Giant Revel 3 Suntour Crank Arm Loose
05-27-15, 11:42 PM
#26
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You probably dont have to replace your bottom bracket (crank bearings and spindle). I would chase the threads, replace the bolts (if you havent already), and use the blue locktight. I have to use threadlock, and I have an expensive crankset so buying a new/better one as suggested above, most likely wont help.
05-28-15, 08:29 AM
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Your crank arm could have a crack where it attaches to the axle, causing it to flex and become loose.
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05-28-15, 08:57 AM
#28
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You probably moved to quality cranks. That's what's up here. Anything is possible but generally speaking what happens is that the left arm is more flexible (it doesn't have the additional structural design/material that contributes to stiffness on the drive-side). This slight flexibility does act on the retaining bolt which holds the crank to the axle, it stretches the bolt minutely and at the same time it acts, like a good lever, to move material around the square taper of the axle. All this is very slight and generally is not significant enough to loosen the crank arm. However, provided enough force and enough bolt stretch/movement, the crank will work continuously to enlarge the hole into which the axle is stuck.
The 2-piece design offers a few advantages. The entire structure, cranks/axle/bearings, is much stiffer because the drive-side crank has the axle spindle permanently affixed and this spindle is of a significantly larger diameter (eg stiffer) than the crank style you currently have. There are some measurements that I am not able to determine so, I'm afraid, I can't make more than general suggestions.
The 2-piece design offers a few advantages. The entire structure, cranks/axle/bearings, is much stiffer because the drive-side crank has the axle spindle permanently affixed and this spindle is of a significantly larger diameter (eg stiffer) than the crank style you currently have. There are some measurements that I am not able to determine so, I'm afraid, I can't make more than general suggestions.
It feels like moving to a higher quality, two-piece crank is the way to go primarily because my previous experience with my BMX bikes. I broke through three sets of pedals before finally upgrading my crankset and getting new pedals. Since then, I never ever had a problem with either one and both were holding up really well. I even dusted off the old bike before moving to my current Giant setup, and everything worked fantastic even after a few years of storage.
No worries about general suggestions, those are very useful too. I think I'm just going to talk to the bike tech about upgrading and figure it out that way. That said, another bike forum suggested this crankset, any opinions on it?
Shimano Deore M590 9 Speed Triple Chainset | Chain Reaction Cycles
I'm only familiar with the Shimano brand and heard they're good quality. But at this point I'm willing to defer to the bike tech's judgment and by what he has in stock. Or if general suggestions are a bit too tedious, can anybody suggest what brands to stay away from or they've had poor experiences with?
You probably dont have to replace your bottom bracket (crank bearings and spindle). I would chase the threads, replace the bolts (if you havent already), and use the blue locktight. I have to use threadlock, and I have an expensive crankset so buying a new/better one as suggested above, most likely wont help.
Thanks all for your help and information provided. I'm a bit tired of toying with the crankset I currently have, so I think I'll bite the bullet and drop some cash on a better quality crankset. I'll be sure to update the thread with what happened in the end.
05-28-15, 09:50 AM
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I have ridden entry level components for the past 10+ years at weights ranging from 300-365 (up and down) and have never had a crank arm come loose. There is a problem, and it should be resolved.
I would imaging that if the taper is off even a little on the BB that it could be causing your problem, especially since the crank arm has been replaced.
I don't think that there is even any significant rotational force that should impact the crank bolt if everything is working right, since the bolt is designed to hold the crank to a pretty rigid square taper. If there is any rotation at all, it again points me to a faulty crank arm or BB.
I wouldn't even try red Loctite. Since Blue didn't work, there is an issue that should be resolved with the bolt, crank arm or BB. Red Loctite would kjeep the bolt from turning, but it wouldn't address the core issue (whatever it is).
I would imaging that if the taper is off even a little on the BB that it could be causing your problem, especially since the crank arm has been replaced.
I don't think that there is even any significant rotational force that should impact the crank bolt if everything is working right, since the bolt is designed to hold the crank to a pretty rigid square taper. If there is any rotation at all, it again points me to a faulty crank arm or BB.
I wouldn't even try red Loctite. Since Blue didn't work, there is an issue that should be resolved with the bolt, crank arm or BB. Red Loctite would kjeep the bolt from turning, but it wouldn't address the core issue (whatever it is).
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05-28-15, 11:24 AM
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As a point of reference, many thousands of 350 pound riders have ridden many millions of miles on square taper cranks without problems. You might want to actually identify the source of your problem before picking a solution, especially since it appears you have not obtained adequate technical service up to now.
05-28-15, 11:24 AM
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A quick update: took the bike to the bike shop I got it from, and called them first. By the time I showed up, they'd ordered another crankset from Giant, because it's still under warranty. This time they said that the crankset is going to be splined rather than the square taper, and that the newly ordered crankset will be brand new. And it's all free since it's under warranty.
Here's hoping that this will solve the problem. And thanks again everyone. Will be sure to update as it all progresses in case somebody else encounters a problem like this.
Here's hoping that this will solve the problem. And thanks again everyone. Will be sure to update as it all progresses in case somebody else encounters a problem like this.
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