Aftermarket springs

[EricJB]

So I'm looking around for a pair of rear springs for my V8 Z. I need something stiffer, and don't want to go with a whole coilover set up. What do you guys run, or have run in the past?

 

What's too soft or too stiff?

 

 

[datzenmike]

This is something only you can answer. Same as buying a bed or a pair of shoes. My idea of firm may be too soft for you. If you carefully measure the thickness of the wire on the coil spring, the diameter or the coil (outside to outside and the number of coils that are actively working* I can work out the spring rate for you.

 

* Coils may be flattened where the contact the top hat or spring perch so start counting the coils where they stop making contact. Try to be as accurate as possible. A small error can make a large difference. A picture helps also.

[EricJB]

Was mostly wondering which aftermarket spring was stiffer. Eibach vs tokico, ect. I figured someone had tried them. 

[metalmonkey47]

Was mostly wondering which aftermarket spring was stiffer. Eibach vs tokico, ect. I figured someone had tried them. 

 

Stiffer has more to do with spring rate then brand.

 

Basically, the higher the spring rate, the stiffer the spring. 

 

http://www.tuninglinx.com/html/spring-rate.html

 

Spring Rate is the amount of weight needed to compress a spring a certain . Springs are rated in LB/in (in metric system kg/mm), or specifically, how many pounds of weight are required to depress the spring by one inch. To convert LB/in to kg/mm international, you must divide divide figure by 56.

Consider you have 2 springs having different spring rates: One with 345 g/mm and the other with 480 g/mm. So what does it mean?

 

It means the 1st spring will compress 1 mm if you put a load of 345 grams, while the 2nd one will not. The 2nd one will need a 480 g. load to compress 1 mm. According to this, we can say that the 2nd spring is harder than the 1st one, or we can state that:

 

Springs that have a low Spring Rate are soft, while springs that have a high Spring Rate are stiffer.

 

 

 

If there are 2 different values listed, it means that the spring starts at one rate, and ends at another rate under full compression.

 

For example: a 10lb to 25lb progressive spring will need 10lb to compress it the first inch, then 13lb the next inch, and so on, until the end of the travel; it will take 25lb to compress it the last inch. The benefit of this is that the spring can be soft enough at the start of the travel to offer a soft ride yet be stiff enough at the end of the travel to performance well during hard braking and turning.

 

[EricJB]

Good info. So at the risk of coming off like a smart ass. Does anyone know which aftermarket spring co. offers the highest spring rate for stock strut assemblies?  

[metalmonkey47]

Probably Eibach.

 

Why do you want the stiffest spring possible?

 

 

What kind of driving are you planning on doing? AutoX. drag, street, circuit? Sometimes stiffer doesn't always mean better. 

 

http://www.chevyhiperformance.com/tech/chassis/suspension_steering/1002chp_how_to_pick_the_right_spring_rate/

 

 

http://www.westpennmazdaclub.com/files/Car%20Setup%20and%20Troubleshooting%20Cheatsheet.pdf

[EricJB]

76 280/ 406sbc/auto. Setting it up for drag racing. Everything I've read about trying to use the stock ass end, they have squat problems. I will only be footbraking it, but pretty sure it will hit the bumpstops.Just need to get it on its wheels and moving till I eventually change the whole thing.

[metalmonkey47]

In that case, stiffer would be a necessity. Squat would be a HUGE problem in a built V8 Z car. 

 

 

 

Unless the role of a spring in relation to overall suspension dynamics is made clear, the procedure required to select the right rate-and why it's necessary-won't make any sense at all. Consequently, at the risk of being redundant, we'll briefly recap some info covered in previous installments of CHP's ongoing suspension tech series. According to the vast majority of chassis tuners we've consulted, a spring's job is to simply support the weight of the car. Although a higher spring rate reduces body roll, it comes at the expense of a harsher ride. "Not only will a softer spring improve ride quality, it will also enable the tires to follow uneven road surfaces more precisely for improved grip. A tire that momentarily loses contact with the road due to having too stiff of a spring won't produce any grip at all," Chris explains. "Upgrading to bigger sway bars is a far more effective method of limiting body roll and managing weight transfer. Once the spring rate is dialed in, the bulk of track tuning is accomplished by adjusting the shocks and trying out different sway bars. If you prescribe to this school of thought, where the purpose of the springs is to merely support the weight of the car, then picking out the right rate isn't hard."

Read more: http://www.chevyhiperformance.com/tech/chassis/suspension_steering/1002chp_how_to_pick_the_right_spring_rate/viewall.html#ixzz2lu2rgQF7

 

Since it seems like the majority of your power will be used going in a straight line, it seems from my understanding of the article that there may not be "too stiff" of a spring for your application. The S30 chassis isn't too heavy in relation to most other cars built to go fast straight, so it's hard to pick a good spring rate based off of what other people are using. I see lots of discussion of 1000lb springs on Chevelles, Camaro's and close to that. But those cars are also using a hell of a lot bigger motor.

 

https://www.cachassisworks.com/Attachments/Instructions/899-031-226_drag.pdf

 

Read page 5 in this PDF, they talk about weight transfer and spring rates for front suspension. 

