Spring waits?

[wun911]

I got some tens coilovers they come with both the 6 kg and 7 kg rear springs, I think the fronts are 7 kg and 9 kg.

1: Are the "stiffer" springs heavier and by how much?
2: Is the spring itself considered "unsprung" weight?
3: What is the lightest spring and shock combo available for the NB8B?

[lee]

I don't know if there is a technical term for it, but I'd imagine the suspension components (A arms, shocks, springs etc) would be 'semi-sprung' weight, as they move (roughly, depending on geometry) as much as the hub assembly and related components.

If you don't already know, the 6kg/7kg unit should actually be 6kg/mm, as that dictates how much mass is required to move the spring one millimetre. They have no direct relation to the actual mass of the spring itself, apart from the fact that for the same material, coil diameter, pitch and length, you'd need to make the wire diameter slightly bigger to create the extra spring constant, which would add some mass to the system.

From what I hear, Ohlins engineer their coilovers with mass in mind, but they are quite expensive.

You'd be much better shaving weight from other areas, such as removing the sound damping material under the carpets, removing the carpets themselves, getting a fixed back bucket seat and bolting it straight to the floor, removing any AC systems, removing the soft top and using a hard top instead, and if you've got crazy money, replacing body panels with fibreglass or carbon fibre, and getting a titanium exhaust system.

EDIT: Also, talk to Lightyear and NitroDann.

[Black_Penguin]

The spring/shock combo is considered to transfer from sprung to unsprung weight about halfway along its length.

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[wun911]

So technically the 7 kg spring should weigh more than the 6 kg spring; because it needs more mass to create more stiffness??? Or because it has the potential to store more energy per mm so therefore it needs to have more mass to store that energy???

If a spring is compressed the force it exerts must be proportional to its change in length thefore "stiffness" must be created from the number of 'coils' ie length???? ie the number of helical revolutions of the spring itself??
Does the stiffer spring have more coils in its overal hight and therefore must weigh more???
(I cant really tell because one is in the coilover and held in a compressed state and the other one is 'free' and I only have clothes hangers to take it apart)

How do you calculate the "50%" of the weight of the coilover is considered as "unsprung weight" therefore savings of 'say' 0.532kg and 0.254kg front and rear respectively are actually quite substantial and better to pursue than say removing a air con at 10.321Kg especially if you belive in a 10:1 ratio of sprung vs unsprung weight etc. Hence if you gave me a choice of one or the other I would still rather have 1kg shaved off the 'unsprung weight' than shaved 10kg off the 'sprung weight'.

[PaulF]

The performance of your suspension, and your car as a whole, is going to be altered far more by the spring rate than by the mass of the spring.

If a spring is compressed the force it exerts must be proportional to its change in length thefore "stiffness" must be created from the number of 'coils' ie length???? ie the number of helical revolutions of the spring itself??

This is incorrect. The length being referred to here is along the axis of compression, i.e. parallel to the shock absorber.

[project.r.racing]

In answer to the question regards how much springs may weigh compared to eachother. Yes there'd be a difference. But the is no equation or answer to figuring it out. As the metals/materials used and manufacturing process is not known. you'd really have to have both springs in front of you to know the extact difference.

but the differences in weight would not be much. 100-200g. The ID, thickness, length and no. of coils would change the actual weight of the spring more than that the resistence stiffness is.

also the only componenets of a car that are unsprung are the parts connected/attached to the wheels. insert a pivot point, and it becomes sprung.

[lee]

How do you calculate the "50%" of the weight of the coilover is considered as "unsprung weight" therefore savings of 'say' 0.532kg and 0.254kg front and rear respectively are actually quite substantial and better to pursue than say removing a air con at 10.321Kg especially if you belive in a 10:1 ratio of sprung vs unsprung weight etc. Hence if you gave me a choice of one or the other I would still rather have 1kg shaved off the 'unsprung weight' than shaved 10kg off the 'sprung weight'.

Because the top of the shock assembly is fixed to the car (sprung weight) and the bottom is fixed to the suspension assembly (~unsprung). It may not be exactly 50%, but it's a fair assumption.

I have a feeling the 10:1 is relating to the mass of the brake rotor, driveline shafts, wheel hub, wheel and tyre, as they have rotational inertia, which is extremely significant. I'd really like someone to correct me if I'm wrong, but I don't think a set of lightweight shocks and springs isn't going to have nearly as much of an effect as lightweight wheels and tyres.

[tbro]

Sounds like a load of bulls%^t, ^^^^^^^^^^^^^^^^
So wun911 "what does spring wait for ????????????????????????????????????????



























spell check

[Steampunk]

So wun911 "what does spring wait for ????????????????????????????????????????

...for love
Spell check won't work as he spelled "waits" correctly.
'Waits' is only five letters, whilst 'weights' is seven and wun is all about minimalism.

[stb]

How do you calculate the "50%" of the weight of the coilover is considered as "unsprung weight" therefore savings of 'say' 0.532kg and 0.254kg front and rear respectively are actually quite substantial and better to pursue than say removing a air con at 10.321Kg especially if you belive in a 10:1 ratio of sprung vs unsprung weight etc. Hence if you gave me a choice of one or the other I would still rather have 1kg shaved off the 'unsprung weight' than shaved 10kg off the 'sprung weight'.

Because the top of the shock assembly is fixed to the car (sprung weight) and the bottom is fixed to the suspension assembly (~unsprung). It may not be exactly 50%, but it's a fair assumption.

I have a feeling the 10:1 is relating to the mass of the brake rotor, driveline shafts, wheel hub, wheel and tyre, as they have rotational inertia, which is extremely significant. I'd really like someone to correct me if I'm wrong, but I don't think a set of lightweight shocks and springs isn't going to have nearly as much of an effect as lightweight wheels and tyres.

Agreed, the rotational inertia is significant in terms of acceleration, braking, and suspension movement. I propose that your car will overall be faster if you lose 10kg from weight saving in the body than saving 1kg of suspension components because of the acceleration/braking improvement rather than the suspension movement improvement.

Does what I've said make sense?

[M1474]

Yep, and waits is lighter than weights.

[Magpie]

To do unsprung weight disconnect your shock (at the lower point) and then put a set of scales under the wheel and see what the unsprung weight is. Do this for each corner. Simply you have to isolate the suspension from the rest of the car at the shock.

[lee]

Sounds like a load of bulls%^t, ^^^^^^^^^^^^^^^^

i don't know if you're serious, but if you are, i'd love to know how it is "a load of bulls%^t".

[NitroDann]

Often a pair of springs with different stiffness's from one manufacturer will use the same metallurgy and diameter of wire however the stiffer spring will have less coils. Forcing each coil to carry more load is what makes it stiffer. So you may find the stiffer springs are actually lighter as they use less wire.

Consider what is stiffer a broom handle 10m long or a broom handle 10cm long. This is how it works.

Dann

[lee]

Often a pair of springs with different stiffness's from one manufacturer will use the same metallurgy and diameter of wire however the stiffer spring will have less coils. Forcing each coil to carry more load is what makes it stiffer. So you may find the stiffer springs are actually lighter as they use less wire.

Consider what is stiffer a broom handle 10m long or a broom handle 10cm long. This is how it works.

Dann

Good point, I didn't consider using fewer coils...

What's your take on the light suspension topic?