6UL wheels still cracking...
 

A facebook user posted pics of his 6UL wheel breaking on track on Sept. 1 2019. That's 7 years after the issue was first reported to 949/Emilio. Check your wheels.

Newsflash: wheels used regularly on track will crack. You should regularly inspect your track wheels, and 6ULs are not unique in this regard. Early 6ULs were more prone to this, but later generations have been performing within expected parameters.

EDIT: Since the OP couldn't be bothered to link anything, here is the m.net thread:

https://forum.miata.net/vb/showthread.php?t=701617

Owner has a legit gripe IMO, wheels should last through several sets of tires barring abuse. Important to note that these are the 17" wheels, not the 15" wheels that had the issues 7 years ago. As far as I'm aware 3rd and 4th gen 15" wheels have been lasting as long as would be expected. Looks like there may need to be some changes to the 17" wheels.

Are people dye checking them?

That's how i check my props for cracks i can't see.

"Wheels are a wear item" bla bla bla
My experience, and that of many I know, is that other wheels last much longer than 6ULs. My second gen 6UL's made it through about 10 HPDE track days - with no curb impacts, running street tires - before cracking. I was told to pound sand when I voiced my concern, like pretty much everyone else. 949 may make some good stuff, and I'm glad for their contribution to the community, but I stay away from 6ULs because I cant afford to replace them every season and their service if something breaks is awful. The only reason I felt comfortable buying XIDAS was because they're made by Tractive.

Totally unscientific as well, but put "miata wheels cracked 6ul" in google and see how many more people have issues with this wheel than anything else - TRM, Advanti storm, etc. have almost nothing, while there are pages of people with cracked 6UL's. One recent thread suggests a serious design flaw in the current 17x9 6UL, as 3 separate customers in that thread alone had 3-4 of their wheels cracking in the same spot.

A Miata is a car that weighs 1/2 of some other track day cars. We don't see a 7 year track record of cracks and catastrophic failures for other brands. At least Emilio is consistent about offering excuses.

Wheels are a wear item. You should change your 6ul wheels every time you change tires.

Your miata is a wear item. Replace it every 3000 miles.

Be careful out there.

Saw the pictures on FB, it’s gnarly couldn’t just imagine going at speed and literally have the whole wheel fall off, I think 949 should take a step back and reassess how they are making their wheels.

That's laughable. I really hope that was a joke(kinda hard to tell sarcasm from text). I have 15 year old Kazera wheels on my track Miata and they haven't failed.

There's really only two possibilities, either it's a design flaw or it's a manufacturing (metallurgical) issue. Either way, 949 is liable.

Chinese wheels will be chinese wheels, man.

They way some of you guys act I’m suprised were not throwing miatas away ever season...

I dunno about you guys but I throw all my knowledge out and start over in DE1 every season. Brains are a wear item.

If you are running 6UL's you just might need a new brain after the wheel fails and you crash.

BTW, more broken and cracked 6UL's are being posted on facebook. Repeat after me, consumables, and drink the 949 Kool Aid

Hard to tell how many are just regurgitated 15"s from 5+ years ago.

Some might be older cases but some were just a few weeks ago. If you feel lucky roll the dice.

The 15s seemed to have an issue that was fixed, right? I'm unaware of the latest-gen 15" 6ul's having this mode of failure (correct me if wrong) Does seem odd they didn't apply that fix to the 17" version.

I'm not aware of all the sizes involved. There is a thread on miata.net. Seems it involves at least two wheel sizes that are different product lines. Here's what I've noticed, the wheels all crack in approximately the same area. This suggests to me that it could be a design issue. Questions that need to be answered is who designed the wheels and what were the design specs? The next question is whether the manufacturer is actually producing them to the material specs.

Just play it safe and replace your wheels with your tires. Simple, forehead.

i'll stick to my konigs.. thanks.

Stupid answer, period. That would mean every weekend for some users and every couple months for others. This "consumables" BS is beyond stupid.

i initially saw it on a thread on somethingawful, and then i decided to see what was out there on mnet and facebook

the dude who's going scorched earth uses a lot of interesting sentence constructions that totally doesn't make it seem like he's trying to hide something

Just to clarify, Keith from FM has responded and stated that the failures spread beyond a single wheel. They are multiple different wheel lines by different manufacturing facilities over an extended time period. Someone else also confirmed that there was a production change to the 15 inch wheels but the reason for that is not known. Maybe it was an attempt to correct an issue maybe it was just a random change.

To clarify:
There are four generations of 15" that have distinct design changes and were built with different manufacturing techniques. We know there was a problem with the 15" Gen 2. I'm not aware of problems with the current 15" Gen 4.

