Topic: Reducing unsprung weight.

[J_Bond]

I'm looking into purchasing the Forgestar F14's in 18x8.5 front and rear with 23lb Conti DWS tires.  the F14's are only 17lbs in this size!!!  the DWS's are consistently lighter than every tire I've come across.  
I weighed my stock wheels and tires at 54.5lbs, so 17 + 23 = AWESOME weight reduction and decreased rotational mass!!!  a decrease of 14lbs per hub!!!  56lbs reduction overall!  very nice.  For us lame 2.4L guys, it's a very effective upgrade.

[joshmass]

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

I love your optimism.   

[J_Bond]

ENJOY.
http://www.mini2.com/forum/wheels-tyres-brakes/21269-0-60-simplified-wheel-physics-garfields-wheel-test.html

 you are in fact subtracting 1.8lbs from the chassis from every pound removed from rotating mass.  if you remove 48lbs unsprung weight from the wheels, you are taking 86.4lbs off the sprung weight!  48 x 1.8

[Gentleman Jack]

ENJOY.
http://www.mini2.com/forum/wheels-tyres-brakes/21269-0-60-simplified-wheel-physics-garfields-wheel-test.html

 you are in fact subtracting 1.8lbs from the chassis from every pound removed from rotating mass.  if you remove 48lbs unsprung weight from the wheels, you are taking 86.4lbs off the sprung weight!  48 x 1.8

How does the calculation change for unsprung, non rotating mass?  Is that a 1:1 relationship?

[SKY888]

I love your optimism.   

im very positive bro 

[tbone]

Does anyone know the weight of a stock GXP chrome wheel?  Wait... that would be 26 lbs.

[ophidia31]

I'm looking into purchasing the Forgestar F14's in 18x8.5 front and rear with 23lb Conti DWS tires.  the F14's are only 17lbs in this size!!!  the DWS's are consistently lighter than every tire I've come across. 
I weighed my stock wheels and tires at 54.5lbs, so 17 + 23 = AWESOME weight reduction and decreased rotational mass!!!  a decrease of 14lbs per hub!!!  56lbs reduction overall!  very nice.  For us lame 2.4L guys, it's a very effective upgrade.

Hey, Im not lame.... wait.... nevermind.  lol

Anyway, that is why Im really contemplating the brake kits from TCE. Getting rid of these heavy ass calipers and swap in the light as a feather wilwoods along with dropping a one or two lbs off the rotating mass because of the 2-piece design (possibly breaking even because theyre larger diameter) and also lighter wheels and tires like you mentioned. All around handling and acceleration upgrade. Not many upgrades can do that.

[ophidia31]

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)

You can only account for two of the wheels for helping the vehicle accelerate. So its only a 100lbs difference and .1 in the 1/4mi. If youre awd, then you can say 200lbs.

[HAMMER DOWN]

^^^ No, you count all 4, because you still have to get the front ones moving & stop. The lighter something is, the quicker it can be speed up & then slowed down, bottom line.

Mike  
 

[ophidia31]

I understand that, and i guess if you have to full think about thing, but you arent using anything to drive those extra two wheels, therefore, would only equate to what they would lose from the over all weight of the car, NOT on the driveline of the vehicle where lighter wheel/tire combo would make the biggest difference in acceleration. Sure friction needs to move the non driveling wheels and tires, but it wont equal out to an exact number for the rear like he is saying, it would maybe be 3/8 to 1/2 the theoretical weight loss in acceleration. So 5lbs off the front wheel/tire is just 15-20lbs in the sense of acceleration. Then take into account weight transfer off the front wheels and your lowering the friction lowering that number more. I personally dont look at non driveline wheels because the gains from them arent as much as on driveline wheels. Handling is a different story where then, yes it would seem as 200lbs are removed from the car. Its a variable weight loss when it comes down to it really.

[HAMMER DOWN]

You mite be over thinking it a bit. Not saying your wrong if you want the most accurate calculation. Non drive wheel still getting there mass rotated by the drive line, though indirectly. The liter they are the quicker they spin up to speed.  A good ex. is Funny cars & Top fuel dragster. They use those lite weight, small ,skinny front wheel. Because they have less drag & take less HP to get them moving.

Mike

[J_Bond]

Simply switching to my cheap after market wheels and DWS tires (which were only 5-6lbs lighter a piece) made my 2.4L feel a LOT quicker from a dig.  I'm anxious to see how she does with either the Allegerittas or PF01's I plan on getting.  

Conti DWS tires might not be the most bad@ss performer, but they are much lighter than most tires on the market. and I specifically chose them for that reason.  They do have great ratings for rain and hydroplaning though.

BTW, my stock wheels and tires weighed a hefty 55.4lbs on my scale, so imagine 18lbs PF01's and 23lbs DWS tires at 41lbs....  that's 14lbs of reduced rotating mass per wheel!!!  That will be a noticeable mod for sure! Especially on my 2.4L

[elff]

This is why I stayed with 18x8 wheels.  OZ Ultraleggera's shaved 11lbs each themselves and at the time I purchased them were the lightest weight 18x8 rim made. 

The other thing not mentioned here is outer circumference of tires.
People going with larger rims and thus tires are slowing their vehicle down.

Sly Bob.
I'm well versed in that truck example with my Jeep.  I bet that guy didn't regear so his truck probably feels like a pig.
When I went from 31" tires to 37" tires I went from 4.10 axle gears to 4.88 axle gears.
I also needed to change out the speedometer gear in my T-Case to make it accurate again.

[kennysabarese]

I understand that, and i guess if you have to full think about thing, but you arent using anything to drive those extra two wheels, therefore, would only equate to what they would lose from the over all weight of the car, NOT on the driveline of the vehicle where lighter wheel/tire combo would make the biggest difference in acceleration. Sure friction needs to move the non driveling wheels and tires, but it wont equal out to an exact number for the rear like he is saying, it would maybe be 3/8 to 1/2 the theoretical weight loss in acceleration. So 5lbs off the front wheel/tire is just 15-20lbs in the sense of acceleration. Then take into account weight transfer off the front wheels and your lowering the friction lowering that number more. I personally dont look at non driveline wheels because the gains from them arent as much as on driveline wheels. Handling is a different story where then, yes it would seem as 200lbs are removed from the car. Its a variable weight loss when it comes down to it really.

This note cleared up your first.

There are 3 different concepts here.

Overall weight: Hammer down is correct about.
Unsprung Weight: The topic of this thread... and primarily concerned with handling, and ride comfort on bumps.
Rotating Mass the engine has to turn: is what you are talking about.

All are important for different reasons. Ideally you want all 3 to be as low as possible. But if you forced into a compromise and only had enough money for two wheels, I agree with you and I'd lighten the rears. Also if you are drag racing you can fit smaller/lighter wheels on the back since the calipers are smaller to get it even lighter.

One guy on the BB fit 15's back there I think.

[ophidia31]

You mite be over thinking it a bit.

I have a habit of doing that. Lol

[QuickBlack]

This article which is explaining the benefits of reducing unsprung weight is containing upon valuable information for all those people who are planning to bring some modifications in their vehicles. However this is not good idea to add 14 inch Civic rims on it as it will look ugly.