How Much Will You Feel a 35-55 Lb. Reduction in Unsprung Weight?
10-16-2011, 06:31 PM
#1
Member
Thread Starter
Join Date: Oct 2011
Posts: 105
Likes: 0
Received 0 Likes
on
0 Posts
09 Steel Gray C63
How Much Will You Feel a 35-55 Lb. Reduction in Unsprung Weight?
For those who have done it before...if I were to go with light weight forged 18's and the lightest tires I can get, what kind of an impact would that 35-55 lb. reduction in unsprung weight have on acceleration, handling, gas mileage and seat of the pants feel?
Photoshop...
Photoshop...
Last edited by AMGeez; 10-16-2011 at 08:46 PM.
10-16-2011, 06:32 PM
#2
I only ever notice it in handling response and the cars ability to deal with uneven pavement. The car is sharper, feels "lighter" and more compliant. I never notice it in power acceleration.
10-16-2011, 06:34 PM
#3
Member
Thread Starter
Join Date: Oct 2011
Posts: 105
Likes: 0
Received 0 Likes
on
0 Posts
09 Steel Gray C63
10-16-2011, 08:31 PM
#5
Member
Thread Starter
Join Date: Oct 2011
Posts: 105
Likes: 0
Received 0 Likes
on
0 Posts
09 Steel Gray C63
I was just reading some info. from a guy that dropped 10 lbs. per corner off of his car. It was a different vehicle than a C63 but he had made multiple 1/4 mile passes with each set of wheels and the elapsed time improved by an average of 8/10's of second. That is pretty huge.
10-16-2011, 08:49 PM
#6
MBWorld Fanatic!
I was just reading some info. from a guy that dropped 10 lbs. per corner off of his car. It was a different vehicle than a C63 but he had made multiple 1/4 mile passes with each set of wheels and the elapsed time improved by an average of 8/10's of second. That is pretty huge.
10-16-2011, 08:53 PM
#7
Member
Join Date: Jan 2011
Location: Everywhere
Posts: 204
Likes: 0
Received 0 Likes
on
0 Posts
C63 AMG
I was just reading some info. from a guy that dropped 10 lbs. per corner off of his car. It was a different vehicle than a C63 but he had made multiple 1/4 mile passes with each set of wheels and the elapsed time improved by an average of 8/10's of second. That is pretty huge.
Trending Topics
10-16-2011, 08:54 PM
#8
Member
Thread Starter
Join Date: Oct 2011
Posts: 105
Likes: 0
Received 0 Likes
on
0 Posts
09 Steel Gray C63
Yeah, that is what he said... "I have proven this point to many people with a set of 18" chromies and my normal 15" steelies on my drag car .... there was a 10 lb. difference per wheel (18's were heavier and my car ran a consistent 10.90's - 10.97's on 6 runs with the eighteens and 10.10's - 10.20's with my 15's." I'm not sure if the overall wheel+tire diameter was the same in his example.
10-16-2011, 08:57 PM
#9
Member
Thread Starter
Join Date: Oct 2011
Posts: 105
Likes: 0
Received 0 Likes
on
0 Posts
09 Steel Gray C63
That seems more realistic. Did it impact the MPH in the 1/4 or just the elapsed time? Did you have the same tires on before and after?
10-17-2011, 02:45 AM
#10
MBWorld Fanatic!
You'll notice just a bit more snap in acceleration feel, suspension reaction time, and perhaps some braking improvement. Just don't go too crazy and get super light wheels for the street which can't deal with our poor road conditions.
10-17-2011, 07:57 AM
#11
Member
Join Date: Jan 2011
Location: Everywhere
Posts: 204
Likes: 0
Received 0 Likes
on
0 Posts
C63 AMG
Picked up almost 2mph. Looking at the slips I would say average of 1.8mph or so.
10-17-2011, 08:21 AM
#12
Member
Join Date: Jan 2011
Location: Everywhere
Posts: 204
Likes: 0
Received 0 Likes
on
0 Posts
C63 AMG
Yeah, that is what he said... "I have proven this point to many people with a set of 18" chromies and my normal 15" steelies on my drag car .... there was a 10 lb. difference per wheel (18's were heavier and my car ran a consistent 10.90's - 10.97's on 6 runs with the eighteens and 10.10's - 10.20's with my 15's." I'm not sure if the overall wheel+tire diameter was the Isame in his example.
