matarile

Let’s start by saying I got this car as a CPO, with 13k miles. It is a 2018 GLS 63 with the standard 21” wheels and Conti summer tires, and it’s been to the MB Manhattan shop twice already in less than a month and 1,000 miles.

• The first time, they replaced all rotors and brake pads. Rotors were warped by previous owner (I thought this was supposed to happen during the CPO certification but go figure)
• The second time they “aligned the wheels along the g-line” (I don’t know what that means other than wheel alignment) and they also balanced all wheels

Nothing has solved the problem. Now, this is the question: am I the one who’s crazy? I’ve never had driven a car that does this when braking. But I’ve never owned an AMG before, so was wondering whether this is normal operation. I am assuming no, but just posing the question to GLS 63 owners from 2017-2019 and whether they’ve experienced the same.

Golfather

Probably an obvious one, but have all 4 wheels been correctly balanced?
This would also reveal if any of the wheels are warped or buckled.

matarile

Hi Godfather. Yes, all 4. Which is what has me worried. Tires are brand new as well.

chassis

Narrow down the problem.

Vibration at 60mph on straight smooth road with no bakes applied?

Vibration when turning at 60mph with non tales applied, such as using a (large) off ramp from a freeway? No brakes applied.

Vibration with light brake application at 60mph on a straight smooth road?

Vibration with light brake application around 40mph as you gradually decelerate to a light or stop sign?

It can only be a few things:

- warped rotors with or without used up pads
- out of balance wheels and tires, with or without damaged (bulged or cut) tires
- bent wheels

Most likely is warped rotors and bent wheels.

Assume a high performance vehicle hasn’t lived an easy life before you got it.

matarile

Hey Chassis. You’re right, the problem was very poorly defined. Here we go:

- Vinration happens at around 40mph when STARTING to apply pressure on the brake pedal. If I press it a bit harder, it’s gone. Very strange. Mind you, VIBRATION IS VERY LIGHT, but again, based on cars post 2010 I’ve driven, there should be none.

Now, the 4 rotors are pads are brand new. The wheels were roadforced aligned and balanced. The 4 tires are brand new. That’s why I thought maybe o should expect some minor vibration on the wheel given the weight of this car. But that being said, I’ve had an Alpina B7 for a while already, very heavy car as well, and the steering wheel NEVER EVER vibrates when braking. Cheers.

chassis

Strange that the vibration disappears. What do you think it is?

Golfather

Independent inspection by an MB specialist would be my next move.
Get them to drive and experience what you're experiencing and see if they can get to the route cause.
That said, it's a 2018 car so under manufacturers warranty with genuine new parts so there should be some duty of care from the main dealer.
Not sure what else to suggest.

matarile

Well, I have an inkling it may be the new brake pads wearing in. Again, just a thought. Today the weather was nasty, loads of rain, and the vibration was barely noticeable. I have to drive again on dry conditions to see if maybe it is gone. The whole thing is doing my head in.

matarile

Thanks Golfather. I must say the dealership has performed all repairs for free. So at least they are showing some care. But yeah, it does no harm to look for a third-party to assess.

matarile

@Golfather @chassis Since you were the two ones who replied to my cries for help, I thought I owed you both a post-mortem: turns out it was the propeller shaft. Which is crazy. I had no turning problems, no clunking noise but what I was feeling above 35mph when braking is no longer present. The dealership ended up booking a case with MB Engineering which took a while (15 days), but now the car feels and drives the way it should be. I guess these GLS63 are more akin to a lorry than what they let out! Anyway, thanks again for replying and case closed (finally!)

Golfather

Glad it's sorted out. No doubt a complex bit of machinery so a 2nd or 3rd look probably pays dividends.