Model Y has a aluminum traction arm on the rear suspension (3 and old Y has stamped and folded steel)

[osunick]

Looks like enough Ys are dismantled that you can get these pretty cheaply on ebay now.

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Should be dimensionally identical between 3 and Y, I assume the change is for strength and corrosion resistance.

 

[Gauss Guzzler]

Suspension arms typically don't have strength or corrosion issues. This change is surely just a cost reduction transition.

Stamped/welded steel arms are cheap and quick to get into production because the tooling is simple and the job can be outsourced to very low-skilled suppliers. The drawback is that they require several minutes of labor per part to stamp, inventory, inspect, transport, fixture, weld, clean, inspect, paint, label, and inspect.

Cast/forged aluminum arms are much more expensive to develop as they require sophisticated presses and furnaces - but in high quantities they become much less expensive than steel since a single unattended machine can squirt out dozens of fully finished parts every second, 24/7/365. You just press a button and millions of perfect control arms gush right out into a bucket.

From the owner's perspective, aluminum control arms might only reduce unsprung weight by 0.00%, but they will definitely make a better impression on the kid changing your tires. If the kid notices.

 

[MountainPass]

Make sure you install it the right way up! The main weakness of the stock traction arm is the bushing itself, which is still rubber on the Model Y.

 

[osunick]

Suspension arms typically don't have strength or corrosion issues. This change is surely just a cost reduction transition.

Stamped/welded steel arms are cheap and quick to get into production because the tooling is simple and the job can be outsourced to very low-skilled suppliers. The drawback is that they require several minutes of labor per part to stamp, inventory, inspect, transport, fixture, weld, clean, inspect, paint, label, and inspect.

Cast/forged aluminum arms are much more expensive to develop as they require sophisticated presses and furnaces - but in high quantities they become much less expensive than steel since a single unattended machine can squirt out dozens of fully finished parts every second, 24/7/365. You just press a button and millions of perfect control arms gush right out into a bucket.

From the owner's perspective, aluminum control arms might only reduce unsprung weight by 0.00%, but they will definitely make a better impression on the kid changing your tires. If the kid notices.

I’d almost agree with you except the stamped/welded part is still in production for all 3s. The witness marks on the aluminum parts also suggest some machining after leaving the tool, so I’m still unconvinced it’s for cost reduction. If what you said is true, then aluminum suspension components would be on every high volume mass produced vehicle, which is definitely not the case. The ’several minutes’ of labor per control arm is also hard to believe given the prevalence of automated stamping and MIG welding on parts that are clearly designed for manufacturing. These are identical halves welded together with arrow straight beads- this isn’t rocket engineering here.

 

[osunick]

Make sure you install it the right way up! The main weakness of the stock traction arm is the bushing itself, which is still rubber on the Model Y.

Good to know- obviously I’m not claiming these are anywhere near the cyber arms. What are your thoughts on NVH with heim joints for a street driven car?

 

[Gauss Guzzler]

...except the stamped/welded part is still in production for all 3s.

That's why I used the word "transition".
To prematurely discard perfectly good steel stamping tools before the end of their useful life would negate much of the cost benefit of cheaper castings. So if they can make the next 5 million arms for $2/ea using tooling they've already paid for, it'd be much cheaper than buying a $6M casting tool to make arms for $1/ea. Plus, they could invest that $6M lump sum into production expansion instead of trying to shave pennies off a 6-year old chassis.

We know production works that way. What we don't know is that this arm has any issues with corrosion or strength. We don't even know if the aluminum version is actually stronger (or lighter), it might even be intentionally weaker in order to improve crash safety.

 

[evrepair]

They are interchangeable. Functionally pretty much the same. They started putting aluminum ones on model Ys sometime in 2022 I think.

 

[evrepair]

Actually there is one benefit to the new arms: the rear subframe is less likely to be damaged in accidents, instead the control arm will bend (in theory).

 

[osunick]

They are interchangeable. Functionally pretty much the same. They started putting aluminum ones on model Ys sometime in 2022 I think.

Late 2021 at least. Our sept 2021 build has one.

 

[osunick]

I

That's why I used the word "transition".
To prematurely discard perfectly good steel stamping tools before the end of their useful life would negate much of the cost benefit of cheaper castings. So if they can make the next 5 million arms for $2/ea using tooling they've already paid for, it'd be much cheaper than buying a $6M casting tool to make arms for $1/ea. Plus, they could invest that $6M lump sum into production expansion instead of trying to shave pennies off a 6-year old chassis.

We know production works that way. What we don't know is that this arm has any issues with corrosion or strength. We don't even know if the aluminum version is actually stronger (or lighter), it might even be intentionally weaker in order to improve crash safety.

View attachment 916471

That's why I used the word "transition".
To prematurely discard perfectly good steel stamping tools before the end of their useful life would negate much of the cost benefit of cheaper castings. So if they can make the next 5 million arms for $2/ea using tooling they've already paid for, it'd be much cheaper than buying a $6M casting tool to make arms for $1/ea. Plus, they could invest that $6M lump sum into production expansion instead of trying to shave pennies off a 6-year old chassis.

We know production works that way. What we don't know is that this arm has any issues with corrosion or strength. We don't even know if the aluminum version is actually stronger (or lighter), it might even be intentionally weaker in order to improve crash safety.

View attachment 916471 View attachment 916472

I spent a few years working for an automaker and this answer makes no sense to me. Thanks for making the effort, I hate being wrong too.

 

[osunick]

Actually there is one benefit to the new arms: the rear subframe is less likely to be damaged in accidents, instead the control arm will bend (in theory).

That makes a lot of sense since the gigacasting is only on the Y and that looks nearly impossible to repair.

 

[MountainPass]

Good to know- obviously I’m not claiming these are anywhere near the cyber arms. What are your thoughts on NVH with heim joints for a street driven car?

I wouldn't say it increases the volume in the car, but the frequency of the sound when you run over cracks in the road will become higher pitched. If you've driven a newer Porsche that has these bearings in all the arms from the factory, you can expect that type of experience.

 

[tom @ eas]

Late 2021 at least. Our sept 2021 build has one.

We started seeing them in 08/21 come into the shop.

 

[osunick]

I wouldn't say it increases the volume in the car, but the frequency of the sound when you run over cracks in the road will become higher pitched. If you've driven a newer Porsche that has these bearings in all the arms from the factory, you can expect that type of experience.

I think only the GT2/3/4 have the heim joints- I had a 991 Turbo S and the car definitely had bushings.

 

[MountainPass]

I think only the GT2/3/4 have the heim joints- I had a 991 Turbo S and the car definitely had bushings.

The last one I had my hands on was a 997 GT2 RS and it had all the same bearings as our arms! Definitely too much car for me.

 

[osunick]

The last one I had my hands on was a 997 GT2 RS and it had all the same bearings as our arms! Definitely too much car for me.

My friend and fellow https://candash.app contributor has practically the entire MPP catalog on his 3 including the coilovers so I will go for a ride and check it out!