severely cracked/broke oem c7 wheel.
02-01-2016, 07:01 AM
#1
Melting Slicks
Thread Starter
severely cracked/broke oem c7 wheel.
Setup:
2016 C7 Z51
stock other than brake pads and pirelli slicks on oem wheels.
The setup was 18x8.5/19x10. I truly feel the 8.5 wheel along with the 245 front tire is working extremely hard and not enough wheel/tire for this car when it is pushed. I have -2.3* camber in the front and I was still shoulder the tires before the incident.
The Track was NOLA MSP in new orleans. I was running consistent upper 1:54's with the setup. I felt a small vibration under right hand turns and it gathered my attention. The next right hand turn I took, I felt the vibration a little stronger. I immediately slowed down (VERY SLOW track was light) and made my way into the pits.
This was the drivers side front wheel (track is heavy right hand turns)
2016 C7 Z51
stock other than brake pads and pirelli slicks on oem wheels.
The setup was 18x8.5/19x10. I truly feel the 8.5 wheel along with the 245 front tire is working extremely hard and not enough wheel/tire for this car when it is pushed. I have -2.3* camber in the front and I was still shoulder the tires before the incident.
The Track was NOLA MSP in new orleans. I was running consistent upper 1:54's with the setup. I felt a small vibration under right hand turns and it gathered my attention. The next right hand turn I took, I felt the vibration a little stronger. I immediately slowed down (VERY SLOW track was light) and made my way into the pits.
This was the drivers side front wheel (track is heavy right hand turns)
Last edited by Chets LS3; 02-08-2016 at 03:58 PM.
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Mike hoppe (02-13-2016)
02-01-2016, 09:51 AM
#5
Instructor
I saw that, I was there, in the TT3 silver C5Z06. beautiful car BTW.
Scary that happened. could have been a bad scenario if you kept pushing it.
It may look funny, but I would recommend going with C5Z speedlines for the front. or possibly all around. My PR at NOLA (1:52.7) is on 18x10.5 speedlines on 315 hoosier R6's (my old EB C5Z). and I hammer on those speedlines and never had an issue. it would give you more footprint, less weight, and possibly higher factor of safety.
Scary that happened. could have been a bad scenario if you kept pushing it.
It may look funny, but I would recommend going with C5Z speedlines for the front. or possibly all around. My PR at NOLA (1:52.7) is on 18x10.5 speedlines on 315 hoosier R6's (my old EB C5Z). and I hammer on those speedlines and never had an issue. it would give you more footprint, less weight, and possibly higher factor of safety.
02-01-2016, 11:40 AM
#9
Le Mans Master
I don't know anything about the OEM C7 wheels, but every wheel I have had crack over the years I was able to trace back to the wheel recently not torqued properly when out on track. In my cases of cracked spokes on CCW Classics, C5 OEM and Forgestars, I was on track and could feel or hear a clicking sound. Upon coming in it was found not all lug nuts were properly torqued. Not long later the wheel would crack.
Like you, when spoke crack you can here the clicking sound of the crack opening and closing when under load in a turn.
Part of my pre-session check list is to check the wheels/spokes for cracks. For those of you who have not cracked a wheel, yet, the cracks usually appear closer to the center of the wheel and often on the widest part of the spoke as shown in the picture, or even where two spokes merge into one.
Like you, when spoke crack you can here the clicking sound of the crack opening and closing when under load in a turn.
Part of my pre-session check list is to check the wheels/spokes for cracks. For those of you who have not cracked a wheel, yet, the cracks usually appear closer to the center of the wheel and often on the widest part of the spoke as shown in the picture, or even where two spokes merge into one.
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JEPopp (02-09-2016)
02-01-2016, 12:35 PM
#10
Melting Slicks
First off, kudos to the OP for feeling something wrong and finding a small problem before it became a big problem. Secondly, thanks for posting here, good lesson learned for all of us and good discussion to be had around the situation.
