As I pedal my bike I get a definite knock one time during each rotation.
It feels like it from the pedal area can you help me with this problem?
The first thing to look at is if your crank arm is hitting the frame. If you get off the bike and turn the cranks backward can you see them hitting anything each rotation?
Does it only happen on one side?
Check things like:
Is the crank arm tight?
Is the pedal tight? (It's also a good idea to grease the pedal threads before installing)
Are the bearings in both the bottom bracket and pedals lubed and well-adjusted?
Check what position the crank arm is in when it knocks, is it the same place every single time you get it, also try pedaling lightly without putting load on the pedals and see if it still does it.
I had a similar knocking on my bike when I first bought it new, it would make a knocking noise when the non drive crank arm was going from straight up to forward with my pedaling load on it.
I took the crank arm off to make sure the inside was still square with no burrs and it was fine, I put it back together nice and tight with some loctite on the crank bolt, since then it's been quiet as a mouse.
I guess it hadn't been put together properly when made or assembled in the bike shop.
Cannondale, handmade in USA............................................Refined in Surrey, England.
- Cannondale F500, Kona Blast, Kona Caldera-
With all due respect, I'm not sure I would recommend locktite on the crank bolt. I know that there are different "strengths" of the product, but I've never seen a need for using it on a crank bolt. If the spindle tapers are in good condition, along with the flats in the crank arm hole, all you really should need is a coat of grease on the bolt threads. Don't apply grease to the spindle flats or in the crank arm hole. I've practiced this procedure for over 25 years, being tested with everything from sprints to mountain climbs, and have never had a crank loosen up.
There are two camps about greasing crank arms.
One thought is, if greased, this allows the arm to slide too easily on the crank which may give rise to spreading of the square hole when being tightened.
The other if not greased will cause the crank arm to jam up as Joe explains.
Me, I make sure that the hole and crank spindle is clean but with just the very slightest smear of grease. Especially if not expecting to remove them for an extended period of time.
I would not though use any form of thread lock on it. In fact I never use thread lock on any parts of my bikes. Usually I check the tightness after a few rides on a new installation.
Ride hard or ride home alone!
Maybe Copper grease instead as a middle ground? It's not really a lubricant; its main purpose is as an anti-seize compound, particularly in areas with bad weather.
I don't know where you live Marke, but here in Wales we go MTBing in pretty bad weather quite often (even during the winter). It's quite common for loads of things to seize out there and you really do have to look after your bike; and yes I have seen a few seized crank bolts.