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[ANSWERED] Grand Sport / Z06 Wheels Bending

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[ANSWERED] Grand Sport / Z06 Wheels Bending

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Old 10-18-2017, 09:09 AM
  #1  
jvp
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Default [ANSWERED] Grand Sport / Z06 Wheels Bending

The original question is here.

Jedi-Jurist asked:
There have been a lot of reports of stock wheels bending on Grand Sports and Z06s here lately, and I've had one of my own front wheels bend on a brand new Grand Sport. In my situation, there was absolutely no damage, scratch or even a mark anywhere - the wheel just went out of round with less than 1000 miles on the car.

Why is this happening, is Chevy aware of this happening on more than an isolated occurrence, and what is being done to remedy the situation? Will you improve the strength of these Chinese-made wheels and offer a recall/replacement?
Tadge answered:
Thank you for the question, Jedi-Jurist. And I hope you are enjoying your Grand Sport! Your question raises a number of issues which I will try to address. I would like to start with your comment about ďChinese wheelsĒ. No Grand Sport wheels come from China. In fact, the majority of our wide Corvette wheels (those most susceptible to bending) are produced by a company named Ronal which is based in Switzerland and manufactures wheels here in North America. A couple of our low-volume Z06 wheels do come from China, but regardless of where they are made, all Corvette wheels are built and tested to GM and Corvette specific standards.

Wheel design is very complex and has to balance many attributes. Everyone wants beautiful wheels, but they also have to be stiff for good handling, strong to resist road damage and low weight. Un-sprung mass is the most important mass in the vehicle. You want light wheels because they enable the suspension to keep the wheel tracking the road surface and you want low rotating inertia because it affects how quickly the car can accelerate and brake. High mass wheels not only hurt handling, but they drive additional mass in the rest of the car. When you hit a pothole, high mass wheels generate higher loads into the suspension and body. As wheels get wider to accommodate wider tires, all these challenges are increased. For these reasons we spend a huge amount of engineering resources on optimizing wheels. We design wheels to withstand extreme pothole loads and test them on high speed laboratory equipment that can simulate the entire life-cycle of the vehicle. I have heard from some people that there is a theory that running the car in sport or track can contribute to damaging a wheel. That is not true.

People are often surprised that a wheel can be bent or cracked without any visible damage to the tire or obvious scratches on the wheel. Our tires have very stiff sidewalls for great handling and the ability to drive the car with no tire pressure whatsoever. As a result they can transfer loads to the wheel without being damaged themselves. A frequent sequence of events is that a wheel gets bent by a road hazard but the damage is initially almost undetectable to the driver. Maybe the driver notices a little more vibration, but many times not if the wheel is only slightly out-of-round (just a millimeter or two). A wheel that is not perfectly round puts stress in the rim that varies with every wheel rotation. Over time fatigue cracks can form after thousands or even millions of cycles. The wheel doesnít look any different but begins to leak air at the rim. Since it is hundreds or thousands of miles after the damaging event, the driver often canít remember hitting anything that would justify a crack in the wheel. I have actually experienced this myself. Obviously the wheel has to be replaced since there is no way to reliably repair a rim crack. Tires should be inspected carefully after being dismounted. Sometimes there is no damage on the outside but a blister, bulge, tear or crack can be visible on the inside. With safety as the top priority, any defect would justify a tire replacement.

The question postulates a ďrashĒ of wheel failures. Our field data does not suggest a recent significant increase in the wheel damage rate on our cars. There may be more reports of damage than historically, but, between the Z06 and Grand Sport, we are selling lots more wide-wheel cars than we ever have before. More cars on the road means more chance of hitting something in the road.

We do keep a keen eye on what our customers are experiencing in the field. I donít know where you live, but the roads here in Michigan seem to be getting worse every year. I can promise you we will continuously improve our designs and validation procedures based how the world is changing.
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Old 10-18-2017, 11:54 AM
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I appreciate the answer and insight. However if you havenít heard of more bent wheels on these cars then GM needs to being listening better. Iíve bent two wheels which is a first in all of the vehicles Iíve ever owned. Further the use of cast rather than forged wheels in a performance car of this caliber is disappointing. Iíve owned sports cars that cost 1/2 as much and had OEM forged wheels. So while the engineering efforts may have been made to ensure wheel sufficiency, my experience as well as those of many others on this forum have been dramatically different. Wheels are one of the Achilles heels of the GS/Z06.
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Old 10-18-2017, 12:33 PM
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"North America" = Mexico

There are very few cars that come from the factory with forged wheels. Some Porsches come to mind.

