Unsprung weight and what rim weight does
11-10-2002, 02:14 PM
#1
Registered User
Thread Starter
Join Date: Sep 2002
Location: Noblesville IN
Posts: 283
Likes: 0
Received 0 Likes
on
0 Posts
Unsprung weight and what rim weight does
on the rim weight thing: (look at bottom for specific 350z info)
Unsprung weight is the total weight of components not supported by the springs. This includes control arms, brake components, spindles, wheels and tires. Reducing unsprung weight is a key factor to improving a vehicle's handling.
The higher the vehicle's unsprung weight, the more force with which your suspensions' springs will compress and extend under hard cornering or over bumps. The greater mass of higher unsprung weight causes the springs extend and contract further; compressing and releasing again and again until they finally achieve their resting state. To illustrate this idea, think of a pendulum. The heavier the weight at the end of pendulum, the longer it will take it to come to rest. This excessive movement in the suspension produces a poor ride and reduces cornering grip. In addition, higher unsprung weight forces you to run stiffer shocks to control the extra spring movement, which also contributes to a stiff, harsh ride.
Reducing the weight of the parts not supported by the springs, or the unsprung weight, allows the suspension to react faster. Reducing the unsprung weight reduces the number of compression and release cycles need to achieve a resting state
what does this mean to us (350z owners):
using a edge weighted moment of inertia (bascially the hardest to accellerate because the mass is in position to have most torque towards resisting movement, in other words takes more torque ot turn the wheel), looks liek 7 pounds per wheel = about 91 pounds of dead weight added to the car itself
what this means is that the 28 or so pounds that is taken from the wheels in the fasion that it is and its resistance to movement = dropping 91 pounds off the car .. 100 pounds = +.1 sec in quarter mile (someone once told me this correct me if i'm wrong) so we'd be dropping about .1 sec off a quarter mile by dropping wheel weight... however with a larger wheel 19" even at 7 lbs lighter will have more weight further out changing the moment of iniertia thus possibly canceling the weight savings to some extent and hindering breaking ability by having more mass at further leverage point against the hub of the wheel.
basically if your drag racing this thing you dont want 19's stick w/ 18s... if you autox or race this thing it wont matter much to you on the accelleration matter because you'll spend more time at speed and need to worry more about the driving characteristics such as understeer and turnIn.
Unsprung weight is the total weight of components not supported by the springs. This includes control arms, brake components, spindles, wheels and tires. Reducing unsprung weight is a key factor to improving a vehicle's handling.
The higher the vehicle's unsprung weight, the more force with which your suspensions' springs will compress and extend under hard cornering or over bumps. The greater mass of higher unsprung weight causes the springs extend and contract further; compressing and releasing again and again until they finally achieve their resting state. To illustrate this idea, think of a pendulum. The heavier the weight at the end of pendulum, the longer it will take it to come to rest. This excessive movement in the suspension produces a poor ride and reduces cornering grip. In addition, higher unsprung weight forces you to run stiffer shocks to control the extra spring movement, which also contributes to a stiff, harsh ride.
Reducing the weight of the parts not supported by the springs, or the unsprung weight, allows the suspension to react faster. Reducing the unsprung weight reduces the number of compression and release cycles need to achieve a resting state
what does this mean to us (350z owners):
using a edge weighted moment of inertia (bascially the hardest to accellerate because the mass is in position to have most torque towards resisting movement, in other words takes more torque ot turn the wheel), looks liek 7 pounds per wheel = about 91 pounds of dead weight added to the car itself
what this means is that the 28 or so pounds that is taken from the wheels in the fasion that it is and its resistance to movement = dropping 91 pounds off the car .. 100 pounds = +.1 sec in quarter mile (someone once told me this correct me if i'm wrong) so we'd be dropping about .1 sec off a quarter mile by dropping wheel weight... however with a larger wheel 19" even at 7 lbs lighter will have more weight further out changing the moment of iniertia thus possibly canceling the weight savings to some extent and hindering breaking ability by having more mass at further leverage point against the hub of the wheel.
basically if your drag racing this thing you dont want 19's stick w/ 18s... if you autox or race this thing it wont matter much to you on the accelleration matter because you'll spend more time at speed and need to worry more about the driving characteristics such as understeer and turnIn.
11-10-2002, 03:50 PM
#3
Registered User
Thread Starter
Join Date: Sep 2002
Location: Noblesville IN
Posts: 283
Likes: 0
Received 0 Likes
on
0 Posts
weight inst the most imporant factor when it comes to upsized wheels ,, the distribution of weight is. the way the weight is distributed around the axis the wheel spins is called moment of inertia.
the majority of the weight on a rim is going to be located in the actual rim of the wheel along with the tire its much heavier on the outter edge of the wheel than the inside. Thereby requiring more torque to change the rate of change (accellerate) .. basically because the rim is larger the weight is out further and requires more torque both for braking and accelerating.
when accellerating (positive or negativly) even if a wheel is lighter, if more of the mass is located further out from the hub its going to take more work to create a change
ok ok i am really bad at explaingin things like this, i understand the concepts myself but i'm not good in the verbal dept thats why i make everythign so wordy, can someone else make a quicky version of what i just said? lol
the majority of the weight on a rim is going to be located in the actual rim of the wheel along with the tire its much heavier on the outter edge of the wheel than the inside. Thereby requiring more torque to change the rate of change (accellerate) .. basically because the rim is larger the weight is out further and requires more torque both for braking and accelerating.
