Welcome Guest!!!

Thank you for visiting the GM Kappa Performance Forum. This forum is the only performance oriented forum for all GM Kappa Platform Enthusiasts.  We hope you will join and share your experiences.  Becoming a member is FREE! If you want to advertise on this forum, email KappaPerformance at yahoo.com.


Registration required to view the forum attachments. Below is a sample of the current top 25 topics.
Supporting Membership has many advantages.


More information on becoming a supporting member or vendor can be found on the sub forum; Site Help and Suggestions; thread - Supporting Members and Vendors.

Author Topic: Reducing unsprung weight.  (Read 8721 times)

0 Members and 1 Guest are viewing this topic.

Offline Sly Bob

  • Administrators
  • Shop Foreman
  • *
  • Posts: 7528
  • Karma: +12/-10
  • Location: Welland, Ontario, Canada
  • My new grandson
    • Kappa Performance Forum
Reducing unsprung weight.
« on: January 26, 2011, 11:06:43 AM »
In doing research regarding aftermarket wheels I came across this article that explains the benefit of reducing unsprung weight when purchasing or modifying vehicle components. It's an interesting read.

For those that would prefer to download it and read it I have created a .doc file that you can print out. I usually prefer to read long posts this way.

[ Guests cannot view attachments ]



Unsprung Weight - Part 1

By: Eric Albert

Introduction

Every car built today has some type of suspension on it. Whether it's a double-wishbone or a MacPherson Strut design, we, as tuners, need to know a little more about suspension that just 'dropping' the chassis down a little bit. Let's take a deeper look at what exactly the job of your car's suspension is.

Suspension on the Clock

So we all know that suspension works. It works for you, but it never gets paid. In the same way as you and I work, we probably have different jobs. Suspension is no different. There are a few different ways your suspension works.

The main job of your suspension is to suspend your car above the road. If that was the only reason for the existence of springs and shocks though, why don’t we just solidly mount the car to the axles? “That’s obvious!” you say. Of course, you’d have a lot of trouble with bumps and corners with a solid suspension. This is because a suspension is supposed to allow your wheels and tires to follow the road, irregularities and all, while the body of the vehicle travels smoothly. Turning things around, the suspension should also keep the wheels and tires in maximum contact with the road for the best performance (this is more important than ride for us driving enthusiasts). So, to continue, for a suspension to be effective, it must allow the wheels and tires to accelerate and decelerate rapidly up and down while not allowing them to make excess motions (example - axle hop). The springs prevent the wheel assembly from traveling too far, while the dampers prevent oscillation by the spring.

Sprung Weight

Sprung weight is the weight supported by the springs. For example: the vehicle's body, frame, motor, transmission, interior, fuel, and passengers would be sprung weight. A simple concept to grasp. Basically, the sprung weight of the car is the car's mass as seen to the suspension components.

Unsprung Weight

This is one of the most critical factors affecting a vehicle's road holding ability. Unsprung weight is that portion of a vehicle that is not supported by the suspension (i.e. wheels, tires and brakes) and therefore is the most susceptible to road shock and cornering forces. By reducing unsprung weight, alloy wheels provide more precise steering input and improved "turning in" characteristics. So what. SO WHAT!? This is a key concept that many people overlook. We have been telling you for a long time now to get light weight wheels and tires. Here's how it all comes together.

Every time you hit a bump, the wheel assembly is accelerated upwards, decelerates to a stop, then accelerates downward till it reaches equilibrium. If the wheel can’t accelerate fast enough, shock is transmitted to the body, which may upset the balance of the car. A s an example think of small, sharp edged speed bumps versus those gigantic, but wide, monsters in some lots. The sharp edged ones are much more annoying to traverse, aren’t they? That’s because they require the suspension to accelerate more rapidly. Now imagine going over some stutter bumps in a corner. You’ll have a very rapid series of accelerations and decelerations. If the wheel is lighter, it will accelerate upwards and downwards faster (a=F/m). This means it will follow the road better and, even more importantly, it will allow the suspension to work better. The shock and spring will have to control less unsprung weight/mass, which means they can stop and start the motion of the assembly easier and at a rapid pace.

Why Reduce Unsprung Wieght?

