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Hi everyone, I am new to this forum and searched for my answer in many threads but couldn’t find exactly what I was looking for. I have a 2026 GLC43 AMG with all the assisted driving options. I put a Kuat bike rack on and drove it for one week without any problems. On a rainy day, I was driving to work and all of a sudden the active brake assist started going off and braking my car on the highway and then on the surface roads. It was quite unnerving and it did this several times. I took it to the dealership and after having it for a week, they said I need to deactivate the active brake assist every time I drive the car with the bike rack on. I am confused because I drove it for a week without any problems. Is this a known problem? I can’t be the only person to experience this and it was fine for a week. Looking for any insight. Thanks. Traveling at 25 mph and active brake assist kicks in Decelerates to 17 mph all of a sudden
Put the bike inside the car, it's safer there anyway.
Or, just hit the button and turn that system off. That said, I have the radars on my E the GLS and our Sprinter….in each case I will put hitch mounts with bikes and none have issues with it once I am moving and do not as I drive.
Your car can't differentiate between the bike carrier and a real car behind you or in your blindspots. Disabling rear parking sensors is the only option. I haven't carried our bikes in the hitch carrier in our GLC300 Coupe yet, but I need to disable rear parking sensors when I carry them in our 2021 Toyota Sienna. Good thing about Toyota is that it keeps it off until I turn it back on, and also that you can disable just the rear parking sensors by themselves.
That being said, your car braking while in motion doesn't make any sense (I believe you that applies brakes. What doesn't make sense is why it does that). Or may be it stopped you from changing lanes thinking something was in your blind-spots?
Btw, I vaguely remember seeing an option in the MB menu about carrying things in the back? May be it will disable only the the rear sensors. I need to RTFM!
Again - I do this all the time. In general we are higher than our sensors in the bumper...BUT, on occasion we are not. In those instances the radar complains till I get about to the corner of the drive way and is just fine after that.....
The head mechanic at MB SLC said that the bike Trailer option/ selection in the assisted drive menu does NOT turn off the rear sensors. In fact, it only aids in route selection(?). They agreed that there are many GLCs out there driving around with bike racks that don’t have this problem. Each time the brake assist braked suddenly, it was always on rear left side of car. Never on the right side where the bike rack also extends near the sensors. I wasn’t changing lanes, but I was always in the left lane of the roads and near concrete medians. It was also raining.
They have suggested that I just need to deactivate the brake assist each time I start the car when the rack is on. If this were the case, other GLC drivers would have mentioned this. Apparently, there were faulty sensors in the 2025 models that they had to switch out, but my sensors are the most updated. Anyway, just thought I would see if anyone has experienced this. Thanks for all your input.
Judging from your description and the warning image you are getting, this is neither your parking sensors, nor the active braking assist. It's the Active Blind Spot Assist that thinks you are moving into the left lane and it sees your bike in the blind spot. So it applies the brakes to pull you back into your lane. This is using radar sensors behind your bumper, not the parking sensors. Unfortunately, if your rack or the bikes on it stick into the blind spot, this can happen. It's a very common issue and doesn't only affect the GLC.
Last edited by superswiss; Apr 10, 2026 at 11:43 PM.
Thank you for clarifying this. This makes a lot of sense and I am going to relay it to the service dept this morning. I will reply back to this thread with any updates about this problem If it is the active blind spot assist, then I would need to deactivate any driving assistance while driving with the bike rack? I just wonder why it started happening over 2 weeks after driving with no problems with the bike rack. It only started happening on a light rainy day.
I should have mentioned that it was just my bike rack.There was no bike on the rack in the rain at the time of these incidents. I love my bike! Thank you for your response so I could clarify that there was no bike on the rack.
After 2 weeks of the head mechanic trying to replicate the problem, they are no closer to a reason why these events occurred. They think it is because the bike rack needs the wiring harness plugged into the car in order to turn off the advanced driving features. I told them that if that were the case, the problem should have happened from the moment I put the bike rack on the car, with or without a bike on the rack. As it is, I drove the car for 2 weeks with no problems at all. I also think that if MB was aware of this problem, it would be common knowledge, and I would have been told about it from both the dealership and the bike rack store that I need to disable these features. The service mechanics have been driving the car around the city without any problems with the bike rack plugged into the wiring harness and without it plugged into the harness. I worry that it is actually a software glitch and that this will happen again randomly with potentially bad consequences if the car slams on the brakes in rush hour traffic and someone tailgating me. Anyone think it could be software-related?
Superswiss is correct (as usual), it is the blind spot assist. Even the images you show have the bsa functioning so I don’t quite understand why it is so much a mystery except you keep referring to the first two weeks you had it. If at all possible try a different rack manufacture, borrow a different rack? The shape and overhang of a different rack might not trigger it.
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Bike rack & active brake assist