when accellerating (positive or negativly) even if a wheel is lighter, if more of the mass is located further out from the hub its going to take more work to create a change
ok ok i am really bad at explaingin things like this, i understand the concepts myself but i'm not good in the verbal dept thats why i make everythign so wordy, can someone else make a quicky version of what i just said? lol
11-10-2002, 05:53 PM
#5
Registered User
Thread Starter
Join Date: Sep 2002
Location: Noblesville IN
Posts: 283
Likes: 0
Received 0 Likes
on
0 Posts
no it has nothing to do with the gear ratio.. that would be more inline w/ changing the outside diameter of the wheel + tire itself (larger outter circumference would be changing the gear ratio)
this is more about something resisting change... for instance, when using a hammer you swing it from the end and it takes more torque in your forarm to swing the hammer, whereas if you held it by the head itself and moved it around it moves much more freely, thats because the majority of the mass of the hammer is closer to where the torque is coming from (your hand),, yet the hammer size is still the same and weighs just as much.
basically it works the same way as your wheel, the axis of the hammar would be your hand or wrist (like the hub of a wheel) and the head of the hammer is the outer edge of the wheel
http://ic.arc.nasa.gov/projects/engi..._intertia.html
and this
An object's moment of inertia is a measure of how resistant it is to changes in rotation. This is determined by two factors: how much mass the object has and how far that mass is from the object's axis of rotation. Increasing mass makes an object harder to rotate and harder to stop rotating, as does increasing the distance between the mass and the axis of rotation (a rolled-out slab of clay, for example, is harder to spin than a tight clay ball with the same mass).
from : http://www.howstuffworks.com/yo-yo2.htm
this is more about something resisting change... for instance, when using a hammer you swing it from the end and it takes more torque in your forarm to swing the hammer, whereas if you held it by the head itself and moved it around it moves much more freely, thats because the majority of the mass of the hammer is closer to where the torque is coming from (your hand),, yet the hammer size is still the same and weighs just as much.
basically it works the same way as your wheel, the axis of the hammar would be your hand or wrist (like the hub of a wheel) and the head of the hammer is the outer edge of the wheel
http://ic.arc.nasa.gov/projects/engi..._intertia.html
and this
An object's moment of inertia is a measure of how resistant it is to changes in rotation. This is determined by two factors: how much mass the object has and how far that mass is from the object's axis of rotation. Increasing mass makes an object harder to rotate and harder to stop rotating, as does increasing the distance between the mass and the axis of rotation (a rolled-out slab of clay, for example, is harder to spin than a tight clay ball with the same mass).
from : http://www.howstuffworks.com/yo-yo2.htm
11-10-2002, 09:46 PM
#6
Registered User
What Tyr is referring to is rotational inertia. In theory, a 15 lb 18" rim can be slower than a 25 lb 17" rim if all the mass is situated at the outer diameter, rather than centralized towards the hub. This is even more pronounced if the rims are of equal weights!
An analogy would be a string with a rock at the end of it. If you were to swing the rock around your head while holding the srting only a few inches away from the attached rock, you'll notice how easy and faster you can spin it. OTOH, if you were to hold the rock a few feet away, it takes more effort to make it spin at the same speed as before.
An analogy would be a string with a rock at the end of it. If you were to swing the rock around your head while holding the srting only a few inches away from the attached rock, you'll notice how easy and faster you can spin it. OTOH, if you were to hold the rock a few feet away, it takes more effort to make it spin at the same speed as before.
11-10-2002, 09:52 PM
#7
Registered User
Join Date: Aug 2002
Location: Los Angeles
Posts: 808
Likes: 0
Received 0 Likes
on
0 Posts
And that is why I am not getting the SSR's (at least one reason)... Not only are they heavier by several lbs, but they are also larger (at 19") and will definately slow the car down.
Trending Topics
11-11-2002, 06:16 PM
#8
Registered User
Thread Starter
Join Date: Sep 2002
Location: Noblesville IN
Posts: 283
Likes: 0
Received 0 Likes
on
0 Posts
thankyou fdao.. i just saw this topic mentioned in a few other threads and thought i'd make an attempt to explain it in one place for everyone... but you did it better :P
11-11-2002, 06:17 PM
#9
Registered User
Thread Starter
Join Date: Sep 2002
Location: Noblesville IN
Posts: 283
Likes: 0
Received 0 Likes
on
0 Posts
however i'm still getting the 19" te37's if i can ever find a way to afford them and teh Z at the same time 
i wouldnt be using the volks on trackdays, way too much money for possible tenths of seconds... not worth it.. i'm not competing for money only to makemyself a better driver... plans for my z = purchase blizzaks lm-22s for winter on stock wheels. ,, spring time = track my stock bridgestones off purchase 19" volks + new tires, purchase softer track type (cant afford hoosiers or anytying) tires for stock wheels and leave them that way till the next winter....
make the most outta my tires and eventually have some good setups depnding on driving environment (for a poor man)
i wouldnt be using the volks on trackdays, way too much money for possible tenths of seconds... not worth it.. i'm not competing for money only to makemyself a better driver... plans for my z = purchase blizzaks lm-22s for winter on stock wheels. ,, spring time = track my stock bridgestones off purchase 19" volks + new tires, purchase softer track type (cant afford hoosiers or anytying) tires for stock wheels and leave them that way till the next winter....
make the most outta my tires and eventually have some good setups depnding on driving environment (for a poor man)
Last edited by ^Tyr; 11-11-2002 at 06:20 PM.
Thread
Thread Starter
Forum
Replies
Last Post
ars88
Zs & Gs For Sale
18
04-04-2016 07:52 AM
