Weight saving

FazerBoy · 01-16-2009, 10:21 AM

Hiya,

How significant would a weight saving of just over 4 pounds be as compared to the stock wheels? Would this result in any performance advantage?

Cheers

Jack

randomquickness · 01-16-2009, 10:30 AM

4 lbs per wheel or 4 lbs total?

arrutled · 01-16-2009, 12:20 PM

the difference would be more of a feeling from less unsprung weight. It would be a bit less jarring. performance enhancement and gas mileage would have minor improvements if any from what i understand. I also would think you gotta look at the tire too, from company to company tires can vary 3 pounds or so in the same size. Just My opinion.

HighQ · 01-16-2009, 07:03 PM

I don't remember the exact formula but saving 1 pound of unsprung weight has about the same effect as saving 4 pounds from other parts. The point is saving weight fomr the wheels is GREAT!

ZIPNBYE · 01-16-2009, 09:08 PM

The car will handle better (bumps, etc...), brake and accelerate faster (less flywheel action to counteract).

Losing that much on a wheel, tire, or brake rotor is always worth it!

FazerBoy · 01-17-2009, 11:53 AM

Quote:

4 lbs per wheel or 4 lbs total?

I was talking about 4lbs per wheel.

Jack

Citizen Z · 01-17-2009, 01:19 PM

I don't know where I read this by I heard that 100lbs of sprung weight is equivalent to 15ish wheel horsepower. By that ratio, removing 16lbs of unsprung weight is roughly equivalent to about 8-9hp bump.

singular · 01-17-2009, 02:38 PM

Quote:

Originally Posted by Citizen Z

I don't know where I read this by I heard that 100lbs of sprung weight is equivalent to 15ish wheel horsepower. By that ratio, removing 16lbs of unsprung weight is roughly equivalent to about 8-9hp bump.

Just a question: what is sprung vs. unsprung weight?

Thanks!

Lester · 01-17-2009, 03:12 PM

Sprung weight is everything "above" the springs. Everything else, including wheels, brakes and axles - below the springs is unsprung.

This explanantion is from Wikepedia.

In a ground vehicle with a suspension, the unsprung weight (or, more properly, the unsprung mass) is the mass of the suspension, wheels or tracks (as applicable), and other components directly connected to them, rather than supported by the suspension. (The mass of the body and other components supported by the suspension is the sprung mass.)

Unsprung weight includes the mass of components such as the wheel axles, wheel bearings, tires, and a portion of the weight of driveshafts, springs, shock absorbers, and suspension links. If the vehicle's brakes are mounted outboard (i.e., within the wheel), their weight is also part of the unsprung weight.

ZIPNBYE · 01-17-2009, 04:49 PM

Furthermore, unsprung weight (or properly mass) must be overcome to get moving (the power of the engine must start four non-rotating flywheels (wheels, tires, brake rotors, and wheel bearings) and overcome to stop moving (the brakes must stop the same items). The suspension system must overcome the mass upon every irregularity in the road and absorb it's momentum.

Obviously, the less this stuff weighs, the better your car will accelerate, corner, brake, and soak up bumps.

Reducing unsprung weight is one of the many arguements against run-flat tires, as they are a lot heavier than normal tires.

Forged wheels are better than cast wheels for weight. Some tires weigh a surprising amount less than others. Two-piece brake rotors weigh less than one-piece rotors. Etc...

It all comes with a price though...like everything in life.

arrutled · 01-17-2009, 05:05 PM

how much do our RFT's weigh?

singular · 01-17-2009, 06:14 PM

Lester and ZIPNBYE,

Thanks for the great explanations, I must have been sleeping during physics.

ZIPNBYE · 01-17-2009, 08:27 PM

Quote:

Originally Posted by arrutled

how much do our RFT's weigh?

For a comparison, go to a tire manufacturer's website, compare the weight (many list this) for a run-flat vs. a normal summer tire in the size your car has. It's likelly around 4-5lbs per tire more for the run-flat.

Ya gotta do some of the work yourself!

