Quote:
Originally Posted by 86-75309
If an aluminum knuckle weighs 8 lbs and is the typical cast aluminum density, then a cast iron part of the same exact volume would weigh 21 lbs, or 13 lbs more than the aluminum one. Iron is typically about 2.67X the density of aluminum.
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Quote:
Originally Posted by mike2100
There is no way the aluminum knuckle saves 13 lbs per side, as said in the video.
Also, it's a little hard to compare ride differences (he says the BRZ is more supple) when one car is on 17" Michelin Primacy and the other is on 18" Michelin Pilot Sport 4.
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Quote:
Originally Posted by mike2100
Engineering to the rescue! Thanks for the scientific explanation. That is a significant weight savings and I'm surprised Toyota didn't want to also incorporate the aluminum knuckle.
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Quote:
Originally Posted by fredzy
The Al knuckles are a lot bulkier, so the weight difference isn't quite so big. User on here measured less than 4 lbs per side, though I saw elsewhere mentions of 6.5lbs which is where the 13 might have come from.
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Very late to this but 13lbs total unsprung weight off one axle makes the most sense.
I had Z32 NA rear uprights (aluminum) before on my S13, about 20 years ago. Each side was approx. 7lbs lighter than the cast iron version found on the S13/14/15 rear. This was before the era of CAD and other design variations meant to maximize strength for modern standards.
The difference was night and day running the same wheel/tire/suspension setup before/after.