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Help wanted on springs


dirtydiesel

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Right i'm fed up with having no travel on the back of the trialler, i'm going to 4 link it on a set of 8" travel ally bodied coil overs these are going to be mounted in board of the chassis so shock length isn't a problem.

But I need to know what spring rate to order, car weighs 990kg with about a 40/60 weight split, so that'd be 200kg ish on each back spring.

As for length to "fill" the coil overs I need a length of 17" so i'm planning on going for a 14" long main spring and a 4" long 30lb lay flat under that.

I'm guessing that my springs will need to be about 70lbs

Anyone on here have a table to work it out?

This is what they're going on,

jimny1.jpg

suzuki jimny based!

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Hi, I suppose technically the mounting angle is going to affect the spring rate you need.

Have you thought about dual springs (in series)? Is it an option on your coilovers?

Do you know the mount geometry? Have you completed the design of the 4-link yet?

Cheers, Al.

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At rest do you expect to have equi up/down travel or less up/more down,..

Assuming equi so 4in up and 4in down and vertical mounting then we used 4in of compression to support the 200kg (say 400lbs) which give a nice simple rate of 100lbs/in.

Doesn't sound like a lot of travel though? If you had longer travel shocks you could do a lot with dual springs and then have fun tuning not just static ride height but tender point as well which would be a great way to get lots of soft movement for the lower extremes of travel without losing stiffness as the suspension becomes more compressed.

What rates are you running at the front?

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Hi, I suppose technically the mounting angle is going to affect the spring rate you need.

Have you thought about dual springs (in series)? Is it an option on your coilovers?

Do you know the mount geometry? Have you completed the design of the 4-link yet?

Cheers, Al.

I'm going to mount the coilovers vertically as viewed from the side but angled toward the centre of the vehicle as viewed from the back, so mounting angle shouldn't be a problem.

I have thought briefly about dual springs, but in the past i've found it even harder to get the rate right with dual springs.

The design of the 4-link is as it should be fluid (as yet), the whole drawing process doesn't really work for me!

At rest do you expect to have equi up/down travel or less up/more down,..

Assuming equi so 4in up and 4in down and vertical mounting then we used 4in of compression to support the 200kg (say 400lbs) which give a nice simple rate of 100lbs/in.

Doesn't sound like a lot of travel though? If you had longer travel shocks you could do a lot with dual springs and then have fun tuning not just static ride height but tender point as well which would be a great way to get lots of soft movement for the lower extremes of travel without losing stiffness as the suspension becomes more compressed.

What rates are you running at the front?

4" up and down at the shock should give me somewhere nearer 6-7" up and down at the wheels, which compared to what it's like now will be awesome.

The axle will be centre strapped to limit droop to ride height -2", axle roll is the real target, to much droop and it'll "endo" on descents.

As for the front springs they are (or used to be) KAP +3" hd's, no choice on the 8" shocks I’ve already got them

100lbs/in sounds a little hard, rr fronts are 135lbs/in!

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