Last edited by ersatz928; 10-18-2017 at 12:34 PM.
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Old 10-18-2017, 02:13 PM
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Originally Posted by spearfish25 View Post
I appreciate the answer and insight. However if you havenít heard of more bent wheels on these cars then GM needs to being listening better.
They can't "listen better" if people don't go to the dealer and get them taken care of. That's how GM listens: service reports.
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Old 10-18-2017, 05:26 PM
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Originally Posted by jvp View Post
They can't "listen better" if people don't go to the dealer and get them taken care of. That's how GM listens: service reports.
^^exactly.
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Old 10-18-2017, 08:35 PM
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Dealer has replaced all 4 wheels on my 2016 Z06 with 9k miles
Also 6 tires because of out of round or road force balance
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Old 10-18-2017, 10:45 PM
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I have bent 4 rims so far and knew exactly when each happened. The road repairs that caused them to bend were not note worthy. Dealer refused to replace them therefore no report was filed. I would bet that there are many more situations similar to mine that GM is totally unaware of.
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Old 10-19-2017, 03:37 AM
  #8  
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The speedline rims used to be made in Italy, right? Now, it's Mexico. The proving grounds is eating tons of wheels (bending, cracking).
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Old 10-19-2017, 06:15 AM
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Of course they can Ďlisten betterí. GM just sits behind their dealers who tell customers itís their own fault. Itís a GM dealership these cars are taken to for evaluation. Listening and appreciating the problem starts with the service advisors. This pattern should be readily evident to them. Instead the dealers get away with price gouging customers for $700 a wheel for a replacement.

My Nissan 370Z had forged wheels and cost me $36,000 when purchased new. Never bent one on the street or the track and I drove it through Chicagoís potholed streets 12 months a year. The Z06 wheels would bend in a week there. I donít know how anyone drives a corvette and doesnít bend these wheels on northern roads.

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Old 10-19-2017, 09:58 AM
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I'm really pretty confused about this response. I was just at my dealer this week and told them I had bent two rims on the car with less than 2800 miles on it and asked whether this would be a warranty claim. I was told quite clearly that it must have been the results of them being acted on from an outside source and as such would not be covered.

I tended to agree that this isn't a warranty item which is why I paid out of pocket to replace the previous 6 bent or cracked rims on my 2015. However, GM appears to not believe it's an issue because they aren't hearing about it from dealers. Should I go back to the dealer with this note from Tadge?
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Old 10-19-2017, 11:27 AM
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Originally Posted by spearfish25 View Post
Further the use of cast rather than forged wheels in a performance car of this caliber is disappointing........ Wheels are one of the Achilles heels of the GS/Z06.
Is it confirmed the wheels are cast?

If so, GM did the same thing from the GEN5 to GEN6 Camaro 1LE. The MY12-15 ZL1/1LE wheels were made by AlCOA and extremely durable. The GEN 6 1LE wheels were stamped made in China.

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Old 10-19-2017, 02:39 PM
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My previous C6 ZR1 had the same wheels dimensions, never bent a wheels!!! The Z06... whole different story. They cheaped out on everything, its crazy!!
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Old 10-19-2017, 06:00 PM
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Originally Posted by Poor-sha View Post
I was told quite clearly that it must have been the results of them being acted on from an outside source and as such would not be covered.
While I have not bent a rim (knock on wood) Poorsha makes an excellent point. If dealers are declining warranty coverage then how is GM ever going to know about the problem. No warranty claim equals no problem to GM.
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Old 10-19-2017, 06:19 PM
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Originally Posted by ersatz928 View Post
"North America" = Mexico

There are very few cars that come from the factory with forged wheels. Some Porsches come to mind.
Are you implying a lower quality? Do you even know what you're talking about?
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Old 10-19-2017, 06:52 PM
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Originally Posted by Poor-sha View Post
Should I go back to the dealer with this note from Tadge?
No. They're not only pulling warranty claims but also (paid for)
service claims when looking at this data. So if you go in, they tell you that you need a new wheel and you don't get it from them, there's no record of "wheel replacement".

At least that's how I interpreted Tadge's response. I'm not interpreting this as an invitation to get your wheels replaced under warranty.
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Old 10-19-2017, 08:07 PM
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The speedline wheels are definitely made in Mexico. The question is, do they meet the quality asked for by gm? The secondary question is, is the quality level requested by the vendor high enough?

Again, i know they are breaking a significant amount of wheels at the proving grounds testing new models and are looking for new vendors right now..

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Old 10-19-2017, 11:29 PM
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First, let me thank you for answering my question, and every question posed to you here. We appreciate having this direct line of communication more than you can know.

I believe the Z51 wheels (my last car was a 2015 Z51) are made in China, but you are correct, the origin of the wheel doesn't really matter, it's the wheel's strength and other characteristics that are important. As others have pointed out, the problem seems to be that GM chose a cast wheel over a similar forged design.

