Brake discs issue?!

[merckdan]

So last month (7th Dec) I bought a new set of brake discs and pads from Mercedes - cost just over £300, for my W205 Coupe. I got them fitted at a local garage near me. From the evening I picked the car up the brakes didn't seem right - the brake pedal would slightly shake when braking at higher speeds i.e. on the motorway. I thought it might just be that they're soft as they've just been changed but it didn't go away and started getting worse. I took the car to the garage yesterday and they've said there is a slight 'deviation' in them so basically they're warped.

Now garage is saying could be due to faulty brake disc and I should contact MB to have a look. I called MB and they're saying they can take it in and look at it - if its a fault of their part then they will replace for free but if its not their parts fault then I will get charged £55 diagnosis fee for 30 mins (and then obviously however much to replace the discs if I want them to do it).

I honestly now don't know what to do - in my head I'm thinking Merc will say yes the discs need replacing but its because they weren't put on properly or something so I will just be more out of pocket. Shall I buy another set of MB discs for £150 or wait 2 weeks and take it to MB to look at?

Any advice?

 

[whitenemesis]

My first question is always, were the hub faces cleaned properly before fitting the new discs?
You'll never know unless they are removed and inspected. Perhaps refitting after thorough cleaning might fix the problem

 

[csadair]

So last month (7th Dec) I bought a new set of brake discs and pads from Mercedes - cost just over £300, for my W205 Coupe. I got them fitted at a local garage near me. From the evening I picked the car up the brakes didn't seem right - the brake pedal would slightly shake when braking at higher speeds i.e. on the motorway. I thought it might just be that they're soft as they've just been changed but it didn't go away and started getting worse. I took the car to the garage yesterday and they've said there is a slight 'deviation' in them so basically they're warped.

Now garage is saying could be due to faulty brake disc and I should contact MB to have a look. I called MB and they're saying they can take it in and look at it - if its a fault of their part then they will replace for free but if its not their parts fault then I will get charged £55 diagnosis fee for 30 mins (and then obviously however much to replace the discs if I want them to do it).

I honestly now don't know what to do - in my head I'm thinking Merc will say yes the discs need replacing but its because they weren't put on properly or something so I will just be more out of pocket. Shall I buy another set of MB discs for £150 or wait 2 weeks and take it to MB to look at?

Any advice?

Did you ever get sorted. I was in the same boat as youeself. Third time I took back to the dealers as they said Indy done wrong, long story short is that judder is back again. Always after 3 months. Head fried. Judder always at 40/30 mph, seems fine at higher speed and slower speed. Braking from 100 down to 40 judders to 30 then ok.

 

[jasonh]

I'd say in the first case the garage simply chucked the discs on. What they are supposed to do is clean the hub until it is spotless and flat then fit the new discs. If the pedal felt spongy as well then the brakes weren't bled either (although technically not required, it's a good idea to flush and bleed the brakes at the same time as new pads and discs).

So OP's case poor workmanship.

In the case above is the vibration only on braking? Vibration at 30mph to 40mph can be a deformed tyre.

What needs to happen is a competent garage (maybe not a Main Dealer) needs to inspect the discs for runout and hot spots. That's a quick check with the right tools. Literally take the wheel off, attach the gauge, spin the disc by hand.

If that looks OK then the problem could be elsewhere, I'd be looking at wheel bearings and suspension bushes (both checked in an MOT), in fact the MOT tester can check the brakes for problems too by holding the pedal partially depressed on the brake tester.

So actually an MOT test, even if not officially recorded, would be cost effective first step. Just ask if the garage can give an opinion on "warped" discs when on the brake tester. Warped is the term widely used but it rarely is actual warping (it's disc thickness variation or pad transfer onto the disc).

 

[Bellow]

What needs to happen is a competent garage (maybe not a Main Dealer) needs to inspect the discs for runout and hot spots. That's a quick check with the right tools. Literally take the wheel off, attach the gauge, spin the disc by hand.

When the wheel comes off the clamping force restraining the disc vanishes and what ensues is not representative of the car as it is driven on the road.

 

[jasonh]

When the wheel comes off the clamping force restraining the disc vanishes and what ensues is not representative of the car as it is driven on the road.

That's why when you do the runout test you refit some of the wheel bolts/studs. There is already a retaining screw so just one bolt/stud should suffice.