The 17" NC and ND wheels are built on different tooling and designed to different load ratings. The one that I'm particularly interested in is the 17" ND wheel. If you personally have inspected a set of your own and found cracks, please drop me a line so I can get a clear idea of how many are experiencing problems.

Right now, there are at least three different basic wheel designs for 6ULs: 15", NC 17" and ND 17". They all look alike but they vary enough to be considered different wheels when looking at failures. I don't know enough about the manufacturing of the 15s to know if the different widths of 15 should be treated differently in that regard.

Emilio obviously frequents the forum, I would be interested to hear his side of the story. Whether or not his wheels have a design flaw, sounds like one (or more) of his customers could use a hug right now. Unfortunately this whole internet thing makes it easy for one or two upset customers to rally the torch/pitchfork crowd. I’ve been using Konig and Advanti wheels with no issues, but it’s mostly because I couldn’t justify the price difference for the 6UL’s.

I'll have another data point soon. I have a track day at VIR coming up, and plan to get a lot of hours on my gen 2's.

gen 2 what? 15"? 17"? 17" with 4 lug?

6 uls, 15x9

Two of my 15x8 Gen 1 6ULs finally developed cracks in the spokes just a couple of months ago. I believe I purchased them in 2009 and drove the crap outta them on track when I was new to HPDE, and more recently as my no tire/brake change option. I have two non-cracked 15x9 Gen 2s that I retired after one season, lost somewhere in the garage. The other two were taken to the dump.

No aluminum wheel is immune. I felt that the Advanti S1 fatigued a bit too early at around 8 sets of tires. But it cracked in a very safe manner, so no real complaints. The 6UL failure mode in the pictures is gnarly. I've also seen several of the Team Dynamics SM wheels (i.e., built heavy) fail in exactly the same way. So . . . .

Pictures of how the S1 cracks:

https://www.miataturbo.net/wheels-ti...parison-95534/

Any idea how to tell the difference between the NC & ND 17"s? Is it just 4 bolt vs 5 bolt?

Asking because I have a set of "S2000" 17" 6ULs on my FD... :)

--Ian

RIP in peace.

What do the "I" and "P" mean?

RIP in pepperonis my friend.

I have a set of 15x9 S1s. I swore to myself I would never buy another wheel with spokes that stick out past the edge of the rim.

I've seen some pics posted to facebook of severely failed 6UL's. I'm not sure of exactly what sizes were involved and I don't know exactly why they failed. Regardless, it should be taken seriously by everyone as a few people are probably very lucky that they weren't seriously injured or killed. Go ahead and roast me if that makes you feel manly. But this isn't an issue for a stand up comedy routine.

That seems like a dumb design for a track type wheel.
I've seen one pic of a failed Team Dynamics and it was as bad as the 6UL pics. Has there been issues with the latest versions of that wheel?

Seems dumb unless the wheel is meant only for track. Unless the purpose is to avoid curb rash on the rim...

...by moving the rash to the spokes. :rolleyes:

Or to give adequate room for bbk's and maintain a decent amount of material in the spokes with a crummy offset.

In W2W the contact with other cars can be catastrophic to spokes if they stick out.

Strange that an advertiser and responsible person for these is completely absent. No response.

I'm 900% positive he has seen the threads all over the internet, facebook, and now here.

Kinda makes it seem like he doesnt care at all doesnt it.

Guys, failures happens on track cars, not much you can hope from the supplier... I can understand why they don't reply to this type of forum threads. Maybe they are working on something with there own cast supplier, maybe not.

If the failures would happen on road cars and causing injuries and what not, it would be a different scenario.

At least people are aware and can make their own decisions when it comes to buying a new set of wheels.

On miata.net on the 6UL ND wheel thread, page 10, someone does math analysis of the 6UL and points out a design flaw. I'm not a math whiz and don't understand the math but he uses the term "infinitesimal stress factor" to show the wheel is poorly engineered. If he's right that's a game changer from a legal and ethical standpoint.

Post a link

I found what he was referencing, post #246.

https://forum.miata.net/vb/showthrea...701617&page=10

The guy posted some equations. He did not do any analysis that points out a design flaw and he did not show the wheel is poorly engineered. They guy posted a few equations for calculating fatigue life.

A lot of assumptions would have to be made regarding loading before any calculations could begin. Choosing what loads to design for would be quite a difficult task. Go too far towards safety and you end up with a wheel nobody wants. Customers want cheap and light weight and good looks.

If his wheels are failing more than they should, then most likely one or more of his assumptions was off and worst case loading is higher than expected thus shortening the life of the wheel. I think it sucks if this happened but it's a pretty complex problem to solve, and if people want cheap and light you can't have super high safety factors on your product.

