New Pads, New Rotors -> Testing

Metallo · Post by **Metallo** » 22 Jul 2017, 20:15

Hi guys,

So, after having changed control arms bushings, wheel hubs, tie rods, ball joints, new Brembo rotors and new ceramic pads from Akebono, I drove my XC70 for 10 minutes and I found the following marks on the rotors.

Obviously, both rotors have been cleaned before putting on the wheels and I still have to take the car to the garage for alignment.
The car seems to drive well, although I did not drive on a highway at higher speed, but I am concerned about those marks on the rotors, what could be causing it?

Thank you
Alex

Post by **jimmy57** » 22 Jul 2017, 20:31

Looks normal. If you had bedded in the pads to rotors there would be some bluing of the rotors. It will take some time and the rotors will get the more polished look. What you are seeing is the early signs of pad material depositing into pores of the rotor metal.

Metallo · Post by **Metallo** » 23 Jul 2017, 03:49

Hi,

Thank you so much for having reassured me

Cheers,
Alex

Georgeandkira · Post by **Georgeandkira** » 23 Jul 2017, 07:44

Were the "wheel hubs" you changed the bearings? How many miles on your '06? thx, Kira

Metallo · Post by **Metallo** » 23 Jul 2017, 16:33

Hi,

I bought this car a few weeks ago, so this is a 2005 with 128000 miles.
I am not sure to understand your question regarding the hubs, but yes they are the bearings, this is the P/N 274298.

Alex

jbeebo · Post by **jbeebo** » 26 Jul 2017, 23:02

Looks normal Alex, I agree with Jimmy57.

When I worked at Bosch braking systems, they used this procedure to bed pads to the rotors before they would do braking performance testing and ABS tuning. Simple really. Accelerate lazily to 30mph, coast for a bit and then brake at 0.2-0.3g. Do this 100 times. After this you can increase speeds to 45mph and again brake at 0.3g. Do this 50-ish times. It took a driver a couple hours to do this. After this the rotors and pads have fully seated, pad material has transferred to the rotor surface and all volatile materials have been evacuated. Brakes are ready to go.

Because you don't have instrumentation to guide this process, do this instead: drive your car. That cycles above looks a lot like a normal commute. Take it easy on the brakes for the first few weeks, no hard stops, give brakes time to cool between stops. Basically drive defensively like you're a fuel-saving hyper-miler. But please, if you ever need to stop aggressively in an emergency by all means mash the brakes. Would rather replace rotors and pads then cause a crash.

PS: you did service the caliper slide pins right?