Unsprung Weight!
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,750
Likes: 37
From: Stockton Ca
Unsprung Weight!
Can anyone comment on the before / after handling of their car after reducing the unsprung weight "brakes, springs, alloy wheels". In every form of motorsport this is critical. How has it effected the ride and handling of your street car? I know that a few members have gone to Wildwood brakes, how do they preform? Was it worth it? Thanks for sharing your experience.
Le Mans Master
Joined: Aug 2000
Posts: 6,273
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From: Austin TX
Re: Unsprung Weight! (Taijutsu)
You need to consider the relation between wheel/tire/caliper weight and spring rate.
As the unsprung weight goes down, the relative spring rate goes up. I think this is why most report improved handling with reduced unsprung weight. The calculations to quantify this are complex and include several squares and cubes so the relation is not linear.
I think you will see more improvement cheaper by going to an alum wheel than by changing calipers. For example, a late 80s OE alum wheel is about 8 lbs lighter that a Rally with trim. A 17" alum wheel is even lighter.
As the unsprung weight goes down, the relative spring rate goes up. I think this is why most report improved handling with reduced unsprung weight. The calculations to quantify this are complex and include several squares and cubes so the relation is not linear.
I think you will see more improvement cheaper by going to an alum wheel than by changing calipers. For example, a late 80s OE alum wheel is about 8 lbs lighter that a Rally with trim. A 17" alum wheel is even lighter.
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,750
Likes: 37
From: Stockton Ca
Re: Unsprung Weight! (flynhi)
This post goes back to my old post of Ride vs Handling. I believe that up to a point, you can have both. I already have alu wheels. I mailed 427V8 about any improvements w/Wildwood Brakes. Getting a firmer ride w/o heavier springs is almost a free lunch. I'm waiting for 17' wheels to go w/larger rotors. My new engine has made the stock brakes marginal. I want to know if the reduction in unsprung weight can be felt on the street!
Drifting
Joined: Oct 2000
Posts: 1,825
Likes: 56
From: Shawano WI
Re: Unsprung Weight! (Taijutsu)
Unsprung weight is benifical because it is easier for the springs and shocks to keep the tire in contact with the road. If the road is perfectly flat then there is little benifit but if there are any defects in the road the less unsprung weight there is the easier it to control. Lightweight wheel are the greatest benifit because you are decreasing both unsprung weight and rotating mass so the benifits are twofold. The farther the weight is from the pivot point (the a-arm bushings, ect) the greater the benifit in reducing weight, so lightweight calipers or spindle would be more of a benifit than a lightweight A-arm.
Will you feel it on the street? Probable not unless you autocross. But any reduction in weight will improve acceleration and braking.
Will you feel it on the street? Probable not unless you autocross. But any reduction in weight will improve acceleration and braking.
Burning Brakes
Joined: Apr 2000
Posts: 1,145
Likes: 1
Re: Unsprung Weight! (Pete79L82)
It is also weel documented that a 1 pound reduction in unsprung weight is equivalent in terms of handling as a 4 pound reduction in sprung weight. I have the 17" aluminum wheels and wilwood brakes and will soon install some tubular upper A arms. I cant give a quantative breakdown of the benefits other then the 1 to 4 ratio, but I can tell you that my car handles amazingly well. It is smooth and very quick to respond to steering and road input.
I think the largest possible weight savings is with the calipers. Those old iron calipers are soooo heavy.
Chris
I think the largest possible weight savings is with the calipers. Those old iron calipers are soooo heavy.
Chris
Le Mans Master
Joined: Aug 2000
Posts: 6,273
Likes: 14
From: Austin TX
Re: Unsprung Weight! (71roadster)
Don't expect any weight savings with VBs tubular A arms. I weighed each and they're just about the same weight. They do look cool though.
I think I remember that SSBC's alum calipers weigh about 8 lbs less each than the OE cast iron.
Never heard that before about one pound unsprung equalling 4 sprung. Wonder how they calculate that?
BTW. Beautiful Vette - what brand tire are you runnin?
I think I remember that SSBC's alum calipers weigh about 8 lbs less each than the OE cast iron.
Never heard that before about one pound unsprung equalling 4 sprung. Wonder how they calculate that?
BTW. Beautiful Vette - what brand tire are you runnin?
Burning Brakes
Joined: Sep 2000
Posts: 922
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From: Maine
Re: Unsprung Weight! (flynhi)
Will,
I think it has more to do with acceleration of rotating components than handling - moment of inertia is lower, therefore, less energy required to change the speed of the drivetrain (which is what ultimately changes the speed of the vehicle). Unsprung weight reductions are always good!
I think it has more to do with acceleration of rotating components than handling - moment of inertia is lower, therefore, less energy required to change the speed of the drivetrain (which is what ultimately changes the speed of the vehicle). Unsprung weight reductions are always good!