Reducing unsprung weight minimizes the load placed on controlling the motion of the wheels and tires. This means that suspension springs and shock absorbers will have a greater reserve capacity to control body motion -- just as they were intended to! The result is better handling, which we, as tuners, are all after.

In part two of this article, we will discuss the other end of the spectrum: why it is good to have a low weight wheel/tire, but not for suspension, for acceleration.

Unsprung Weight - Part 2

By: Eric Albert

Introduction

In the first part of this series, we took a look at the effects of high unsprung weight on suspension and handeling. In this part, we will look at rotating mass. Be careful not to confuse unsprung mass with rotating mass. Reducing both is good, but they are not the same. Let's take a look.

Rotational Inertia (or Momentum)

Rotational inertia is a concept a bit more difficult to deal with than unsprung weight. Inertia can be thought of as why a car wants to keep rolling once moving, or remain in place once stopped (unless you forget to set the parking brake on that hill). I believe the terms momentum and inertia are interchangeable. The term “flywheel effect” also refers to these concepts. In a car, there are a number of rotating masses which require energy to accelerate. Up front, ignoring the internal engine components like the crankshaft, we have to worry about the flywheel, clutch assembly, gears, axles, brake rotors and wheel/tire. Out back its a little simpler (for FWD) with just the brakes and wheel/tire contributing most of the mass.

The more mass an object has, the more energy it takes to accelerate it. To accelerate a rolling object such as a wheel, you must both accelerate its mass plus overcome its rotational inertia. As for braking, you must overcome its rotational inertia plus decelerate its mass. By reducing the weight of the vehicle's rotational mass, lightweight wheels provide more responsive acceleration and braking.

Before continuing with our informal analysis here, I want to point out something very important about rotational inertia. We’ve all seen the ice skating move where the skater starts spinning. She pulls her arms in and speeds up, then extends them again and slows down. Why is this? Well, the further a mass is from the center of rotation, the faster it must travel for a given angular speed (how many degrees of an arc it traverses per time unit). The faster anything moves, the more energy it has, so when the arms are pulled in, conservation of energy says that the rotation rate must increase due to equal energy being applied to the same mass over a smaller diameter. Applying this to wheels and tires, which have most of their mass spread as far as possible from the rotation center, I think you’ll agree that it naturally takes more energy to accelerate them. Example: Take a two identical masses, but one is a solid disk of diameter D, the other is a ring of diameter 2D. The ring will require more force to accelerate it (in a rotational manner). Therefore a heavier rim with a smaller diameter could have less rotational mass than a lighter rim of a larger size, and accelerate faster with the same force applied.

The effect of rotating mass can be calculated using Moment of Inertia (MOI). MoI is related to not only the mass of the rotating object, but the distribution of that mass around the rotational center. The further from the center, the higher the MoI. The higher the MoI, the more torque required to accelerate the object. The higher the acceleration, the higher the torque required.

Because of this, the weight of rotating mass such as wheels and tires on a car have a bigger effect on acceleration than static weight such as on the chassis on a car. When purchasing new wheels and tires for a performance car, it can be useful to compare the effects of different wheel and tire combinations. This is especially true when considering upgrading to larger wheels or tires on a car.

The use of light-weight alloys in wheels reduces rotational mass. This means that less energy will be required to accelerate the wheel. Given that each pound of rotational mass lost provides an equivalent performance gain as a 10 pound reduction in vehicle weight, the benefits of light alloy wheels on vehicle performance cannot be overlooked.
For example:
A reduction in the weight of the rim/tire assembly of 5lbs x 4 (all around the car) is equivalent to a 200lb weight reduction in vehicle weight (thats worth 0.200 in the 1/4 mile)

So What's the Point?

The point of this discussion is as follows: There is a great deal of rotational mass to deal with in a car and tires and wheels may only make up half of it. Estimates for weight (o.k. for comparison since they’re all in the same gravity field, therefore the mass would be a similar ratio)
Front: Rear:
Wheel/tire: 30-35 lbs each 30-35 lbs each
Flywheel: 15-20 lbs
Clutch: 15 lbs
Halfshafts: 7-10 lbs each
Gears: 5-7 lbs
Rotors: 3-5 lbs 3-5 lbs
Misc: 3-5 lbs 3-5 lbs
------------------------------------------------------------------
Total: 115-148 lbs 76-90 lbs

So a couple pounds here and there on wheels and tires will make a difference, but that difference is magnified because that weight is placed further from the axis of rotation than any other mentioned (remember the ice skater). All these masses must be accelerated, so any reduction is a good thing. Now you know why we always say don't get those 18" rims for your civic. Not only are the heavier, they have a larger overall diameter. Even with lower profile tires, most plus sizing leaves us with a slightly larger wheel.

