REDHOTS

A customer brought me a 02 rear tire with a leak. It was pretty obvious right away the wheel was cracked. How come GM isn't taking care of these??? It is the 3rd one I've seen.

Evil-Twin

OEM wheels are not bullet proof... a road hazard impact that is bad enough can cause this issue. If thin spokes were defective, you would see more problems. All wheels are susceptible to damage. A hard enough impact ( deep pot hole , or road hazard can cause a slow deterioration of the integrity of a wheel ) . These cars are old. Even a poorly operated tire changer could cause the start of internal stress , that after many miles , turn into a crack..

when a wheel become slightly out of round, as it turns supporting the weight of the car, this area is flexed back an forth until internal stress turns into failure.. think about bending a piece of metal back and forth, and then it breaks.

OEM wheels are strong by design and have to be certified by the manufacturer. Standards are design by GM and the manufacturer has to submit certs to show that aggressive statistical process control ( SPC ) ( quality control ) is met. GM monitors these certs to insure a quality control trail and to keep the manufacturer honest.

This is my wheelhouse... that why I cringe when I see people asking about cheap wheels... the cost of quality is very expensive, When many Chinese companies do not have any quality control measure, and are not held to any standards at all. Remove quality control from a wheel and the profit increases dramatically. Cost of quality is about 1/3 the total cost of manufacture of the product.

Corvettes are, in many cases pushed harder than other cars... the condition of some streets and highways are not favorable to aggressive driving. We have all hit unsuspected road hazards, pot holes, run over things we should have avoided etc. Even the side wall of the tire ( aspect ratio ) plays a big part in the compression and impact of the wheel. These 20 and 25 aspect ratio tires might look cool, but they are a wheel disaster waiting to happen, on a public street. They are fine on a race course where the surface is properly maintained.

Just some feedback on how and why wheels can crack, and the chance you take with cheap wheels.

Bill aka ET

4XLR8N

While it does seem that the thin spoke design may be more susceptible to cracking than other designs in the real world of driving on crap roads, I'm pretty sure the failure rate itself is pretty low.

I will agree with ET 100% on his comments about OEM quality in wheel design/engineering/construction vs. cheap aftermarket wheels. I will throw brakes into the same category. Two areas where I NEVER try to go cheap to save a buck. Doesn't mean you gotta spend a million bucks, but "you get what you pay for" certainly applies here.

jim993

I run OEM thin spoke wheels. My first set came with the car but the rim edge was bent on both right wheels from some sort of impact when I got the car. They ran true and did not leak, so I ran them on the track for several years.

Then I hit a curb on the track and bent both left side wheels and decided to replace all four with used straight OEM thin spoke wheels.

That was a couple of years and six track days ago. No cracks in any of the eight wheels so far.

jackthelad

There have been occasional pictures of OEM C5 thin spoke wheels with cracks for many years now. Not knowing whether they have been subject to impact loads, and never having seen any analysis, I suspect no-one really knows a specific cause - if there IS a common cause. Never seen pics of cracked wagon wheels, though....those things are tough.

But that crack (above) looks horribly like the sort of thing I have seen when stress relieving has not been done properly. If it was impact caused, you would expect to see significant rim damage.

Jeff T.

I'll bet your customer wasn't happy...

I remember a thread where someone posted a video of knockoff wheels being tested in the UK I believe. Quite eye opening to be sure.

S.C. vette

... nothing lasts forever, considering the age of our OEM wheels, it's rather surprising this does not occur more often.

REDHOTS

Sorry, but I can't agree with most of what you said in regards to C5 thin spoke wheels. I've worked on thousands of wheels and tires. Why is it that this is the only wheel I've seen do this? I have seen plenty of bent wheels, usually on the back side, with even lower profile tires, but never a crack on the face of a rear wheel. The front wheel hits the same pot hole.

S.C. vette

Sorry redhots, I've owned 6 Vettes thru the past 40 yrs, have lost 5 mags to cracks like this. It's the price we pay to play.

Vetteman Jack

Over the years I too have seen posts here on the forum about cracked thin spokes. The numbers haven't been excessive that I can recall and many times the potential cause of the crack was not really determined.

Evil-Twin

I will only say that you are certainly entitled to your opinion. Ive seen results of fatigue on wheels using GM's Tinious Olsen stress machine . It set the standards for wheel certifications. Testing is done to failure. There is such a wide range of wheel characteristic that are effected. Tested in both destructive and non-destructive characteristics.
I wont argue the point and concede to your opinion... Only that an unknown pot hole when struck with a front wheel will cause immediate braking to reduce total impact which is transmitted to the back wheel at less than half the force. front tires are 4 time more susceptible to damage with unknown road hazard impacts then rear tires. Some times a rear tire will not tack to the same spot because of driver correction.

Choreo

What are the markings on the back of the wheel - were they Speedlines? Just curious as I ran the same set of GM Speedline Thinspokes -Made in Italy (which I had chromed) for 14 years everyday with no issues. I had the chance to buy a new set of identical chrome Speedlines a couple years ago, so I jumped on them (they are my favorite style wheel on the C5) and I kept the 14 year old set as backups since they still looked like new.

Since the Corvette is rear wheel drive and the diameter of the rear wheels is greater, I would assume they would see far more torsional stress? The front spokes are not trying to tear themselves away from the barrels every time you take off!

