steering wheel vibration when braking above 50mph - skim or replace front discs?
 

My Mazda 5 has done over 50,000 miles, and recently I've noticed the steering wheel vibrating when braking lightly on the motorway. After doing some research it's quite clear that this must be warped brake discs, which leaves me with some questions:

1. Is it better to get these discs replaced or should skimming them fix it? I would image a skim would produce a smooth surface, but wouldn't eliminate a warp?

2. Do I have to get the brake pads replaced at the same time? I only had the current ones replaced about 10,000 miles ago (could cheap pads have caused this problem I wonder?)

3. Is this something I should get done at the main dealer (any need to update the ECU or anything?)- or would kwikfit do it just as well and cheaper?

Many thanks

iainso:
Most pwople will call that condition "warpage". Warpage would look like a disk that is bent like a potato chip, just not as much so you can't see it with the naked eye.
there is another condition called Thickness Variation. That means it is not potatochipped but thinner or thicker at various sectors of the disk. The naked eye won't see that either.
And fianally: there is a minimum thickness a rotor must have to handle the braking for the next 20 or 30 thousand miles or so. That minimum thickness is specified by the manufacturer.
What really shoud be done is this: use an indicator dial to measure runout on the inside and the outside of the rotor, right on the car. Use calipers to measure thickness variation and the thinnest spot on the rotor. The thinnest point will tell you if a resurfacing is possible.
As a general rule you would want to mate a new set of pads to a fresh surface.
My guess is that you will need new rotors since manufacturers have reduced the thickness of rotors so much in order to save weight. That saves fuel but as you find out there is no free lunch!

Take it to a reputable independent shop. Something like "bill's automotive" but check the reputation! See what kind of customers they have, how clean the shop is. Ask friends and colleages who they use. Then frequent that shop for everything but "dealer only" issues. I.e. an abundance of rickety hatch backs with fart cans, 20" wheels and rear spoilers in the parking lot would make me look elsewhere.

And keep doing what you are doing now: research so you can't be taken for a ride!

Thanks Tan,

The discs do look pretty thick, so I reckon there might be scope for skimming. I guess I really need to find out what Mazda recommends, and suspect it will be replacement - really annoying because I just got some new pads last year - I do wonder if the new pads could have caused this damage.

It's hard to tell what causes that condition. these brakes go through many heat cycles and eventually stuff happens. That said, it is important to have the lugnuts propeerly torqued.
Take it to a shop for a free estimate, ask them specifically about resurfacing the rotors.

Get the disc's thickness measured, if they are 0.5mm or more above minimum then get them machined. De-glaze the pads and reuse them.