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As per my troubleshooting to find a bike creak (Ultegra FC-R8000 Right Crank Arm Creak) - I have installed and removed the same chainring bolts ~8 times. In the process I snapped one of them. Each of my installs have used a torque wrench at 14Nm with a Torx T30 bit.

I have noticed that when installed on a crank it seems more difficult to push the T30 into the bolt, but when they are removed it is easy to slide the bit into the bolts.

Has anyone else experienced this behaviour from these (or other Shimano) chainring bolts? Am I doing something wrong if this is happening?

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  • Did you buy the crankset from the LBS you mentioned in the other question? Was the one that snapped from the old crankset or the new crankset? Jun 17, 2019 at 4:42
  • I did buy the cranks from my LBS. The one I snapped was from the old crankset. The new set came with a new set of bolts so I used one from there. I'll update the other question with this - but I did try all 4 new bolts in my troubleshooting as well.
    – Vitamin-T
    Jun 17, 2019 at 13:45
  • Good work - I'd replace all the bolts if one has snapped.
    – Criggie
    Feb 25, 2020 at 7:23
  • the bolts sound like they are made of cheese just to save a few grammes of weight. Buy some steel bolts instead
    – Vorsprung
    Feb 28 at 10:04

4 Answers 4

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Just sheared one of mine on an Ultegra R8020 11-speed crank. It's a Torx 30 screw made of aluminium, so it sheared quite easily when I tightened it to the Shimano recommended 12 - 16 NM. This seems far too much and even 8 NM seems too much.

I managed to get a Sora screw, which gets me back on the road, from the LBS and they recommend 6 NM with alloy screws.

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  • I also had a creak in my Ultegra crank which I'm still trying to sort out. I switched a Praxis Zayante crank for the Ultegra yet even with a new BB it still creaks. I tightened the chainring bolts (and snapped one - see previous post) but when checking the box of bits left over from the swap I noticed a spacer on one of the Praxis BB cups,the Ultegra doesn't have this so I think adding the spacer could solve the problem - I'm doing this tomorrow.
    – Mike Carey
    Aug 2, 2021 at 20:51
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I’ve sheared off 5 now on my ultegra 6800 send Duraace 9100 at 13NM. Took spec recommended by Shimano seems way too high.

Just called Shimano. They said the torque setting is correct and are sending me 8 new bolts FOC. One thing I noticed was that the Trek dealership that did my inspection on both units must have applied some grease when reinstalling bc there was a big clump of red grease in each bolt socket. Shimano rep recommended not using any grease as could lead to over torking??

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  • Hi, welcome to bicycles. Can you confirm the source and type of the bolts you were using?
    – DavidW
    Feb 27 at 15:18
  • They were what ever bolts Shimano provides with the original component new. I believe they are alloy they were both black on the Ultegra and DA whereas I noticed on 105 the bolts are silver.
    – Matt
    Feb 28 at 12:47
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For what it's worth - the best answer I've been able to come up with/figure out is that when I was torquing the bolts down I might have been putting force on both the crank arm and the torque wrench and maybe doubling up on the force...

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    'Every force has a equal and opposite reaction.' To tighten a chainring bolt you have to put an equal torque on the crank to keep it from rotating, that does not mean the torque is doubled. Jan 26, 2020 at 12:47
  • I agree with Argenti, it does not seem likely. Shimano’s specs for the R8K cranks do say 12-16 Nm of torque. Ultegra should have steel bolts as well, which I’d expect to be more resistant to fatigue. Best guess is just a faulty bolt, unless your torque wrench is terribly miscalibrated.
    – Weiwen Ng
    Feb 25, 2020 at 14:31
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    Hmm. I found a site that said that the 6800 version of Ultegra uses alloy chainring bolts, so I'd assume the current generation also does. Again, if the OP used the correct torque, these should not have cracked, but I do wonder if failures may be more common with alloy bolts. Most users don't need to repeatedly install chainrings. handsonbike.blogspot.com/2016/10/…
    – Weiwen Ng
    Feb 26, 2020 at 19:30
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I read a forum post that, like a couple of the answers, attests that Shimano chainring bolts can crack at Shimano's official torque spec (12-16 Nm).

The poster reported that Park Tools' torque guide, while it is generic, lists 5-10 Nm for chainring bolts. The guide is dated to 2015, when Shimano was generally on 4-arm cranks. Based on all the info provided so far, I'd use that spec. Users should consider using threadlocker pre-emptively. If you grease the bolts and then need to threadlock them later, you will need to degrease the threads.

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  • I would caution readers to tighten to more than only 5Nm because cyclic fatigue failure may be more likely with that reduced preload. 12-16 might be too much but you should definitely aim for a fairly high torque value.
    – MaplePanda
    Apr 11 at 16:37

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