Topic: Disc brakes and the Main car.

[Rupert]

   Electric only vehicles are a feature now and for most it might mean having two cars...a gas powered one for longer distances. Since most driving might be done locally in the home charged electric, it could mean that the gas powered one will be sitting around on the driveway for long periods.

   This is not a good situation for the disc brakes on the mostly parked vehicle since the disc brakes seriously rust away just standing still. Not having the constant rubbing action to remove the surface rust. I would not have believed it if I had not experienced this phenomena myself on two vehicles and we are not talking about a long period of time here...a few weeks. Serious rusted craters can be formed...maybe the size of a brake pad or more.

[draghon]

There must be more to it than just sitting. Wet environment perhaps? Plenty of people put cars away in winter storage without the brakes rusting away.

[rrocket]

There must be more to it than just sitting. Wet environment perhaps? Plenty of people put cars away in winter storage without the brakes rusting away.

Yep...my Forester sits for weeks at a time.

No rust craters.

[Fobroader]

My Cherokee sat sometimes for months and never had issues with the discs. The drums filled up with mud, water and grit and were a maintenance nightmare.

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[tenpenny]

that makes no sense, iron doesn't rust that quickly.  sure, it will form surface rust quickly, but not craters.

[bridgecity]

^ I have a feeling he's making a crater out of some surface rust.

[Sir Osis of Liver]

The rear brakes on my Escort GT would rust and pit from sitting outside when I lived back east. It's not that uncommon a problem on the coasts.

[erich]

Don't buy cheap crappy Chinese rotors

[tpl]

There is no doubt that some discs pick up more surface rust and more quickly that others.  I have always assumed that discs are not pure FE but are an alloy and different manufacturers specify different alloys...and then there are the crappy Chinese rotors.

[Sir Osis of Liver]

Bill Gardiner from Motoring addressed disc brakes a couple of times and rust was mentioned as an issue, especially on rear rotors.

If it's iron and it's exposed to salt and water, corrosion is going to happen. That's hardly a revelation.

[Rupert]

   Yeah, well, tell the dealership where to buy the discs.

   No...it does happen and has happened to me three times with this van. And...yes craters for sure. Heck...if it rains over night, check your discs in the morning and see the rust surface. Always the back discs for craters though...which have a solid disc and not a vented one like the front. Whatever difference that makes. Maybe they get hotter. It could be vehicle related though.

   Check the web. Parking in a garage would be an improvement, if you have one. A relative left her car on the driveway when she could not drive anymore due to age and after about 18 months one of the front rotors had rusted half way through...this is not exaggeration. We actually drove this vehicle in this condition not knowing.

[tenpenny]

I wonder what they make the rotors out of, because iron and steel don't rust that quickly.

(They're supposed to be an SAE grade of cast iron, and that won't develop 'craters' even when exposed to salty wet air).

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[Rupert]

   I wonder if moisture collects in the very small gap between the pads and the disc and perhaps leaving the emergency brake on might eliminate this from happening. It always occurs on the inner surface of my rear brakes, maybe that pad moves further away from the disc surface than the outer pad, allowing moisture in. I never leave my parking brake on, on the driveway which is flat. Over a longer stationary period this moisture would perhaps not dry out. Hmm...no, I tried leaving the emergency brake on when away for two weeks in another vehicle and I think that was when it all started.

   Bridge city, don't assume that someone who has been around cars...having to do his own maintenance...for 59 years, does not know what he is talking about. Check the web...Rock Auto.

[Seafoam]

   I wonder if moisture collects in the very small gap between the pads and the disc and perhaps leaving the emergency brake on might eliminate this from happening. It always occurs on the inner surface of my rear brakes, maybe that pad moves further away from the disc surface than the outer pad, allowing moisture in. I never leave my parking brake on, on the driveway which is flat. Over a longer stationary period this moisture would perhaps not dry out. Hmm...no, I tried leaving the emergency brake on when away for two weeks in another vehicle and I think that was when it all started.

   Bridge city, don't assume that someone who has been around cars...having to do his own maintenance...for 59 years, does not know what he is talking about. Check the web...Rock Auto.

Why don't you use the parking brake? I set mine after every park.

[bridgecity]

 

   Bridge city, don't assume that someone who has been around cars...having to do his own maintenance...for 59 years, does not know what he is talking about. Check the web...Rock Auto.

It was meant as a joke, mountains out of mole hills, craters out of surface rust.  . Lighten up.

I've never had an issue with discs, and service on them has been a cake walk. Obviously your experience is different.

[jamie1]

Very common problem in the car biz, we call it 'lot rot'. If you look at new vehicles on the transport trucks, you will see a lot of them have plastic covers on the wheels. Those are there to prevent the lot rot. Some vehicle are worse than others. I've seen it happen to vehicles that have sat at the airport for a couple weeks. Those are usually cleaned up with a couple of hard stops, but some that sit on a car lot for a few months may need the rotors machined or replaced. Of course ,new units will always get new rotors.

[Cord]

I wonder why they can't make car rotors out of the same material as motorcycle rotors, as those don't get rusty. Cost? Performance? Durability?

I recall the Honda CB550 from the early 80s that had its front rotors encased in a shroud so they couldn't be seen. Apparently it was because high iron content rotors were used for superior friction characteristics and the shrouds kept the inevitable rust out of sight. That was the last bike I saw with that setup.