Wondering what's a good spring rate for street use for a 1600. 6kg for the front and 4kg for the rear? Its my daily driver. Don't want to feel every dimple on the road But also want something that will stick to the road if I decide to take if for a nasho run. It will have r31 coilovers and custom lowered rear springs.

You'll need much more than that on the rear due to the geometry of the 1600's suspension. Something like 750lb/in (14kg/mm).

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1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

6k fronts will be really stiff you want like 200lb front springs and 800lb rear unless you do rear coilovers then 200 rear

So like 4kg for the front and 14kg in the rear. Just as we'll I asked did a bit of google searching ppl were saying 6-4 or 8-6 for street this was for other cars tho. Cheers

You cant judge springs by 'other' cars...

For rear coilovers I'm taking u have to reinforce top and bottom mounts? How come u can go a softer spring if u go coilover rear?

Some people reinforce the bottom but alot of people dont and have not had issues. because its a differant leverage point than where the stock spring goes

Shocks will have more influence on ride quality than springs ( within reason)
R31 struts front 250lb Z31 KYB shocks, rear 700 lb with KYB mono gas shocks gas pressure in the monos increases spring rate by approx 60lb
static & increases depending on velocity.

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A little knowledge is a dangerous thing.
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"R.I.P. Baz. 29 April 2022. Thank you for all your contributions to the Datsun community over the years. You will be missed." - OZDAT

6k (334lbs)springs ride stiff even with good shocks 250 is about as much as you would want to go on a street car

The stock front strut springs are around 90 pounds per inch. Assuming the rear is somewhat matched to th fronts they would be 'around' 350 pounds per inch. This is because the spring is not over the wheel but ahead of it between the wheel and the hinge point on the control arm giving the wheel a mechanical advantage. This ratio is about 3.8

My 710 stock front strut springs were about 100 as per the formula for working out spring rates. I removed a coil and it works out to 150 now. I'm good with 150 on the street (with the damping oil in the struts replaced with much thicker 20W hydraulic oil) and can't imagine a 300 pound rate on the front... but racing car 510s do this. If a serious driver you might like 200 or 250.

As to the rears you would need a spring rate of just over 1,100 pounds to get a 300 at the wheel. A 750 pound spring would give a 200 pound at the rear wheel. There is a write up in the Dime Quarterly for installing Dodge D-50 front coils in the rear of a 510. Trimmed slightly they provide a 600 pound rate spring that gives 160 spring rate at the wheel.

We previously supplied 230Lb spring with R31 inserts.
A fair percentage of customers wanted a slightly firmer ride.

We have supplied over 400 front strut kits with the 250lb & Z31 KYB.
Its the non stiction & superb auto valving of the shocks that does the trick.

200Lb with Z31 has a slightly bouncy ride at street speed than the 250s.
Damper rate is a tad too high IMO for 200LB

_________________
A little knowledge is a dangerous thing.
www.datsport.com

"R.I.P. Baz. 29 April 2022. Thank you for all your contributions to the Datsun community over the years. You will be missed." - OZDAT