Ullapool Trials Rider Posted December 11, 2009 Report Share Posted December 11, 2009 I Had a loose crank for about 3 weeks. I had to keep tightening it up every 5 - 10 mins for 3 weeks. then 2 days ago it stayed tight and it hasn't come loose since. Is this normal for trials cranks. Quote Link to comment Share on other sites More sharing options...
Nic84echo Posted December 11, 2009 Report Share Posted December 11, 2009 I Had a loose crank for about 3 weeks. I had to keep tightening it up every 5 - 10 mins for 3 weeks. then 2 days ago it stayed tight and it hasn't come loose since. Is this normal for trials cranks.In a word; no. If it's working itself loose constantly theres obviously something wrong. If they've stayed tight all of a sudden without you doing anything else then I'd be pretty suspicious as to why. Maybe take 'em apart, make sure everything is ok (incidentally, what kind of crank/bb combo are you running?), then re-grease them properly and tighten everything up again. That way, if you're doing any serious damage to your crank/bb, you at least have a chance to prevent any more and possibly save them. Quote Link to comment Share on other sites More sharing options...
davey1991 Posted December 11, 2009 Report Share Posted December 11, 2009 This can happen and is quite normal acctually....If they are new cranks the taper will wear slightly at first and will settle eventually.If they're older cranks then its probably you not trying hard enough.But if they are constantly working loose then you've damaged the taper or splines, the only way to sort this is by replacing your cranks. Sorry. Quote Link to comment Share on other sites More sharing options...
Nic84echo Posted December 11, 2009 Report Share Posted December 11, 2009 This can happen and is quite normal acctually....Really? I've never had this happen on a trials bike. I have only ever used isis splined cranks/bbs though, is it a square taper issue? The only time I've had a similar sounding problem was on my downhill racer, and that was a case of too much pressure moving metal = buggered. Quote Link to comment Share on other sites More sharing options...
davey1991 Posted December 11, 2009 Report Share Posted December 11, 2009 Really? I've never had this happen on a trials bike. I have only ever used isis splined cranks/bbs though, is it a square taper issue? The only time I've had a similar sounding problem was on my downhill racer, and that was a case of too much pressure moving metal = buggered.Its more of a thing with taper cranks.Your using the taper to hold the cranks so your forcing hard steel into softer aluminium so there is some initial movement.Isis shouldn't. Quote Link to comment Share on other sites More sharing options...
duncan_echo26 Posted December 11, 2009 Report Share Posted December 11, 2009 My crank kept coming loose so I put a tiny dab of superglue on the bolt, tightened it up and its all good now I'm not too sure if this is a good idea though Quote Link to comment Share on other sites More sharing options...
Nic84echo Posted December 11, 2009 Report Share Posted December 11, 2009 Its more of a thing with taper cranks.Your using the taper to hold the cranks so your forcing hard steel into softer aluminium so there is some initial movement.Isis shouldn't.Fair do's, that makes sense, and is really exactly what happened with old square taper cranks I raced on. Which begs the question, why do people still use taper cranks? Quote Link to comment Share on other sites More sharing options...
duncan_echo26 Posted December 11, 2009 Report Share Posted December 11, 2009 (edited) Which begs the question, why do people still use taper cranks?They are cheaper (for the bottom brackets) . I think that's about it. Edited December 11, 2009 by duncan_echo26 Quote Link to comment Share on other sites More sharing options...
Nic84echo Posted December 11, 2009 Report Share Posted December 11, 2009 They are cheaper (for the bottom brackets) . I think that's about it.So the bb's are cheaper, the bit thats steel, so the expensive bit, ie the crank, breaks quicker, being the softer aluminium bit.......see where I'm going? False economy. Isis for the win Quote Link to comment Share on other sites More sharing options...
Luke_zoo Posted December 12, 2009 Report Share Posted December 12, 2009 Isis for the win Quote Link to comment Share on other sites More sharing options...
davey1991 Posted December 12, 2009 Report Share Posted December 12, 2009 So the bb's are cheaper, the bit thats steel, so the expensive bit, ie the crank, breaks quicker, being the softer aluminium bit.......see where I'm going? False economy. Isis for the win It seems to be a personal thing.If isis come loose they can fall of or damage themselves, if taper bolts come undone the taper holds the crank, atleast for a while.Square taper cranks also have more material around the BB so are infact less likely to break. Quote Link to comment Share on other sites More sharing options...
Ashley-Wood Posted December 12, 2009 Report Share Posted December 12, 2009 well what id normally do is tighten harder than i did before... Quote Link to comment Share on other sites More sharing options...
Nic84echo Posted December 12, 2009 Report Share Posted December 12, 2009 Square taper cranks also have more material around the BB so are infact less likely to break.I don't really see how that's possible. Granted, it's been a very long time since I've had a square taper crank/bb. But isn't the whole point of the isis system a greater surace area in contact between the crank and the bb? If I'm not mistaken, the isis bb spindles are larger in diameter than their square taper equivalents too. So, larger diameter + multiple splines (instead of 4 flat sides) = less likely to strip or round. No? Quote Link to comment Share on other sites More sharing options...
duncan_echo26 Posted December 12, 2009 Report Share Posted December 12, 2009 I don't really see how that's possible. Granted, it's been a very long time since I've had a square taper crank/bb. But isn't the whole point of the isis system a greater surace area in contact between the crank and the bb? If I'm not mistaken, the isis bb spindles are larger in diameter than their square taper equivalents too. So, larger diameter + multiple splines (instead of 4 flat sides) = less likely to strip or round. No?Yes isis bb spindles have a much bigger diameter. And they are less likely to round too.I would choose isis every time.. If I had the money Quote Link to comment Share on other sites More sharing options...
craigjames Posted December 12, 2009 Report Share Posted December 12, 2009 Because of the larger axle diameter, Isis BB's tend to have smaller bearings compared to square tapers BB's. Obviously with the impacts and loading that you get from trials on the bearings they used to die pretty quickly, its the same reason mountain bikes went to external bearings, you can retain the large diameter axle for better strength but also increase the size of the bearings and their ability to handle loads and as such increase their lifespan.But with the square taper, its totally normal for the cranks to settle over a period of time. Quote Link to comment Share on other sites More sharing options...
ogre Posted December 14, 2009 Report Share Posted December 14, 2009 Fair do's, that makes sense, and is really exactly what happened with old square taper cranks I raced on. Which begs the question, why do people still use taper cranks?you can run large bearings in a square taper BB, and in a riding situation with low stress (such as roady-ing) the strength is less of an issue, plus the bearings will last for ever and be smoother etc, so they're great for just spinning, square taper really isn't suitable for trials. that said onza muscleman cranks are very sturdy and quite hard to round... Quote Link to comment Share on other sites More sharing options...
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