Can't say that I've ever cracked/broken a wheel on any of my track cars. I usually stick with OEM wheels tho, or fairly high dollar wheels like SSR Comps. I kept a close eye on the Kosei K1s on my E36 M3 but they were fine too...
Can't say that I've ever cracked/broken a wheel on any of my track cars. I usually stick with OEM wheels tho, or fairly high dollar wheels like SSR Comps. I kept a close eye on the Kosei K1s on my E36 M3 but they were fine too...
In reply to Keith Tanner :
They are rated at 1280 pounds per wheel which is more than enough for the car and aren't showing any signs of failure. CMP has a couple of curbs you need to cross to stay on the fasted line. The one at the kink comes to mind because I cross it at about 100 mph. That's a lot of load on the wheels so I keep a pretty close eye on them.
Those load ratings don't really take track use unto account. It's rated for steady state load, not the big transients you get on track. Keep an eye on them.
OEM wheels don't necessarily help. The 15" wheels that came on NB Miatas will crack with autox use. SSR Comps are more likely to bend - BTDT.
BTW, my mistake. I thought there was an NC and and ND failure recently. Turns out there were two sets of ND 6ULs that saw significant cracking and/or failure.
Definitely inspect them if you have them.
I haven't had any cracked wheels so far, or even seen a wheel break apart without some kind of impact (the lightest being an aggressive racetrack curb-smashing). And me and my buddies run cheapo wheels that aren't particularly light. Coincidence?
There was some rucus a few years back about Konig wheels failing similarly as I recall. Also It seems that new corvette Z06 wheels have problems as well.
Its not unique to 6UL or 949. Its a lightweight wheel thing. Any design pushing the performance is going to possibly fail eventually and some may fail prematurely.
A good company would be responsive, though I can understand being less than supportive of track failures (think about it, all they have is your word about curb pounding, etc). It also makes sense for the company to acquire the wheels for inspection to ensure that they have a handle on any potential quality issues (not that this is conclusive that they do).
I have seen a wheel fail from autocross and street only use that was fairly new and again, claimed no potholes/etc. It was a no-name chinese wheel and that happens.
The harder you use a car, the more you have to consider EVERYTHING a wear item. If you track it, inspect inspect inspect.
I think I'll do bassetts soon enough... Steel is real!
I'll also say, congrats to Flyin Miata. What I've learned from this thread is that they provide a CX I like to support. You don't have to be Amazon to take care of your customers.
Following. I'm not a metallurgist by any means, but I've encountered metal fatigue related failures before.
Do you think slight bending be resulting in work hardening on the wheels? I know aluminum aircraft parts have a specific hour rated lifespan due to this. Or is it more of a sudden impact?
Not a metallurgist either - but the cracks on the not-broken wheel would indicate a fatigue problem instead of an impact.
Streetwiseguy said:6UL. Bad double entendre.
IIRC, Emilio came up with the name as "6 U (shaped spokes), Lightweight." At one point, he'd considered releasing a "8U" or "9U" design as well.
Brett_Murphy said:Following. I'm not a metallurgist by any means, but I've encountered metal fatigue related failures before.
Do you think slight bending be resulting in work hardening on the wheels? I know aluminum aircraft parts have a specific hour rated lifespan due to this. Or is it more of a sudden impact?
Fatigue cracks don't necessarily mean work hardening or enough stretch to take a permanent set. You're looking at nearly infinitessimal bending that opens up a set of cracks in the material over time. Aluminum is especially prone to this, compared to steel or titanium.
Keith Tanner said:Those load ratings don't really take track use unto account. It's rated for steady state load, not the big transients you get on track. Keep an eye on them.
OEM wheels don't necessarily help. The 15" wheels that came on NB Miatas will crack with autox use. SSR Comps are more likely to bend - BTDT.
And FD R1 wheels would crack with street use.
At a local RX-7 meet, someone showed up with an FD with the original wheels that apparently had missed the recall. I mentioned that they were known for cracking. "What does it look like when that happens?" I looked down - the first one I looked at had one spoke cracked all the way through. Don't remember what the other ones looked like but I advised him to sit out the cruise portion of the meet...
Am I the only one surprised by the lack of body damage from a catastrophic wheel failure on track?
Definitely not saying it didn't happen, but I have seen commuter cars on the side of the interstate with mangled bumper covers and fenders from a blowout.
NoviceClass said:Am I the only one surprised by the lack of body damage from a catastrophic wheel failure on track?
