effectiveness of getting light weight wheels, brakes, etc?
 

in Japan, if you go to any tuners or shops...they'll tell you getting light weight wheels, tires, brakes, are 15x more effective than getting carbon fiber hood and stuff.

so for example, if you reduce 5 lbs from each wheels, (20 lbs total) that would be equivalent to 300lbs (15x20) weight reduction. so you will get better performance and gas milage just as if you actually reduced 300 lbs.

is this true? because pretty much anywhere you go, they will tell you it is 15 times more effective...in terms of performance, gas mileage, etc..

anyone here an engineer? or engineering major?

Unsprung mass: http://en.wikipedia.org/wiki/Unsprung_mass

wheels tires brakes rotors etc anything in that wheel area = un-sprung weight...more weight saving there = easier on your engine to turn the wheels (don't need as much torque to get up to the same rotation)...carbon fiber hood = sprung weight...and really you sitting in the car alone brings up the weight of the entire car

*edit*..damn thought i would be first

i think the same goes with getting a lighter flywheel. a 10pound less flywheel can mean a big difference in acceleration, as if you shed a couple hundred pounds off the car.

it might be simply due to physics. its always easier to start moving something lighter, but easier to KEEP something moving if it were heavier. (in the case of lighter flywheels, slowing down your car faster when you let go of the gas pedal)

the wheels and brakes etc, being at the center of where the force is being applied to move your car. the lighter those are, the easier it is to get them to start turning.

i could be totally wrong here, but thats how i always explained it to friends xD

EDIT: lol, yeah... probably just read what sonick posted ;]

soon as I get a new car, my first mods in Gran Turismo are made in the Drivetrain section, car response after those mods is :fullofwin:

Isn't it called rotational mass? You get more WHP if you have lighter wheels, lighter flywheel, lighter driveshaft. I dont know about lighter brakes tho.. I know bigger brakes and also what they are made of makes a differance, but weight? not to sure about that..

The notion that removing unsprung or rotational weight is much more effective than static weight is certainly true, however, if your JDM tuner is telling you the effects are 15 times as noticeable and that is a consistent number in all situations, you are certainly getting a load of BS.

It is simple... consider two sets of wheels on your car, both are 17" wheels and both have identical tires on them.

Consider this theoretical exampe...
Wheel #1 is 20lbs but has 99% of the mass on the outermost rim of the wheel.
Wheel #2 is 21lbs but has 99% of the mass on the hub and only a fraction on the outermost rim.

Despite wheel #2 being heavier, it will actually be MUCH easier to rotate and will actually lead to the vehicle accelerating faster, despite being heavier overall.

This is some good reading here:
http://victorylibrary.com/mopar/sprung-c.htm

Mark

also a nice example :werd:

the weight of brake rotors do make differences...

there's a JDM Corvette tuner called WEST and they said that the Z06 will move much faster if you switch to light weight brake system like Brembo.

less weight = easier to rotate...

My race car went from stock 16x7 and 16x8 rims and 10" rotors with 4 piston calipers to HEAVY 17x9's all around and 13" rotors with brembo big reds.

At low speeds, is far more resistant to changing direction. I doubt it's 15 or 20x more, but I immediately noticed the heavier steering. This is not an improvement you want to make for a street car or autocross car.

HOWEVER, on the race track, especially at larger tracks, the larger brakes resist fade from high speeds, whereas the smaller brakes get spongy after a day of lapping (even with fresh motul and good pads) and the wider tires are worth the better braking performance and higher cornering speeds.

You only need to go 0-60 once at the start.. which is where the unsprung mass gives the most penalty. Once you are moving and the tires and brakes are already rotating and have some momentum, the added benefits literally outweigh the negatives.

Just got some new lightweight wheels on the astra and loving it, shaved about 30lbs of rotational mass I'm guessing. Also picked a lighter tire even though the car is just for daily driving but better fuel economy and acceleration is always good. :)

Carbon fiber hoods are one of the biggest ripoffs out there.

holy crap a real car thread on rs

Anybody serious about weight reduction for performance will strip their interior before plonking coin on a CF hood... and that's after wheels and tires. Only exception would potentially be for a racing class that may permit CF panel replacement while keeping interior bits.

Started by Timpo of all people, lol
Posted via RS Mobile

I thought Timpo has his own thread.

most CF hoods out there are like fibergrass hood with wet carbon layer on it anyways...that can be bought from $500+

it's not like carbon material you would see on F1 or any race cars...

I heard that if you wanted to get a real dry carbon hood, it would cost you at least $3500+

In theory, since there is less rotating mass, it should also allow you to stop the car quicker, and brake later in the turn. Its not just for 0-60. Its for every acceleration and deceleration you will do into and out of a corner.

Bigger brakes will definitely help resist fade, but with most high end brake systems now-a-days, I believe the calipers are forged as supposed to cast, making it stronger and lighter as well. No one will exchange large brakes for smaller brakes just to save weight (I hope). For a street car, fading brakes are not common, and usually a good set of pads and good rotors should be more then enough.

:fullofwin:

good read
i'd like to learn more about brakes resisting fade idea :whistle:

Brake discs are heat sinks. Bigger heat sink = higher capacity before overheating.

Anybody serious about weight reduction for performance will start by going on a personal eating diet.

fml

I know on a motorcycle that reducing the weight of the wheels has triple the effect of reducing it elsewhere on the bike. I'd guess that it's similar for cars.

There seems to be some gross over inflation in the op's numbers.