Cattle Grid - Snapping Sound

[BrynCP]

I rode over a cattle grid today, it's one I ride over regularly although I approached from the opposite direction.

I heard a snap as I rode over and first thought was a spoke. I stopped and checked but every spoke is still in place, none appear to be looser than the others.

As I rode on though, there is some horrible vibration sound coming from the front of the bike, like two bits of metal or plastic occasionally rubbing. It only seems to sound while pedalling,

Any ideas what I might have done?

I have removed and replaced the front wheel in the mount, I have checked the forks and frame, there is no rub on the brake, the wheels seem as true as my pre ride check, dérailleurs don't seem loose, chain seems fine. I had thought the sound could be a cable rattling against something, but all cables are operating and seem fine.

 

[Svendo]

On occasion hitting big bumps etc. causes the handlebars to rotate slightly in the stem which makes a big cracking noise.
I'd check the front brake is secure then try checking the headset for movement.
Sit on the bike with the front brake tight, using one foot rock the bike forward whilst holding it with the front brake and use your free hand to 'hold' the junction between the fork and frame, which should detect any movement. A loose headset is usually most obvious under braking where it causes a judder, but the technique above can detect movement before it's obvious. Good luck.

 

[bpsmith]

Chain slap tends to be the only noise I always notice on cattle grids. Have a good look at front and rear mechs.

 

[windym]

A few years ago I hit a cattle grid at speed heard a sharp crack thought cr@p over-egged that one continued to ride again with an odd noise from the front. On inspection of said area it turned out I had snapped a head set spacer, no play in the front end surprisingly until I moved it then ride over.

 

[BrynCP]

Thanks for those suggestions.

I have looked closely again at the bars, headset etc. and all looks fine. I have also tried to rock the bike and can feel no play.

I also forgot to add earlier that rotating pedals in the highest gear with the back wheel lifted does not cause the sound.

I have spotted one of the reflectors was loose, could it be as embarrassingly simple as that has perhaps popped out from behind a spoke and is responsible? Cannot see why it only happens when I pedal though if it was that, and why it's not constant. I've tightened it and will see if it is that anyway.

 

[Crackle]

Reflectors!

One nearly sent me over a drop when it rotated and shattered, spraying me with fast moving plastic cand causing a severe wobble. Get rid.

 

[Trevor_P]

Probably rotation of the handlebars in the stem causing a change in the tension of the front derailleur cable which in turn causes the mech to rub whilst in certain gears.