2023 Subscriptions George Posted October 28, 2015 2023 Subscriptions Report Share Posted October 28, 2015 Got 100 yards from work tonight when my left crank fell off. Now regretting not attending the maintenance workshops. Is there any reason this might happen other than the bolt working loose? Quote Link to comment Share on other sites More sharing options...
Members Richard Posted October 28, 2015 Members Report Share Posted October 28, 2015 What sort of crank/bottom bracket is it? Quote Link to comment Share on other sites More sharing options...
2023 Subscriptions George Posted October 28, 2015 Author 2023 Subscriptions Report Share Posted October 28, 2015 Shimano 105 chainset. Think it's a tiagra bb. Quote Link to comment Share on other sites More sharing options...
Members Richard Posted October 28, 2015 Members Report Share Posted October 28, 2015 Is the chainset for a cartridge bottom bracket with spindles or is it one of these Hollowtech things? Quote Link to comment Share on other sites More sharing options...
2023 Subscriptions George Posted October 28, 2015 Author 2023 Subscriptions Report Share Posted October 28, 2015 Hollowtech Quote Link to comment Share on other sites More sharing options...
Members Richard Posted October 28, 2015 Members Report Share Posted October 28, 2015 I don't have any real experience of Hollowtech (though I bet lots of other folk on here do.) Could it just be that the pinch bolts haven't been torqued properly? From what I can see online they're meant to be torqued to 12-15nM, which is a lot for a bolt of that size. If you were to tighten them without a torque wrench I think there's a real risk that you'd leave them loose. My Campag Ultra Torque cranks are secured with one bolt which holds the two crank arms together. Even when it's properly torqued it's prone to working loose unless you use threadlock on it. George 1 Quote Link to comment Share on other sites More sharing options...
Members Richard Posted October 28, 2015 Members Report Share Posted October 28, 2015 Tightening the pinch bolts and the preload bolt in the wrong order is another possible cause of the problem you're having. The preload bolt needs to be tightened first. George 1 Quote Link to comment Share on other sites More sharing options...
2023 Subscriptions George Posted October 28, 2015 Author 2023 Subscriptions Report Share Posted October 28, 2015 Cheers, Richard. I note that when I put the crank back on the bolts took a lot of tightening before I was satisfied they were secure. The preload bolt is a rather tragic rubber bung that doesn't inspire much confidence but it's the same on all my other bikes & I've had no issues. Hopefully it's just a matter of the bolts work loose under my immense wattage. Quote Link to comment Share on other sites More sharing options...
DavieB Posted October 28, 2015 Report Share Posted October 28, 2015 George, I suspect the preload bolt is designed to be rather "tragic" to prevent people "horsing" it up. So more design intent than crap design. It is sufficiently engineered to preload to the point your cranks will not freely turn. You should achieve torque to the required settings no problem but make sure you tighten both in sequence a bit at a time, also ensure that the safety catch is located correctly - this catch should effectively stop the cranks coming off even if the bolts loosen. I like the design and find the maintainability a vast improvement v's Campag. KennyS and George 2 Quote Link to comment Share on other sites More sharing options...
DavieB Posted October 28, 2015 Report Share Posted October 28, 2015 Check tightness regularly. Quote Link to comment Share on other sites More sharing options...
2023 Subscriptions George Posted October 28, 2015 Author 2023 Subscriptions Report Share Posted October 28, 2015 Cheers Davie Quote Link to comment Share on other sites More sharing options...
Committee Alan McLean Posted October 29, 2015 Committee Report Share Posted October 29, 2015 Hi George, I echo Davie. Not an original thought in my head. For the lh crank to fall off the bolts would have to be very loose, then the safety catch falls out then the preload plastic bolt would have to be forced off the axle. I suspect something went wrong in installation. Maybe even buy a torque wrench. your preload bolt must be stripped/bent so suggest you get another. Main message from maintenance night was that Shimano et al. have very clever engineers so we might as well follow their fitting instructions (all online) to the letter. Plastic bolt is a good example. I feel daft when I get round to actually reading the fitting instructions and realise how much time/watts/money I could have saved by doing it properly. Of course you learn a lot more by stripping threads, wrecking frames and Pringling wheels yourself but that is not really the point. duncan thomson, KennyS and George 3 Quote Link to comment Share on other sites More sharing options...
2023 Subscriptions George Posted November 5, 2015 Author 2023 Subscriptions Report Share Posted November 5, 2015 Ordered a shimano 105 10 speed replacement crank cap from Evans (the black plastic thing) It doesn't fit. It is much smaller in diameter than the original. Does anyone have any idea or experience of differing diameters in these thingys? Quote Link to comment Share on other sites More sharing options...
2023 Subscriptions thejanullrichdietplan Posted November 5, 2015 2023 Subscriptions Report Share Posted November 5, 2015 I recently made the same mistake too with 5600 series 105 (the last one with unhidden cables) i've not got round to getting the proper size yet because while the crank cap is smaller it still works as long as i dont tighten it too much. Anyway here is the one i should have ordered http://www.sjscycles.co.uk/shimano-ultegra-fc-6600-crank-arm-fixing-bolt-1g3-1100-prod14200/ Quote Link to comment Share on other sites More sharing options...
2023 Subscriptions George Posted November 5, 2015 Author 2023 Subscriptions Report Share Posted November 5, 2015 Cheers Iain, I've ordered that part now & am panting with anticipation. Quote Link to comment Share on other sites More sharing options...
2023 Subscriptions George Posted November 7, 2015 Author 2023 Subscriptions Report Share Posted November 7, 2015 Part came. It's the same as the one I ordered previously. I now have 3 of these ill fitting plastic bung things. Went to see if Willie Cosh had one. Nope. The hunt goes on for the fabled larger diameter crank bung doodah. I did buy a new winter frame while there tho. Quote Link to comment Share on other sites More sharing options...
2023 Subscriptions George Posted November 7, 2015 Author 2023 Subscriptions Report Share Posted November 7, 2015 I've decided to fashion the crank bolts into those big plug type earrings that bohemian youths wear these days. Like the big Maori guy in moby dick. Quote Link to comment Share on other sites More sharing options...
2023 Subscriptions P McDonald Posted November 8, 2015 2023 Subscriptions Report Share Posted November 8, 2015 George I ran my winter bike all last winter without said bung. And will do so this winter. For exact same reason that I could not get one! Anyway you can literally just push the LH crank on whilst keeping an opposite push on the RH crank then nip it up. Check there is no play and off you go. Looks a bit odd with no bung but hey ho. Quote Link to comment Share on other sites More sharing options...
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