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 UnSprung Weight Reduction Opinions

 Created by: 6464
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 Posted: Nov 7, 2019 06:06AM
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CA
Part of the recipe for wheel control is the springing and damping. If the springs are too stiff they will be less likely to deflect/rebound when the wheel hits a bump. The impact will be absorbed partly by the tire and partly by the displacement of the sprung mass (the car body). Every spring tends to oscillate until internal resistance overcomes the oscillations. With no or bad dampers (aka shock absorbers) on a car, the spring will cause the wheel to hop and/or the car body to bounce up and down. The intent of a damper is to overcome this. Logically, the damper selection should be tuned to the type of spring installed. Too soft and the spring will oscillate. Too hard and the spring will not be as compliant to the road and contact will be diminished. Finer point: good quality shock absorbers have two rates of damping: compression (generally higher to assist the spring in resisting the compressive force) and rebound (generally softer to allow the spring to react quicker to the unloaded condition and push the wheel down onto the ground sooner).

The traditional "bounce the car" test to assess damper condition really doesn't do much. It will only tell you if the dampers are completely useless. I once saw a demonstration (and had my car tested) of a shock testing machine. It consisted of a small platform on which a subject wheel is placed to be tested. The platform could be vibrated at varying frequencies to simulate various road surface conditions ( like washboard  for instance). At critical frequencies, a wheel with a weak shock absorber would begin to bounce and the car would shake/bounce. A good shock absorber would keep the tire in contact with the platform at all frequencies. My car aced it!

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"Hang on a minute lads....I've got a great idea."

 Posted: Nov 6, 2019 02:03PM
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Thanks Dan, I read the wiki page. Like Cooper Tune and you are saying I'm not going to feel much difference. I guess if I was racing and trying to go as fast as I could I would need the rubber to be making continuous contact with the road surface wether accelerating, braking or turning. Rather than skipping over the surface. I'm not racing so this would be a brag factor.

Thank you to all for the enlightenment.

 Posted: Nov 5, 2019 01:03PM
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CA
Quote:
Originally Posted by 6464
I just switched back to Minitastic Town and Country Metal 4 coil springs because i really like the softer ride. I'm wondering if the lighter swivel  hubs, drive flanges and calipers would enhance the ride like the springs did. Where are the alloy parts now?
Reducing unsprung mass probably won't improve comfort. From Wikipedia; "However, the lighter wheel will soak up less vibration. The irregularities of the road surface will transfer to the cabin through the suspension and hence ride quality and road noise are worse. "

See the article https://en.wikipedia.org/wiki/Unsprung_mass

As I understand it, the lower the unsprung mass, the quicker the tire regains contact with the road surface, improving control. A Mini's tire, wheel hub and brake are already significantly smaller than those of a conventional vehicle, so unsprung mass is already comparatively low. (I can pick up a Mini wheel with one had; can't do it for our other vehicles. Ditto break disks/drums.)

.

"Hang on a minute lads....I've got a great idea."

 Posted: Nov 5, 2019 10:43AM
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Quote:
Originally Posted by 6464
Hi All, What would I feel if I was able to lose about 6lbs per front wheel besides lighter in the wallet? 
A light alloy wheel, 10 inch Mamba's used to be the lightest.

If in doubt, flat out. Colin Mc Rae MBE 1968-2007.

Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.

 Posted: Nov 5, 2019 05:57AM
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I am confused once again. The parts we have been working with are on the customers car. I'm sure in my notes some place I have the weight difference for the different parts. Doing suspension this week I once again have noticed the high unsprung weight with these cars. Assembled a fully adjustable single bolt front sub with Alloy four pots calipers. It still required two to move it from bench to sub frame rolling stand. After running power units on test stand I install power unit into front sub on a low rolling stand which I can lower the shell onto.

Moving the complete rear std swing arms they are very heavy as well. KAD swing arms, alloy hubs and super mini fins would help there as well. That's what we did to the white car. It also rides on S racer red springs. The goal is to go faster around corners. Improved ride would just be a by product of our efforts.

When a car is in parts for some time it is hard to compare ride and when it's not a car you drive often ( belongs to someone else who lives somewhere else ) more interested in my entry and exit speed thought my test section and not collecting the guard rail they replace weekly. Steve (CTR)

 Posted: Nov 1, 2019 05:35AM
 Edited:  Nov 5, 2019 09:30AM
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I just switched back to Minitastic Town and Country Metal 4 coil springs because i really like the softer ride. I'm wondering if the lighter swivel  hubs, drive flanges and calipers would enhance the ride like the springs did. Where are the alloy parts now?

 Posted: Oct 31, 2019 04:26PM
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We have been tuning suspension for several years and it's hard to tell a difference. More fun to work on. If building a serious auto cross car it might be worth the cost. Steve (CTR)

 Posted: Oct 31, 2019 08:15AM
 Edited:  Oct 31, 2019 08:16AM
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Jedduh, No racing. 

Steve, what was your reaction to the changes you made?

 Posted: Oct 31, 2019 07:12AM
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Been down that road, KAD hubs and drive flanges, alloy calipers or magnesium if you really want to go broke. Just a friendly little street car. Lightest wheels and tires help. I have pictures if anyone want me to text them pics and they can post. Steve (CTR)

 Posted: Oct 31, 2019 06:51AM
 Edited:  Oct 31, 2019 06:53AM
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Butt dyno might react a bit faster.
      Less rolling mass might require a bit more gas pedal to keep momentum in things.

YOU would know you lost 12 lbs of metal, That will make ya faster!

Who are you racing?

The most improvements might be with Passenger weight loss + drivers skill...

 Posted: Oct 31, 2019 05:41AM
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Hi All, What would I feel if I was able to lose about 6lbs per front wheel besides lighter in the wallet?