"Fatigue Life" and Aluminum do not go together, unless there has been some recent breakthrough.

Posts 30583 and 30584 shows where 949 has addressed the subject.

Here is a copy of the email:

Except, that by labeling his wheel as a "consumable", Emilio has asserted his wheel has a finite lifespan. That means that the failure would be stress induced. It obviously won't fail under static conditions. So I don't see how Miko71's assertion is wrong.

This. You can engineer steel wheels that remain below an endurance limit (ever wonder why taxis and cop cars use steel wheels?). You can't do this with aluminum wheels. Check 'em.

https://www.amesweb.info/Materials/M...ty-Metals.aspx

That chart shows various aluminum alloys as having roughly 1/3 the elasticity as compared to steel. Aluminum is therefore more brittle than steel.

https://www.amesweb.info/Materials/M...ty-Metals.aspx

Seems aluminum does have a fatigue life but has no fatigue limit.

Tire Rack article on checking your wheels for track use.

https://m.tirerack.com/tires/tiretec...jsp?techid=110

How come super lightweight steel wheels arent a thing? If its stronger than aluminium alloys then whats to stop someone from just designing a thin spoke steel wheel design that was really light weight. Can someone help me understand?

It's not a 1-to-1 relationship. Steel is 2.5x denser than aluminum, but it's not 2.5x stronger. You could design a steel wheel that is exactly as strong as an aluminum wheel, and it would be thinner, but because of the density of the material, it would still be heavier.

Pretty much.

the same as how many people are shocked to find out that titanium is heavier than aluminium. (roughly 60% denser from a brief google)
But since it's about double the strength, you can use much less of it for the same strength as alu



From memory Magnesium (or at least, an alloy containing it) is another fairly strong, yet lightweight, material used for wheels.
But I remember it being fairly brittle, and cracking more readily than alu (plus the whole reaction to water thing once it ignites)

Magnesium is used because it's stiffer AFAIK. Back in the day all of my karting wheels were magnesium for that reason. The new hotness for wheels is carbon fiber, not because it's dramatically lighter, but because it can be made much stiffer. Wheels move A LOT under normal use. At the spokes, up to 2mm of flex under normal operation. At the inner bell of the wheel, a lot more than that. That flex degrades tire performance.

I have no dog in this fight, but there is a lot of trash engineering speculation going on in this thread.

We keep talking about “aluminum”, but there are lots of different aluminum alloys, and we have no idea which alloy these wheels are. I would speculate that they are 6061, but there are even different variations of 6061. The mechanical properties of the different alloys vary dramatically.

Aluminum doesn’t have less “elasticity” than steel. It has a lower elastic modulus, which means that a similar size/shape object will be less stiff if it is made from aluminum.

The failures being discussed are fatigue failures, not static failures. This makes things like elastic modulus almost irrelevant.

There are two steps to fatigue failure, crack formation and crack propagation. Aluminum is more notch sensitive than steel, meaning that a small scratch or defect can generate a fatigue fracture more easily. Unless there’s a sharp step or corner designed into the wheel where the cracks are starting, there is probably not a design defect per se. The recommendation to inspect wheels frequently is good advice.

The most important characteristic with regard to fatigue is how cracks propagate through the crystal lattice of the metal. As Sav pointed out, all aluminum alloys are inferior to steel in this regard, because cracks propagate more easily. Steel has a way of partially “healing” these cracks, where aluminum does not. Therefore steel has a finite fatigue limit, where aluminum does not.

https://en.m.wikipedia.org/wiki/Fatigue_limit

None of this is unique to 6UL’s, every manufacturer has to wrestle with these inherent properties and design accordingly. The “fix all” for these problems is to make the heaviest smoothest wheels possible, which none of us would probably buy.

Small differences in wheel design can make big differences in stresses. For instance, a 15x9 wheel is going to apply a lot more stress to the spokes than a 15x8 wheel because the inside edge of the barrel is a cantilever, and the stress on the spokes goes up exponentially with the length of the cantilever.

Manufacturing methods play a critical role in fatigue properties. Good wheels are forged or cold formed because it work hardens them, which basically means that the crystal lattice gets all tangled up and the material gets stiffer. If the work hardening is not evenly distributed then the stresses won’t be properly distributed either, which could lead to point stresses and crack initiation. I am in no way implying that there is an obvious issue with 6UL’s, but I would guess that there are substantial differences in how different wheels are made, and that differences here could be important to fatigue life. OEM auto manufacturers have teams of PhD’s that do things like forging and mold flow analysis.

Berrylium is the true baller metal.

i got an equation for you

F = m*a

checkmate