Are wheels a wear item? Yes, they are.

Staff
By Staff Writer
Apr 20, 2022 | Sponsored Content, wheels, König | Posted in Tires & Wheels , Safety , Features | Never miss an article

Sponsored article presented by König Wheels.

 

Wheels are a wear item. The trick, though: Knowing when to pull one from service so a little problem doesn’t become a big problem.

A wheel does have a lifespan, and unfortunately it’s not clocked on a mile basis,” explains Scott Weiss, marketing director at König Wheels. “It can last 10 seconds to an infinite amount of time.”

Wheels as Wear Items

“Wheels are metal,” Weiss continues. “They’re not magic.”

No matter the construction technique, a wheel in use continuously encounters stresses. Every acceleration, every braking, every turn and every bump adds up to a nonstop barrage of forces. 

Then add in the forces encountered every time tires are mounted and dismounted, plus each time the wheels are bolted and unbolted from the hub.

“Those little impacts continuously work that metal,” Weiss continues. “Then a Big Bang will send it over the edge.”

And that Big Bang can cause a major wheel failure–and often leave a bewildered driver. Did one impact just knock a wheel out of contention? Likely, Weiss explains, it might have been a death from a thousand cuts. 

What Stresses Wheels?

Then add in the additional stresses found in motorsports. 

Sticky tires? Additional stress.

High g-load turns? Additional stress. 

Fast pitstops involving impact tools? Additional stress.

Banging over curbs in order to tighten a turn? Additional stress. 

Lower profile tires that minimize the cushion from road hazards? Additional stress.

“When tracking the car, be conscious that you’re working your wheels really hard,” Weiss says, adding that the load ratings assigned to each wheel are based on a static car. They don’t take into account hanging two wheels in the air. Or curb checking. Or contact with another car. 

For a perfect storm, Weiss says, picture the leverage exerted by a tall, sticky slick fitted to a smaller wheel on a powerful drag tire. When the light turns green, the wheels are placed under enormous stress.

How to Inspect Wheels?

“What are you doing to inspect this wheel?” Weiss asks, adding a big take-home message: Be aware that wheels are a wear item–especially when subjected to severe use–and develop some kind of inspection schedule. 


That schedule can be rather simple, he continues. For a street car, periodically look over the wheels–say whenever you’re stopping for gas.

Any curb rash? Do the lips look misshapen? Regularly look for obvious signs that hints towards a big impact. 

Do you have a second set of wheels and tires for autocross or track events? Take a few minutes to clean and inspect the wheels–front and back–when swapping over.


Photography Credit: Christina Lam

Make that inspection part of the routine. Give the wheels a good wash and take a few minutes for a full visual look-over.

Methodically inspect the entire wheel: lips, barrel, spokes and center section. Are any little cracks manifesting? Do the lug seats still look fresh? 


Are you road racing, running stage rallies or tracking a car with a lot of aero? Those situations can put even more stress on the wheel, so maybe perform even deeper inspections on a tighter timeline–again, Weiss stresses, make it part of a routine. The goal, as before, is to spot small issues before they become big ones. 

Did you have a big off lately, perhaps one that dragged the wheels sideways across the infield? Rub wheels against those from another car while going side to side? Encounter a rougher than usual rally stage? Again, inspect the wheels–and this time, ideally, do it as soon as possible. 

Two relatively easy ways to make a deeper inspection: DIY crack testing can be done at home with a dye penetrant kit, while a bare wheel can always be checked on a balancer. The unmounted wheels likely won’t spec out to zero, Weiss notes, but if it’s calling for a lot of weight, you might have a problem that warrants further inspection.

“Don’t treat them as a set-it-and-forget-it-type of part,” Weiss says of wheels. Be conscious of their use and keep a regular eye on them. 

 

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Comments
jharry3
jharry3 GRM+ Memberand HalfDork
6/25/20 9:16 a.m.

Metals have a fatigue life.  Within a certain band of negative/positive stress (compression/tension) it can  have infinite fatigue life. 

Get out of that zone then you start counting stress cycles. 

