Mazdax605
Mazdax605 PowerDork
3/17/21 8:48 a.m.

Hey guys, 

 

On December 11th I was issued a brand new 2020 work van with 9 miles on the odometer. I was super excited because I had put 187k on the previous 2011 van that was pretty much a stripped down model aside from A/C. The new 2020 has all the toys and a really cool V6 engine. 

 

Exactly one month later it was street parked at one of our facilities and side swiped by a hit and run driver. Not a ton of damage aside from some scuffed up paint, broken centre cap, sheared valve stem, and broken mirror housing. It was towed away to our local dispatch garage and sat for 7 weeks before finally getting sent to a local body shop. 

 

Last Thursday I picked up the van. It was exactly 2 months after it was hit. The body shop guy tells me that it shakes when braking from higher speeds. I assured him it didn't do this before and has to be a result of the collision. He said it's most likely a factory defect. I'm sure it wasn't as it only had 1500 miles on it and didn't do it before the collision. I take the van and away I go. 

Sure enough it shakes like crazy under almost all braking, but definitely more when at higher speeds. I mentioned it to our shop mechanic and he says he'll get it to the dealership because it's under warranty. I don't know if chevy will cover it though. 

 

I didn't drive it much on Thursday as I picked it up late in the day. Friday I didn't use it too much either, but this week I've been driving a lot. Now it seems like the issue is completely gone. What could've been wrong with the brake rotor (seemed only the drivers side front) that would cause e this problem? Deposits sitting on the rotor? Why just the one? If it were bent, I'd think you'd have feel it all the time, no? 

outasite
outasite HalfDork
3/17/21 8:59 a.m.

The brake rotors rusted on the surfaces exposed to the air. The surfaces covered by the brake pads did not rust. The braking was uneven because of the different surfaces contacting the pads as you were braking. The rust was eventually scrubbed off by the pads and the rotor surface is the same all the way around. This happened in dealerships I worked at if new cars sat for long periods of time. We would lightly sand the rotors and they were good to go.

Mazdax605
Mazdax605 PowerDork
3/17/21 9:02 a.m.
outasite said:

The brake rotors rusted on the surfaces exposed to the air. The surfaces covered by the brake pads did not rust. The braking was uneven because of the different surfaces contacting the pads as you were braking. The rust was eventually scrubbed off by the pads and the rotor surface is the same all the way around. This happened in dealerships I worked at if new cars sat for long periods of time. We would lightly sand the rotors and they were good to go.

Why just the one rotor though? 

Streetwiseguy
Streetwiseguy MegaDork
3/17/21 9:14 a.m.
Mazdax605 said:
outasite said:

The brake rotors rusted on the surfaces exposed to the air. The surfaces covered by the brake pads did not rust. The braking was uneven because of the different surfaces contacting the pads as you were braking. The rust was eventually scrubbed off by the pads and the rotor surface is the same all the way around. This happened in dealerships I worked at if new cars sat for long periods of time. We would lightly sand the rotors and they were good to go.

Why just the one rotor though? 

That wheel was near the floor drain?  Its really hard to tell which rotor is shaking just from a drive.

Mazdax605
Mazdax605 PowerDork
3/17/21 10:03 a.m.
Streetwiseguy said:
Mazdax605 said:
outasite said:

The brake rotors rusted on the surfaces exposed to the air. The surfaces covered by the brake pads did not rust. The braking was uneven because of the different surfaces contacting the pads as you were braking. The rust was eventually scrubbed off by the pads and the rotor surface is the same all the way around. This happened in dealerships I worked at if new cars sat for long periods of time. We would lightly sand the rotors and they were good to go.

Why just the one rotor though? 

That wheel was near the floor drain?  Its really hard to tell which rotor is shaking just from a drive.

It was sitting outside for those 7 weeks. You're right that it's hard to determine which rotor was causing the problem but it felt like it was the left front. 

ultraclyde (Forum Supporter)
ultraclyde (Forum Supporter) GRM+ Memberand UltimaDork
3/17/21 11:29 a.m.

The side that was damaged? Was it still sitting on the flat tire? that rotor would be closer to the ground, maybe with more moisture exposure. Was the fender wrinkled up? More moisture exposure. Did they pull the rim and tire off while it was stored? More moisture exposure... You get the idea.

If it hadn't disappeared on it's own I would have thought a bent or damaged suspension piece, but it does sound like rust. 

I'm going with rust. It's pretty common on vehicles that sit. And it's probably not one rotor, it's usually one spot on both rotors. If the spots are in different areas of the rotation and slide through the caliper at different times, you get steering wheel shake. 

Why does the steering wheel shake when braking at high speed? | Steering  wheel, Brakes and rotors, Automotive repair

Mazdax605
Mazdax605 PowerDork
3/17/21 1:35 p.m.
ultraclyde (Forum Supporter) said:

The side that was damaged? Was it still sitting on the flat tire? that rotor would be closer to the ground, maybe with more moisture exposure. Was the fender wrinkled up? More moisture exposure. Did they pull the rim and tire off while it was stored? More moisture exposure... You get the idea.

If it hadn't disappeared on it's own I would have thought a bent or damaged suspension piece, but it does sound like rust. 

Yes it was sitting on the flat tire the whole time. It felt like it was that same wheel that was the source of the vibration, but who knows exactly, right. Fender wasn't wrinkled up. 

Our Preferred Partners
Peo4aaUzk10xFK0xWcGv6QnJhh9IWnfIDTMJg8l7GtdkRQxFya81RSOZqj439Zcj