REDHOTS

Tested, certified, doesn't mean much with these wheels, when they crack in the strongest part of the whole rim area. There is NO sign of any impact damage at all anywhere on the back, front, part of the wheel or tire. I would also expect to see a radial crack and the rear barrel out of round with impact damage. This car is not driven hard either. It just cracked backing out of the garage.

leadfoot4

I'm pretty sure that I posted it, just did a search, but can't find it......

Mag_Red

I never hit a bad pothole or other obstruction. I bought my 2001 Vette new and one morning I went to my garage to take the vette out and had a flat rear wheel. I put air in and checked the tire but no visible signs of leak. I waited 30 minutes and the tire lost 12 lbs of air and so I took it off the car and after putting air in I dipped it into a tub of water and behold I had a 2 inch crack st the spoke. This was in 2006 and after calls to my dealer and GM had no reasonable solution. I replaced them and also found 31 other cases of cracked OEM rims.

Evil-Twin

Please don't try to use your logic. Metal fatique occurs internally, that's why its called internal stress, a cross section has to be taken after destructive testing to see if the metal was fatigue or a clean impact break.. WE at GFM know ( and have the resources, millions of dollars worth or R&D testing equipment ) how to measure internal structure, molecular stress. Some guy at a tire shop has no clue as to how or why a failure occurred without sophisticated testing equipment and data collection. How many wheels have you Zyglow-ed? Do you have a degree in metallurgy and destructive and non destructive testing?

IM not trying to argue with you, but some street racer or shade tree mechanic can not compete with GM and their resources in research and development. Our wind tunnel is used ( rented ) to manufactures because it is state of the art. WE rent it out at 1200 dollars an hour, minimum of 16 hours. People here have no clue how we can take a clean piece of paper and in two years design and test and manufacture 6000 parts to create something like a C5. I started on the C5 project with hundreds of colleagues in 1995 with a clean sheet of paper and a vision from a real car guy. Two years later, history was made.

REDHOTS

Whatever. Since everything GM ever designed, and tested, is perfect, someone should have spent a little more time on design and testing these wheels. You don't need to be a genius to see that a crack like this should not happen period. Yes, there is a tremendous amount of force on the face of these wheels with the 9 inch open barrel/high offset trying to bend the spokes.

Evil-Twin

Just to show your lack of knowledge... offsets are designed in for a specific load on the bearings. ( its why I am adamant about not using spacers ) Since the bottom line is the focus, project mangers control the process. (Time management and budget management ) there is no longer bearings that can take a 1500 lb corner load, because a 900 lb corner load will work on a stock C5. the difference in cost between the two, brings up the bottom line or lowers it. Most structural load aspects are 10 % above actual design specs. but no more. Its not 19 60 anymore where off the shelf specs from Timken are used.

Most people have no clue about how a car is built and what are the parameters of the design. I had a design revision turned down because it added 7 cents to the bottom line of each unit, multiply that by a quarter million units and it all adds up. . it was shot down as a revision because when submitted it did not reduce weight or the cost to manufacture. Keeping a 2 year project within budget and on time is a monumental task that very few people understand. (Hats off to GM Project managers ) You are obviously one of them. The budget for wheels does not preclude that they will be bullet proof for life, but that they pass a 200,000 mile testing process. Certification are sent monthly to GM from 2nd and third tier manufacturers to make sure that the process stays within GM guidelines. WE have a paper trail of quality control and a trail to keep the manufacturer honest and to oversee any deviation .

Usually when someone like you is back peddling, they throw in things like , they should be perfect, like some sort of a tongue in cheek slap in the face to us engineers. The reality is, comments like that show just how clueless you are... if C5 was perfect it would cost 3 X as much and even then it would not be perfect. Cost of quality on a Corvette is 1/3 the total cost to manufacture.

The first three things in a design project.. the demographic ( who is our target consumer ) then the next thing is the budget, ( cost to build ) and then the time. time to build and design and the money allotted to do that is not open ended. If you can't see what I am trying to show you from an insider's point of view.. you are blind. WE also had to design in a no gas guzzler tax build, plastic every where because of the specific gravity. not because it was cheap. All the clueless complain about the plastic but don't understand a metal part is heavier and costlier. That's why the gas guzzler tax and the push to reduce weight were a priority.

I could spend hours here talking about bathroom talks with Dave Hill about concept and reality. Arguments over value and quality... things that never made it into any book. I could write a book on all the thing that never made it into the design. People here talk about a C5 design as if they knew something about it. then tomorrow they go to their home depot job, or their surgical assignments as a doctor. I see bankers and lawyers and dry wall contractor here all playing engineer and saying what is wrong with this car, instead of all that is right with it... There are Not too many car designs out there where people embrace an 18 year old car as much as this one.

derz_vette

Dunno about the thin spoke design... but I have some CCW 505 and they are pretty tough.. I smacked one on a curb pretty good and it didn't break My subframe and radiator didn't do very well though..... wups.

nottofast

Love this thread. Very interesting opinions. Just got my 1998 Coupe about 10 days ago and found the drivers side front wagon wheel with a crack in it. No real theory on why, maybe an impact? I was wondering if anyone has concerns over EMT tires not being able to absorb pot holes and road irregularities as much as a standard performance tire? It must transfer much more of the point impacts to the wheels?