breeze247

I'm running a 2003 CLK55 fitted with the original Brembo calipers. They are paired with a 345mm rotor, as fitted to the earliest 209 cars (the later CLK55 had much larger Brembos with two piece rotors).

The issue that I have is vibration when braking. I suspect that one or both of the calipers has a sticky piston that is overheating the pad / rotor and I am wondering whether this is a common issue with the Brembo calipers.

Background:

• I bought the car at 110k miles and it was fitted with good quality Pagid rotors and pads
• The car braked pretty well
• I did a track day with the standard rotors and pads (and also uprated brake fluid)
• After the track day I started getting a lot of vibration through the pedal, which I took to be pad deposits (I was expecting it to be honest, and yes, I have read the Stoptech article!)
• I had the rotors skimmed and fitted Project Mu Racing 999 pads - car drove perfectly for around 500 miles
• The vibration returned within a week or two. I have noticed that the vibration is worst at highway speed and / or when the rotor is hot.

I've been ruling out the likely causes one by one:

• 'Warped' rotors - I don't really believe in them, sorry...
• Warped hub - possible, although the skim was done with the rotor on the hub so they would have been matched at that point
• Wheel bolts too loose or too tight - checked
• I was hoping that the Project Mu pads, a race compound, would be aggressive enough to clean off pad deposits. I have used Pagid RS29s like this in the past and they have been great. That did not work here.

All of the above makes me suspect that the caliper is sticking (more accurately one or more of the pistons), heating up the pad / rotor and in doing so causing Rotor Thickness Variation (RTV) through pad deposits on the rotor.

Thoughts? I guess I am looking for the classic forum response to say that this is a common issue, but I haven't yet found it. What I have found is a few examples of the same problem with no cure - on both 203 and 209 cars. A couple of references to the Sport package cars too, of which many (I think) came with the Brembo.

What I would like to avoid is repeatedly fitting rotors and pads but not getting anywhere. Any advice much appreciated!

breeze247

Interestingly, I am finding quite a few posts talking about issues with Pagid rotors too. Hmm...