My wife and I recently went on a 7,900 mile drive around the northern US and southern Canada in our brand new 2018 VW Golf. About halfway through the trip, while driving through the Canadian Rockies, she started doing something that worried me greatly. She would be driving uphill just fine, at or just below the speed limit, then when starting down a 7% to 8% grade on the other side, she would put the brakes on hard enough to slow from 72mph down to 57mph within about 2 seconds. Despite my attempting to convince her that this was extraordinarily hard on the brakes, she continued to do it. We had already driven in the US Rockies, and she had not exhibited this behavior in them, although she did later do it again in the Appalachians. Her explanation was that she was getting used to the new car, and just tapping the brakes. Am I being overly protective of the new car, or is she being very hard on it? (BTW, the car she normally drives typically goes for about 60,000 miles before needing new brake pads.)
I donât see any harm in this, assuming she does this once per hill. A bit more brake wear than you would have without it, but a microscopic amount. Do it a lot and you will accelerate brake wear.
I calculated the G force on that braking as about 1/3 G, not really heavy braking, but not light.
google:
Not only will harsh braking wear the brake pads quicker, it can also overheat and damage the rotors either by creating glazing, hotspots, parallelism and/or (if lug nut torque improper) excessive runout. In addition to this, just about every part of the car will be experiencing more stress.
I would recommend a light application of the brakes, coupled with shifting down one or two gears.
Does your wife not know about compression braking, courtesy of down-shifting?
Brakes are for âŠâŠbraking and slowing down. I have crossed the Rockies a number of times and on a steep downgrade itâs best to gear down one speed and let the engine do most of the braking. On my Toyota thatâs 3rd gear
As mentioned, an occasional stomp on the brakes does no harm. My wife often drives in traffic that way.
Brakes are a lot less expensive than a transmission.Use the brakes for slowing down.Your wife does that probably to stay within the speed limit.
That is true, but I have been downshifting on steep downgrades for all of the 53 years that I have been driving, and I have never had to rebuild or replace a transmission. Those who rely solely on their brakes on steep downgrades run the risk of losing their brakes by the bottom of a long hill as a result of boiling brake fluid.
Downshift. You donât want the brakes overheating right when youâre coming to that switchback with a 2,000 foot drop.
You probably wonât do long term damage to the brakes by overusing them in the mountains, but you can reduce their performance until they cool down, and thatâs not what you want when loss of braking performance can mean sudden unplanned flight. 
Some brake pads actually perform better when pads are hot. Brake fade is a thing of the past on todays cars.
My vote would be let it go. Itâs small on the scale of things to worry about.
If you let your wife brake the way she chooses, sure it might cost you a few more dollars in brake work. But you not nagging her will pay much larger dividends.
Maybe thereâs a little extra wear, but I wouldnât call this âextraordinarily hardâ by any means. Regardless, as others have asked, did she downshift to the proper gear? Thatâs the more important issue here.
Going off the road because the brake fluid has boiled is more expensive than brakes or a transmission. I vote for using the transmission as itâs designed to be used.
Readersâ Digest published a melodramatic story about a rookie driver in a semi who decided to descend the west side of the Sierras himself instead of waking up the senior trainer driver. He burnt out the truckâs brakes because he didnât down-shift. Somehow the senior driver took over and enlisted the CHP to clear the way for him. If you pay attention you can see drive-off ramps for run-away vehicles (sand, those big rubber tubs full of sand) on steep highways.
It was overdone (the CHPâs wife had just had a baby, etc.) but perfect for an impressionable kid to read. I havenât forgotten it in, say, 55 years. Canât remember the title.
My understanding is that that is more of an issue for those who downshift to force a decrease in speed rather than for those who set a lower gear early to prevent excessive speed.
Example near me is a small hill of about 400 feet with a road of about a mile â thatâs roughly 7%.
If I down shift my automatic out of âoverdriveâ at the start and accelerate gently at the start of going down, gravity will speed me up to just over the speed limit if I donât tap a little bit on the brakes.
If I donât downshift first, and even with gentle acceleration, gravity will have me pumping the brakes multiple times on the way down. Downshifting in the middle of the hill to slow down would be dumb.
And then thereâs this:
My CVT doesnât allow a useful downshift.
Actually there is a âlowâ but the engine revs way up a low speeds, I would not use it at 50 mph or above. The ownerâs manual is silent about this. I just says use L for downhills.
That is entirely false. Itâs better than it used to be thanks to better materials and ventilation, but even high-end pads like Porterfield or Hawk will fade if you push them hard enough.
Do todayâs automatic transmissions shift into a lower gear to maintain a speed set on the cruise control?
some do, some donât.
Husband and wife driving the same car for thousands of miles. Oh no! This is a tough one ⊠lol ⊠My suggestion is to let her drive the car the way she wants. As long as they continue to work, donât worry so much. Brake parts are easily replaced.
If that were my wife and my car, Iâd be sure to keep my high-mounted third brake light clean. And my headrest properly adjusted. Get my drift?
I thought this must be another ten year old conversation. At any rate, brakes are cheap but wives are expensive. So what if she wears the brakes out?
Now my experience is that the worst thing you can do on a long grade is to ride the brakes because it will heat them up, burn them, and boil the brake fluid-then you have no brakes. By braking hard for a short time and then letting off the brakes again to let them cool is far better than applying them lightly for a long time.