:

arrutled · 01-18-2009, 09:15 AM

argh, you search buttoned me! I was assuming they weighed around 26-27 pounds as i have looked on tirerack but I didnt know if anyone knew off the top of their head. I also looked at some other tires on tirerack, but you can get some good rubber at only 22-23 pounds so thats a nice weight saving right there!

arrutled · 01-18-2009, 11:23 AM

its permanently posted on wikipedia!

Luvmybmw · 01-19-2009, 08:38 AM

Quote:

Originally Posted by arrutled

how much do our RFT's weigh?

Stock 264 style wheels are 11kg (24.2 lbs) front and 11.92 (26.2 lbs)kg rear.:wink:

ZIPNBYE · 01-19-2009, 09:23 AM

Quote:

Originally Posted by arrutled

argh, you search buttoned me!

So you had already anticipated it eh? :biggrin: I couldn't help myself, as the invitation was too big. :wink:

Add1ct · 02-16-2009, 03:13 PM

from what I've read elsewhere on here, stock 264s- 25lbs front, 26lbs rear, stock bridgestone runflats, 24lbs front, 26lbs rear- tirerack-

I am thinking either breyton gts-r 18s at about 17 front and 18 rear or Enkei RPF1s at 18lbs or OZ Alleggeritas at about 18lbs and contisportcontact3s 235/40 18 all around at 21lbs

this would take me to about 39lbs/ corner vs 49 front and 52 rear so a net savings of 20lbs unsprung front and 26 lbs unsrpung rear, or a total of 46lbs!!

add on the BMW performance rotors at 3.1lbs less per corner and now I'd be down 58lbs-ish of unsprung weight- so if 16lbs is about 8 whp per above then that's almost 30 whp equivalent!!!, probably optimistic but probably would be able to feel this

akak1997 · 02-17-2009, 11:34 AM

talking about unsprung weight, anyone know if there's any manufacturer out there planning on a light weight one piece CF drive shaft for the 135?

Add1ct · 02-17-2009, 11:48 AM

^ probably- I saw on e90 or maybe here- Wed Sport I think, in Japan has developed CF WHEELS!!! 6lbs each!!!

