A Skin­flint’s Guide to Cy­clocross

I went cy­clocross rac­ing in 2010. I’d bro­ken my arm badly while cy­cling home from a party one night a cou­ple of years ear­lier, and some kind of overde­vel­oped “HON­ESTLY, I’M FINE” re­flex had trans­formed me in the in­ter­ven­ing pe­riod from an en­thu­si­as­tic cy­cle com­muter into a cy­clocross bore who knew every­thing about the sport ex­cept how to race. I lapped my lo­cal park over and over; I dis­mounted and re­mounted un­til my per­ineum cried out “no more”; and, most of all, I ob­sessed over my bike.

Cy­clocross is great for this. Cy­clocross in 2010 was even bet­ter. Disc brakes were mak­ing waves in am­a­teur races and the UCI was about to make them le­gal at the top lev­els of com­pe­ti­tion. Se­ri­ous rac­ers rode tubu­lar tyres but tube­less was gain­ing ground. Best of all, 1× – a favourite of cy­clocrossers, mean­ing one chain­ring and one shifter only – was still a DIY af­fair. No CX1 or Ri­val 1 groupsets yet: if you wanted a 1× set-up, it was up to you to do it. These were the av­enues down which a bike nerd might joy­ously lose them­selves.

Lack of money lim­ited just how ex­per­i­men­tal I could get, and eBay was my friend. In­stead of disc brakes, I plumped for Em­pella Frog­g­leg can­tilevers, a set of brakes ad­justed pri­mar­ily by bend­ing them with a big span­ner. I went for plain old clinch­ers rather than tube­less tyres. And, most im­por­tantly, I cob­bled to­gether a 1× dri­ve­train us­ing the cheap­est com­po­nents I could lay my hands on – while still re­tain­ing a mod­icum of élan, of course. This meant Shimergo all the way.

Cyclocross racing at Strathclyde Country Park in 2010. (Image courtesy of Steven Turbitt.)
So much for élan. In action at Strathclyde Country Park in 2010. (Image courtesy of Steven Turbitt.)

What is Shimergo?

The word it­self is a mash-up of “Shi­mano” and “Er­gopower”, the lat­ter of which is Cam­pag­nolo’s name for its in­te­grated brake/​shifter levers. What Shimergo means in prac­tice is that it’s pos­si­ble to mix and match dri­ve­train com­po­nents from Shi­mano, Cam­pag­nolo, SRAM and other man­u­fac­tur­ers to save weight or money, or, if you’re lucky, both. Add 1× to the mix and you shed yet more weight and save yet more money. As a tight-fisted bike nerd with delu­sions of cy­clocross grandeur, I found it im­pos­si­ble to re­sist.

How does it work?

Be­fore we start, it’s worth men­tion­ing that be­cause we’re talk­ing about 1× set-ups, what fol­lows re­lates to rear shift­ing only. It’s pos­si­ble to put to­gether a Shimergo set-up for front de­railleurs but I haven’t ever done so. With that out of the way, let’s get to how Shimergo works.

In any de­railleur sys­tem with in­dexed shift­ing, when you change gear the shifter re­tracts or ex­tends a cer­tain amount of ca­ble per click. Change to­wards a larger sprocket on the cas­sette and the shifter pulls in the ca­ble; change to­wards a smaller sprocket and the shifter re­leases it. For most shifters, the amount of ca­ble is the same per click – but more on that later.

Now, this move­ment of the ca­ble causes the rear de­railleur to move in­wards or out­wards by a set dis­tance, as de­ter­mined by the amount of ca­ble pulled or re­leased by the shifter in con­junc­tion with the de­railleur’s ca­ble pull mul­ti­plier. For ex­am­ple, in a 9-speed Shi­mano groupset,

  • the shifter pulls or releases 2.5mm of cable per click
  • the derailleur multiplies shifter cable motion by 1.7, and
  • the centrelines of each adjacent pair of sprockets are 4.35mm apart.

Putting this to­gether, de­railleur move­ment per ca­ble click is around 2.5mm × 1.7 = 4.25mm, which is just 0.1mm dif­fer­ent to the sprocket spac­ing. Across a com­plete 9-speed cas­sette, if the de­railleur is per­fectly aligned with the small­est sprocket, that’s a cu­mu­la­tive er­ror of just 8 shifts × 0.1mm = 0.8mm – that is, the de­railleur will be less than 1mm out of align­ment with the largest sprocket. And if Shi­mano is happy with a 0.8mm mar­gin of er­ror, you should be too.

Given all this, the trick is to choose a shifter, de­railleur and cas­sette so that the de­railleur’s move­ments as ac­tu­ated by the shifter match the spac­ing of the rear sprock­ets as closely as pos­si­ble. There are lots of pos­si­ble com­bi­na­tions here: a 9-speed Shi­mano de­railleur and cas­sette with a 10-speed Cam­pag­nolo shifter, as I used; an 11-speed cas­sette from any man­u­fac­turer with an 11-speed shifter and de­railleur from any an­other; a 10-speed Campy shifter and a 10-speed SRAM de­railleur on a 10-speed Shi­mano or SRAM cas­sette; and so on.