The greater the stress per cycle the fewer cycles the metal will last before cracking.

  We have all probably read about metal fatigue being the root cause of some airplane crashes. 

The compromises of weight vs strength for wheels, especially wheels used in racing,  put them into the stress zone where fatigue life is used up and they must be changed.   

Makes you think about the wisdom of buying used wheels from an upper level  racing team.

ShinnyGroove (Forum Supporter)
ShinnyGroove (Forum Supporter) Reader
6/25/20 9:48 a.m.

^ interestingly, aluminum does not have an infinite fatigue life, no matter how low the stress.

From Wikipedia, a chart comparing S-N curves for steel vs. aluminum:

You can see that steel has an endurance limit.  Below this amount of stress, you can cycle steel infinitely without a fatigue failure.  By comparison, aluminum has no such limit.  In theory, if you cycled aluminum with 5 lbs of force for an infinite amount of time, it will eventually fracture.  Design also plays a critical role in fatigue life.  The point being- those lightweight aluminum racing wheels we all love are more prone to fatigue failure than steel wheels or heavily built wheels, and should definitely be inspected frequently.

Colin Wood
Colin Wood Associate Editor
6/25/20 9:50 a.m.

I'll be honest, I really take my wheels on my Fit for granted.

I think I'm going to give them a good look-over when I get home today.

David S. Wallens
David S. Wallens Editorial Director
6/25/20 10:19 a.m.

In reply to jharry3 :

Yup, metals have a fatigue life. My favorite line in that piece:

“Wheels are metal,” Weiss continues. “They’re not magic.”

Tom1200
Tom1200 Dork
6/25/20 11:30 a.m.

I have two sets of wheels for the Datsun, both are 13"x6", the Hotwires are 13lbs and the CSS (Shelby) are 12.5 per wheel. I could save 2-3lbs per wheel by going to something lighter but I know that I pound the kerbs mercilessly so I stick with the wheels I have. 

I've seen people bend the lighter wheels by taking a lot of kerb, they only discover it because the car picked up a vibration.

On the used racing wheel front; I once got offered a set of magnesium wheels for super cheap and  I politely declined.

Amazingly I've only ever seen one person with wheel failure trackside; that came from the wheel not seating properly on the hub. The wheel cracked and plucked the center right out of the rim. The remaining part of the rim was still firmly attached to the car......scary stuff kiddies.

wearymicrobe
wearymicrobe UberDork
6/25/20 12:06 p.m.

I know of at least one person who uses dye penetrant testing around the holes in three piece wheels. Its semi cheap cheerful and easy to use. 

some_guy79
some_guy79 New Reader
6/25/20 12:21 p.m.

In reply to ShinnyGroove (Forum Supporter) :

Good info for understanding the trends in fatige life. I hope people reading your post realize that these two curves really only represent one material spec each.

Different alloys, different heat treatments, different levels of cold-working, chemical exposure, heat cycles will have an effect on fatige life.

Not all steels will have a 29 ksi endurance strength, and cycles to failure may be different than the pot given here.

The cycles to failure are not deterministic, but typically given with a probability of failure. Stuff can break earlier or later than the graph might lead you to believe.

wspohn
wspohn Dork
6/25/20 12:37 p.m.

Interesting graph.

I raced with 5 year old steel rims for a bit - until I ripped the centre right out of one (centre remained tightly bolted to the hub).  Switched to mag alloy wheels and no issues - still running when probably 40 years old (but that graph would make me leery if I still owned the car with the wheels). Now run (stronger) steel wheels (no options - OEM peg drive knock offs with alloy substitutes unavailable).  

BlindPirate
BlindPirate Reader
6/25/20 5:53 p.m.

There was a popular Miata wheel that was cracking earlier this year. The vendor stated they were a wear item. Internet unhappiness followed.

jwagner (Forum Supporter)
jwagner (Forum Supporter) Reader
6/25/20 7:10 p.m.

I've been wondering for a while if a lug with a spinning seat (not mentioning brand names) would be easier on the wheels.

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