Outer Limits 4x4 Board

Original Nissan spring rates are:

Front 180lb x 2 and Rear 190lb x 2 = 740lb

Sprung weight of car = approx 4000lb??

Any bright sparks know the answer

cheers

obviously they forgot to minus the 7



Whats the question

Hi Sir (good name )

The big upper chunk of the car that the springs hold up weighs around 4000lb.
Yet the springs have a combined rated upforce of only 740lb, how come they are not flattened straight away??

cheers

id say the spring have a treatment in them to hold the weight the same way , you strenth steel by heating right up and cooling in a pacific solution it become harden , or the springs are mad of a mix of steels ,
eg an plane air frame is made up from a alloys light as but strong as or somthing like that

how much do the diffs, wheels and tyres weigh???????????????????????

Heath I dunno for certain, but those bit's are the unsprung portion of the car.
I think the transport department considerer's my car to be around 5100lb in total?. Bloody heavy beast!

I was just guessed 4000lb for the rest that ride on the springs.

cheers fnq

I know this is going to sound dumb because I can't explain it simply and properly, but spring rates refer to the amount the spring will deflect under a given amount of pressure. Eg: 190lbs/in in my mind means the spring will will compress 1" for every 190lbs of weight placed on it. This is calculated after the static weight of the car is being supported by the spring or else you would be correct. Put a 2.5 tonne vehicle on a pair of springs designed to hold 380 lbs and it would indeed collapse. Spring rate relates to additional load the spring can support, not its total capacity. If anyone disagrees or can explain it better, the floor is yours.

rhymus wrote:I know this is going to sound dumb because I can't explain it simply and properly, but spring rates refer to the amount the spring will deflect under a given amount of pressure. Eg: 190lbs/in in my mind means the spring will will compress 1" for every 190lbs of weight placed on it. This is calculated after the static weight of the car is being supported by the spring or else you would be correct. Put a 2.5 tonne vehicle on a pair of springs designed to hold 380 lbs and it would indeed collapse. Spring rate relates to additional load the spring can support, not its total capacity. If anyone disagrees or can explain it better, the floor is yours.

to follow on from you then it sounds like that the spring poundage, taking the rear springs as an example of 190lb, will support an addtional 190lb per square inch on top of the sprung weight of the Nissan. Therefore the actual strength of the springs is way above the 190lb quoted.

Therefore the actual strength of the springs is way above the 190lb quoted.

Yes, it is.

it's pounds per inch. How many inches of spring?

Thanks for the replies, it all now makes sense I was unsure if the force kept doubling with each extra inch of compression but it must be more of an addition not a multiplication/log - if that makes sense.

Anyone use aftermarket progressive springs on the rear of their car?, what did you think.

Now I understand better how these things work I am in a somewhat better position to make a choice -the right one or the wrong one .

cheers fnq

Spring rate is defined as the force required to produce a given deflection and is proportional for linear springs.
eg 180 pounds produces 1 inch of deflection. 360 pounds causes the spring to deflect 2" etc. The difference in unloaded length and installed length x the spring rate = the load (weight) on the spring.

For the best combination of ride and articulation you want the bumpstops to just be touching when the car is cross axled.

Its hard to achieve this with progressive springs which is why the correctly rated linear spring is generally better off-road.

A softer (lower rate) spring will always give better traction for a given payload.