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Making 13-speed work for you

5 November 2020
Making 13-speed work for you

Great gravel riding demands the right gear ratios, and carefully considered cadence – here’s how we made Ekar’s 13-speed concept work on the dirt.

“What’s important to the rider is the spacing between those gears, so that the cadence can progress smoothly when you shift from one gear to the next”

When we designed Ekar, one of the things we knew was fundamental was getting the total range of gears correct for so many different gravel riders’ needs.

We also knew that 1x is the best idea all-round and that to achieve both, a 13-speed system was required. But before we could make it, we had to work out how that range works.

It started with studying what and how gravel riders ride – beyond the ‘feel’ that we knew as riders – and then, some maths...

“We made considerations about the percentage changes and the meters that you can pedal with one pedal turn,” explained Ekar’s Product Manager. “So we needed to make something that is smooth. We made a lot of studies with the numbers in the early stage, and then we could develop all the other features.”

 

Creating the right ratio range

 

Ekar has three cassette options, their sprockets having 9-36, 9-42 and 10-44 teeth. They can be partnered by four front chainring options: 38, 40, 42 and 44t. So there are potentially 12 combinations of gearing ‘off the shelf’ with Ekar, that can each give wide, but different overall gearing ranges. 

 

 

Let’s look at the gearing ratio range that two typically combined chainring and cassette offer. The combination of your single chainring and the cog you select at the back determines the gear ratio.

This ratio, combined with the circumference of your wheel and tyre determines how far you will travel with each revolution of the cranks. Ekar was envisaged for 700c or 27,5” / 650B wheels, and with the range of tire profiles now available do mean there is a marginal additional tailoring.

The gearing is expressed as a ratio (sometimes as a percentage, or in meters, and even inches) but the ratio should work wherever you are, and whatever rubber you run.

Consider the ‘hardest’ (or ‘longest’) gear as a combination of the biggest chainring (44t) and the smallest rear cog (9t) and to express that as a ratio we divide 44t by 9t = 4.89. The ratio, or ‘mechanical advantage’ is 4.89, so for every time you pedal one full turn of the crank, the rear wheel turns 4.89 times. This is ‘road territory’: at high speed, this gives a great ‘top end’ range to the fastest of gravel rides.

 

 

The 9-tooth cog means Ekar offers something no other 1x gravel groupset can.

Using the same single 44t chainring and the 9-36 cassette, our lowest ratio is 44 ÷ 36 = 1.22. That’ll be our friend in some steeper climbs.

Look at the other end of the ratio range possible with Ekar, using the ‘shorter’ options: a 38t front ring and the 10-44 cassette. For our higher road speed, 38 ÷ 10 = 3.8, giving a gear ratio of 3.8:1, for a medium top speed, if that suits your gravel game.

Again, using Ekar’s 38t chainring and the biggest ‘plate’ on the 13-speed rear cassette, check out the bottom end it gives you: 38 ÷ 44 = 0.86, the ‘easiest’ gear for steep climbing and/or the most technical’s off-road hazards. Now we’re in mountain bike territory and this will get you through the toughest gravel challenges.

 

Managing cadence

 

 

How fast you can push these gears at the top or the bottom of the ratio range – your cadence in spinning your pedals round – depends on a number of factors, but chiefly, the incline, the surface conditions and your power output.

While the total range is fundamental both to the riding experience and to the design considerations, what’s also important to the rider is the spacing between those gears, so that the cadence can progress smoothly when you shift up or down from one gear to the next.

With the smallest and largest cogs determined, and a thinner chain and a new derailleur designed to access them, it’s more maths to devise the best spacing of our 13 options.

The principle is ensuring closer low gear spacing – one-cog jumps, creating steady, natural cadence progression at slower speeds. And then there’s progressively wider spacing on the higher gear, with 2, 3, 4, 5 and ultimately 6-tooth steps, creating bigger jumps to provide longer top-end speed options, delivering the full range, with this considered spacing:

 

Endurance (9-36T): 9-10-11-12-13-14-16-18-20-23-27-31-36

Gravel Race (9-42T): 9-10-11-12-13-14-16-18-21-25-30-36-42

Gravel Adventure (10-44T): 10-11-12-13-14-15-17-19-22-26-32-39-44

 

The progression would not be possible across 12 cogs, and even with 13 cogs, it was the use of a 9-tooth that made it achievable, and triggered further development.

“A nine-tooth cog was something that was impossible to put on a freewheel body, without a special fixture.” explained Ekar’s Product Manager. “And this is something that we worked out with the new Next 3 Ways freehub body.”

 

Making the cassettes a reality

 

 

A two-part cassette comprises a lightweight alloy component inside the spider supports the main part of the sprockets, which are made from hard-wearing tempered steel.

A new process was developed to guarantee the stability of the measure after the heat-treating process, and so the steel doesn’t deform. This was important to ensure that the bigger sprockets stayed in the perfectly correct shape and size, for the highest possible efficiency and longevity. And it’s even more important than ever given Ekar’s narrower sprocket widths required for fitting the 13-speed system into the standard hub width to work with the wheel choices demanded for gravel.

Like every other aspect of the Ekar groupset, the cassettes were subject to a cycle of development, testing and refining to prove the theory.

“I think the spacing between gears are perfectly placed throughout the range,” said former road pro turned adventure and endurance cyclist Mattia De Marchi, who helped us with testing prototypes and giving feedback.

 

Discover Ekar cassettes and more

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