NineVettes

Re rim type - it is my understanding that chrome treating the wheels may weaken them a bit. Aside from that, it does not make sense to me that any other surface finish would cause additional weakness.

Also, another member posted previously that his wheels failed as a consequence of doing some serious G's while dicing with a Porsche on the Tail of The Dragon. I am 99% sure that my wheel failures were a consequence of my two track days - especially on the area of the track at the end of the fastest straightaway a sharp right hand corner had to be negotiated. As is my usual nature, and what is normal track placement, when cutting apexes (that have slightly higher curbing) and especially at the end of the fastest straightaway, that is where the bending occurred. I started getting vibrations shortly after and had to cut my track day short both times. Done this countless times with many previous Vettes, never had a problem before with wheels. I believe that G-force loading can be a potential cause.

And, as I mentioned previously, `I believe it is highly possible that poor surveillance of the production process of GM's foreign lowest bidder manufacturer of oem wheels may have led to some wheel batches being of slightly higher quality (barely meeting marginally acceptable oem specs) while other batches may have been lower quality, thus coming in below the already marginal specs. It is no secret that GM has changed manufacturers of these wheels at least once, maybe more times.

And outside of a class action suit (in progress) no way GM is going to admit any fault here and make them potentially liable for the replacement of thousands of wheels. As normal corporate practice, their green eyeshade brigade and the lawyers have been consulted and (as with many other corporations) GM remains confident that the best way forward for profits is to remain silent. And now with the class action suit underway, they are even more incented to maintain corporate omerta.

The only tow things that will change that is if either the class action suit is won years from now, in which case you will get a $10 coupon while the lawyers make millions, or God forbid, someone running these wheels is involved in a serious or fatal accident attributable to the wheels - and NHTSA gets involved.

I am not gonna waste my time badgering the local dealerships and Mary Barra is no way in hell going to address this with a lawsuit in progress. The OP is wise to go with high quality forged wheels, and like may others, I will be doing the same.

elburrito99

Thanks for your post. With 15k miles I don't have bent or cracked wheels (as far as I know), but I think you may be on to something regarding instances where the point of impact is closer to the inside of the wheel.

Also, I agree that getting the data points you noted above may help narrow down the true cause of the issue. I hope owners with damaged wheels provide that info.

ShagVette

Wouldn't VIN be the most important? Once a list is compiled, give to GM, so they can try to isolate dates and place of manufacturer?

GeoGS

Like most of all us that have a Grand Sport or Z06 I also have thought long and hard about the wheel problems. While changing out my brake pads to less dusty ones, and looking over my rims. Every thing still ok. But this is only with 750 miles on my 19 GS. I noticed a dimple on the edge of one of rims. I should have taken a picture. Now this looked like they did a Rockwell test on this wheel/rim to me. Rockwell is hardness test. They used to do this kind of test where I used to work. It would leave a dimple in the metal. Too hard the metal cracks, too soft it bends. Not sure what scale GM uses. Not sure what range they have either or how much the hardness varies around the wheel/rim.

Would be interesting to see how thick the OEM Flow forged rims are in respect to third party Flow forged rims. Would there be a difference where all third party are thicker?
Would be interesting to see how long they apply pressure (and how much) when flow forming in respect party flow formed wheels. Is it just once around like a can opener, or is many times with pressure reduced each time? When Ford had a problem with the Firestone tires it was found that they were rushing the process of heating and curing the tires, to get more tires out the door. With the shorter curing time it created a weaker tire. With less pressure and less spinning times more rims out the door with maybe a weaker rim ? Not an engineer, but still think about the rim problem.

Wheels that bend would seem to be softer then the ones that crack which would seem to be be more (brittle) hard. Wonder if GM does any testing on the ones that are bad? That would be to see if they were too hard or soft. Or even if the hardness (rockwell number) is uniform around the wheel or hot spots on the wheel?

With leverage theory and it always cracking/bending on the inner barrel seems right. The question that comes up why the third party Flow forged wheels not cracking or bending like the OEMs both have cast faces? If they were I would think we would have/had some members on here talking about. Now I seen a few pictures of third party wheels cracked, but it did not say how or if there was an accident or damage at a track. Granted there are less of them than OEM ones. But I think not hearing of one on here says something.

With the leverage theory it also must take into account the unsprung weight. Not sure what every OEM weighs and comparison to the wheels problems. You would think the ones that weigh more would be the ones that had the most cracks and bends. Are third party Flow forged that much lighter? Now the Full Forged ones are. If weight a big factor in all of this. Then the ones that have ceramic fiber rotors should not have much of a problem with bending or cracking the rotors. As they are about 6 lbs lighter of unsprung weight.

Maybe this all has to do with the thickness of the outer edge of the wheel. As this is where the crack starts. Or even the shape of the outer edge. Not an engineer, just throwing this out there.

NineVettes

I may be wrong, but I am under the impression that the entire Z06 wheel is cast and that part of the ZR1 wheel is flow formed or what some call rotary forged - a half step above cast wheels. That's what Bob from House of Wheels told me, anyway. Full forged monoblocks can save a lot of weight, but here you do not want to just think about weight savings alone as using too little material can make even a forged wheel much more prone to bending. A balance must be struck, I think - and of course using a forged wheel derived from an APP forging brings higher quality materials to the forged wheel table.

