On Tuesday, February 12, 2019 at 5:43:08 AM UTC-5, Tanguy Ortolo wrote:
Hello all,

For a few days, I have noticed a new cracking noise that seems to come
from the front of my bicycle. It only starts when I am riding at more
than 25 km/h, and it is the same no matter how bumpy or smooth the
ground is.

I have already experienced cracking sounds from the handlebar in the
past, but it does not come from it in this case, as it continues even if
I release the handlebar and ride without the hands.

The fact that it is related to speed makes me wonder if it could not
come from the front hub ball bearings, what do you think? This is a
Shimano hub dynamo, do you know if its balls can be replaced?

I don't know how easy it is to inspect bearings on a
Shimano dynamo hub, but I'd be very reluctant to try
opening the hub until I'd eliminated all other
possibilities. My guess is that your noise originates
elsewhere.

Things I might check are wheel reflectors, if you have
any installed. They can rattle against spokes in strange
ways. Check fenders, if you have them; check each
attachment point, and also check that the fender is not
slightly touching the tire. Check any bags or baggage on
your bike. (I've had mysterious noises come from items
rattling in my handlebar bag or saddlebag.) Check
attachment points for all accessories - water bottles
and their cages, racks on the bike, lights, bells, etc.

I'd also advise re-checking the tightness of your axle
nuts or quick releases, your headset, handlebars, stem,
etc. even though it sounds like your problem is
elsewhere. And I'd lightly grease the stem and bar
attachment points.

Good luck. It can be devilishly difficult to track down
an intermittent noise.

- Frank Krygowski