Spongy brakes/pedal loss

[Embidd]

I have a 2022 A90 3.0 with pretty low mileage on it. I let the car sit for a few months (I know) and the rotors god super rusty and had to be changed out. Well since I’ve gotten them changed the brakes are spongy and I basically have to go to the floor to stop. The first 50% of brake pedal travel does literally nothing, all my stopping power is in the final 25% of brake pedal travel. I’ve taken it back to the shop who did the work and they found nothing wrong. I took it to the dealer and they flushed the system and said everything was good, but it still acts the same.

At this point I’m unsure of what to do, I don’t mind throwing all new pads and rotors at it if it’ll fix the problem but idk if it will.

Does anyone have any suggestions on what I should do? Any help would be appreciated

Also they were OEM rotors from a dealership according to my mechanic and judging by the price I’m pretty sure they were

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[ZupraGuy]

I dont think rotors can cause a pedal drop that low, but it's good you changed them out regardless. Usually, low pedal and spongey feel it would either be pads nearing their end life or air in the lines/low fluid. But you said you bled the lines? If that's the case then the master cylinder could be faulty. Highly unlikely as it's still a new car.

The only time I got bad pedal drop was when one of my pads went down to the metal backing plate after a track session.

 

[Eplejus]

Most likely air in the ABS module. Need to use ISTA to trigger the ABS pump and re-bleed the system again.

 

[Embidd]

Most likely air in the ABS module. Need to use ISTA to trigger the ABS pump and re-bleed the system again.

i can take it back to the dealer and have them rebleed it and see what that does.

I dont think rotors can cause a pedal drop that low, but it's good you changed them out regardless. Usually, low pedal and spongey feel it would either be pads nearing their end life or air in the lines/low fluid. But you said you bled the lines? If that's the case then the master cylinder could be faulty. Highly unlikely as it's still a new car.

The only time I got bad pedal drop was when one of my pads went down to the metal backing plate after a track session.

I’m thinking I might end up doing all new pads and rotors just in case. Have you had any experience with the R1 Concepts kits they offer on A90 shop? They seem kind of cheap for what you get lol

 

[Ryan P]

A simple pad and rotor change shouldn't require even getting into the fluid at all. Did you specifically request the fluid be changed as well?

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