When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Anyone have any real world proof that lighter wheels shaves time off a 1/4 mile trip?
Realistically, what would they (if at all) take away from the 1/4 mile time? I've been debating a set of lightweight wheels for mine. Few months ago it was time for new rotors so I replaced the OEM rotors with Girodisc lightweight 2 piecers.
Debating on swapping to my Rohana cast wheels (29 & 31#s) for a set of lighter wheels, 23-25#.
Minutely
Less at lower gears (numerically higher) and increasing as the gear is higher ( numerically lower)
Crank torque 300 lb ft
Tire radius 1'
Wt 4000 lb
1st gear overall ratio 10:1 axle T 3000 and thrust is 3000 lbs
You have 3000 lb force to accel 4000 lb
Accel g = 3000/4000 = 0.75
If you reduce the static weight by 4 x 10 lbs
3000/3960 = 0.758 a 1% increase
Using torque
Assume the center of inertia is 0.5'
Heavy wheel T = 0.5 x 10 lbs = 5 lb ft x 2 wheels
So you have 10 lb ft less parasitic losses
10/3000 = 0.33% less loss or net gain
The front wheels don't factor in for T
So you have less mass and less losses 1.33% in this estimation
You can see as gearing decreases the % goes up
If ratio is 5:1 then 1500/4000 = 0.375 and 1500/3960 = 0.379
But not by much 0.004 vs 0.003 g
But the % advantage is pretty much constant
Torque
10/1500 0.67% less losses
Twice the gain
Total ~ 1.67%
Minutely
Less at lower gears (numerically higher) and increasing as the gear is higher ( numerically lower)
Crank torque 300 lb ft
Tire radius 1'
Wt 4000 lb
1st gear overall ratio 10:1 axle T 3000 and thrust is 3000 lbs
You have 3000 lb force to accel 4000 lb
Accel g = 3000/4000 = 0.75
If you reduce the static weight by 4 x 10 lbs
3000/3960 = 0.758 a 1% increase
Using torque
Assume the center of inertia is 0.5'
Heavy wheel T = 0.5 x 10 lbs = 5 lb ft x 2 wheels
So you have 10 lb ft less parasitic losses
10/3000 = 0.33% less loss or net gain
The front wheels don't factor in for T
So you have less mass and less losses 1.33% in this estimation
You can see as gearing decreases the % goes up
If ratio is 5:1 then 1500/4000 = 0.375 and 1500/3960 = 0.379
But not by much 0.004 vs 0.003 g
But the % advantage is pretty much constant
Torque
10/1500 0.67% less losses
Twice the gain
Total ~ 1.67%
Awesome, thank you Ingen
Does anyone have any 1/4 mile runs w stock wheels and then again with light weight wheels?
I have no physics formula's, laws. or scientific proof to contribute like you want, but what I can add is dont only think about acceleration in increasing speed, think about braking also. I've experienced light wheels vs heavier and braking is changed dramatically also. I think anyone who's driven something with and w/o 24" wheels can agree. youtube search so videos of reviews of carbon wheels.
Speaking of light weight wheels: I've noticed that the early model years and even some '13s with the 18" star wheels have solid spokes from the hub to the wheel. My '13 with the p31 package has the 18" wheels but they're hollow from the hub to the wheel as in they are more like two spokes. Is this specific to the p31 package? And I assume that they are a bit lighter than the solid ones no?
Not sure if this was mentioned but for every pound you remove from the wheel and tire combo that equals roughly 7-8Lbs off of the car. So if you switch to wheels and tires that are overall 5Lbs lighter each then that would be as if you were removing 160Lbs from the vehicle. (5 x 4wheels x 8lbs).
I have wheels on my 135i that are 18Lbs compared to 24Lbs stock, it's really noticeable in terms of torque how much of a difference it makes.
RacingBrake offers light weight front and rear two piece rotors for Mercedes C63's, shaving a complete total of 21 lbs!. In fact, We are currently offering a Group Buy special for MBworld members. This group buy will include front and rear two piece rotors and brake pads.
Click on the link below for more information. Offer ends August 15th only 4 days remaining.
^^^^^ Not sure what this has to do with my thread... You could've at least offered up some info instead of this BS attempt at a free plug for yourself.
Anyways, glad I went with GIRODISC instead of RB. The Giro rotors are LIGHTER than the RB... And weight reduction is the name of the game. Thanks for sharing :-)
BTW, Tal at ACG gave me a great price on the a set of the rotors and pads for all 4 corners.
Am I interpreting Igen's calculations to suggest something in the order of a 1.5% benefit...a 12 sec 1/4 mile might become 11.82 sec?
Not sure if that increase equates to TIME. The whole calc is done in Tq, not time. Idk if a 1.5% increase in Tq would necessarily equate to .18 secs lower time.
lighter wheel in combination with a skinny tire - will allow alot less rolling resistance. This is why the smart car rocks 155 fronts and 175 width tires. too bad they are only 3 lug or id totally try it.
I think you guys are looking at 1/4 mile times so this may not be of any interest.