Best estimate of real world effect of unsprung rotational weight is that it is worth 1.6 lbs of sprung weight. This was told to me by someone who knows a lot more about this than me, and probably most of you. It is not the 3 or 4 to 1 ratio often bandied about. But the 1.6 figure is still pretty significant in my book. Based upon what I have been able to learn, a good set of high quality forged monoblock wheels with the requisite strength to run track days will run about 28-30 lbs total less weight than the oem cast wheels, so worth about 46 lbs of equivalent sprung weight. Of course lighter tires would also contribute..

That is what I understand it all to mean at this point.

GeoGS

According to Tadge All of the GS and Z06 are Flow forged which I take it are supposed be the same as Rotary Forged. I remember this quite clearly as I thought all of the wheels were cast, and were being replaced again and again. While all the one that switched to Rotary Forged did not seem to have a problem. But then I seen that Tadge said they were Flow Formed Forged which to me is the Rotary Forged. I have not seen anywhere where GM has come out and stated anything about its wheels.

tertiumquid

I've posted this before on other threads but it would be helpful here also, I think

1. Cast aluminum wheels
2. Flow-Formed wheels
3. 1-piece "Monoblock" forged wheels
4. 2-piece welded construction wheels
5. 2-piece bolted construction wheels
6. 3-piece bolted construction wheels

Cast Aluminum Wheels
These are the lowest priced wheels, and are typically what are found on production vehicles. Cast aluminum wheels are created by pouring molten aluminum into a mold that is shaped like a wheel. This produces a wheel casting. Some final machining work is then done to clean up the rough surface, and paint/finishing is applied.

Pros: Lowest price, easiest to mass-produce.
Cons: More brittle than forged wheels. Spoke details and edges aren't as sharp as a machined forged wheel. Heaviest weight of all wheel construction types. Lowest quality. Limited offsets, width increments, diameter selection available. Nearly impossible to repair when cracked or severely bent - safely, that is. A damaged cast wheel usually needs to be replaced.

Flow-Formed Wheels (Rotary Forged)
Flow-Formed wheels start out identical to cast poured wheels, but with different hoop thickness. The casting process above is used to create the spoke pattern only. Then the wheel castings are put into a flow-forming machine to form the outer hoops. This is done using high heat and high pressure rollers, which "flow-form" the outer hoop. This results in a stronger outer hoop, with aligned aluminum grain structure. The resulting wheel is a cast faced wheel with a hoop that has properties similar to a forged wheel. They are stronger and lighter than cast wheels.

Pros: Low Price, Lightweight, Higher strength than cast wheels.
Cons: Cast face still lacks the sharp edges and details of a machined forged wheel. Limited width increments and diameters available. Hard to repair when severely bent or cracked.

1-Piece Monoblock Forged Wheels
The term "Monoblock" is used throughout the industry to describe the 1-piece forged wheels. "Mono" meaning one, and "Block" meaning it was created from one block of aluminum. The block in this case is actually a round bar stock of high quality, aerospace-quality 6061-T6 Aluminum Alloy. The round bar is pressed in a huge forging machine, to stamp out a wheel shaped blank. Forging is a hot working process, and helps to align the grain structure of the alloy. This results in a very strong, very lightweight wheel construction material. The wheel blank is then flow-formed to create the outer barrel shape. Following that process, the wheel blank is loaded into a CNC milling machine and there the spoke pattern is milled out.

Pros: Lightest of the forged wheel construction methods.
Cons: Priced about the same as expensive 3-piece construction. Difficult to repair when bent or severely damaged.

2-Piece Welded Construction Forged Wheels
These are considered the entry level forged wheels, as they are priced slightly lower than 3-piece forged wheels. The centers start out as a blank of forged 6061-T6 Aluminum alloy, and the spoke patterns are CNC machined with a milling machine. The wheel hoop is also a forged aluminum material. On a 2-piece wheel, the center is simply welded to the hoop on the backside of the wheel. Some manufacturers also offer cast aluminum centers, to reduce cost. Quality and weight of the cast centers is not as good as forged/machined, however.

Pros: Lowest Price of the Forged wheels. Same weight, appearance, quality as 3-piece wheels.
Cons: Limited widths increments available. Cannot easily chrome plate or paint the lip, since it has to be welded on. More difficult to repair a bent lip compared to a 3-piece wheel, as the center has to be cut out and a new hoop welded on.

2-Piece Bolted Construction Forged Wheels
These are built very similar to the 2-piece welded construction wheels above, but use a hoop that has a bolting ring already in place. Instead of welding the center to the hoop, it is simply bolted on. This is the least common method of forged wheel construction, as the hoops tend to cost more than simple welded hoops. Some manufacturers also offer cast aluminum centers, to reduce cost. Quality and weight of the cast centers is not as good as forged/machined, however.

