9 replies to this topic

[riczito]

Hi all,

 

On my new Mini, I have noticed that at low speed, when braking gently to come to a stop, over the last few metres the car kind of "oscillates". It slows unevenly, almost as if a wheel were not round, but slightly ovalised. It feels a bit like cadence braking. But it only happens when braking, not freewheeling, and is only noticeable at around walking speed.

 

I wonder if one or other of the brake discs are warped, or if there's some issue with the pads? Has anyone any experience of this? If I replace the discs and pads, do I need any special tools to do the job?

 

Thanks,

Ric

[Spider]

It could be a warped disc or an out of round drum. You also usually notice a pulsation in the pedal too when this happens.

 

Rather than blindly lash out wads of cash, replacing everything, why not have the car looked at by a professional as it could also be something else.

[Steve220]

Can't hurt changing the discs, they're not exactly expensive.

[dotmatrix]

when I have experienced this it has been the rear drums that had "high-spots"

[harrythehat]

brake discs can warp when you put them on new you are supposed to break  them in as such

using gradual braking increasing pressure as you go.

 

hitting the anchors hard on a new set of discs can warp them as they hav'nt hardened to heat etc

[luismx123]

have the same issue. Will need looking at soon :/

[Icey]

What most think is warped disks usually turns out to be wear in suspension components, typically bushes. Have a good poke around at everything that holds the wheel on the car, give everything a good push/pull and see if there's anything which looks like it's starting to break down.

 

If you have a DTI you can check the run-out on the discs yourself or if you micrometer you can check the disc thickness at a few points.

[viz139]

Check for a buckled wheel or tyre . Jack up each wheel and spin by hand and watch the thread pattern.

[expat_cat]

In addition to some of the comments above.

Discs do NOT warp, i.e. twist or deform due to the heat generated by braking.  This is one of those myths that get around.  The symptoms are of course real, and can have several causes, often due to pad material unevenly sticking to the disc surface due to bad bedding-in or sitting on the brake at rest.  Or as mentioned suspension problems.  One thing to check is that the discs are seated cleanly on the hub.  Even a small grain can induce a bad disc alignment.

 

This is important in understanding what to look for to cure the actual problem.

 

See

http://www.brakeandf...ed-rotors-myth/

http://www.hendonpub...details?id=1787

[croc7]

+1 expat_cat