01-16-2009, 10:21 AM	#1
FazerBoy Lieutenant 50 Rep 511 Posts Drives: BMW E92 M3 Join Date: Jul 2008 Location: London, UK iTrader: (0)	Weight saving Hiya, How significant would a weight saving of just over 4 pounds be as compared to the stock wheels? Would this result in any performance advantage? Cheers Jack
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01-16-2009, 10:30 AM	#2
randomquickness Brigadier General 219 Rep 3,668 Posts Drives: 996tt Join Date: Sep 2008 Location: Georgetown, TX iTrader: (13)	4 lbs per wheel or 4 lbs total? __________________
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01-16-2009, 12:20 PM	#3
arrutled Colonel 104 Rep 2,474 Posts Drives: Olsa Join Date: Jun 2008 Location: Western Mass iTrader: (0)	the difference would be more of a feeling from less unsprung weight. It would be a bit less jarring. performance enhancement and gas mileage would have minor improvements if any from what i understand. I also would think you gotta look at the tire too, from company to company tires can vary 3 pounds or so in the same size. Just My opinion. __________________ AW 135i w/ blackette, performance short shift kit, BMW alarm, Performance rotors, APEX ARC-8 wheels, Direzza Star Spec 235/275, Dinan stage 3 suspension, M3 wishbones/tension rods/front sway/rear subframe bushings and thats all folks!
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01-16-2009, 07:03 PM	#4
HighQ Quality is everything 12 Rep 756 Posts Drives: you mad Join Date: Jul 2008 Location: USA iTrader: (0)	I don't remember the exact formula but saving 1 pound of unsprung weight has about the same effect as saving 4 pounds from other parts. The point is saving weight fomr the wheels is GREAT!
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01-16-2009, 09:08 PM	#5
ZIPNBYE Let's save military ranks for those who earn it! 45 Rep 1,161 Posts Drives: ...on the Ragged Edge Join Date: Dec 2008 Location: Edmonton, AB, Canada iTrader: (6) Garage List 2013 BMW e92 M3 Cou ... [7.50] 2013 BMW e84 X1 xDr ... [7.00]	The car will handle better (bumps, etc...), brake and accelerate faster (less flywheel action to counteract). Losing that much on a wheel, tire, or brake rotor is always worth it! __________________ Richard 2013 BMW M3 Individual -- Fire Orange (sold) 2013 BMW X1 xDrive35i M-Sport -- Valencia Orange (sold) 2011 BMW 1-series M Coupe (#205/220) -- Valencia Orange (sold) 2009 BMW 135i M-Sport Coupe -- Space Grey (sold)
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01-17-2009, 01:19 PM	#7
Citizen Z Alpine Master 111 Rep 1,310 Posts Drives: '08 135i AW Sport Join Date: May 2008 Location: Kansas iTrader: (1)	I don't know where I read this by I heard that 100lbs of sprung weight is equivalent to 15ish wheel horsepower. By that ratio, removing 16lbs of unsprung weight is roughly equivalent to about 8-9hp bump. __________________ Alpine White with Taupe Leather 135i, Sports Package, Heated Seats, Comfort Access, iPod Adapter Fastness: http://www.1addicts.com/forums/showthread.php?t=252727
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01-17-2009, 03:12 PM	#9
Lester Brigadier General 295 Rep 3,350 Posts Drives: Join Date: Oct 2007 iTrader: (0)	Sprung weight is everything "above" the springs. Everything else, including wheels, brakes and axles - below the springs is unsprung. This explanantion is from Wikepedia. In a ground vehicle with a suspension, the unsprung weight (or, more properly, the unsprung mass) is the mass of the suspension, wheels or tracks (as applicable), and other components directly connected to them, rather than supported by the suspension. (The mass of the body and other components supported by the suspension is the sprung mass.) Unsprung weight includes the mass of components such as the wheel axles, wheel bearings, tires, and a portion of the weight of driveshafts, springs, shock absorbers, and suspension links. If the vehicle's brakes are mounted outboard (i.e., within the wheel), their weight is also part of the unsprung weight. Attached Images
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01-17-2009, 04:49 PM	#10