10-17-2011, 11:38 AM
#13
My experience is with a 40 lbs reduction.
10-17-2011, 01:36 PM
#14
Administrator
Join Date: Nov 2001
Location: THE Orange County, California
Posts: 11,921
Received 795 Likes
on
495 Posts
2020 Audi R8 V10, 2016 AMG GTS, 2018 E63S Edition 1, 2018 Porsche GTS Cab, 2012 C63 BS
I think the rule of thumb is for each lb of unsprung weight you shave is equal to about 4 times the sprung weight amount reduced.
Eg lets say you drop 40 lbs in unsprung weight via wheels, rotors, etc; it would be the equivalent of taking 160 lbs out of your car (sprung) like an imaginary passenger that was sitting there the whole time.
Unsprung weight makes a nice difference in acceleration. On my W211 E55 I had a set of HRE comps made but while they were in production I bought a cheap set of TSW 5 spokes that weighed about 30lbs each. Once I put the HRE's on that weighed 21lbs each I could easily tell the difference in start acceleration. I dropped about 36 lbs in unsprung weight or about 144 lbs of sprung.
Im think the 4:1 ratio is fair but im sure there are experts who may have better empirical data. As for the gains--- I dont know exactly but the launch was faster.
Eg lets say you drop 40 lbs in unsprung weight via wheels, rotors, etc; it would be the equivalent of taking 160 lbs out of your car (sprung) like an imaginary passenger that was sitting there the whole time.
Unsprung weight makes a nice difference in acceleration. On my W211 E55 I had a set of HRE comps made but while they were in production I bought a cheap set of TSW 5 spokes that weighed about 30lbs each. Once I put the HRE's on that weighed 21lbs each I could easily tell the difference in start acceleration. I dropped about 36 lbs in unsprung weight or about 144 lbs of sprung.
Im think the 4:1 ratio is fair but im sure there are experts who may have better empirical data. As for the gains--- I dont know exactly but the launch was faster.
10-17-2011, 02:10 PM
#15
MBWorld Fanatic!
It will also "free up" some HP. When I switched from my stock forged Black Series wheels to my Dymags I saved about 14 pounds per wheel and that translated to about 20 hp on the dyno. you will also notice a slight difference in stearting input feel as well as shorter braking distances. Reducing unsprung weight is one of the best things you can do to imporve a cars performance. If you have the money switch over to some lighter weight 2-peice brake rotors and compound the performance gains.
10-17-2011, 02:18 PM
#16
It will also "free up" some HP. When I switched from my stock forged Black Series wheels to my Dymags I saved about 14 pounds per wheel and that translated to about 20 hp on the dyno. you will also notice a slight difference in stearting input feel as well as shorter braking distances. Reducing unsprung weight is one of the best things you can do to imporve a cars performance. If you have the money switch over to some lighter weight 2-peice brake rotors and compound the performance gains.
10-17-2011, 02:27 PM
#17
MBWorld Fanatic!
Yes, it actually showed up as a 20+rwhp gain on the dyno. Have you heard the term "driveline loss" when talking about HP figures? generaly there's a 17-20% "driveline loss" in power, that loss is attributed to all the mass and stuff the car must move/turn to push the car down the road. Things such as pulley, belt, drive shafts, torque converters, axles, rear-ends, brake rotors and wheels/tires all add to the driveline loss. That's why crank HP figures are always 17-20% higher than rwhp numbers. The lighter you can make the driveline the more of that HP you will recapture, you're not "making" more HP you are simply freeing up HP that was lost with the higher weight stuff.
10-17-2011, 02:30 PM
#18
MBWorld Fanatic!
Join Date: Aug 2008
Location: N.Jersey and New York, stationed in Germany
Posts: 1,291
Likes: 0
Received 1 Like
on
1 Post
W164 ML500,SMART For two,1994 C280(5speed manual) 1999 C230k station wagon
Very informative you guys, one of the better threads in a long time and this comes at a good time since I am looking right now for light weight wheels for one of my vehicles.Please carry on.
