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 crankarms 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