unsprung weight

Slartibartfas · 05-21-2016, 11:46 AM

Quote:

Originally Posted by totopo

spacers are kind of interesting from a vehicle dynamics standpoint. They increase the wheelbase, which is super great for decreasing weight shift, but it changes your scrub angles in the front, and changes your overall suspension geometry (and i think kills bushings).

Change wheelbase to track and that's right. Track is lateral width while wheelbase is longitudinal length.

Most of you are beating around the bush. The unsprung weight works exactly like totopo wrote for handling and is a linear relationship. 1 lb reduction in unsprung weight is 1 lb in regards to handling and wheel frequency.

However, the rotational inertia is very much a non-linear effect. 1 lb of rotational inertia is the equivalent to 10 lbs (or your favorite number from your favorite source) in regards to vehicle acceleration, whether it be forward (mash the gas), backwards (slam the brakes), or turning. Take ten pounds off each corner and it feels as if you've removed 400 pounds out of the car when you measure at the drag strip or race track.

Lighter wheels and brakes will make the car feel livlier but, from direct experience, the ride isn't as good. The heavier wheels force the tires to absorb small imperfections so the imperfections aren't as strongly transferred into the springs. Also, if you have a wheelspin problem, heavier wheels can help.

Like everything else in life, there are compromises to wrangle.

Sorry to practice necromancy but felt it worthwhile.

Riptide67 · 10-17-2013, 10:46 PM

In my case I'll be dropping 8lbs from switching out OEM Rays and Spacers to ForgeStar F14 wheels.

I doubt the difference will be noticed. But when I upgrade the front rotors to Z1's 2 piece, I'm sure that will be much more noticeable.

Tick64 · 05-21-2016, 05:01 PM

Interesting thread. A little was over my head, but I think I got the gist of it.

10-17-2013, 10:46 PM	#2 (permalink)
Riptide67 A True Z Fanatic Join Date: Jul 2013 Location: Oak Harbor, WA Age: 37 Posts: 1,610 Drives: 09 Nismo #0483 PW Rep Power: 69	In my case I'll be dropping 8lbs from switching out OEM Rays and Spacers to ForgeStar F14 wheels. I doubt the difference will be noticed. But when I upgrade the front rotors to Z1's 2 piece, I'm sure that will be much more noticeable. __________________ 2009 Nismo 370Z and 1975 Datsun 280Z 2+2 - PNW_INC - Legacy_Ohana Follow me on Instagam @s3zero_z3four

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05-21-2016, 05:01 PM	#3 (permalink)
Tick64 Enthusiast Member Join Date: Jul 2011 Location: Vancouver Island,Canada Posts: 341 Drives: '11 370z Nismo MB Rep Power: 2478	Interesting thread. A little was over my head, but I think I got the gist of it.