Sponsored

Rock chips next to rear plate

BlackandBlue

Well-Known Member
Joined
Jun 27, 2019
Threads
17
Messages
886
Reaction score
849
Location
Texas
Vehicle(s)
Mustang
I agree! Very odd but that could be the case. I'm still not convinced it hasn't been happening on a transport truck though. These cars are (supposed to be) loaded back-first when transported to dealers.

I would think you are completely right BUT...

I know every rock chip and scratch on my car. I bunch of rock dings and chips wouldn’t just go unnoticed on a brand new car normally. Especially with the level of fanaticism that is attached to these cars.
Sponsored

 

S650D&R

Member
Joined
Oct 29, 2018
Threads
1
Messages
18
Reaction score
10
Location
Michigan
Vehicle(s)
multiple
I would think you are completely right BUT...

I know every rock chip and scratch on my car. I bunch of rock dings and chips wouldn’t just go unnoticed on a brand new car normally. Especially with the level of fanaticism that is attached to these cars.
I completely understand, I'm the same way with my cars! It really doesn't make sense that the dealer and the new owner would both miss something so big. I just don't think the spoiler produces enough down force to pull up rocks from the ground and cause damage. It might be true but I'm trying to think of any other reason for the rock chips...that isn't driving 70mph in reverse :wink:
 

StangTime

Well-Known Member
Joined
Apr 16, 2019
Threads
77
Messages
3,491
Reaction score
3,884
Location
Ontario 🇨🇦
First Name
Todd
Vehicle(s)
19' GT PP1 Manual
In order for these rock chips to happen, the car has to create enough negative pressure in the rear that it lifts the rocks off the ground. Then accelerate the rocks to over-take the speed of the car to make impact with the rear. Impossible physics due to the laws of energy. Whatever caused this, it happened when the car was sitting still and the rocks were propelled by some other means against the car.

Where do you park?
 

Edward

Well-Known Member
Joined
May 16, 2017
Threads
10
Messages
101
Reaction score
35
Location
ATX
Vehicle(s)
Ford Lightning
In order for these rock chips to happen, the car has to create enough negative pressure in the rear that it lifts the rocks off the ground. Then accelerate the rocks to over-take the speed of the car to make impact with the rear. Impossible physics due to the laws of energy. Whatever caused this, it happened when the car was sitting still and the rocks were propelled by some other means against the car.

Where do you park?
This assertion assumes that all the debris causing this damage are at rest on the road surface. Personally, I would guess that the debris is already in flight flung up by the tires. At this point, the rocks are already at or near the speed of the car and the force required to propel them into the bumper cover. Even before the swing was implemented, Ford actually put holes at the bottom of the exhaust tips specifically to let accumulated rocks exit. So flying debris has been a known issue. I suspect that the swing/Gurney flap combo has exacerbated the problem.
 

StangTime

Well-Known Member
Joined
Apr 16, 2019
Threads
77
Messages
3,491
Reaction score
3,884
Location
Ontario 🇨🇦
First Name
Todd
Vehicle(s)
19' GT PP1 Manual
This assertion assumes that all the debris causing this damage are at rest on the road surface. Personally, I would guess that the debris is already in flight flung up by the tires. At this point, the rocks are already at or near the speed of the car and the force required to propel them into the bumper cover. Even before the swing was implemented, Ford actually put holes at the bottom of the exhaust tips specifically to let accumulated rocks exit. So flying debris has been a known issue. I suspect that the swing/Gurney flap combo has exacerbated the problem.
I would agree with what you are saying. Regardless if the debris is at rest or not.... It's going to take one hell of a negative pressure zone to reverse the direction of debris already lifted up and generally travelling in the opposite direction of the car. Tires are going to kick it up and back with a small percentage of debris getting locked into a tread and then flung forward. For debris flung forward, it can't ever hit the outside of the rear bumper as it is going to make impact with the fender lining and lose energy. We are talking about something that was under the car, has become airborne and has somehow managed to do a 180 and increase velocity to hit the painted bumper surface. It's not going to happen as long as the car is moving forward.
 

