Campagnolo Compact Chainring Stupidity

Campy Compact cx chainring guard As tech-minded readers may already know, double chainring cranksets for roadbikes generally are described as either “standard” meaning a 53 tooth big ring and a 39t small, or “compact” with a 50t/34t combination. Compact road cranks have a 110mm bolt-circle-diameter which will accommodate rings smaller than 38t, down to a 34t….except for Campagnolo. No, they decided to make the their compact BCD 110mm for four of the bolts and the fifth “hidden bolt” (positioned behind the right crank arm) lies a little further outside a 110 circle. Why?

Stupid, stupid, stupid. I remember years ago when I first started wrenching, the old hands would bitch about Shimano creating ridiculous standards. I would like a Campagnolo designer to explain to me what performance benefit could possibly come from placing one of the five bolts 2mm outside the 110 BCD. A rational person could only assume that they did it to make their cranks incompatible with other manufacturers’ chainrings (though Specialties TA does make some). I have to say that I am personally offended….you suck Campy!

The Campy ring situation puts a crimp in my attempts to tailor custom bikes to suite a customer’s needs. For instance, no one makes a Campy compact compatible cyclocross chainring guard. But I’m not going out like that. I took a Campy 50t ring, ground off the teeth and combined it with a 46t Campy ring. Voi la!

Campy Compact cx chainring guard



5 Comments

110bcd Salsa Crossing Guards fit the silly haha-not-really-110bcd Campy Compact cranks. I’ve made a single ring work on my cyclocross bike (with a Chorus UT compact crank) by filing out one of the chainring bolt holes on a burly FSA BMX ring. The Crossing Guard required no modification (the holes were just big enough). The whole thing squeaked in a terrifying fashion, though, so a couple seasons later I subsequently ordered a TA ring and run it backwards (due to the chainring bolt aperture size on the cranks themselves) with some filed down extra-long chainring bolts.

yeah, i thought about getting a salsa guard with a file as my final authority, but the customer is actually trying to run a big-ish single ring on this sporty commuter bike.  The filed down 50t seems to be just big enough to shadow the 46t Campy cx ring.  It’s still a work in progress but the prognosis looks good.

I did the same thing with my first cross bike.  1x7 I think with a single bar-end shifter.  I ground the crap out of an older 53 tooth Campy ring.  The bench grinder wheel was pretty much silver by the end of that home-job.

A shot in the dark, but as one of the holes is slightly out, might it be to make sure the chainrings always have the same alignment? Maybe the tooth profiling is created in such a way as to aid shifting, as the rings would always be in the same place.

A bit like the ‘new’ shimano directional chain?

Personally I’ve not come across this before, but have worked with the directional chains!

Just my 2 cents.

Marc

@Marc
most high-end rings do have a specific intended orientation…they simply have a small mark or tab to indicate alignment.  it’s not even remotely necessary, intuitive, nor desirable to enforce alignment by bastardizing the bcd.

@Andrew
I used a bandsaw to cut the teeth off first, then a belt sander to smooth it out.  i try not to use the grind wheel too much with aluminium, since as you’ve found out, it tends to foul the stone.

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