High pitched chitter - where from?

[User10571]

My 2 speed Brompton has developed a high pitched chitter, up there with chalk on blackboard - but definitely chittery, whenever/ not always (but I can induce it 90% of the time) I go over rough tarmac, speed bumps, potholes, drain covers etc.
It is coming from the front end of the bike, and as I say it it chittery, rather than cyclical.
It has that dry metal on dry metal flavour to it.
I thought it might be from the points of contact between the main hinge clips and the frame (I have the Brompification variety) so I've given the mating surfaces of both some lithium grease - with little or no effect - which makes me think a) Try Copaslip and b) it is something else.
Anyone else experienced anything similar?
It isn't a high mileage bike and has hardly ever been out in the rain.

 

[Yellow Saddle]

My 2 speed Brompton has developed a high pitched chitter, up there with chalk on blackboard - but definitely chittery, whenever/ not always (but I can induce it 90% of the time) I go over rough tarmac, speed bumps, potholes, drain covers etc.
It is coming from the front end of the bike, and as I say it it chittery, rather than cyclical.
It has that dry metal on dry metal flavour to it.
I thought it might be from the points of contact between the main hinge clips and the frame (I have the Brompification variety) so I've given the mating surfaces of both some lithium grease - with little or no effect - which makes me think a) Try Copaslip and b) it is something else.
Anyone else experienced anything similar?
It isn't a high mileage bike and has hardly ever been out in the rain.

Your attempt with grease was enough, no need to try copper compound as well. The function of these "greases" on squealing parts is to act as a damper and lithium grease and copper compound damp equally well. The latter is only used in brakes because of its very high melting point. Your instincts are good, keep on greasing.

 

[raleighnut]

Fork stem?

 

[Yellow Saddle]

He does still need to swap hinge catches with someone else though.

I'll leave the rest to you, I'm out of my league there. I don't even know what a hinge catch is, never having seen a Brompton close-up. I was merely commenting on why grease is good enough for what he rightfully tried.

 

[User10571]

I suggest that you should swap those hinge catches with someone else in order to test it.

Can I ask why?
The Brompton ones were silent, as were the Brompification ones when I fitted them over a year ago.
The hinge clips may be an entire red herring on my part - it was merely my first point of (instinctive, but not necessarily correct) call....

 

[User10571]

Just to save me buying some.

They are a good thing. And will give you a distinct advantage when you next compete in the Smithfield Nocturne folding bike race.
ETA - Unfortunately you will be a tad stuffed on this score as Brompification ceased trading about a year ago.

 

[User10571]

Arse, they were on my list of things to buy sometime.

Could we get back to my chitter?
It is starting to make my teeth curl.

 

[I like Skol]

Are there any aluminium components in the mix? If so then expect a catastrophic failure some time soon. Fatigue in aluminium parts can often be heard before the cracks suddenly reveal themselves (with the ensuing shock and hilarity that results, DAMHIKT!)

 

[User10571]

Are there any aluminium components in the mix? If so then expect a catastrophic failure some time soon. Fatigue in aluminium parts can often be heard before the cracks suddenly reveal themselves (with the ensuing shock and hilarity that results, DAMHIKT!)

Yes. A few. Relatively unstressed ones with ~ 1 year's use.

 

[User10571]

Cables?

Nah.
All the cableage is sweet. This is weighty metal on metal type noise.

 

[User10571]

Have you stashed anything in the frame?

I'd like to categorically state that there is nothing Columbian in my bicycle frame. Thank you.

 

[raleighnut]

I'd like to categorically state that there is nothing Columbian in my bicycle frame. Thank you.

Moroccan?

 

[mitchibob]

I noticed an annoying rattle at the front recently... turned out that the front reflector was a little loose.

 

[TheBlueBrompton]

I have a two speed Brompton (S2L). I have some rattling noises as well. What I found out was that it was the cables, the ones that pass by the front hinge on the main frame. When I hit the bump, the cable would move a little and spring back and hit the frame. That was the source of the noise on my bike. I wrapped some velcro around the cables where it touches the frame, noise is gone. Remove velcro, noise comes back. Hope that helps.

p/s - my Brompton is pretty new (less than one year), but not with the new shifters.

 

[Brommyboy]

Try dribbling some oil into the front wheel bearings. If they are dry, this would cure it.