mikapen

New tires on our 2019 GLC300.
The tire shop has not been able to get a good balance on the tires. I have gone back twice after the original mount and balance, and it's still off.
After the latest effort, it is worse, but instead of feeling like a balance issue, it seems like I'm driving on rocks.

Which makes me wonder just how the tire shop is fitting the wheels to their balance machine.
So, This Question:
Should they be mounting the wheels on the balance machine via Hub-Centric, or Lug-Centric attachment?


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superswiss

Well, basically hub centric. The OE wheels are hub centric on the car. Lug centric is a crapshoot, but they have adapters to make sure the wheel is properly centered on the balancer. Also, there are two ways to balance tires. Spin balancing and road force balancing. You might wanna take it to a shop who can do road force balancing. With road force balancing a roller is applied to the tire after it got spin balanced first. The roller simulates road force and roots out low and high points of the tire and wheel. If the road force numbers are off, the balancer tells the technician how far to rotate the tire on the wheel to match the high and low points. It will also reveal defective tires from the factory, which is not unusual, as well as bent wheels.

mikapen

Thanks. Good description of Road Force balancing. I knew M-B wheels are hub-centric, but I suspect that my tire shop may not know which adapters to use. I'm trying a new one, disappointed at the moment.

I have been out of the tire business long enough that I'm not familiar with the new equipment. I used to look for Hunter 97xx balance machines, which do Road Force balancing, but they are two generations old. I don't know what adapters, or visual aids the new crop of machines provide to eliminate simple "wrong adapter" problems.

@superswiss Do you think a lazy technician might actually use a lug-centric adapter, or wrong cone or spacers?

BTW I think all M-B shops are required to employ Hunter 97xx balancers at the minimum, so Road Force is possible at any M-B shop.

superswiss

Well, it'd be purely guessing what's going on at that shop. I wouldn't be surprised. I used to use a tire shop here in town that seemed to know what they are doing until I once observed them repairing one of my tires and then not balancing it afterwards. They just chalked the tire and wheel and lined it up in the same place again by eye. I didn't have vibration afterwards, but clearly they cut corners. These days I go to my performance indy where I know the owner and know they road force balance and take their time to properly mount the tires. They are also a Tire Rack recommended installer, so I just have the new tires directly shipped to them. I never asked my MB dealership if they road force balance, but I did have them mount new front tires on my C63 during the last Service B. The car needed an alignment, and I didn't feel like going to two places, so I just had them mount the new tires and also make sure the car gets aligned with the fresh tires. I have found that independent shops struggle aligning modern cars, because there are so many electronic systems that need to be properly reset, that I only trust the dealership to properly align my car and make sure all the assistance systems etc. work properly afterwards. I should ask next time if they actually road force balance, however, the car drives perfectly fine now.

ItalianJoe1

It shouldn't be hard to balance the tires on a GLC, they are nothing crazy or special.

What type of tires did you put on? What shop are you using?

I found, in my years at Firestone and multiple dealerships, that most techs just have no idea how to properly balance a tire. I 'fixed' many balance problems just by balancing the tires properly. Seems simple, but many people working in the industry couldn't fix a sandwich, let alone a complex modern automobile.