Jump to content

reducing unsprung weight


AWW$HEEET

Recommended Posts

IMO unsprung wieght has a tremendous impact on performance. Hell, ask anyone involved in engineering of race cars Reducing unsprung weight will improve acceleration, braking ability, just about all all aspects that are critical to performance.

 

 

 

I can easily feel the impact of putting my 18" 24lb stock wheels on my car vs the 17" 17lb OZ's I also run.

Link to comment
Share on other sites

Think of it as installing a LW flywheel. Reduction in weight is always gonna help. When you're talking about unsprung, it'll help with acceleration, braking as well as handling. The less parisitic drag the better. Adding power is a good thing, but it will only help with acceleration.
Link to comment
Share on other sites

I feel like this was recently brought up somewhere...maybe I saw it on Top Gear about how BMW decreased unsprung weight on the new M3, or maybe somewhere else. Anywho...

 

It makes sense that it would improve handling, acceleration and braking.

Link to comment
Share on other sites

I feel like this was recently brought up somewhere...maybe I saw it on Top Gear about how BMW decreased unsprung weight on the new M3, or maybe somewhere else. Anywho...

 

It makes sense that it would improve handling, acceleration and braking.

 

I think I can lose about 4lbs from each corner with wheels alone. hmm. anyone know if eagle F1s are heavy/light in the tire world?

Link to comment
Share on other sites

Accelerating in any direction takes energy, so if you slam on the gas, hit the brakes, turn left or right, you're using energy to accelerate the mass of your car in a certain direction. This is why everyone wants to reduce weight in a racecar. It's a no-brainer.

 

Rotational weight (i.e., wheels, flywheels, engine internals) is even worse, because the effect gets multiplied by some factor based on the rotational speed and the radius. Accelerating and stopping your wheels rotationally takes more energy than if you were to throw them in the trunk and drive around with them. It's also a no-brainer.

 

Unsprung weight often gets overlooked, but it includes your wheels, brakes, hubs, and some control arms. When you throw the car into a corner, it's very clear that you're using energy to alter the direction of the mass of your car. When you go over a bump, it's not as clear, but when you think about it, you're moving the wheel/brake/hub/control arm mass up and down, and that also takes energy. That energy ultimately comes from gasoline. The car itself might not be moving up and down, but the unsprung weight is.

 

On the racetrack, any time you change directions quickly or drive over bumps or elevation changes, your unsprung weight is moving more than your sprung weight. Not only is it moving, but then you need to stop it from moving. To stop it from moving, you use the shock absorber to slowly transfer the energy into the mass of the car. Believe it or not, you then use more energy from gasoline to counteract the energy received from the shocks. This is why people care more about unsprung weight than sprung weight. Reducing unsprung weight has a greater effect on the overall "snappiness" of the car.

Link to comment
Share on other sites

I hope to god that's a dedicated drag car. Based on the A arm and the 4-lug I'm guessing it's a Fox body, so no real loss I suppose.

 

ETA: Dammit, didn't even notice it's FWD. Nevermind, I = tard.

 

Nope, its a VW. Unfortunately I reconized it by the oil pan, and how the crank trigger is rigged on there. God i need help.

Link to comment
Share on other sites

Drill press is out of order at them moment but the cutting torch is ready to rloll, just need a steady hand.

 

The car pictures was an scca autocross rabbit which actually kicked a huge amount of ass, I think they banned ultra-drilling the next season.

Link to comment
Share on other sites

Drill press is out of order at them moment but the cutting torch is ready to rloll, just need a steady hand.

 

The car pictures was an scca autocross rabbit which actually kicked a huge amount of ass, I think they banned ultra-drilling the next season.

 

lol, i would love to see the definition "ultra-drilling"

Link to comment
Share on other sites

Drill press is out of order at them moment but the cutting torch is ready to rloll, just need a steady hand.

 

The car pictures was an scca autocross rabbit which actually kicked a huge amount of ass, I think they banned ultra-drilling the next season.

I don t think so...there is a badass C-Street-Prepared miata that has ultra-drilled rotors and weighs less than 2000 lbs..... he overheats rotors in a single 50second run (ridiculous)

Bill Schenker

http://images44.fotki.com/v1355/photos/1/1209929/6823155/CSP-vi.jpg

http://lh6.ggpht.com/_-G4gMz5adZc/TMhisldvsQI/AAAAAAAALK4/X2tazqkQhTg/race-the-tire-rack-scca-solo-nationals-img16_gallery_image_large.jpg

 

 

Do it man, do it.

 

http://forums.pelicanparts.com/uploads15/joke+brake+rotor+over+drilled1250112699.jpg

 

 

why is the caliper still there? calipers are heavy

 

 

Colin Chapman once said:

Simplify, then add lightness

 

 

 

OP....i changed to lighter wheels (7lbs per corner) and immediately noticed quicker turn-in at corners........less weight is always a good thing on cars....less weight makes you faster everywhere but power only makes you quicker in a straight line.

That explains why a turbo miata with only 170-200whp will own left, right, up and down Corvettes on a road course.

Less weight also makes you use up less brake pad :)

Link to comment
Share on other sites

Didnt see it mentioned but use this as a test for unsprung mass. Tie a small weight to the end of a leash or something. Swing it around. Now, tie a big 5lb weight to it. Swing it around. Notice how much heavier it gets as you swing it? You're exponentially increasing the mass of the object as you swing it out and thereby having to increase the amount of energy needed to maintain it.

This is the same on your car. It's said that for every pound of unsprung weight you remove, is equivalent to removing 8lbs of static weight. Of course, that wont come into consideration when the car isn't moving, however, once you get going it equates. And of course, nothing improves every aspect of a vehicle's performance except removing weight. Unsprung weight is weight + bonus.

Link to comment
Share on other sites

Early e39's used aluminum front and rear calipers, might be possible to install them on your spindles with a little work. If you're going to that trouble it's probably smarter to go Willwood or other aftermarket race calipers just to open up the pad possibilities.

 

edit: Early e39 528i and e36 M3 actually share the same front brake pad, offset is likely buggered but at least the pad size is correct.

Link to comment
Share on other sites

you guys talking about wheel weight are wrong and right at the same time. yes that is unsprung weight so you are correct.

 

what you are wrong about is the reason why your car handles better with lighter wheels. its not because of the unsprung weight its because of the rotational weight reduction.

 

now on topic this is roughly what you have unsprung. i say roughly because it could be different from car to car based on how the components are mounted.

 

Front:

100% of:

Rim

Tire

Spindle

Brake

Bearings

 

50% of:

Sway bar

Shock

Control arms

Spring

 

Rear

100% of:

differential

Rims

Tires

 

50% of:

Sway Bar

Shocks

Springs

Link to comment
Share on other sites

Long ago I heard that every pound of unsprung weight removed is equivalent to 4-5lbs of sprung weight removed, as far as performance gains.

 

If lightweight rims and wheels could net you 10lbs a corner, it adds up to a pretty significant amount.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...