Looking for spring rates

[Force Fed Mopar]

Bump...

[Force Fed Mopar]

Bump, still looking...

[Force Fed Mopar]

ttt...

[neonturbo]

Napaonline.com has very good specifications listed for their springs. They even give wire diameter, coil diameter, free and loaded heights. They usually are even divided out from L to R side, and by A/C, and trans type. I am not sure I would take them as 100% accurate, but they seem close in my experience.

I took the numbers they gave for ID, added spring wire size times 2 to get the OD, then plugged the number of active coils (the coils listed on NAPA are total coils) and the OD into a spring rate calculator. The spring rate matched NAPA numbers for rate, so I guess that they are accurate.

Spring rate calculator: http://www.stockcarproducts.com/pstech10.htm

There are a couple things to watch out for:

• Shelby and other "special" models are not usually listed separately.

• They usually, but not always use the largest inside diameter for the specification. I saw a few cases where they must have used the smallest I.D. when they measured. It was easy to spot when they show a 4" or so front spring diameter. I plugged the wire size and number of coils into the calculator and adjusted OD to get what was listed for spring rate. Most TD, and Neon have around a 6.5" to 7" OD for the front springs.

By the way, front spring rates are ridiculously weak on these cars. I seem to recall 80-100 lbs for most springs. I think there are two ways they can design the suspension, long but weak springs or short and stiff springs. TD use the first method and Neon and the later cars use the second method. Even base Neon have 140 lb springs but most of us upgrade to 225 lb springs at a minimum.

[Force Fed Mopar]

Bumpity...

[capev86]

i put cargo coils (specifically for a k wagon) on the back end of my 86 aries wagon. they are progressive rate so they ride good but still firmed up the handling (less rear body sway) thanks to a 270 lb-in rate. two problems i have are they lowered the rear end (last thing i'd want to do on one of these cars) by nearly an inch and with rear seat passengers/cargo it sits about as low as it ever did with the softer, taller factory springs.

contrary wise, i put them on the back of my 89 spirit es for a short while and it actually raised the tail end a little (i hate leveled or low slung rear ends). i swapped the spirit springs onto my wagon and it actually slammed the back end of the car....actually tucked the tires......yuck!

i haven't decided if i want to run the front shelby lancer springs (-1.5" on a lancer) i have and the cargo coils or keep the k car HD option front springs and get some cargo coils for a 86 LTD II wagon. that would give the back end a 330 lb-in rate and raise the back end 3/4" (over stock) which would be better for cargo hauling, towing the utility or motorcycle trailer and for getting in and out of my dirt road that is full of pot holes. these cars are light enough that between the strut brace and 1-1/4" sway bar the front end will be plenty firm. it's the rear that needs more stiffness to counteract the under steering tendency of front wheel drive!

[Force Fed Mopar]

What cargo springs do you have? From where?

[Vigo]

I have some cargo coils from either moog or trw. I emailed both and got the spring rates but they are both progressive springs and the rates are expressed as an average. So they both say spring rates in the mid 200s.. but you have to compress the springs like halfway to bind to actually get to that rate. Until you put a lot of weight on them, they aren't really much stiffer than stock. They are designed to ride close to stock, but keep the car off the bumpstops when it's overloaded.. so they dont actually get stiff until the car is already sagging in the back from weight.

It would be really easy to eliminate the low-rate coils if they were on the bottom like an eibach.. but on mine they are on the top where it is tapered for the upper seat, so it's not as easy to just eliminate them.

Next time i take my cargo coils out i'll probably try to isolate/solidify the top coils so they aren't affecting the spring rate. Not sure how yet.

[chilort]

This is good info.

So, basically, if you were throwing it in a corner, the spring would act normally, allowing for some body roll for the beginning, and would then start to get stiff. For a street brawler, it seems like this might be a nice compromise. You get daily comfort but then some good cornering manners. It seems like if this were paired with a well matched shock you could slow down the initial reaction of the spring too. Or am I way out in left field?