Sponsored

SVTinAR

Well-Known Member
Joined
Sep 29, 2017
Threads
17
Messages
473
Reaction score
193
Location
Arkansas
First Name
Dan
Vehicle(s)
2017 Shelby GT350, 2003 Lightning & ERA FE Cobra
Unless you can identify some plausible mechanical damage excuse, I would take it to a dealer and submit a defective paint claim.
 

03reptile

Well-Known Member
Joined
Mar 6, 2019
Threads
5
Messages
280
Reaction score
268
Location
Maryland
Vehicle(s)
2019 Shelby GT350
I've got a 2019 GT350 with the Gurney flap installed. I've got 700 miles on the car and some roads I've traveled have surfaces with small gravel. That said, I just checked the rear facia and I have no rock chips or anything similar to what you've described. Could it be a paint issue from the factory, and the paint is not adhering properly in that area, causing it to flake? Just spit balling.
 

Sponsored
OP
OP
slikk66

slikk66

Well-Known Member
Joined
Mar 24, 2019
Threads
7
Messages
88
Reaction score
60
Location
Denver Metro, CO
Vehicle(s)
2019 gt350, 1966 Mustang Coupe
I'm going to take it in for first service soon, oil change and couple warranty issues. I'll ask them about it, say I'm not aware of the cause.. ask about defects etc.

I've now taken it through big and little tujunga canyons in Los angeles, and if you've driven those you know there is a ton of small rocks/debris on those canyon roads.

The first time thru, I had the gurney flap on it. And also for about 200 miles of some freeway driving. Maybe it was from higher speed gurney flap time? Not sure.

This last time I didn't have the flap on, and I don't see a big difference in the bumper but I swear there are a couple more. You hear it constantly pinging rocks off of "something" as you drive those roads. Rocks are kicking up and making contact somewhere.. that part is obvious.

Since it's on both sides and above the aero exits I know it's not from where it's parked, but yea sure seems odd.
 

jlauth

Well-Known Member
Joined
Jan 29, 2018
Threads
3
Messages
107
Reaction score
37
Location
IN
Vehicle(s)
2017 GT350
I agree! Very odd but that could be the case. I'm still not convinced it hasn't been happening on a transport truck though. These cars are (supposed to be) loaded back-first when transported to dealers.
I think you have a good theory, but in reality these cars are feet off the ground during delivery and I dont see that quantity of rocks impacting 4-10 feet in the air. Maybe one or 2 but he has them all over.
 

S650D&R

Member
Joined
Oct 29, 2018
Threads
1
Messages
18
Reaction score
10
Location
Michigan
Vehicle(s)
multiple
I think you have a good theory, but in reality these cars are feet off the ground during delivery and I dont see that quantity of rocks impacting 4-10 feet in the air. Maybe one or 2 but he has them all over.
Very true, it would have to be a very unlikely series of events to get that many chips. Like the transport truck following a gravel truck or something
Regardless, best of luck slik66!
 

Voodoo Velocity

Well-Known Member
Joined
May 4, 2019
Threads
5
Messages
516
Reaction score
573
Location
Tampa Bay
First Name
Mike
Vehicle(s)
2019 Shelby GT350 / 2016 Acura RLX Sport Hybrid
The back of the car does pick up a lot of dirt from the aerodynamics. One normal drive after a cleaning and the rear panel is a mess. The tires are super sticky and pebbles stick to them only to be flung off at higher speeds. That is one reason there are 'drain holes' in the exhaust tips. - so gravel flung in them will fall out. That said, even if gravel makes it past the diffuser, I cannot image the aerodynamics could divert gravel back on itself with enough force to mar the paint of the rear panel to the extent you show.
Sponsored

 
Last edited:
 




Top