In short, it basically explains that when the front end lifts, the weight is transfered onto the rear tires increaing traction, so the optimal spring rate would be far lower then the rear to assist in weight transfer. So where you may run a 750lb spring in the rear, you may run a 300lb spring in the front. (Just throwing numbers out there.)

 

 

 

What Happens During Launch?

 

      As a drag vehicle front suspension separates (the front of the car comes up) more weight is transferred to the rear tires 

to aid traction. How fast the front end rises is mostly controlled by the spring rate and front shock force. As the rebound 

valving of the shocks is softened it will be easier for the front end to lift. Not so obvious is if the car had a softer front spring, 

the front suspension will lift easier also. The explanation is quite simple. A heavier rate front spring will take more force to 

lift the front end a fixed vertical distance, than a lighter spring. If you have 500-lb/in front springs and the acceleration force 

transfers 1000 pounds of front end weight to the rear; 500 from each front spring, the front end lifts one inch. With 250-lb/

in front springs, the same 1000 pound weight transfer will lift the front end a total of two inches. The lighter 250-lb/in rate 

benefits a drag car in two ways. The front end will move faster and farther because less force is required to initially extend 

the spring. And, it will rise higher, transferring more weight as the center of gravity rises, further assisting traction. However, 

too much weight transfer can hurt your ET by causing excessive wheel stands and lost forward motion.

 

 

Tuning Front Suspension with Spring Rate

 

     A drag race car should run the lightest front spring rate possible, without letting the shocks bottom out when making 

a pass. As a general guideline, lighter springs allow the car to easily transfer weight, and settle faster down track. 

Changing spring rate affects ride height and the rate at which weight is transferred to the rear tires. A softer rate makes 

the front easier to rise during acceleration. A stiffer rate makes the front harder to rise during acceleration. If you are 

having trouble getting the front end to rise, you can soften shock rebound valving or change to a softer spring. 

When using lighter rate springs, preload must be added by screwing the lower spring seat upward. Compressing the 

spring to achieve proper ride height will store energy in it. This is the very simple theory behind stored energy front 

drag-race springs. If you preload a spring, it is imperative that you verify that the spring has enough travel to not coil 

bind before the shock bottoms out. VariSprings feature a very high strength steel that allows them to be wound more 

coarse then traditional springs, which makes VariSprings travel farther before coil bind.

In general terms, the worse a car hooks, the more shock extension travel it will need. If you need more extension 

travel, preload can be removed to lower ride height. Using this method will cause the car to have less ground clearance 

and reduce the amount of compression travel. If you are going to operate the shock at a ride height shorter than 

recommended, the upper chassis mounts must be relocated to correct any major vehicle ride height issues. It may take 

some work with spring rates and upper mount relocation to get the correct combination of vehicle ride height and front 

suspension travel for your application.

 

 

http://www.competitionplus.com/2004_11_18/springs.html

 

 

Interestingly enough, this page suggests near the bottom that cars using a standard strut assembly will run a lower spring rate in the rear. MUCH lower then I was thinking. I've always thought drag cars should run very high spring rates to counter squat, but it seems I may have been wrong all along (not a big suspension guy, just good with google.)

The chart's recommended spring rate for a 3000lb car:

Approximate

Front: 250lb

Reat:  150lb 

[datzenmike]

Don't forget this is for maximum hp, drive in a straight line application. A V8 Chevelle is going to have traction problems even in stock configuration let alone modified. In this case some weight transfer is desirable but it would not be if on the track or the street. Datsuns are not known for having traction problems so altering the springs to jam un-needed weight to the rear is counter productive. Firmer rear springs will reduce un needed transfer. What about the front??? You come out of a corner and jam the throttle open and the front end lifts removing weight and traction from the wheels and... you're suddenly in severe understeer. Not such a problem in a straight line, but in a corner???

 

The 510 and Z car have IRS and some strange things happen to camber and toe when there is weight transfer to or from the back. Look up trailing throttle steering. As for springs, they have to be stiff enough to prevent bottoming at high speed on a lowered car. No sway bar or shock will stop that on a too soft spring. Not saying to run 1000 pound springs just that they will need to be stiffer.

[EricJB]

I thought I would revive this thread, now that I found the answer. Believe it or not the answer is...

 

Chevy Chevette springs. Moog# 6556. I cut 1 coil out, and they fit perfect.  $36.00 a pair.

[yellow zee]

I thought I would revive this thread, now that I found the answer. Believe it or not the answer is...

 

Chevy Chevette springs. Moog# 6556. I cut 1 coil out, and they fit perfect.  $36.00 a pair.

Serious? Whats the spring rate and did you use stock dampners? Also PICS please?

[datzenmike]

Fit is good but the spring rat is just as important. Measure the diameter across the coil, the thickness of the wire and how many movable coils are there? Picture of one is good. The rate can be calculater. Front ZX coilsa are  probably around 150 so rears would be close to that.

[EricJB]

Looks like 1/2 diameter, 197lb spring rate.

http://www.rockauto.com/catalog/moreinfo.php?pk=200831