steering knuckles

[Spuds]

Originally Posted by ZDan

Should point out that manufacturers will design aluminum components to survive multiple lifetimes of the most harsh usage. So even though theoretically with enough load cycles parts will begin to fatigue and crack, in most cases you'd have to drive over rough roads for 250k+ miles to get to that number of cycles. Tons o testing to validate designs and analysis as well. When I was in the two-wheeled world, a company specializing in vehicle testing rode our vehicles day and night for weeks. The guy who rode at night was known as "The Night Rider"

So typically aluminum components will actually be a bit stiffer due to being bulkier (higher sectional moments of inertia) while also being lighter-weight, while being sufficiently stout to withstand multiple lifetimes of load cycles without loss of stiffness due to fatigue/cracking.

Yes, I didn't mean to imply that the aluminum knuckles on the BRZ were likely to fail or even fatigue within the lifetime of the rest of the car given anything but very extreme circumstances. Metallurgy and design of isotropic materials is quite well understood and precise.

One thing I forgot to mention that might be important was the heat absorption and dissipation properties will be different between the two materials. (I never actually took thermodynamics [because robotics class was cooler] so I don't want to guess as to what the difference is)

[Opie]

Originally Posted by timurrrr

Wrong.

It's possible to attach the caliper without that bar/bracket and with shorter bolts.

Exactly what I said...

[timurrrr]

Originally Posted by Opie

Exactly what I said...

You said "will work fine". For most people, "will work fine" implies no compromises or modifications needed.

I'm saying the PP Brembos can only be attached to the BRZ aluminum knuckles by modification
(i.e. removal of parts that I presume are otherwise useful; and changing the bolts),
and who knows how much it affects the longevity of the overall system.

IMO, that can only be called "fine" with a huge asterisk.

[Opie]

Originally Posted by timurrrr

You said "will work fine". For most people, "will work fine" implies no compromises or modifications needed.

I'm saying the PP Brembos can only be attached to the BRZ aluminum knuckles by modification
(i.e. removal of parts that I presume are otherwise useful; and changing the bolts),
and who knows how much it affects the longevity of the overall system.

IMO, that can only be called "fine" with a huge asterisk.

Calls my statement false because of my assumptions by using own assumptions as reasoning, got it.

Let me make it clearer...

PP Brembo's will bolt up to the 2022 knuckles, and I would not hesitate to use them on the street, or track.

If you are concerned with using 2004 STI mounting bolts and removing the tie bar, you can instead purchase one of the seven (7) brake kits now available for the 2022 BRZ from Essex.

[timurrrr]

Originally Posted by Opie

PP Brembo's will bolt up to the 2022 knuckles, and I would not hesitate to use them on the street, or track.

If you decide actually doing that, it might be a useful data point how it looks after 10/20/etc. track days!

[NoHaveMSG]

Originally Posted by Spuds

One thing I forgot to mention that might be important was the heat absorption and dissipation properties will be different between the two materials. (I never actually took thermodynamics [because robotics class was cooler] so I don't want to guess as to what the difference is)

Wonder if this would save front hubs on cars that are tracked. I have been through 5.

[timurrrr]

Originally Posted by NoHaveMSG

Wonder if this would save front hubs on cars that are tracked. I have been through 5.

What brake rotors? Did you keep the OEM heat shields, removed or trimmed them?

[NoHaveMSG]

Originally Posted by timurrrr

What brake rotors? Did you keep the OEM heat shields, removed or trimmed them?

I still have the heat shields but I may pull them. Brakes are ST 4 pots with 328mm rotors.

[timurrrr]

Originally Posted by NoHaveMSG

I still have the heat shields but I may pull them. Brakes are ST 4 pots with 328mm rotors.

Do you sufficiently cool down the rotors before parking after a session?

[Spuds]

Originally Posted by NoHaveMSG

Wonder if this would save front hubs on cars that are tracked. I have been through 5.

I guess aluminum knuckles would conduct heat better, thus absorbing and dissipating more heat from the hub, assuming it can stand up to the amount of heat it soaks up.

Again, I have no idea what I am talking about. Google knows everything though lol.

[timurrrr]

Originally Posted by Spuds

I guess aluminum knuckles would conduct heat better, thus absorbing and dissipating more heat from the hub, assuming it can stand up to the amount of heat it soaks up.

Again, I have no idea what I am talking about. Google knows everything though lol.

The knuckles aren't really shaped like a radiator, and aluminum is a good conductor.
I can imagine that if you park a car with rotors too hot some of that heat will be conducted into the ball joints and also into the damper; neither of which like excess heat.

[NoHaveMSG]

Originally Posted by Spuds

I guess aluminum knuckles would conduct heat better, thus absorbing and dissipating more heat from the hub, assuming it can stand up to the amount of heat it soaks up.

Again, I have no idea what I am talking about. Google knows everything though lol.

LOL

The anodizing on my rotor hats has faded from black to a pinkish purple from the temps. I am not sure I want to run ducting to cool the hub though as it will cause more heat checking with the rotors. I was thinking the AL may help pull heat away.

[gpshumway]

Originally Posted by Spuds

Yes, I didn't mean to imply that the aluminum knuckles on the BRZ were likely to fail or even fatigue within the lifetime of the rest of the car given anything but very extreme circumstances. Metallurgy and design of isotropic materials is quite well understood and precise.

As well as the mechanical design may be understood, the forces may not. Practical experience says we should have some slight concerns.



I don't have time to dig up the NASIOC thread right now, but Karen Kraus failed at least one aluminum control arm on her 2006 WRX autocross car. R-comp tires and lots of cornering may put the car in a usage space not envisioned by the designers.

[Spuds]

Originally Posted by gpshumway

As well as the mechanical design may be understood, the forces may not. Practical experience says we should have some slight concerns.



I don't have time to dig up the NASIOC thread right now, but Karen Kraus failed at least one aluminum control arm on her 2006 WRX autocross car. R-comp tires and lots of cornering may put the car in a usage space not envisioned by the designers.

So you are comparing aftermarket control arms to OEM steering knuckles?

And no, static and dynamic forces and their effects on materials are quite well understood. The difference is whether the maker of the part decided to spend time actually doing the math rather than slapping some parts together and saying it's good.