"Clacking" noise coming from drivetrain

Question

I have a 2005 Specialized S-Works Tarmac with Dura-Ace components and Mavic Ksyrium SL wheelset.

I get a "clacking" noise coming from the drivetrain area only when pedaling forward. I say "clacking" because it's not a click or creak noise. It reminds me of the noise those acrylic Clacker toys from the 70s made when they hit, but obviously not that loud.

If I backpedal the noise will go away temporarily. I do notice if I backpedal, then pedal normally, the noise goes away; it will not typically return until I freewheel then pedal forward again. The noise has been around for about 2 years on this bike and I have changed the following: Cassette from 7800 to 7900 series, chain, 53T chainring and pedals from 7800 to 7900 series. The issue is still there. It happens in the small or large chainrings regardless.

The "clacking" noise does not happen freewheeling at all only pedaling. It does not correspond with wheel revolutions or even crank revolutions. It's more of a loud clack immediately followed by a smaller clack happening about every 3/4 crank revolutions.

Last time I took the bike in for a overhaul I told them about the noise that I thought it was coming from the bottom bracket that I wanted that rebuilt. Once I got the bike back the clacking was gone for about a week, then returned.

Thanks for any help on what to look for!

Mike

Answer 1

I had a similar problem until recently, initially thought it may be the BB, but after cleaning, greasing, and eventually replacing the problem was still there.

Turns out it was the freewheel hub on the wheel, and fairly quick to fix, if that is your problem, open up the freewheel hub, I needed 2 5mm allen keys for this, but various wheels have different methods of opening up. Don't force anything, these are easy to destroy, and expensive to replace.

Once you have the freewheel open, make sure that the little pins stay in place, most new hubs will have springs keeping them in place.

Apply grease, I used the Park Tool one (personal preference), and close everything up again.

Answer 2

It's possible that the chainring bolts are loose. This would allow the chain rings to shift slightly when under load, which creates a clicking or clacking noise.

To tighten them, you'll want a 5mm allen wrench for the bolts and a large flat-head screwdriver (or a tool specifically designed for chainring nuts, like the one from Park) for the nuts. The allen wrench approaches the bolts from the drive side of the bike and the screwdriver approaches from the non-drive side.

You don't say which edition of Dura-Ace is installed on your bike. The 7900 edition uses Torx chainring bolts (in the T30 size) instead of 5mm allen bolts.

Answer 3

This may sound ridiculous but grease the seat post. I had a similar problem on my mtb solved it by greasing the seatpost, only the portion remaining inside the frame ofcourse.

Before using grease, things I tried include,

• tightening the bottom bracket and the crankset
• replacing pedals
• replacing the chain

and none of them worked.

Answer 4

Thanks guys! I was able to put the bike on a trainer to at least give it some loading while I rotated the drivetrain. The clacking noise, while faint in this set-up, was definitely coming from the rear cassette, freewheel, hub area. I could even feel a slight vibration on the seatstay and chainstay as I pedaled by hand. I did tighten the hardware associated with the hanger and derailleur figuring that may help.

After reading the responses, I think I will take Baldy's advice above and take a closer look at the freewheel assembly. There is either some lubrication or wear issues that may be causing this.