Originally Posted by PLF69 (Post 3494993)

What's the final verdict on this ?

Did Toyota use the steel ones to save cost or because they are stiffer than the aluminum ones (may give better steering feel)

Originally Posted by PulsarBeeerz (Post 3495071)

They will lessen the un-sprung weight as well. I assume there are published weights somewhere of each.

Originally Posted by Opie (Post 3488562)

2013-2020 Steel knuckles: 12.41lbs each
2022 Aluminum Knuckles: 9.08lbs each

3.33 lbs less each (6.66 lbs net weight less)

Originally Posted by racingfool (Post 3494977)

I prefer the looks of the GR but I want the aluminum knuckles from the BRZ.

Are they interchangeable?

Originally Posted by Spuds (Post 3495026)

I believe Toyota SAYS they are stiffer, and my guess it is technically a true statement. But is a person actual going to notice a difference in stiffness of the knuckle considering you've got rubber bushings, tires, and coil springs all moving about? Hell no.

Some possibility not considered is that Subaru and Toyota started with some baseline and then it was Subaru that decided to make aluminium knuckles independent of Toyotas engineering team.

Originally Posted by racingfool (Post 3494977)

I prefer the looks of the GR but I want the aluminum knuckles from the BRZ.

Are they interchangeable? Geometry the same?

Any thoughts as to why the difference?

Originally Posted by Blighty (Post 3495164)

According to reports of Toyotas 3 month tuning delay, these knuckles were changed to the old ones at the very last minute.

There is a chance it was done to improve the balance of the car at the limit, Toyota was (again according to reports at the time) really struggling with some of the tuning.

Originally Posted by Blighty (Post 3495164)

According to reports of Toyotas 3 month tuning delay, these knuckles were changed to the old ones at the very last minute.

There is a chance it was done to improve the balance of the car at the limit, Toyota was (again according to reports at the time) really struggling with some of the tuning.

Originally Posted by RZNT4R (Post 3495279)

The aluminium knuckles by themselves are probably not better or worse

Originally Posted by PBR (Post 3495186)

Aluminum provides better NVH as well as less unsprung weight.

Originally Posted by racingfool (Post 3495302)

I respectfully disagree.

As long as they don't prove to be a weak link, think I would have to go with the BRZ.

Originally Posted by saltywetman (Post 3495312)

yeah most gen 1 bbk's are compatible with the gr86 but not the brz cuz of the knuckle.

Originally Posted by Opie (Post 3495574)

performance pack Brembo's ... will work fine, aluminum or steel.

Originally Posted by PBR (Post 3495186)

It's a cheaper part and more durable. Most likely nothing to do with any kind of performance. Aluminum provides better NVH as well as less unsprung weight. But balance and feel? That sounds like a marketing department not an engineer.

Originally Posted by Opie (Post 3495574)

All BBK's, performance pack Brembo's, etc. that use a caliper that bolt directly to the knuckle will work fine, aluminum or steel. BBK's that use a bracket between the caliper and knuckle may have an issue. Specifically the AP Essex kits from the 2013-2020 the braket does not clear the knuckle. Essex already has measured a 2022 and is developing an new bracket that will fit. So if you are looking to lose unsprung weight on an older gen, the aluminum knuckles are a benefit.

Originally Posted by DAEMANO (Post 3495578)

"Feel" could definitely translate to steering feel (of which most that tested the 2022 BRZ say the steering is actually lighter than the outgoing model (lighter steering is not desirable.)

Originally Posted by PBR (Post 3495186)

It's a cheaper part and more durable. Most likely nothing to do with any kind of performance. Aluminum provides better NVH as well as less unsprung weight. But balance and feel? That sounds like a marketing department not an engineer.

Originally Posted by Blighty (Post 3495646)

Probably.

A couple of kg of unstrung weight at the very edge of the car will add resistance to a cars rotational inertia, and iron and aluminium flex quite differently.

Whether or not its enough to feel different only time will tell - I'm sure people will be doing swaps right.

Originally Posted by Spuds (Post 3495684)

Ok, here's the advantages/disadvantages of each.

Steel
-is 3lb each heavier in this application. More unsprung weight (well, mass) is generally bad because it increases the vertical momentum of the wheel when it goes over bumps and such
-has a fatigue limit, meaning it can be designed to last literally for ever. No amount of force oscillation within the stress limit will cause fatigue if designed this way.
-is typically stronger than aluminum at key points that cannot be changed, such as interfaces to other components. Aluminum parts usually have different designs than their steel counterparts to make up for lower strength. However, things like holes and threads used to attach other parts have to be the same between both materials
-is cheaper

Aluminum
-is 3lb lighter
-can be designed to be as strong and stiff as a steel part, usually with less total mass (though slightly greater volume) as seen above
-has no fatigue limit, meaning the part will become less strong/stiff over time and eventually fail, regardless of design.
-is weaker than steel at key interface points.
-costs more

Originally Posted by raisingAnarchy (Post 3495716)

Great summary!

Just to add, if you live in the rust belt, the aluminum will last longer than the steel because the steel won't live long enough for the fatigue limit to matter :bellyroll:

Originally Posted by Spuds (Post 3495684)

Aluminum
-is 3lb lighter
-can be designed to be as strong and stiff as a steel part, usually with less total mass (though slightly greater volume) as seen above
-has no fatigue limit, meaning the part will become less strong/stiff over time and eventually fail, regardless of design.
-is weaker than steel at key interface points.
-costs more

Originally Posted by ZDan (Post 3495743)

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" :D

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.

Originally Posted by timurrrr (Post 3495575)

Wrong.

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

Originally Posted by Opie (Post 3495843)

Exactly what I said...

Originally Posted by timurrrr (Post 3495844)

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.

Originally Posted by Opie (Post 3496002)

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

Originally Posted by Spuds (Post 3495780)

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)

Originally Posted by NoHaveMSG (Post 3496128)

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

Originally Posted by timurrrr (Post 3496129)

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

Originally Posted by NoHaveMSG (Post 3496134)

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

Originally Posted by NoHaveMSG (Post 3496128)

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

Originally Posted by Spuds (Post 3496139)

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.

Originally Posted by Spuds (Post 3496139)

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.