A 1×9 Shimergo set-up

For my ’cross bike, I set­tled on a 1×9 setup us­ing a 10-speed Campy shifter with a 9-speed Shi­mano de­railleur and cas­sette. In the event, the fin­ished bike did not ex­actly live up to my vault­ing am­bi­tion, even if it did rock Campy’s svelte and sinous brifters rather than Shi­mano’s lumpen coun­ter­parts. Wit­ness the mis­matched frame and fork! The taped-over bot­tle bosses! The ques­tion­able ca­ble rout­ing! But if the bike was aes­thet­i­cally chal­leng­ing, its dri­ve­train worked like a dream. Sim­ple, cheap and re­li­able – with a few caveats.

Kinesis Crosslight 5T with 1× Shimergo drivetrain.
My Kinesis Crosslight 5T in June 2011. Forgive the terrible photo. And the bike.

The maths worked out like this:

  • the 10-speed Campy shifter pulls or releases 2.83mm of cable per click,
  • the 9-speed Shimano derailleur multiplies shifter cable motion by 1.7, and
  • the centrelines of each adjacent pair of sprockets are 4.35mm apart.

Thus, de­railleur move­ment per ca­ble click is 2.83mm × 1.7 = 4.81mm.

Wait, what?

4.81mm per shift is very dif­fer­ent to the 4.35mm spac­ing of the sprock­ets. The key to mak­ing this par­tic­u­lar set-up work is to use “Hub­bub” ca­ble rout­ing, in which the shifter ca­ble is clamped to the de­railleur at a slightly dif­fer­ent an­gle, thereby chang­ing its mul­ti­pli­ca­tion ra­tio. (Cy­clocross Mag­a­zine have a good pho­to­graph of Hub­bub ca­ble rout­ing.) This changes the de­railleur’s ra­tio to ap­prox­i­mately 1.6 and, with that tweak, my de­railleur’s move­ment per ca­ble click be­came 2.83mm × 1.6 = 4.53mm. Rel­a­tive to the sprocket spac­ing of 4.35mm, this pro­duces a cu­mu­la­tive er­ror of just 8 × (4.53 - 4.35)mm = 1.44mm across the whole cas­sette. In prac­tise, it turns out, this is per­fectly fine.

Now, there’s an­other wrin­kle here, in that Cam­pag­nolo’s 10-speed shifters ac­tu­ally pull a slightly dif­fer­ent amount of ca­ble per shift, with more ca­ble pulled to­wards the larger sprock­ets. From the small­est sprocket to largest, ca­ble pulls in mil­lime­tres are: 2.5, 2.5, 2.5, 2.5, 2.5, 3.0, 3.0, 3.5, and 3.5, av­er­ag­ing out at 2.83mm. (Shi­mano’s 8- and 9-speed shifters, Shi­mano’s 10-speed MTB shifters and Campy’s 11-speed shifters all have the same quirk.) For what it’s worth, I’ve used Campy 10-speed shifters both with a 9-speed Shi­mano de­railleur (as de­scribed here) and a 10-speed “Ex­act Ac­tu­a­tion” de­railleur from SRAM. Get your in­dex­ing right and you should­n’t have a prob­lem.

There’s one last thing to be aware of. Be­cause my shifter was de­signed for 10 sprock­ets but the cas­sette only has 9, I used the “L” de­railleur limit screw (“L” for “low”) to stop the shifter pulling the chain off the largest sprocket and into the spokes. It’s easy enough to do: hav­ing con­nected the ca­ble and ad­justed the in­dex­ing, set the “L” screw as nor­mal to pre­vent the de­railleur from mov­ing any fur­ther. When you get to the in­ner­most sprocket and try to shift again, the shifter lever won’t let you.

Here’s my com­plete set-up:

FrameKinesis Crosslight 5T
ShifterCampagnolo Xenon 10-speed“Quick-Shift” mechanism
DerailleurShimano Deore RD-M591 (9 speed, long cage)“Hubbub” cable routing
CassetteShimano Deore HG61 (9 speed, 11-28)
CranksetShimano 105 FC-5501 (53/42 double)53t chainring removed
Chain retentionSalsa Crossing Guard (44t x 130mm) + Deda Dog Fang

This set-up with­stood three cross races with only one dropped chain and did ster­ling duty as a com­mut­ing bike for many years af­ter­wards – un­til it did­n’t. It’s rel­a­tively well doc­u­mented that the es­cape mech­a­nism in Campy’s low-end Xenon shifters even­tu­ally wears out, which is ex­actly what hap­pened to mine. Hav­ing shifted up the cas­sette to a larger sprocket, the shifter would some­times fail to “catch” and would drop back down to a lower cog. I re­placed them with Ve­loce shifters in­stead, which solved the prob­lem. And that’s where I’ve been ever since: I’ve since added SRAM com­po­nents to the mix, but I’ve been hap­pily run­ning 1×9 or 1×10 Shimergo dri­ve­trains for the past decade.

Many peo­ple far more qual­i­fied than me have writ­ten in de­tail about mix­ing dri­ve­train com­po­nents and so, rather than re­ca­pit­u­late what has been said be­fore, be­low are some links to point you in the right di­rec­tion.