« Last Edit: January 26, 2011, 11:18:12 AM by Sly Bob »
Just trying to do my part...

Mods: Lose the chicklets, VentureShield, Dual horns, AfterShock spoiler, Weathershield cover, Lil Chromies, Red calipers with black Solstice stickers, Opel GT antenna and Solo GXP-RCD exhaust with a Solo hi-flow cat!

Offline pocketcthulhu

  • Tech
  • **
  • Posts: 31
  • Karma: +0/-0
Re: Reducing unsprung weight.
« Reply #1 on: January 26, 2011, 12:31:13 PM »
very interesting read but it makes me wonder about the mechanics of using a lighter weight flywheel from the stock has anyone changed theirs out or have any thoughts?

Offline Kenny

  • "The Professor"
  • Lifetime Supporting
  • Gearhead
  • *
  • Posts: 3804
  • Karma: +0/-5
  • Location: NJ
  • Make or take?
Re: Reducing unsprung weight.
« Reply #2 on: January 26, 2011, 01:08:48 PM »
very interesting read but it makes me wonder about the mechanics of using a lighter weight flywheel from the stock has anyone changed theirs out or have any thoughts?

Way off topic dude. Search the forums or start a new thread please.
2007 Sky Redline - Wester's Tuned - GMPP sensors - RMR Roll Bar - Kirkey Seats
Schroth Harnesses - SSR Wheels - Dunlop Direzza Z1 Star Specs - Complete Mod List
kennysabarese.com - Photos - Facebook - Twitter - RSS

Offline pocketcthulhu

  • Tech
  • **
  • Posts: 31
  • Karma: +0/-0
Re: Reducing unsprung weight.
« Reply #3 on: January 26, 2011, 01:43:48 PM »
unsprung weight - rotational mass close enough for me /shrug

Offline Kenny

  • "The Professor"
  • Lifetime Supporting
  • Gearhead
  • *
  • Posts: 3804
  • Karma: +0/-5
  • Location: NJ
  • Make or take?
Re: Reducing unsprung weight.
« Reply #4 on: January 26, 2011, 01:55:16 PM »
Wheels and tires and suspension and handling vs engine and power. I think they are pretty different.
2007 Sky Redline - Wester's Tuned - GMPP sensors - RMR Roll Bar - Kirkey Seats
Schroth Harnesses - SSR Wheels - Dunlop Direzza Z1 Star Specs - Complete Mod List
kennysabarese.com - Photos - Facebook - Twitter - RSS

Offline Critterman

  • Retired, thank you very much
  • Lifetime Supporting
  • General Manager
  • *
  • Posts: 12491
  • Karma: +17/-56
  • Baltimore/Washington Corridor
Re: Reducing unsprung weight.
« Reply #5 on: January 26, 2011, 02:30:08 PM »
Pocket - Lighter flywheel - accelarate quicker stall easier tried and tested, there you have it in a nutshell.  For more detail do a search.

Great article Bob.
2006 Cool named BIXABEL (BISH-AH-BEL) Mayan for "Good Roads"

DDM
StageIII intercooled Supercharger, Wisco ceramic coated pistons, Carrillo rods, superTech valves and Springs
Ported and polished head
Exedy Stage II Clutch
big brake kit, slotted/drilled Rotors w/Porterfield pads & blue juice
Backbone, Probeam, Cross Strut Brace
Underhood, trunk, & door Lights
ZOK suspension
Lambo Doors

JPM
Center console, door inserts, & dash
Seat bolster & lumbar support

Focuztech Tri-Y Header & hi-flow cat
Solo Performance SQR-2
Norm's Rear facia
Heated Seats
Black Cat inserts

Offline idkfa

  • Violent Jain
  • Lifetime Supporting
  • Master Tech
  • *
  • Posts: 395
  • Karma: +0/-1
  • Location: Virginia Beach
  • mostly harmless
    • Make
Re: Reducing unsprung weight.
« Reply #6 on: January 26, 2011, 06:24:52 PM »
Great article.. and if you have never experienced the immediate difference in loosing 6-8lbs of unsprung weight at each corner, you're missing out.

