Feel occasional knock/bump through the brake pedal when pressing it

[matth321]

Every now and then when I press the brake pedal I feel a sort of knock/bump which seems to feed back through the pedal. First noticed it about a week ago.

Seems to braking OK, haven't tried any hard braking though, anyone have any ideas? It's a Clio 182 with both cup packs, done about £50k miles.

Cheers.

 

[rob_clio197rs]

ive experienced the same thing, always first thing in the morning the first time i press the pedal then it wont do it again.

 

[matth321]

Any idea what it is? Should I be worried? Brake problems make me nervous.

 

[matth321]

This turned out to be warped front discs. Anyone have any idea how both front discs get warped? I don't sit on the brake pedal at lights or anything. Also, they were aftermarket jobs, but I'm having them replaced with the stock ones.

 

[Icarus83]

This turned out to be warped front discs. Anyone have any idea how both front discs get warped? I don't sit on the brake pedal at lights or anything. Also, they were aftermarket jobs, but I'm having them replaced with the stock ones.

Generally warped discs are from a long periods of heavy braking, when driving really hard on heavily roundabout'ed stretches of road or twisties, or if the pads have become locked on for some reason.

As the discs get too warm and overheat, they expand irregulary and warp under the heat and then cool/fix in that position.

Were the discs on the car when you got it or did you fit them? If they are fairly new with little wear they might be able to be machined flat again, but your best bet would be to replace them with new pads.

Anyone agree?

Also, sitting on the brake pedal at standstill wouldnt cause them to warp....

 

[Tom@JMS]

^^ As above:

Warped discs are either caused by a couple of common things:

Not being put on true (not cleaning the hub prior to refitting) so they have a slight wobble which is exaggerated as they are used.

Or extensive braking/heavy use and then the brakes being held at standstill - cause the disc to cool unevenly leaving a permanent warp.

Machining is a big no no, once they are warped sling them!

They will never warp due to just heavy use, as discs are designed for silly high temps that modern braking systems generate. It is usually another factor such as stated that will cause them to warp.