Definitely not saying it didn't happen, but I have seen commuter cars on the side of the interstate with mangled bumper covers and fenders from a blowout.
Not really, a blowout causes a lot more fender damage than a wheel break/loss because often as the tire blows out, a road gator is born, whipping into the fender and bumper as it enters the world.
NoviceClass said:Am I the only one surprised by the lack of body damage from a catastrophic wheel failure on track?
Definitely not saying it didn't happen, but I have seen commuter cars on the side of the interstate with mangled bumper covers and fenders from a blowout.
25 years ago I lost a wheel on track, it was broken wheel studs, not a broken wheel. I got away with no body damage either. So no, it doesn't surprise me.
I suppose this is why good forged and forged 3-piece wheels start at $1200... I should probably inspect all my wheels now.
What I (arrogantly) think is:
How is there not a company that can make a lightweight wheel with a track warranty? It isn't that hard to make these things durable. Maybe I should go into business...
AWSX1686 said:I suppose this is why good forged and forged 3-piece wheels start at $1200... I should probably inspect all my wheels now.
I wouldn't bother with 3-piece wheels for a serious track car. They will be heavier than the equivalent forged 1 piece wheel. But yes, actual forged wheels are super expensive. $3k per set is about the cheapest I've seen them.
The flip side, is there are tons of people tracking on 6ULs, Konigs, TRM, etc, that don't have problems.
tuna55 said:What I (arrogantly) think is:
How is there not a company that can make a lightweight wheel with a track warranty? It isn't that hard to make these things durable. Maybe I should go into business...
Because most guys aren't going to pay HRE prices for wheels.
tuna55 said:What I (arrogantly) think is:
How is there not a company that can make a lightweight wheel with a track warranty? It isn't that hard to make these things durable. Maybe I should go into business...
I'm kind of surprised you don't know the answer: It's the "light/strong/cheap: pick two" problem. To make a light and strong wheel, the best way is to forge them from a solid billet, and for that you need a press about the size of a large bus (but standing on end). Understandably you have to charge more for all this equipment and energy and space to pay off. The next-best thing is the flow-forming process which is a bit cheaper, and then there's casting which is the cheapest. As strength goes down with these more affordable processes you have to add mass to the wheel to keep it together, if you skimp on the mass in an attempt to make a strong, cheap, light wheel and you might end up flying too close to the sun like with these 6ULs.
I don't think there's a lot of ripping-off going on in the world of wheel construction, and what ripping-off is going on is easily avoidable: there are plenty of companies charging reasonable prices for what it costs to make wheels for the size of the market they're selling to.
In reply to GameboyRMH :
right, right... but I R enginerd. I solve hard problems, it's the job. The last time I saw some wheel manufacturer determined to show off their engineering prowess, it made me swear off that company for good.
tuna55 said:In reply to GameboyRMH :
right, right... but I R enginerd. I solve hard problems, it's the job. The last time I saw some wheel manufacturer determined to show off their engineering prowess, it made me swear off that company for good.
You can engineer the wheel and contract someone to make them for you.
However, I suspect you'll be shocked at what it will cost to build a set of forged wheels that are light, well built, and ATTRACTIVE to the consumer.
I seem to remember Carrol Smith saying in one of his books that they did Non-Destructive Testing on wheels regularly. Like Mag particle, x-0ray or ultra-sound, like what is done for welding inspection.
It would be interesting to know the root cause of failure of these wheels. It could be something as simple as an improper radius of the transition at the spokes causing local stress risers leading to cracks. Could be heat treating or stress relieving issues.
Just because metal "X" has a certain yield strength doesn't mean that the way you put it together will give you the full benefit of that yield strength. And a lot of metals are not forgiving like steel. Steel will plastically deform (bend) and stretch a lot before the final fracture; some metals just fracture when past their elastic limit with little plastic deformation to warn you of impending doom.
And if labled "not for motorsports" the manufacturer is saying the factor of safety is lower and this saves on material and inspection costs.
Hey, a whole thread about the awful fatigue properties of aluminum!
After about 1,000,000 cycles magnesium alloys (example AZ91) are stronger than aluminum (example 356). A wheel turns almost 1000 times per mile. If you want a light durable wheel cast it from magnesium and make sure it doesn't corrode...
You don't have to exceed the yield strength of a material to fail under high cycle fatigue.
Aluminum does not have an infinite life like ferrous metals. Given enough cycles, an aluminum component WILL fail under cyclic loading.
1500 track miles is going to be alot more than 5x10^8 cycles.
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