I'm still pretty damn excited about those Team Dynamics wheels.  Finally able to get a lightweight wheel in any offset for our pcd is a freaking breakthrough.  I might relegate my SSRs to r-comps only here shortly.

Offline tallcraig

  • Lifetime Supporting
  • Master Tech
  • *
  • Posts: 101
  • Karma: +0/-0
  • Location: Thunder Bay Ont.
Re: Reducing unsprung weight.
« Reply #7 on: January 26, 2011, 06:33:40 PM »
DON'T DO IT BOB !!! Your car will look like $hit with 14 inch Honda Civic rims on it.... Joking ... Good article and best of luck with your rim search ... Craig  (go wide or go home)
"Little Miss Sunshine" or "Yellow Bastard"

Offline JimmyBaja

  • Lifetime Supporting
  • Gearhead
  • *
  • Posts: 1147
  • Karma: +0/-1
  • Location: Virginia
Re: Reducing unsprung weight.
« Reply #8 on: January 26, 2011, 07:11:05 PM »
Great info Bob, I knew it made a difference but I didn't realize how much, I didn't think about the effects on the suspension.
Thanks for the article.

Offline Sly Bob

  • Administrators
  • Shop Foreman
  • *
  • Posts: 7528
  • Karma: +12/-10
  • Location: Welland, Ontario, Canada
  • My new grandson
    • Kappa Performance Forum
Re: Reducing unsprung weight.
« Reply #9 on: January 26, 2011, 07:27:21 PM »
I know a guy at work that bought a new truck. Shortly after he went to a tire store and told them tho put the biggest, baddest wheels and tires that would fit in the wheel well. He can't keep suspension components on that thing. Wheel bearings, ball joints and all the other parts wear out like crazy.

He's starting to realize now that it might be all that extra unsprung weight. Ya think?   :lol:
Just trying to do my part...

Mods: Lose the chicklets, VentureShield, Dual horns, AfterShock spoiler, Weathershield cover, Lil Chromies, Red calipers with black Solstice stickers, Opel GT antenna and Solo GXP-RCD exhaust with a Solo hi-flow cat!

Offline SKY888

  • Gearhead
  • ****
  • Posts: 2287
  • Karma: +3/-3
  • Location: near you
Re: Reducing unsprung weight.
« Reply #10 on: January 26, 2011, 08:20:59 PM »
Great INFO.   Thanks!
COMPOUND TURBOS (GT2860r & GT4294r) goal 800hp


CAR SPECS and PHOTOS:
https://www.facebook.com/SKY888CompoundTurbo

SPONSORS:
aeroforce.com, nitrofreeze.com, forgestar.com, splitsec.com, turbosmartonline.com, k1technologies.com, supertechperformance.com, specclutch.com, rceng.com, statusracing.com, tceperformanceproducts.com, burnsstainless.com, performanceautowerks.com, ddmworks.com, turbowerx.com, BTF

Offline Critterman

  • Retired, thank you very much
  • Lifetime Supporting
  • General Manager
  • *
  • Posts: 12491
  • Karma: +17/-56
  • Baltimore/Washington Corridor
Re: Reducing unsprung weight.
« Reply #11 on: January 26, 2011, 08:23:30 PM »
I run heavier snow tires on my truck in the winter, cost me 2 miles to the gallon from 16 to 14

Run 265x55x17's in the summer
Run 265x75x16's (6 plies) in the winter
2006 Cool named BIXABEL (BISH-AH-BEL) Mayan for "Good Roads"

DDM
StageIII intercooled Supercharger, Wisco ceramic coated pistons, Carrillo rods, superTech valves and Springs
Ported and polished head
Exedy Stage II Clutch
big brake kit, slotted/drilled Rotors w/Porterfield pads & blue juice
Backbone, Probeam, Cross Strut Brace
Underhood, trunk, & door Lights
ZOK suspension
Lambo Doors

JPM
Center console, door inserts, & dash
Seat bolster & lumbar support

Focuztech Tri-Y Header & hi-flow cat
Solo Performance SQR-2
Norm's Rear facia
Heated Seats
Black Cat inserts

Offline Imaj

  • Founding Member
  • Master Tech
  • *
  • Posts: 329
  • Karma: +0/-0
  • Location: North Texas
Re: Reducing unsprung weight.
« Reply #12 on: January 26, 2011, 11:20:47 PM »
Nice post Bob!

