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My Trek Pure Deluxe 3-speed cruiser has been making a clicking noise when riding for some time. The problem is faint, and is more felt than heard. However, it's been getting worse; it now makes a grinding noise if I'm mashing a bit when going uphill.

The noise seems to happen when the right crank arm is facing forward. Which gear I'm in makes little difference. I've eliminated saddle noise (by pedaling out of the saddle) and have replaced the chain.

Is there anything else at all that this could be, or should I just replace the BB at this point?

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Another possibility is a noisy pedal. I replaced my BB cartridge only to find that the noise was coming from the right pedal. –  Daniel R Hicks Sep 20 '11 at 11:43
    
The problem turned out to be a loose bottom bracket; tightening up the right side took care of the problem. Of course, time will tell, but the bike feels good now. –  Neil Fein Oct 18 '11 at 20:00

4 Answers 4

up vote 2 down vote accepted

Yeah, the first thought would be a loose crank arm, and if it isn't tended to immediately (if it's not too late already) the crank arm and possibly the spindle will be destroyed.

The other possibility, if this is a cartridge BB, is that the cartridge is slightly loose. But in that case the noise is usually only present under high load.

[I'll add that tightening the crank arms is one of the half-dozen or so items that should be taken care of during the free once-over (after a few months use) that you should get from a bike shop if you buy a bike there.]

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Thanks; this turned out to be the problem: The bottom bracket has a tendency to loosen on this bike after a couple of months of neighborhood riding. (It does only show up under load, as in a Clydedale Cyclist (me) standing on the pedals to climb.) Have gotten some tools and a knowledgable friend has showed me how to do this. –  Neil Fein Dec 28 '11 at 5:59
    
To follow up: While there's no visible damage, this BB tends to loosen much more quickly than it should. Currently looking into replacing it. –  Neil Fein Apr 7 '12 at 3:38
    
@NeilFein -- It's common to use a thread lock compound on bottom bracket cups to keep them from loosening. (This is assuming that by "BB loosening" you mean the cups, and not the crank arms.) –  Daniel R Hicks Apr 7 '12 at 14:27

Make sure your crank arms and chain ring are also tight. I've had loose crank arms on a square taper BB make a faint clicking sound/feeling when it was loose. Not sure what kind of BB that bike has though.

If neither of those seems loose, and you have the tools, I would pull off the crank arms and spin the BB axle to see if the bearings feel ok. It is possible that you could have done something to mess up a bearing.


To add some backstory; one of by bikes had a Shimano LX crank and square taper BB (2001-ish), and it had a large hex wrench bolt to hold it on (like 6 or 8 mm i think). I had to tighten the crank bolts so hard to make the arms tight, that my hex wrench's sides are now all twisted into a slight spiral, instead of being straight.

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Square Taper chainsets do this, even if they get checked for tightness before sale. A 'free service' with the bike sometimes involves nothing more than tightening these fellas up.

The problem of square taper crank arms coming loose was why Shimano came along with Octalink splined bottom brackets.

I think you will be able to get away with just tightening up the cranks. A 15mm socket set is what you need, and gloves! (Or else you can smash up your hands or hurt your hand on the socket set lever.)

You can also tighten up these bolts on the ground, back brake on, with a foot on the socket set lever at the 3 o'clock setting. Do both sides and don't bother taking them off or anything like that first. Opinions vary on whether you should have any grease in there, personally I have found grease to not do any harm, but, in general no grease is the norm.

The reason your bike has the square taper design is that Shimano patented Octalink so it did not become an industry standard.

If the problem persists then you might have already 'rounded' one or other of the crank arms. With the left-hand crank you can get a spare 170mm arm, although not necessarily to match the other arm.

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It's almost certainly a deformed square taper. If you winch on tight or carefully grind the surface you may be able to rescue it. Otherwise get a new crank arm and bb, worth buying reasonable quality and maintaining your bike at closer intervals

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You can also fashion shims from beer cans. The AL in beer cans is tapered -- thicker in some places than others -- so you can cut a piece that offsets the rounding over of the crank arm. –  Daniel R Hicks Sep 19 '11 at 22:05
    
you can but it's a poor solution. The problem is the insufficiently hardened crank arms. Although if we're being correct, using a square taper for a torque coupling is a stupid idea. Splines are better, but the loading is cyclical so these will inevitably develop play... –  Mr Rowing Sep 20 '11 at 8:47
    
It may be a poor solution, but there ain't a better one, short of replacing the arm. You can't effectively grind the arm surfaces and grinding the (probably still flat) spindle ends to fit a damaged arm is just silly. And a properly tightened square crank set will last indefinitely -- it's only when the arms are allowed to work loose that you have trouble. (You obviously never had to deal with cottered cranks -- now THERE was a mess.) –  Daniel R Hicks Sep 20 '11 at 11:41

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