What spring rate most people running 4 link mullis dual shock alum head BBC?

Shocks behind rear on a std 4 link or x link non swing arm dragster 110-120lb springs

this ^

sent my shocks into for rebuild because im switching to aluminum block this off season . going with 125lb springs FWiW

if the shocks are mounted on any angle there is a angle correction factor that should be taken into consideration as well.

With an aluminum block 125Lb springs may be to stiff, IMHO.....

My current Racetech weighs well over 1900Lbs and I have a Dart Iron block and use 110Lb springs...

I have rolled across the scales and seen 1960-1970Lbs on the readout.

I always felt you should be able to push down on the chassis at the rear and easily get some downward movement

My old car loved shocks being set soft on compression and it too had 110Lb springs and worked very well.....

It was lighter by probably 100Lbs....

I replaced my AFCO shocks and springs a couple years ago......with newer versions of the same shocks/springs

quote:

Originally posted by SCDIV1:
With an aluminum block 125Lb springs may be to stiff, IMHO.....

My current Racetech weighs well over 1900Lbs and I have a Dart Iron block and use 110Lb springs...

I have rolled across the scales and seen 1960-1970Lbs on the readout.

I always felt you should be able to push down on the chassis at the rear and easily get some downward movement

My old car loved shocks being set soft on compression and it too had 110Lb springs and worked very well.....

It was lighter by probably 100Lbs....

I replaced my AFCO shocks and springs a couple years ago......with newer versions of the same shocks/springs

i sent them off to the guys at Competitive Suspension knowing i was making the switch this offseason. They had 150lb'ers on em when i bought the car apparently, cause thats what coming off of them. Im green with this suspension stuf so. I was told Shane and his team know their stuff so I trust their judgment.

Shock angularity and leverage location are defiantly a player on spring rates, but I don’t feel the calculations are conclusive when looking at those numbers.

FWIW – I will always use the softest spring that I can get by with, while having the spring platform close to the middle adjustment and also having the shock travel somewhat in the middle (or as recommended by the shock builder) all while reaching the desired ride height. If the spring platform is closer to the top, not an issue and possibly better with some shock valving, if its towards the bottom – its probably too stiff.

Then comes in the valving….again – IMO, if you have the spring rate correct, you eliminate the spring energy influencing the shocks job of controlling the dynamics involving things like pitch rotation, suspension settings, tire choices and power levels. The spring should only be supporting the weight of the car without creating an influence on the shock. If you can accomplish the correct shock setting then all else is moot, but if you’re at the extreme on either compression or rebound settings and make a change with tire brand, suspension, convertor, weight …yada yada , you will most likely be sending that shock back out for another re-valve….been there….and kinda still working it on another car. If you over spring a suspended car, the compression adjustment is generally null and void and the rebound will need dumps to work on both ends of the track – “properly”.
There really is no black magic or text book choices here.

I know…he didn’t ask about shocks…..but they do work in conjunction with each other.

Jerry, it all figures into the spring rate seen at the contact patch, many, many factors to arrive at the correct spot for your combination.
1/4 p.s.i. change in tire pressure can show 15-20# spring rate difference at the contact patch.
I believe like you, soft springs help you use the tools your setup provides.