Stuck chainring bolts: Campagnolo Chorus Ultra Torque

I need some clever ideas please!

I have this crank and I'm trying to change the chainring bolts. I am struggling to stop the back/nut half of the bolt also rotating. They are also very tight/seized.

What is the best tool to use in these tiny, shallow, slim recesses that Campagnolo have created in their wisdom?

Guessing you’ve tried the obvious... tip the bike upside down, put a large flathead screwdriver into the slot on the back and correct sized torx driver in the front and twist apart? Slow and careful though, from experience those campy bolts are made of cheese and if you strip one you’ll need to buy a whole new set at around £30... ouch!

Hi , Park Tool CNW-2 fits the thinner slotted chain ring bolts ... I had the same problem recently ....

Thanks for the responses.

Yes I tried a flat-head driver - I failed because the force required meant the driver skipped out. At this point I stopped immediately before I ruined a bolt.

I'll buy the CNW-2 and see how I go. I will probably need to clamp it onto the chainring bolts during use because these bolts are so fricking tight... Unbelievable how seized they are.

i had to get a second person to hold the screwdriver, bloody lethal job. If you absolutely must stab yourself with chainring teeth its probably better to run the ultrasonic cleaner first.

The Park Tool CNW-2 did the trick after a couple of patient applications of TriFlow penetrating oil - that pear drop aromatic wonder fluid.

Using the torx key I rotated each stuck chainring nut so that when the CNY-2 was inserted in the back it could then not rotate (i.e. it was right against the crank spindle or the chainring body). That meant I only needed to use one hand on my torx multi-tool and the other hand on the back, pushing the CNY-2 into the slot really really hard. I can still feel a slight burn in my pecs. The bolts gave high pitched "click" noises as they started to release, turning like 2-3 degrees each click, until finally they turned smoothly. Satisfying.

Many, many years ago (I’m talking about the 1970’s), I bought a Shimano Dura Ace chainset and it came with their version of that tool, and I still have it!