I switched from stock 18" wheels to 20" forged lightweight wheels as well as went for PSS tires. The stock 18" wheels were 29lb rear and 27lb front(quite heavy) and the tires were almost the same.Total rear 58 and 54 front. My new 20" setup were rear wheels 23lb front wheels 21lb and tires rear 26lb front 23lb. I had also gone 20mm wider on the rears. Total rear 49lb and front 44lb.
Weight saving of 9lb at the rear and 10lb
The only comparison I can give is at SPA F1 track and i cut 3 seconds on average. This represents a huge difference. I am quite sure that the diffence was in the increased agility, grip in the corners and braking not in acceleration or top speed(wider rear tire stiffer side walls and reduced weight).
The best thing of all was that with the 20" rims i really didn't notice any difference on the street driving as far as comfort which really surprised me as this was a sacrifice I was willing to make.
My next step is huge 405mm front brakes and 380mm in the rear. I am sure this will not save me any weight due to the increase in size however should give me much less brake fade and shorter stopping distances.
Sorry guys just noticed this is a c63 thread I have a sl600 but the findings from my changes i guess would translate across the board.(to a lesser or greater effect)
I don't think a 2% increase in torque would give you 0.2 in the 1/4 for a rear wheel driven car... Only two wheels get the benefit ... Keep in mind if it's a 4matic, lighter wheels in all four corners makes a bigger difference all else being equal
Guys who have lightweight 2 piece rotors and lightweight wheels w/small skinny's up front can add as much as 3-5+ mph in 1/4 trap speed & drop 3-4 tenths off overall 1/4 ET it's not rocket science.. And the rule of thumb isn't 1 lb unsprung to 1 lb static.. Unsprung weight loss is huge and multiplied as couple others here noted to anywhere from 7-8 times static weight loss etc..
Where unsprung weight really matters is in reducing the weight of wheel + tire as the further the weightloss occurs from the hub is where the most dramatic improvement is seen ie up to 8x static..
IE I dropped 35 lbs in lightweight 2 piece rotors and 50+ in wheels total unsprung weightloss of 85 lbs, you could instantly feel a giant improvement esp in acceleration/handling & braking, if the weightloss was 1 to 1 there's ZERO chance in hell you'd feel ANY 85 lb loss in vehicle static weight (my GF weighs 105 lbs I can't feel a shred of improvment when I drop her off at nail salon lol) ie it's more = to 7-8 x Static or Sprung weight IE equal to dropping 595 lbs - 680 lbs + others have documented & proven these results in 1/4 mile time & time again.. Remember every 100 lbs static weightloss is = to gaining 10 hp etc
RacingBrake offers light weight front and rear two piece rotors for Mercedes C63's, shaving a complete total of 21 lbs!. In fact, We are currently offering a Group Buy special for MBworld members. This group buy will include front and rear two piece rotors and brake pads.
Click on the link below for more information. Offer ends August 15th only 4 days remaining.
I've got two Great Danes (blue female and brindle male).
/offtopic
Originally Posted by Thericker
Guys who have lightweight 2 piece rotors and lightweight wheels w/small skinny's up front can add as much as 3-5+ mph in 1/4 trap speed & drop 3-4 tenths off overall 1/4 ET it's not rocket science.. And the rule of thumb isn't 1 lb unsprung to 1 lb static.. Unsprung weight loss is huge and multiplied as couple others here noted to anywhere from 7-8 times static weight loss etc..
Where unsprung weight really matters is in reducing the weight of wheel + tire as the further the weightloss occurs from the hub is where the most dramatic improvement is seen ie up to 8x static..
IE I dropped 35 lbs in lightweight 2 piece rotors and 50+ in wheels total unsprung weightloss of 85 lbs, you could instantly feel a giant improvement esp in acceleration/handling & braking, if the weightloss was 1 to 1 there's ZERO chance in hell you'd feel ANY 85 lb loss in vehicle static weight (my GF weighs 105 lbs I can't feel a shred of improvment when I drop her off at nail salon lol) ie it's more = to 7-8 x Static or Sprung weight IE equal to dropping 595 lbs - 680 lbs + others have documented & proven these results in 1/4 mile time & time again.. Remember every 100 lbs static weightloss is = to gaining 10 hp etc
2008 CLK63 Black Series 2012 C63 Black Series 2014 SLS Black Series
Want proof? I used to run Dymag carbon fiber wheels on my CLK BS, a 19 inch wheel weighed under 15 pounds. On the dyno they increased my rear wheel hp by about 20whp. Obviously the wheels are not giving you any extra power they are simply freeing up hp. As Thericker mentioned lightweight two-peice rotors are another way to get additional acceleration performance. Another is going with a lightweight carbon fiber driveshaft (availble from Weistec).
Not sure why you guys are saying that loosing weight on the front wheels doesn't matter - unless you are doing a wheelie down the entire 1/4 mile!
The point of loosing wheel (and tire and rotor) weight is that you not only have to move it down the track with the rest of the car but you also have to spin it. So if your front wheels are spinning - whether due to being driven by a drive shaft or just being pushed along on top of the road - they are costing you power.
08-09-2014, 10:43 PM
