I use Puig R12 frame sliders on my Yamaha R3 motorcycle. The frame sliders are held in place by 12.9 grade stainless steel bolts (https://www.boltdepot.com/fastener-information/materials-and-grades/bolt-grade-chart.aspx) such as the ones below:

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I got my frame sliders just 2 week ago and the bolts holding the left frame slider has broken off 2 times in that duration! I was wondering what the issue could be. Also, what sort of bolt grades can I get that is more resistant to breaking off? The frame sliders coming off due to breaking bolts makes them quite useless if my bike was to fall off. Kindly suggest.

  • Get some bolts that are grade 8 or better, anodised or black finish... – Solar Mike Sep 16 '18 at 17:14
  • @SolarMike The black finish bolts same as mild steel bolts (as opposed to stainless steel)? Are they less prone to breaking off? – Amal Antony Sep 16 '18 at 18:25
  • Check out what grade 8 means, they should be stronger. – Solar Mike Sep 16 '18 at 18:26

Grade 12.9 is a low alloy steel , not stainless, although that is not a problem. The 12.9 strength level is exceptionally high . That high hardness makes them prone to cracking during electro-plating unless conditions are very well controlled. They are also subject to cracking during heat-treatment. I think there is a good chance there was a small crack/defect in them originally. Possibly they were over-torqued or an EP lube was used during installation when not recommended. I would try a lower strength fastener like Grade 8 which will need to be torqued to a lower level.

  • Thanks. I will go with Grade 8 now. Is grade 8 prone to breakage if over torqued as well? – Amal Antony Sep 18 '18 at 19:58
  • If over torqued, yes. Here's a chart with recommended torque values: gtsparkplugs.com/bolt-torque-chart-metric.html – Eric Oct 24 '18 at 21:00
  • Check the lube used for the torque tables. If EP lubes ( like moly sulfide) are used and were not listed in the tables , they could be over torqued. – blacksmith37 Oct 25 '18 at 23:21

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