How Much Will You Feel a 35-55 Lb. Reduction in Unsprung Weight?
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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?
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Last edited by AMGeez; Oct 16, 2011 at 08:46 PM.
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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.
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09 Steel Gray C63
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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.
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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.
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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.
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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.
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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?
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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.
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Picked up almost 2mph. Looking at the slips I would say average of 1.8mph or so.
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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.
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My experience is with a 40 lbs reduction.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
.