OP has a similar post in the C7 section. These wheels were powder coated. Over the years I've seen arguments that powder coating can't weaken the metal, and arguments that it definitely could, especially as the cast wheels are like 356-T6. I'm not well educated on the subject at all and can only go by what I've read on the internet (which is never wrong, of course) but it seems that weakening can occur particularly depending upon the temp and time at that temp.
Seems like the OP had the perfect storm of maybe not enough tire, a track layout stressing that particular wheel, slicks, and possibly weakened wheels due to powder coating.
Not sure if we can truly throw in the towel on the OEM wheels yet given the extra variables here.
OP has a similar post in the C7 section. These wheels were powder coated. Over the years I've seen arguments that powder coating can't weaken the metal, and arguments that it definitely could, especially as the cast wheels are like 356-T6. I'm not well educated on the subject at all and can only go by what I've read on the internet (which is never wrong, of course) but it seems that weakening can occur particularly depending upon the temp and time at that temp.
Seems like the OP had the perfect storm of maybe not enough tire, a track layout stressing that particular wheel, slicks, and possibly weakened wheels due to powder coating.
Not sure if we can truly throw in the towel on the OEM wheels yet given the extra variables here.
02-02-2016, 02:00 AM
#13
Thankfully the crack was caught before it completely failed.
A lot of people plastidip their wheels. Here is one more reason in my opinion that you should not plastidip track wheels because the flexible coating might hide hairline cracks you would have otherwise seen during wheel inspections.
It is good practice after each track day event to remove, wash and examine each wheel and tire off the vehicle. Using a bright LED type head lamp really lets you see if there are any crack or defects.
A lot of people plastidip their wheels. Here is one more reason in my opinion that you should not plastidip track wheels because the flexible coating might hide hairline cracks you would have otherwise seen during wheel inspections.
It is good practice after each track day event to remove, wash and examine each wheel and tire off the vehicle. Using a bright LED type head lamp really lets you see if there are any crack or defects.
02-02-2016, 10:15 AM
#14
Safety Car
And, fwiw, that is approximately the same spot that I've seen crack on other wheels (to clarify, not other OEM C7 wheels, this is the first I've seen). Obviously that is a highly stressed area, so when you do your inspection, pay close attention to this area and the same area in the rear of the wheel. Also worth looking a little closer at the area of the spokes that are ~2" from the barrel.
02-02-2016, 04:15 PM
#15
Melting Slicks
Will 18 inch front C6 Z06 wheels fit that car all the way around?
BTW I would chunk all those wheels in that set, sell them at the scrap yard.
BTW I would chunk all those wheels in that set, sell them at the scrap yard.
Last edited by FASTFATBOY; 02-02-2016 at 04:17 PM.
02-02-2016, 04:20 PM
#16
Melting Slicks
First off, kudos to the OP for feeling something wrong and finding a small problem before it became a big problem. Secondly, thanks for posting here, good lesson learned for all of us and good discussion to be had around the situation.
OP has a similar post in the C7 section. These wheels were powder coated. Over the years I've seen arguments that powder coating can't weaken the metal, and arguments that it definitely could, especially as the cast wheels are like 356-T6. I'm not well educated on the subject at all and can only go by what I've read on the internet (which is never wrong, of course) but it seems that weakening can occur particularly depending upon the temp and time at that temp.
Seems like the OP had the perfect storm of maybe not enough tire, a track layout stressing that particular wheel, slicks, and possibly weakened wheels due to powder coating.
Not sure if we can truly throw in the towel on the OEM wheels yet given the extra variables here.
OP has a similar post in the C7 section. These wheels were powder coated. Over the years I've seen arguments that powder coating can't weaken the metal, and arguments that it definitely could, especially as the cast wheels are like 356-T6. I'm not well educated on the subject at all and can only go by what I've read on the internet (which is never wrong, of course) but it seems that weakening can occur particularly depending upon the temp and time at that temp.
Seems like the OP had the perfect storm of maybe not enough tire, a track layout stressing that particular wheel, slicks, and possibly weakened wheels due to powder coating.