Yeah Kenny...the title of the thread is " Reducing unsprung weight". pocketcthulhu's question was totally on target.

Offline DaveOC

  • Master Tech
  • ***
  • Posts: 626
  • Karma: +2/-3
  • Location: SE Wisconsin
  • Running Wisconsin
Re: Reducing unsprung weight.
« Reply #13 on: January 27, 2011, 12:46:37 AM »
Nice post Bob!

Yeah Kenny...the title of the thread is " Reducing unsprung weight". pocketcthulhu's question was totally on target.

Except for one thing . . .  a flywheel is sprung weight, NOT unsprung weight . . . just saying
Aggressive #000741

Offline Imaj

  • Founding Member
  • Master Tech
  • *
  • Posts: 329
  • Karma: +0/-0
  • Location: North Texas
Re: Reducing unsprung weight.
« Reply #14 on: January 27, 2011, 01:11:09 AM »
Yup. I sit corrected. Sorry! I am leaning something new all the time. :)

Offline Sly Bob

  • Administrators
  • Shop Foreman
  • *
  • Posts: 7528
  • Karma: +12/-10
  • Location: Welland, Ontario, Canada
  • My new grandson
    • Kappa Performance Forum
Re: Reducing unsprung weight.
« Reply #15 on: January 27, 2011, 02:22:52 AM »
Any weight reduction is good for performance but reducing unsprung weight especially so.
Just trying to do my part...

Mods: Lose the chicklets, VentureShield, Dual horns, AfterShock spoiler, Weathershield cover, Lil Chromies, Red calipers with black Solstice stickers, Opel GT antenna and Solo GXP-RCD exhaust with a Solo hi-flow cat!

Offline Sly Bob

  • Administrators
  • Shop Foreman
  • *
  • Posts: 7528
  • Karma: +12/-10
  • Location: Welland, Ontario, Canada
  • My new grandson
    • Kappa Performance Forum
Re: Reducing unsprung weight.
« Reply #16 on: January 27, 2011, 02:38:51 AM »
I'm still pretty damn excited about those Team Dynamics wheels.  Finally able to get a lightweight wheel in any offset for our pcd is a freaking breakthrough.  I might relegate my SSRs to r-comps only here shortly.
Similar to what Forgestar is doing now but I have yet to see a set of their wheels on a Solstice or a Sky.  ;)
Just trying to do my part...

Mods: Lose the chicklets, VentureShield, Dual horns, AfterShock spoiler, Weathershield cover, Lil Chromies, Red calipers with black Solstice stickers, Opel GT antenna and Solo GXP-RCD exhaust with a Solo hi-flow cat!

Offline Brazen17

  • Lifetime Supporting
  • Gearhead
  • *
  • Posts: 2452
  • Karma: +0/-0
  • Location: Las Vegas
Re: Reducing unsprung weight.
« Reply #17 on: January 27, 2011, 10:37:59 AM »
The guy who wrote the article  mentions the flywheel and clutch weight so it must count for something even if it is not unsprung weight.
08 Brazen GXP.  GMPP tune + new IC!, Magnaflow exhaust, DDM backbone and brace, rear Z0K sway bar, Eiback springs, debadged (mostly) and dechromed(mostly), black door handles, Hankook Ventus V12 evo K110 on 19" MODA1 wheels, color matching boomerang.

Offline Imaj

  • Founding Member
  • Master Tech
  • *
  • Posts: 329
  • Karma: +0/-0
  • Location: North Texas
Re: Reducing unsprung weight.
« Reply #18 on: January 27, 2011, 10:59:41 AM »
I was told the the lighter flywheel provides faster revving.