ZIPNBYE Let's save military ranks for those who earn it! 45 Rep 1,161 Posts Drives: ...on the Ragged Edge Join Date: Dec 2008 Location: Edmonton, AB, Canada iTrader: (6) Garage List 2013 BMW e92 M3 Cou ... [7.50] 2013 BMW e84 X1 xDr ... [7.00]	Furthermore, unsprung weight (or properly mass) must be overcome to get moving (the power of the engine must start four non-rotating flywheels (wheels, tires, brake rotors, and wheel bearings) and overcome to stop moving (the brakes must stop the same items). The suspension system must overcome the mass upon every irregularity in the road and absorb it's momentum. Obviously, the less this stuff weighs, the better your car will accelerate, corner, brake, and soak up bumps. Reducing unsprung weight is one of the many arguements against run-flat tires, as they are a lot heavier than normal tires. Forged wheels are better than cast wheels for weight. Some tires weigh a surprising amount less than others. Two-piece brake rotors weigh less than one-piece rotors. Etc... It all comes with a price though...like everything in life. __________________ Richard 2013 BMW M3 Individual -- Fire Orange (sold) 2013 BMW X1 xDrive35i M-Sport -- Valencia Orange (sold) 2011 BMW 1-series M Coupe (#205/220) -- Valencia Orange (sold) 2009 BMW 135i M-Sport Coupe -- Space Grey (sold)
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01-17-2009, 05:05 PM	#11
arrutled Colonel 104 Rep 2,474 Posts Drives: Olsa Join Date: Jun 2008 Location: Western Mass iTrader: (0)	how much do our RFT's weigh? __________________ AW 135i w/ blackette, performance short shift kit, BMW alarm, Performance rotors, APEX ARC-8 wheels, Direzza Star Spec 235/275, Dinan stage 3 suspension, M3 wishbones/tension rods/front sway/rear subframe bushings and thats all folks!
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01-17-2009, 06:14 PM	#12
singular Captain 21 Rep 935 Posts Drives: BSM 135i ppk cab Join Date: Nov 2008 Location: SF Bay Area iTrader: (0)	Lester and ZIPNBYE, Thanks for the great explanations, I must have been sleeping during physics.
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01-18-2009, 09:15 AM	#14
arrutled Colonel 104 Rep 2,474 Posts Drives: Olsa Join Date: Jun 2008 Location: Western Mass iTrader: (0)	argh, you search buttoned me! I was assuming they weighed around 26-27 pounds as i have looked on tirerack but I didnt know if anyone knew off the top of their head. I also looked at some other tires on tirerack, but you can get some good rubber at only 22-23 pounds so thats a nice weight saving right there! __________________ AW 135i w/ blackette, performance short shift kit, BMW alarm, Performance rotors, APEX ARC-8 wheels, Direzza Star Spec 235/275, Dinan stage 3 suspension, M3 wishbones/tension rods/front sway/rear subframe bushings and thats all folks!
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01-18-2009, 11:23 AM	#15
arrutled Colonel 104 Rep 2,474 Posts Drives: Olsa Join Date: Jun 2008 Location: Western Mass iTrader: (0)	its permanently posted on wikipedia! __________________ AW 135i w/ blackette, performance short shift kit, BMW alarm, Performance rotors, APEX ARC-8 wheels, Direzza Star Spec 235/275, Dinan stage 3 suspension, M3 wishbones/tension rods/front sway/rear subframe bushings and thats all folks!
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02-16-2009, 03:13 PM	#18
Add1ct Lieutenant Colonel 59 Rep 1,859 Posts Drives: 135i, 335i Join Date: Sep 2008 Location: Palos Verdes Estates (SoCal) iTrader: (3)	from what I've read elsewhere on here, stock 264s- 25lbs front, 26lbs rear, stock bridgestone runflats, 24lbs front, 26lbs rear- tirerack- I am thinking either breyton gts-r 18s at about 17 front and 18 rear or Enkei RPF1s at 18lbs or OZ Alleggeritas at about 18lbs and contisportcontact3s 235/40 18 all around at 21lbs this would take me to about 39lbs/ corner vs 49 front and 52 rear so a net savings of 20lbs unsprung front and 26 lbs unsrpung rear, or a total of 46lbs!! add on the BMW performance rotors at 3.1lbs less per corner and now I'd be down 58lbs-ish of unsprung weight- so if 16lbs is about 8 whp per above then that's almost 30 whp equivalent!!!, probably optimistic but probably would be able to feel this __________________ E82 N54 6MT 6FL 668 KASW turned in E92 Crimson/Cream N54 6MT, ZSP, ZPP, ZCW, Nav, Sat radio, HD Radio, Logic7, PDC, Active Steering, Active Cruise, 6FL, CA
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02-17-2009, 11:34 AM	#19
akak1997 Major 64 Rep 1,159 Posts Drives: BMW 135 @ 135mph Join Date: Aug 2008 Location: Los Angeles iTrader: (2) Garage List 2008 135i [0.00]	talking about unsprung weight, anyone know if there's any manufacturer out there planning on a light weight one piece CF drive shaft for the 135?
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02-17-2009, 11:48 AM	#20
Add1ct Lieutenant Colonel 59 Rep 1,859 Posts Drives: 135i, 335i Join Date: Sep 2008 Location: Palos Verdes Estates (SoCal) iTrader: (3)	^ probably- I saw on e90 or maybe here- Wed Sport I think, in Japan has developed CF WHEELS!!! 6lbs each!!! __________________ E82 N54 6MT 6FL 668 KASW turned in E92 Crimson/Cream N54 6MT, ZSP, ZPP, ZCW, Nav, Sat radio, HD Radio, Logic7, PDC, Active Steering, Active Cruise, 6FL, CA
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