Not sure if we can truly throw in the towel on the OEM wheels yet given the extra variables here.
02-02-2016, 06:00 PM
#17
Burning Brakes
I was warned by John at CCW that power coating the centers would likely weaken them and that's on a forged center wheel. To the OP regarding the slicks, were these scrubs or new? Relates to the wheel weight question.
Last edited by ZedO6; 02-02-2016 at 06:01 PM.
02-02-2016, 07:21 PM
#18
Drifting
Chrome is not good on steel parts as it can cause hydrogen embrittlement and fatigue failures. I could not find anything about chromed aluminum other than FAA does not allow it on spinners for prop planes. No reason for it, it's just their policy evidently.
Are yours chrome or polished?
Possibilities:
1. A defect/notch in the surface. Aluminum is notch sensitive.
2. Although the OEM C5 Z06 wheels seem to be bullet proof for track duty, the OEM C5 2K "Thin Spoke wheels cracked with regularity for cars that never saw the track. Your wheel may just fall somewhere in between as far as fatigue strength goes.
Are yours chrome or polished?
Possibilities:
1. A defect/notch in the surface. Aluminum is notch sensitive.
2. Although the OEM C5 Z06 wheels seem to be bullet proof for track duty, the OEM C5 2K "Thin Spoke wheels cracked with regularity for cars that never saw the track. Your wheel may just fall somewhere in between as far as fatigue strength goes.
Last edited by UstaB-GS549; 02-02-2016 at 07:28 PM.
02-08-2016, 02:48 PM
#19
Former Vendor
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For sure I would try and get it warranted just so you have a set of stock wheels.
Now that being said it is not the first stock OEM wheel I have seen fail but it doesn't happen that often. Given where it broke, I don't think you had a loose lug nut on the wheel. I think it was to much force through the wheel which could have been from the slicks on the car, a wheel defect, or a combo of the two.
Like anything on a track or race car you have to inspect every inch of the car. You never know what is going to happen. I say kudos to you for being on top of your game and finding it before something bad happened.
Over the years I don't know if I have ever heard that powder coating did anything to the strength of the material. They bake them at a relatively low temperature. When you think about it, in a 200-300 degree oven vs having a 800-1000 degree brake rotor a inch or so away? The tires are typically 180-200 degrees themselves. I know during pit stops I had to have gloves on to pull the wheels off the race cars.
I will say most of the race wheels are generally painted because it is lighter than the powder, but we have ran powder coated ForgeLine's on the cars and have not seen cracking on them.
Either way....OEM wheels or a $6k set of ForgeLine wheels you should always inspect them.
Now that being said it is not the first stock OEM wheel I have seen fail but it doesn't happen that often. Given where it broke, I don't think you had a loose lug nut on the wheel. I think it was to much force through the wheel which could have been from the slicks on the car, a wheel defect, or a combo of the two.
Like anything on a track or race car you have to inspect every inch of the car. You never know what is going to happen. I say kudos to you for being on top of your game and finding it before something bad happened.
Over the years I don't know if I have ever heard that powder coating did anything to the strength of the material. They bake them at a relatively low temperature. When you think about it, in a 200-300 degree oven vs having a 800-1000 degree brake rotor a inch or so away? The tires are typically 180-200 degrees themselves. I know during pit stops I had to have gloves on to pull the wheels off the race cars.
I will say most of the race wheels are generally painted because it is lighter than the powder, but we have ran powder coated ForgeLine's on the cars and have not seen cracking on them.
Either way....OEM wheels or a $6k set of ForgeLine wheels you should always inspect them.
02-08-2016, 03:54 PM
#20
Melting Slicks
Thread Starter
Thanks Anthony. I spoke with you about going to the LG set via email.
And the crazy thing was these wheels were just inspected well because I cleaned them for some pictures that morning.
Really wish the LG wheels were 18/18 set
And the crazy thing was these wheels were just inspected well because I cleaned them for some pictures that morning.
Really wish the LG wheels were 18/18 set