Offline Kenny

  • "The Professor"
  • Lifetime Supporting
  • Gearhead
  • *
  • Posts: 3804
  • Karma: +0/-5
  • Location: NJ
  • Make or take?
Re: Reducing unsprung weight.
« Reply #19 on: January 27, 2011, 11:32:10 AM »
2007 Sky Redline - Wester's Tuned - GMPP sensors - RMR Roll Bar - Kirkey Seats
Schroth Harnesses - SSR Wheels - Dunlop Direzza Z1 Star Specs - Complete Mod List
kennysabarese.com - Photos - Facebook - Twitter - RSS

Offline diamoney

  • Master Tech
  • ***
  • Posts: 141
  • Karma: +0/-0
  • Location: The twisting roads of E. Tennessee
  • I coulda had a V8! But I'm not a fan of tomatoes.
Re: Reducing unsprung weight.
« Reply #20 on: January 27, 2011, 01:56:03 PM »
So the rationale for having a larger diameter, heavier wheel tire combo is what?  Better gas mileage on the highway?  More inertia (while the wheels are spinnning) means less added power to maintain the speed once achieved? 

Sounds like just the thing for a roadster for distance or country road cruising rather than autox or dragging (quick accelerations and decelerations).
#000600 S/C
158000+ miles

'07 GXP T/C+
0-100 in what?

Offline pocketcthulhu

  • Tech
  • **
  • Posts: 31
  • Karma: +0/-0
Re: Reducing unsprung weight.
« Reply #21 on: January 27, 2011, 02:04:58 PM »
heh i was just thinking out loud, didn't mean to stir the pot that much  :devil:

Offline SKY888

  • Gearhead
  • ****
  • Posts: 2287
  • Karma: +3/-3
  • Location: near you
Re: Reducing unsprung weight.
« Reply #22 on: January 27, 2011, 03:54:43 PM »
Similar to what Forgestar is doing now but I have yet to see a set of their wheels on a Solstice or a Sky.  ;)

when the snow clears....I'll post photos of LIPSTICK w/ Black F-14 wheels w/ 18x10s  :)

Joshmass saw them.......

I still have to roll out the fenders to make the rear tires fit perfectly.....plus I can lower the car more.....
COMPOUND TURBOS (GT2860r & GT4294r) goal 800hp


CAR SPECS and PHOTOS:
https://www.facebook.com/SKY888CompoundTurbo

SPONSORS:
aeroforce.com, nitrofreeze.com, forgestar.com, splitsec.com, turbosmartonline.com, k1technologies.com, supertechperformance.com, specclutch.com, rceng.com, statusracing.com, tceperformanceproducts.com, burnsstainless.com, performanceautowerks.com, ddmworks.com, turbowerx.com, BTF

Offline idkfa

  • Violent Jain
  • Lifetime Supporting
  • Master Tech
  • *
  • Posts: 395
  • Karma: +0/-1
  • Location: Virginia Beach
  • mostly harmless
    • Make
Re: Reducing unsprung weight.
« Reply #23 on: January 27, 2011, 04:45:46 PM »
when the snow clears....I'll post photos of LIPSTICK w/ Black F-14 wheels w/ 18x10s  :)

Joshmass saw them.......

I still have to roll out the fenders to make the rear tires fit perfectly.....plus I can lower the car more.....

Whoa.  I didn't know they did that as well.  Well that works just fine.


Sky888, I couldn't find much in pricing on their site but I'm digging the F05 and F10s...  It says 1-piece in the left rail so are those bolts fake?  That'd be weird on such a respected name.

Offline SKY888

  • Gearhead
  • ****
  • Posts: 2287
  • Karma: +3/-3
  • Location: near you
Re: Reducing unsprung weight.
« Reply #24 on: January 27, 2011, 04:52:27 PM »
The Forgestar wheels are fully customizable from size/width/offsets.

Im not really sure about the F05 & F10 if they are completely "1-piece" or not.  Never inquired about them since I like the F-14 :)

I'll PM you my sponsor's contact info, you can ask him all the questions! :)
COMPOUND TURBOS (GT2860r & GT4294r) goal 800hp


CAR SPECS and PHOTOS:
https://www.facebook.com/SKY888CompoundTurbo

SPONSORS:
aeroforce.com, nitrofreeze.com, forgestar.com, splitsec.com, turbosmartonline.com, k1technologies.com, supertechperformance.com, specclutch.com, rceng.com, statusracing.com, tceperformanceproducts.com, burnsstainless.com, performanceautowerks.com, ddmworks.com, turbowerx.com, BTF

 

Powered by EzPortal