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► Official APEX VW SM-10 Flow Formed Wheel Thread

GTIfan99

Autocross Champion
Location
FL
Except paper clips are steel, which does not suffer from cyclic fatigue like aluminum, but does fail when pushed past it's limits, like bending it 180 degrees multiple times. There's a reason I replace my aluminum seatposts and handlebars on my bikes fairly frequently but don't worry about the titanium seatpost nearly as much. Nothing worse than a snapped seatpost saying hello to your posterior.

I guess bad example. But yeah, aluminum fails spectacularly when it does. Surprise bunch biopsy of the prostate is no fun.
 

bentin

Autocross Champion
Location
Austin, TX
Car(s)
23 Golf R - 3 Pedals
My dad had a '93 FD RX7, they had comically light wheels, but they cut a few corners and they liked to fail in dramatic fashion. I always give FD RX7s a little extra space on track. There are more graphic pics of the whole hub face ripped out, but I can't find them at the moment.
 

TheProfessional

Go Kart Newbie
Location
Texas
Except paper clips are steel, which does not suffer from cyclic fatigue like aluminum.
Steel DOES suffer from cyclic fatigue, but the fatigue levels off after 1,000,000 cycles.

Also on the paper clip, when you are bending it, you are inducing strain hardening in the material, which in turn makes it brittle, which is why it breaks.

Sorry guys, I'm just being the dork professional engineer.
 

theDoktor

Go Kart Champion
Location
Buffalo, NY area
Car(s)
2017 GTI Sport
Good info on deflection failure everyone- thanks!
 

bfury5

Autocross Champion
Location
CT
It's easy for people to understand that bending a paper clip back and forth will cause it to break, but can't see the same principle applies to track wheels.
This is why track wheels should be considered a consumable, just like wheel bolts and other safety critical items
 

jmblur

Autocross Champion
Location
Massachusetts
Car(s)
2017 Golf R
Steel DOES suffer from cyclic fatigue, but the fatigue levels off after 1,000,000 cycles.

Also on the paper clip, when you are bending it, you are inducing strain hardening in the material, which in turn makes it brittle, which is why it breaks.

Sorry guys, I'm just being the dork professional engineer.
If you dig deeper, the data that leads to fatigue limits is based off a poor interpretation of stochastic data. There's some pretty hefty disagreement on whether or not fatigue/endurance limits are actually a thing.

/Also an enginerd
 

GTIfan99

Autocross Champion
Location
FL
I've seen enough wheels fail on track that I will rotate my track wheels to street duty after 3 years if I'm tracking regularly. YMMV. The last few years my track time has dwindled, so I sound be fine.

I'd imagine forged wheels and wheels designed specifically for track should last longer.
 

ExtraChrispy

Passed Driver's Ed
Location
CA
Car(s)
MK7.5 GTI
So my tire pressure warning came up today. Looks like America's Tires filled the front to 35 psi and the rear to about 31psi....I know I read about different tire pressures for different load ratings but this is just off. Going from the stock bridgestones to Michelin AS4. Should I be setting them to the door jam 39 psi or slightly lower due to the new load rating?
 

GTIfan99

Autocross Champion
Location
FL
So my tire pressure warning came up today. Looks like America's Tires filled the front to 35 psi and the rear to about 31psi....I know I read about different tire pressures for different load ratings but this is just off. Going from the stock bridgestones to Michelin AS4. Should I be setting them to the door jam 39 psi or slightly lower due to the new load rating?

I like 35 psi on the street.
 
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