I am most intrigued by this statement: "I have heard from some people that there is a theory that running the car in sport or track can contribute to damaging a wheel. That is not true." Where we are getting this theory is from none other than ... your dealerships. Yes, it's the service advisors, mechanics and even sales reps that warn of driving in track mode and (some even warn of) sport mode. The theory would seem to have some merit, as the energy of a pothole impact would seem to be less concentrated on the wheel and spread more throughout the suspension with a more forgiving setting like tour mode, and conversely to concentrate more energy transfer (and potential for harm) on the wheel when the suspension soaks up much less of the impact. I would love to hear the science and engineering that went into this comment.

"Our field data does not suggest a recent significant increase in the wheel damage rate on our cars." I don't know from which sources you derive your "field data," but as others have noted, there are too many reports on these pages of wide stock wheels bending for no good reason for GM to sweep this under the rug. I personally had two wheels bend with about 700 miles on the odometer of my new Grand Sport. This resulted in a considerable vibration that made the car essentially undrivable at higher speed for any length of time. The dealership fed me the "we've never heard of this happening to anyone in the history of the world" line and claimed that neither had their GM area rep. After sending the dealership an email (of course, the GM rep would never give out his direct email) linking to story after story after story of people on this forum having the same exact problem AND having their wheels replaced under warranty (thereby giving GM knowledge of the issue), I stopped hearing that line from the dealer, but never got an answer to my MANY questions of "so what did the GM rep say when you showed him my email?" Zip. Zero. Nada. I guess admitting and owning up to your faults, whether intentional or not, is not a strong suit of the Glenview, IL area rep.

The dealer diagnosed that the front left wheel was bent, and the GM rep said they would replace it "as a matter of customer goodwill" since the car was essentially brand new and there was no outward signs of damage. While I certainly appreciated this, he was certain to make clear that this was a one-time only deal. Only problem was that the dealership did not fully diagnose the problem, as I learned after the front wheel was replaced and the car still shook at 80 mph (instead of starting at 40 mph like before). The culprit? The first time around, the dealer failed to notice that the left rear wheel had also been bent.

What followed was 3 weeks of trying to get the GM rep to authorize replacement of the rear wheel, only to be told "nope, we said one and we meant one." Of course, no one could answer what would have happened if the dealership had correctly diagnosed both wheels the first time out, but thankfully my wheel warranty stepped up and paid the bill. I actually feel bad for them because, despite your answer, I see this as a defect in the wheel design, material and/or construction, and GM should have covered it.

This is a long way of saying your "field data" is corrupted and unreliable. You have a GM rep in the "field" out there pretending there is no issue, and then clamming up when shown evidence that there is an issue, all while refusing to take financial responsibility for said issue. I urge you to look further into this because we, the owners who have experienced bent wheels, can most certainly assure you this is a major issue for us.

Again, thank you for your time and consideration. If any of the above came off as harsh or untoward, that was not my intention. I am, I'm sure, venting a little frustration in your direction, but I assure you it's nothing personal. I have the utmost respect for you and your team, and I love my C7 (or I wouldn't have bought two of them), but I do want to see the company that makes by beloved C7 step up and fix something that everyone knows to be a problem. Please be as good a car company as you are sports car designers.
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Old 10-20-2017, 02:35 AM
  #18  
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All I know is that with less than 700 miles on my 16 Z06 I had four bent chrome wheels. Bent another one at 2700 miles, all on public roads. Nothing was covered by warranty and nothing was ever reported to GM since I did the actual repairs myself. Also ordered the OEM GM wheels online. I did talk with my local dealer but they weren't much help since they wanted to charge me full MSRP on the wheels and then farm out the swap to a local tire shop.

I'm 68 years old and never had this type of wheel problem with any car I've ever owned. On the other hand I've never owned a car with this low a profile run flats or this wide a wheel. I still wouldn't trade this car for anything else on the road that cost twice as much but I sure wish the wheels held up better.

If anyone from GM wants to contact me for more specific information or to add to their database, I'm more than willing to help.
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Old 10-20-2017, 08:15 AM
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Started a poll on this, please be sure to vote:

https://www.corvetteforum.com/forums...post1595799836
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Old 10-20-2017, 10:47 AM
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Originally Posted by c7fasteddie View Post
Are you implying a lower quality? Do you even know what you're talking about?
I just was indicating that Tadge was sorta hiding where the wheels are made.....his statement would have more integrity if he just stated that they are made in Mexico, rather than "North America". Also, nobody finds it strange that he indicates that they are made by Ronal, but many people have observed "Speedline" cast into the wheel....has anyone seen a GS wheel that has Ronal cast into it?????

Last edited by ersatz928; 10-20-2017 at 10:49 AM.
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