Let's get this out of the way first: I know it's not ideal, but for the sake of convenience, I regularly use a drive-thru car wash. (I understand that the brushes could cause micro-swirls in the clear coat/paint). I actually use my Defender to go off-roading and have more damage to the exterior from tree branch scrapes anyway.

OK, so to my actual question: I'm considering doing some exterior lighting upgrades such as ditch lights and a roof-top light bar. However, I'm slightly concerned that the large brush machines used in the drive-thru car washes may cause damage to these upgrades (especially the roof-top bar which I believe is secured mostly with double sided tape). It's a fairly unique situation, but just wanted to see if anyone had experience here.

 

I would avoid any drive thru brush car washes if you are planning on adding the upgrades you mentioned. If you must use a drive thru car wash, I would recommend the brushless car washes.

 

Go through the "touchless" car wash if you have any "appendages" like lights, roof racks, brush guard, etc...

The brushes can wrap around things and yoink them off like Indiana Jones' whip.

 

I own an express exterior car wash tunnel for over 20 years now and I can tell you we're not in the business of damaging cars. BUT: Aftermarket accessories can't be our responsibility. Brushes nowadays are made of foam material that won't scratch anything and they're designed to not trap any dirt. In fact, this closed cell foam material helps on making the paint/clear coat shine. I wash my own GLS63 and '25 Range Rover all the time with no issues. And I highly recommend avoiding the so called brush-less washes unless you're okay on bathing your car in highly acidic chemicals. There is absolutely no way to clean a vehicle without friction unless you use very strong acid chemicals. In my establishment I use only alkaline products, on busy days we wash over 500 cars/day. If you want to be even safer, ask what brand of equipment the car wash is equipped with. I bit the bullet and spent over $500K a few years back with all new MacNeil equipment, the best of the best in the industry, occasionally we wash Bentley and Rolls Royce vehicles too, they trust us. But if your aftermarket stuff isn't tightly bolted down and/or sticks too far out, it can cause problems.

 

I drove my previous vehicle, a BMW X3 with cross bars and bicycle racks on the roof, through a brushes car wash regularly. They assured me that they had a button to press that would prevent the brushes from coming down on the top of the car, and they would push it for any car with a roof rack.

That worked fine for several months of washes. Until it didn’t. On the fateful day, the brush came down, the strands wrapped themselves around the bike racks, and the whole assembly was ripped off of my roof. The rotating brush then proceeded to beat the snot out of my car with the roof rack.

By the time they stopped the wash line, it had caused more than $3,000 worth of damage to my roof, A pillars, hood and fenders. And to the bicycle racks of course.

The manager reviewed the video they have - he swore the kid at the entrance pushed the button, but the system malfunctioned. They paid for the body work, of course.

I never took the car through a car wash again unless the cross bars were off the roof.

So… unless you plan for your light bar to be removable, I wouldn’t take it through a “touch” wash. I can’t speak to the touchless acidic chemicals; I’ll trust the expert on that. Maybe there’s a “wash it yourself” bay near you?

 

I love my local car wash and take both my Defender and X3 through regularly. However, I would never do this with the roof rack on the car. One time, after an oil change at my dealership, they gave my Defender a courtesy wash. I happened to have my Thule bars mounted on the roof at the time. Whatever wash system they used grabbed the bars and ripped them right out of the roof channel. I was pissed as I hadn't even asked for a wash and would have assumed the dealer would know better anyway.

 

Yep both replies above show the carwash staff was negligent in 1. Verifying if the crossbars are firmly bolted down and 2. Their equipment calibration. We wash countless cars with the roof bars but we always check - if they're wiggling / slightly loose we politely refuse to wash that vehicle. We automatically refuse and have big signs with pictures informing we don't send cars through with any kind of roof or trunk bicycle racks nor those thule roof trunks. Those are recipes for disaster. And yes, the self-service washes are the best option if you don't want to remove the jewelry before the shower.