Pros: Lips can be easily chrome plated or painted, since no welding required. Easier to replace a hoop when it gets bent.
Cons: Limited width increments available. Few brands offer this type.

3-Piece Forged Wheels
Three piece forged wheels are usually the most expensive wheel construction, mostly due to the assembly labor and components used. The wheels consist of three main pieces; the center, the outer hoop (lip), and the inner hoop. These three parts are held together with a series of perimeter bolts. Silicone RTV is used to seal between the two hoops. Some manufacturers also offer cast aluminum centers, to reduce cost. Quality and weight of the cast centers is not as good as forged/machined, however.

Pros: Most width increments available, truly perfect fitments available. Easiest of all wheels to repair if lip gets bent or damaged, as hoops are easy to replace. Easy to paint or chrome plate lip, since no welding is required. Can have different color rear hoop and outer hoop, since they are two different pieces. Highest resale value for used wheels.
Cons: Most expensive forged wheel construction. RTV silicone seal can be damaged by inexperience tire installers, resulting in leaks.

Zjoe6

Yeah VIN should be added for sure. I added to my list on that post.

Thanks

Zjoe6

I think you're right, they are cast. Not sure where that came from that they are rotary forged or flow form forged etc. I thought they were just straight up cast.

Edit: They are actually cast/flow-formed which is explained in post 27.

golfbone

It is my understanding that the Z06 wheels are cast.

TBF

I attended the Ron Fellows new vette owner course last week. We asked the question and received a very good answer why it happens to some and not all.

1. Any rim that is aluminum and designed for a tire as wide as our Z-06 / GS tires will have issues due to the following
a. The spokes on the rim support the majority of the weight on the out side. this leaves the inner portion of the wheel (tire & rim) with little support.
b. The mode you drive in determines the electronic shock stiffness. SPORT mode is stiff (note the folks at school said the Stingray non elec dampening are set at the same as SPORT mode for dampening effects) Track mode is a noticeable amount stiffer. The stiffer the mode the less give in the suspension the more pressure put on the wheel. This is further compounded by a low profile tire. Result is - Track mode = highest probability of bending/cracking a rim.
c. If you hit a pot hole or curb or steep speed bump at speed you run a risk of bending or cracking a rim.

2. The best way to avoid a bent rim
a. Avoid pot holes, curbs or steep speed bumps.
b. Only use TRACK mode on a track! It's not a guarantee but it will lesson the stress on the wheel when driving on the street..
c. Make sure your tires are properly inflated. The wrong tire pressure will result in even more pressure on the inside of the rim.

Carvin

In another thread someone put up a screen shot of a book (manual?) that says Z51 wheels are forged.

GeoGS

Yes I seen it too while I was trying to find where I seen Tadge said all GS & Zs were flow formed.

GeoGS

Well I found one of the references where Tadge said you GS and Zs are flow formed. A cross between cast and forging . In part of Ask Tadge 05-18-2018 #73 Now I take it Flow Formed, is formed under pressure. But so is Rotary Forged. Are they same process? The pressures they use could be different. Forged I take it as Fully Forged. But here is Tage's answer from #73.

Conventional 5 lug nut wheels vs. forged center lock wheels
The original answer is here.

noel48

While under the car I noticed that the driver's front tire was worn to the cords on the inside.The other tires were ok.Car has 17k miles and tires are at correct pressure(30).When I went to replace the MPSS for the AS3 the tech showed where the passenger side wheels were both bent.Replacing with stock but curious as to the worn tire ( alignment?)

SuperdadZ06

I have a 19 Z06 with only 2200 miles and no problems I am aware of. I am curious if 19's have less problems than prior years or is it too soon to tell.

ukester

2016 w/5300 miles-no bent wheel but pitted. I have been told its because of snow/salt-brake dust-wheel cleaner. I have waxed this car more than I have driven it and to have tell me only on the phone its not there problem is insulting. Yes they made a offer of me paying 2500 and they will replace my wheels when you can buy a set for around 1500 does not sound like they are giving anything. After asking one question and that is will this problem come back again and there answer was yes...



Mark

golfbone

This cast vs forged issue has been asked and discussed many times in the past.....it is my understanding that the Z06 wheels are Cast aluminum.

https://www.corvetteforum.com/forums...or-forged.html

Not sure if the Z51 wheels are the same but pretty sure that we have on the Z06/GS is cast. Whatever it is it ain't working!

CW4L

These OEM wheels are simply put a disgrace to our C7s. Cheaply made cast wheels that are not made for the loads seen by our high HP applications coupled with runflat tires. We have also had ZR1 customers cracking wheels as well so its a problem for all these vehicles.

https://www.corvetteforum.com/forums...r1-wheels.html

Lots of guys dont even know their wheels are cracked till they are taken off and sure enough cracked.

If anyone needs help with wheels capable and worthy of our vettes we have some incredible wheels that are all forged in the USA using the best APP forgings. This isnt a sale thread so not gonna say anymore than that and you can reach me anytime.

Call/Text 440-915-6166

Zjoe6

Yes I knew about the z51 but I was referring to the z06 and GS. Post 34 explains that they are cast/flow-formed. Post 27 explains that process.