[chilort]

This is good info.

So, basically, if you were throwing it in a corner, the spring would act normally, allowing for some body roll for the beginning, and would then start to get stiff. For a street brawler, it seems like this might be a nice compromise. You get daily comfort but then some good cornering manners. It seems like if this were paired with a well matched shock you could slow down the initial reaction of the spring too. Or am I way out in left field?

Crickets?

Anyhoo, I've done a little reading about this and it sounds like a progressive rate spring is actually difficult to setup properly for race like setups because it is hard to pair a damper with it since the rate changes. Looks like I might still be on the hunt.

[ajakeski]

We should add a list of factory part numbers to this thread.
The GLHS spring is part number 4228324

Here are some others:

L BODY FRONT SPRING LOWERING PACKAGE
P4120804 - Right Front Spring
P4120805 - Left Front Spring

L BODY REAR SPRING LOWERING PACKAGE
P4120801 (2 springs included)

L BODY AUTOCROSS FRONT SPRINGS - lowers front end 1"
P4120968 (2 required)

L BODY RALLY SPRINGS (raises car 1')
P4120967 - Front Rally Springs
P4120969 - Rear Rally Springs

[Force Fed Mopar]

Good idea!

[anarchyjet]

I got a set of rear springs from a 86 daytona T1 car free with the motor I bought. We have an arbor press at work with a very accurate scale built in, so I did some testing. Stock free height was 11 7/8" and the rate was 150lbs/in. I cut it so it was a free height of 10". Because the bottom was no longer flat, I had to use a spacer to keep it straight in the press. So that pretty much took another 1/2 of active coil out of the spring. It measured at 207lbs/in.

When I swap these with the springs in my base model 93 shadow, I'll measure the other springs. They are already cut, so no stock measurement on those.

If anyone wants to send me springs, I'll measure them. Shipping is on you if want them back.

[Force Fed Mopar]

Awesome! I have a few springs I'll send you when I have the chance.

[Vigo]

I have never noticed a significant stiffness difference from cutting stock springs, and ive cut a LOT off of a LOT of them. Ive made springs completely unusable by cutting too much off them (sitting on bumpstops instead of springs). At no point did they ever feel much stiffer than stock.

I cant say why.. It is just a fairly large sample size of butt-shockdyno impressions so take it for what it's worth.

[chilort]

Spring rate is a constant (F = k * x, where k is spring rate). Unless it is a variable rate spring, until you cut so much off it is no longer usable as a spring, the spring rate shouldn't be affected.

[anarchyjet]

Spring rate is a constant (F = k * x, where k is spring rate). Unless it is a variable rate spring, until you cut so much off it is no longer usable as a spring, the spring rate shouldn't be affected.

Cutting springs make them stiffer, this is a fact. You even proved yourself wrong by quoting hooke's law. Yes k is the spring constant, but x is the angular displacement of the cross-section. So if you compress 2 different springs both 1 inch and spring 1 has 10 coils and spring 2 has 5 coils; spring 2 will be much stiffer because of the greater displacement (x)

[chilort]

So, if a 5 coil spring has a spring rate of 100lbs/in and a 10 coil spring has a spring rate of 100lbs/in and you compress both springs 1 inch you don't get 100lbs of force effectively pushing back in the opposite direction from both springs? I think you've been reading a little too much Honda tuning.

[chilort]

Damn, I hate to say that it wasn't a Honda guy that came up with this odd way of thinking about springs. It was Gus Mahone. Or, maybe he copied from some Honda guy. Either way, the anarchyjet logic is wrong:
http://www.allpar.com/eek/coils.html

[zin]

I think what you two are thinking about is that a torsion bar (a coil spring unwound essentially), has a certain resistance to twist or spring rate. If you attempt to twist/compress it it will deflect at a constant rate as force is applied, but the longer the bar (or more coils) the greater the deflection for a given force.

It makes a cut spring feel stiffer because the "bar " is shorter, not that the material's properties have changed.

Mike