💾 Archived View for zaibatsu.circumlunar.space › ~solderpunk › bikes › franken-peugeot › log › ag6_2… captured on 2020-09-24 at 02:12:26.
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August 30th, 2018 ----------------- After doing a lot of reading online about crank installation, loosening left cranks, and crank-BB compatibility, I've learned three things which seem relevant to my repeated problem. Firstly, Ofmega, the Italian company who made my cranks, used a proprietary square taper that is not properly compatible with either ISO or JIS square spindles. I'm not sure if *all* their cranks were like this, or if they, at some point, switched to a standard. I think the latter - Sheldon[1] was very particular about always saying "old Ofmega cranks", suggesting that "new" ones are okay. When did they change? I have no idea. If it weren't for the fact that my right hand crank has had zero problems the entire time, I would be tempted to assume this is my problem. That said, apparently left cranks are much more prone to this, for reasons I don't quite understand yet. Maye the right crank will eventually have trouble, too? Secondly, the expert recommended approch to crank installation seems to involve making sure both crank socket and BB spindle are very clean before you start, lightly greasing the spindle and bolt threads, and doing a second tightening of the bolt after an hour or so of riding after the first tighten, because there is a tendency for the crank to snug up further onto the spindle under the forces of riding, which causes loss of the original bolt tightness. I haven't done *any* of these things properly on previous installations, so maybe there is no compatibility issue at all and just shoddy worksmanship. Thirdly, regardless of which of the above is causing my problem, I might be in trouble, because apparently even a little bit of riding on a loose crank can deform the crank socket to the extent that it will never again install tightly. Yikes! So, today I popped to the co-op and reinstalled my left Ofmega crank according to the procedure above, with the cleaning, greasing and second tightening. We'll see what happens. If it stays on, fantastic, score one for careful installation. If it comes loose for a third time, I'll assume it's never going to stay put, either due to Ofmega's proprietary socket taper, or socket deformation from riding while loose. In that case, I'll replace just the left crank with another one that I'm sure has a standard taper and I'll install it right from the start. It will be a shame to have a non-matching set, but I don't want to go through the trouble of replacing the drive-side crank unless I really have to, as the limited range of parts to choose from might force either a change of chainline or gear ratio, which I'd rather avoid. While at the co-op, I had a look and found, as I'd hoped, a box full of loose left cranks, to reassure myself that I would have some options if the Ofmega did not stay put. All I can say is, wow, modern cranks sure are ugly. This is not really specific to cranks, I think a lot of modern bike parts looks gross (and I'm not alone [2,3]), but honestly, I was dealing with what looked like a box of metalised turds. Fat and strangely rounded/blobby is the predominant look. I don't know if the change was driven mainly by fashion or functionality, but I think the slender, fluted cranks with bevelled edges that were made in the 70s and 80s look a *lot* nicer than the newer fat blobby ones. I realise that this doesn't actually *matter* at all, but everything else being absolutely equal, I think just about everybody would prefer a beautiful part to an ugly one. I found an SR Super Custom crank in there (something like this[4]) which, while not as nice as the Ofmega[5], is not too offensive, so I'll probably use that if I'm forced to change. [1] https://www.sheldonbrown.com/bbtaper.html [2] https://bikeretrogrouch.blogspot.com/2018/06/man-derailleurs-just-keep-getting-uglier.html [3] https://bikeretrogrouch.blogspot.com/2014/05/component-style-old-and-new.html [4] http://velobase.com/ViewComponent.aspx?ID=68B0B72D-B8AE-49AF-A5F2-FF45AC2FC97D&Enum=115&AbsPos=294 [5] http://velobase.com/ViewComponent.aspx?ID=3F90F87C-F9EE-47DB-AD01-6F0971C62969