This is very hard to explain, but I will try my best.

I recently got a Shimano Ultegra cassette, crankset, front and back derailleurs, chain, and cables installed on my Giant TCX SLR1 2015 bike.

Every time I pedal, I feel a subtle click or slip on my left foot at a specific interval (when the left arm is going down). However, there is no sounds, I can only feel it in my feet. It’s very subtle.

However, I do not feel it when I put a lot of pressure or when off the seat. I really cannot pin it down to anything, hence I would be grateful for any opinion.

  • I'd start looking at the pedal bearing or shoe / cleat / pedal interface. Sep 2, 2018 at 22:31
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    Just had a close look. Turns out bolts on the left arm are not tighten at all ! 🤦‍♂️. I hope cycling for week like this has not damaged my crankset Sep 2, 2018 at 22:32
  • Did you have a shop install the groupset for you? I'd let them know about the issue straight away. Sep 2, 2018 at 22:34
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    @user9051697 good spotting on the root cause. You should add your own answer to the question, and mark it as accepted, because that's what worked for you. Totally permitted by SE.
    – Criggie
    Sep 3, 2018 at 3:17
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    There was a question recently, which I can’t find sorry, clarifying that shimano tech docs advise that the pinch bolts on the left arm should be tightened after 20 km. so if they loosened, now that they’re tight, don’t forget to tighten them again after 20 km
    – Swifty
    Sep 3, 2018 at 16:28

1 Answer 1


You state in the comments that the (pinch) bolts on the left crank had come loose (Ultegra Hollowtech 2). So you’ve solved the problem by tightening the bolts.

I saw another bike (I think Ultegra cranks) do this yesterday, again it was a very new bike, it was on its first serious outing and the left arm had worked loose.

I found the question with a relevant Shimano publication extract: How to tighten the Hollowtech II (on R2000 Claris) cranks?

In short, any time you install these bolts, tighten/torque check them again after 20 km, much like checking the wheel nuts on a car, a short time after it’s been in for a service.

  • It is important to fix this immediately as it will damage the thread.
    – Herr Derb
    Sep 10, 2018 at 9:09

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