Strange clicking sound – not a loose crankarm
I rescued an old GT aluminum mountain bike from the dumpster a few months back. The bike had a few issues, one of which was a right crankarm which would not tighten sufficiently before bottoming. This problem I attributed to the crankarm’s tapered hole being enlarged due to the previous owner riding the bike with a loose right crank.
This past weekend, I was finally able to replace the crankarms with another set from a bike I had laying around. After pulling off the old cranks and installing the replacements, I took the bike out on a test run around the neighborhood and everything seems great until I apply fairly heavy pressure to the pedals while going up a slight incline. I could hear a clicking sound when the crank arms are in the horizontal position with the left crank pointing to the front of the bike and the right arm pointing to the rear.
Ok, I figure the cranks need to be tightened so I stop and using the appropriate allen head socket attached to a 6 inch rachet, I tighten it a little more. FWIW, I do not have a torque wrench that goes as low as the 25 to 30 foot pounds (as recommended by others on this forum) so I had to do this by feel. I hop back on the bike but the problem still persist. The strange thing is that the clicking noise disappears when I apply really heavy pressure on the pedals such as out of the seat climbing going up a hill. I have also tried the following to no avail:
• Changing the pedals;
• Checking the bottom bracket bearings to see if they are loose;
• Tightening the chainring allen head bolts;
• Tightening the screws that attach the seat to the seatpost;
Another possibility as to the source of the noise may be the right crank arm hitting the frame (right chainstay) as when installing the replacement cranks, I noticed that the end of right crank arm is very close to the rear chainstay, about 1/8 of an inch gap (this may be the result of using longer crank arms as the replacements are 175mm and the ones that came with the bike are 170mm). So the frame may be flexing when applying heavy pressure thereby the crankarm actually is contacting the frame. If this is the case, when applying heavy pressure such as climbing out of the saddle, why does the clicking noise disappear? Could it be that climbing out of saddle shifts my weight (I weigh about 145 lbs) to more of the front of the bike thereby reducing frame flex in the rear where the crankarm would contact the frame? If this is the problem, could I just file the crankarm a little to increase the 1/8 inch gap? If I do not want to spend the money for another set of 170mm length cranks or for a longer bottom bracket spindle, could I just use the bike as is but would this lead to bigger problems in the future? Any other possible solutions (such as making a small dent in the chainstay where the crank arm contact the frame thereby slightly increasing the 1/8 inch gap) ?
Thanks for you input
Uh, 6" portable ratchet wrench would require 50-60 pounds of force from your hand to get to the required torque. Have you lifted a 50-60 ft sack of concrete or rice or beans lately? It's A LOT of force and would most likely puncture your palm with the end of the wrench.
The frequency of the noise would indicate either the bottom-bracket or just one crankarm as being the culprit. If you don't see scrapes on the chainstay, then the arms aren't hitting it.
My bet is on the BB-cups. The threading is typically a little loose to allow for paint and hand-installation. You'll want to test with wrapping multiple layers of teflon plumbling tape around the BB cups before installing. I start with too many and work down. Usually I start with 4-layers and if it doesn't go in, I re-wrap with 3-layers. If it goes in easily, I re-wrap with 5-layers. I've had bikes that squeaked with 3-layers and stopped with 4-layers. Just one more makes a huge difference.
Also be aware that the lockring will pull out the adjustable-cup and loosen your bearing adjustment. Hold the end of the crankarm where it's closest to the chainstay and push in and out, do you feel movement? If so, adjust the bearings a little tighter so that when the lockring pulls out the cup, the bearings will be just perfect.
I've got a 97 GT Avalanche that has ALWAYS clicked. I'm still using the original BB and cranks, but they've been removed and reinstalled with no change. I've just learned to live with it.
Its a little higher pitched and not as loud as a freewheel click. There are very few situations I notice it other than test rides. 12 years and no problems though.
On my bike, that problem was resolved by tightening the pedal. But you've done that. Mine had a distinct click that I felt in my foot at the bottom of the stroke (left side). When I had my bike fit, they put a spacer on the pedal so there are fewer threads for the pedal to grab. The pedal didn't feel loose and didn't really get any worse during the month I continued riding it. I was thinking bearings or something, but apparently there was just enough slop in the threads to cause it.
It looks like you've already looked here... http://www.sheldonbrown.com/creaks.html#bottom