10-17-2011, 02:41 PM
#19
MBWorld Fanatic!
I want to say that some three piece wheels are engineered specifically for racing as removing the weight furthest away from the center of rotation helps the most. Those dymags jr runs are a perfect example.
10-17-2011, 03:32 PM
#20
MBWorld Fanatic!
Join Date: Aug 2005
Location: North Jersey
Posts: 2,207
Likes: 0
Received 2 Likes
on
2 Posts
2012 CTS-V
I bought a set of 18" Forgestars and Evosport 2-piece rotors and saved
70lbs. of unsprung wieght.
Wheels saved me 30lbs and the rotors 40lbs. Also, the Nitto tires I use
are about 1-2 lbs. lighter than the stock Pirelli's. Every little bit helps.
Throw in the hood(31lbs), trunk(14lbs.)and battery(40lbs.) and I saved
155lbs. in total.
The car feels much lighter than before especially at 100+ near the end
of the 1/4 mile.
70lbs. of unsprung wieght.
Wheels saved me 30lbs and the rotors 40lbs. Also, the Nitto tires I use
are about 1-2 lbs. lighter than the stock Pirelli's. Every little bit helps.
Throw in the hood(31lbs), trunk(14lbs.)and battery(40lbs.) and I saved
155lbs. in total.
The car feels much lighter than before especially at 100+ near the end
of the 1/4 mile.
10-17-2011, 04:34 PM
#21
Yes, it actually showed up as a 20+rwhp gain on the dyno. Have you heard the term "driveline loss" when talking about HP figures? generaly there's a 17-20% "driveline loss" in power, that loss is attributed to all the mass and stuff the car must move/turn to push the car down the road. Things such as pulley, belt, drive shafts, torque converters, axles, rear-ends, brake rotors and wheels/tires all add to the driveline loss. That's why crank HP figures are always 17-20% higher than rwhp numbers. The lighter you can make the driveline the more of that HP you will recapture, you're not "making" more HP you are simply freeing up HP that was lost with the higher weight stuff.
10-17-2011, 04:36 PM
#22
I bought a set of 18" Forgestars and Evosport 2-piece rotors and saved
70lbs. of unsprung wieght.
Wheels saved me 30lbs and the rotors 40lbs. Also, the Nitto tires I use
are about 1-2 lbs. lighter than the stock Pirelli's. Every little bit helps.
Throw in the hood(31lbs), trunk(14lbs.)and battery(40lbs.) and I saved
155lbs. in total.
The car feels much lighter than before especially at 100+ near the end
of the 1/4 mile.
70lbs. of unsprung wieght.
Wheels saved me 30lbs and the rotors 40lbs. Also, the Nitto tires I use
are about 1-2 lbs. lighter than the stock Pirelli's. Every little bit helps.
Throw in the hood(31lbs), trunk(14lbs.)and battery(40lbs.) and I saved
155lbs. in total.
The car feels much lighter than before especially at 100+ near the end
of the 1/4 mile.
10-17-2011, 05:03 PM
#23
Senior Member
Join Date: Aug 2009
Location: Sydney & the NSW Central Coast, Australia
Posts: 499
Likes: 0
Received 1 Like
on
1 Post
C63 AMG, BMW 135i
Unsprung weight i.e. rims, tyres, brakes plus a percentage of the control arms, shocks and struts etc is the weight not supported by the suspension.
1lb of unsprung weight is equal to roughly 4lb of dead weight, i.e. the weight of the car body and everything in and on it.
So a 20lb saving on the weight of your rims and tyres will equate to the same as an 80lb saving on the car body, for example removing the back seat from the car.
Reducing unsprung weight will definitely help acceleration and handling and light rims and tyres are noticeable when driving.
.
1lb of unsprung weight is equal to roughly 4lb of dead weight, i.e. the weight of the car body and everything in and on it.
So a 20lb saving on the weight of your rims and tyres will equate to the same as an 80lb saving on the car body, for example removing the back seat from the car.
Reducing unsprung weight will definitely help acceleration and handling and light rims and tyres are noticeable when driving.
.
