Are Wheels a Wear Item? Yes, They Are

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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jharry3
jharry3 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.

john hess
john hess
6/25/20 8:47 p.m.

Question: So, I have had a bad vibration in the steering wheel from about 55 mph and up since I bought a 1978 Fiat spider 35 years ago.  After 3 sets of wheels, numerous alignments, tightening all the bushings and replacing them and tightening the steering box on the right side, at least three sets of tires, Pirreli and Bridgstone, I still have the shimmy. Tightening the steering box helped the most.  For the last 25 years I have had a set of wire wheels on my Fiat.  The other day a fella jacked up my car and spun the front wheels. He measured the run out at .060 max., not at the edge of the wheel but on the inside of the outer lip.   Do any of you fine, knowledgable people know if .060 is good or really bad?

ShinnyGroove (Forum Supporter)
ShinnyGroove (Forum Supporter) Reader
6/26/20 9:28 p.m.

I'm not a wheel expert, but 60 thousands of runout sounds like a lot to me for a heavy rotating object. That's 1.5mm. 

OldGray320i (Forum Supporter)
OldGray320i (Forum Supporter) Dork
6/26/20 9:37 p.m.
BlindPirate said:

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

Yea verily,  with much wailing and gnashing of teeth.

 

ProDarwin
ProDarwin UltimaDork
6/26/20 9:44 p.m.
some_guy79 said:

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.

All of this is true.  Might be easier just to remove the Y axis and graph them separately to demonstrate the concept.

Also, if just demonstrating the concept, it would probably be better to call that blue line 'Ferrous' and red line 'Non-Ferrous'

drock25too
drock25too New Reader
6/26/20 10:28 p.m.
john hess said:

Question: So, I have had a bad vibration in the steering wheel from about 55 mph and up since I bought a 1978 Fiat spider 35 years ago.  After 3 sets of wheels, numerous alignments, tightening all the bushings and replacing them and tightening the steering box on the right side, at least three sets of tires, Pirreli and Bridgstone, I still have the shimmy. Tightening the steering box helped the most.  For the last 25 years I have had a set of wire wheels on my Fiat.  The other day a fella jacked up my car and spun the front wheels. He measured the run out at .060 max., not at the edge of the wheel but on the inside of the outer lip.   Do any of you fine, knowledgable people know if .060 is good or really bad?

That is very excessive runout. The runout on the brake rotor is only a max of .0059, and you have ten times that on the wheel. If you have gone through three sets of wheels, you may have a bent or damaged hub. 

 

Raze (Forum Supporter)
Raze (Forum Supporter) UltraDork
6/27/20 7:39 a.m.

Good article, I mean I know metal fatigues but honestly I don't think about it for my wheels, which is a mistake I'm happy to remedy, so thank you

john hess
john hess New Reader
6/27/20 2:08 p.m.

In reply to drock25too :

ThankShinny Groove and drock25too.  I have been eyeing a new set of Cromadorawheels, well similar to because they are 15 inch, not 13 inch like the originals  The hubs have been repacked several times, so i wouldthinkfolks wouldcheck that out but I havebeen thniking that too.                                           

MrFancypants
MrFancypants Reader
6/27/20 5:25 p.m.

I have Hypergrams like in the picture above. I hope that's not a bad sign for me. Mine are bronze though, so I'm sure I'll be fine.

Dusterbd13-michael (Forum Supporter)
Dusterbd13-michael (Forum Supporter) MegaDork
6/27/20 5:56 p.m.

I have found more cracked track only wheels than i care to admit to. Generally find the crack on the backside of the wheel where the spokes meet the rim. I check wheels EVERY time they are off. Even the street cars. Never cracked a street car wheel without severe impact though. 

drock25too
drock25too New Reader
6/27/20 6:25 p.m.
john hess said:

In reply to drock25too :

ThankShinny Groove and drock25too.  I have been eyeing a new set of Cromadorawheels, well similar to because they are 15 inch, not 13 inch like the originals  The hubs have been repacked several times, so i wouldthinkfolks wouldcheck that out but I havebeen thniking that too.                                           

If your not looking for it, it would be hard to see. have them pull the tire and brake rotor off and check the runout on just the hub. 

flatlander937
flatlander937 HalfDork
6/28/20 12:20 p.m.

I have a dial indicator that resides on my wheel balancer for checking bare wheel run-out/bent wheels and marking high/low spots on the rim to minimize total run-out as measured on the tire.

Most high quality and straight wheels I will measure 0.008-0.015 radial run-out at the most as checked on the bead seats. Had a set of some $$$ 18x10.5 BBS that measured 0.005 on 3 of 4. Last one was bent. I don't typically bother with lateral run-out unless it's noticeable by eye to quantify it. If it has lateral run-out both inside and out the spokes are bent and the wheel is junk.

I check everything for cracks when it will be used for track stuff or has been previously used for track stuff.

A friend bought 5 sets of wheels/tires off a guy getting out of racing, including the BBS wheels mentioned above, some RPF1s, and several Mustang wheels... Every single set of wheels had at least one bend in them over 0.050". A couple had multiple bends in the 0.100-0.110" range.

Personally I will probably never buy used wheels for track purposes unless I can check them prior to purchase. Even then I strongly prefer new.

dinesh
dinesh
7/4/20 7:31 p.m.

wondering the life span of bmw car tyres 

Emilio700
Emilio700 New Reader
7/5/20 1:32 p.m.

In reply to BlindPirate :

Yup, we were roundly attacked by the folks that think any lightweight high performance wheel (that's 2lbs lighter and 3" wider than OEM) should last forever even if it sees a dozen or so track days a year. We published an article about wheel industry test standards and the need for regular inspections about a year ago. Looks like Konig saw it and decided to publish something similar. This is a good thing.  http://949racing.com/how-strong-is-your-wheel.aspx

Tom1200
Tom1200 Dork
7/5/20 4:45 p.m.

Emillio, it is surprising how many people don't understand the trade offs.

 

ProDarwin
ProDarwin UltimaDork
7/5/20 7:00 p.m.
Emilio700 said:

  http://949racing.com/how-strong-is-your-wheel.aspx

Really appreciate the technical info in this article.  Thanks.

clshore
clshore Reader
7/6/20 5:25 a.m.

I've had fatigue cracked steel wheels.

G PROD Spitfire running stock steel wheels. 4-1/2 x 13.

Noticed a vibration in the turns, and pitted.

Inspection revealed cracks in the stamped center sections along the curves where small hub caps pop on.

It could have been nasty.

Lesson: When your car talks to you, listen.

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