when I go beyond 120rpm (and therefore I need to train specifically to increase my tolerance to high cadence), but I know of strong riders who can sustain between 120-130rpm for a whole 10km endurance race, and eventually reach up to 140+rpm on the final sprint for position.
When discussing gearing with track cyclists you might feel in a different world – they don’t generally talk about chainrings/cogs combinations (50/15, 48/14 etc), but rather talk “inches”, intended as “gear inches”. In short, gear inches give “an indication of the mechanical advantage of different gears.” Values for 'gear inches' typically range from 20 (very low gearing - for climbing hills) to 125 (very high gearing for going fast downhill) – from wikipedia (https://en.wikipedia.org/wiki/Gear_inches).
The standard way to compute gear inches is to use the diameter of your wheel as 27” (*) and follow this rule:
27” * #tooths in chainring / #tooths in cog
So a 50 front chainring /15 rear cog setup would correspond to 27” * 50 / 15 = 90”.
The table below shows the various gear inches you obtain from different chainring/cog combinations (with 48-52 chainrings and 13-15 cogs):
So, to conclude, which gear inch is right for track cycling?
While there is no answer to this question (as there are several variables involved... fitness conditions, race type, velodrome length & banking, wind conditions, and many more), the rules of thumb below are helpful:
<90”: easy gearing which trains high cadence
90”: the “average” gearing
91.8”: according to British Cycling this is the optimal gearing for bunch races (ie races with several people involved, featuring fast accelerations and high speeds)
>94”: high gearing (might work for keirin or team pursuit)
Depending on the fitness level and cadence sweet-spot, one rider might prefer a higher or lower gear inch for a specific type of workout or race.
I personally rode on track with cadence levels between 81” (48/16) and 96.4” (50/14), both of which I find too extreme.
I am still exploring with different gearing and I am currently riding 86.4" (48/15) to improve my ability to sustain high cadence.
I prepared the tables below – while daunting at first sight (!), I find them very helpful when choosing my gears as they provide all the inputs I need to find out the relationship between gearing and speed / cadence / lap time (450m) (**). Enjoy!
(*) Is the 27” diameter correct? No, it’s not. But it’s not an issue as long as people use this “standard” number consistently. For your reference, the “ISO” diameter of a 700x25c is 26.4” (670mm) and for a 700x23c it is 26.3” (667mm).
(**) The difference between a 700x23c and 700x25c is very small, in the order of <0.5km/h or <1rpm