Does anyone know why there are two parts and cost difference?

 

I assume there are two part numbers because of the weight difference between the convert and coupe.

JamesC

 

The weight difference is what the Moog catalog data suggests. Different part numbers, same ID, same wire diameter, and same rate but different free lengths and rated loads.

But at the OE level, slightly softer springs are frequently chosen for convertibles (which have a less rigid chassis than a coupe built on the same platform).


Norm

 

the convertible specs moog 5664 (750lb/in) vs the 5660 (650lb/in) for the base coupe.
The Z-28 and equivalent spec the 5662 (700lb/in).
Pick whichever spring rate you like.

 

theres alot of controversy over the spring rates of the moogs.... from what i kno and heard on this forum the moog spring rates are not as high. the 5664 is not a 750lb/in spring just like the 5660 or the 5662. i heard those rates are false. how is it that the moog springs are 750lbs/in and the EBACH prokit is only 705lb/in and they drop the car 1in. the shorter lowering spring has to have a higher spring rate to make up for the loss in ride height. everyone says the prokit increases handling very nicely and this couldnt be achieved with a shorter spring and less spring rate... it would be alot worse than the stock springs.

i would do a search and see what has be said. if i remember right the actual spring rates are much lower i think around 600lbs/in front and 100lbs/in rear. i have the stock WS6 springs and i have the EBACH sportlines and the wire DIAmeter is much thicker than the WS6 springs, and the coils are much tighter together than the WS6 springs... and the MOOGs are a direct replacement for the WS6.

i can tell u that the moogs are not 750 or even 650lbs/in. from what ive heard they are 550-600lbs/in. just an FYI before u start cutting them or assuming new springs. although cutting the springs will increase spring rate u still need to take into account ride height and spring rate. dont cut alot off, as stated do 1/4 coil cuts. and do a search for the spring rates but i kno that moogs rating for the springs are wrong. sumone tested them on a spring rate tester here

 

Interesting customblackbird, you're first i've heard talk of that.
I have the moog 5664's and think they are quite stiff, so if i'm mistaken and they are not 750lbs/in i'd be quite upset.

if you do find a link to some proof (ie the guy who tested them, etc) do let me know.

 

Spohn advertises the 5662 and 5665 (IROC replacements) at 706 and 107 respectively. At any rate, I don't believe I'd want anything stiffer.

JamesC

 

There are some discrepancies in the rates and dimensions for these part numbers, at the very least between my Feb 1996 paper catalog and the spreadsheet that's floating around the 'net.


That is true as long as the two different spring mfrs have the same design philosophy and work under the same restrictions. That's unlikely, especially between OE and the mass aftermarket (where the appearance factor is given different priority, just to name one thing). Let's just say that the OE's have more criteria to satisfy than spring load "Fs" at car ride height "H".


There's more to handling than just the brute spring rates. By itself, "everyone says" is not a very strong argument - heavier understeer is considered by some (many?) to be a clear improvement, as long as the cornering is flatter.


Do you know if the springs were tested for rate at the same compressed length (and range of length) that Moog used? Even "linear" rate springs gain a little rate as more of each end coil flattens against its seat and becomes "inactive".


Norm

 

yes i do kno they tested them on his own spring rate tester... he said the 750lb/700lb moog springs were actually around 650 and by hacking off a full coil he was able to bring the spring rate up to 750lbin or so and drop the car 2" i believe. he said something about a 10% increase for a certain amount cut. he even talked about inactive coils etc.... think it was a memeber named BMmonteSS or something and another memeber 83 crossfire TA.

now about the rear springs? 107 is somewhat soft when compared to the sportlines 107-130lbin rate(thats too soft for the height) and the prokits 130-160lbin rate which seems to be the spring of choice. what i want to kno is how much the spring rate increases when u hack off a 1/4" coil or so. i also just ordered a pair of moog 5665's and i plan on hacking off a bit to get the spring rate up and match the ride height of my sportlines. i would like anywhere from 130-160lb/in rate outa the 107lbin moog 5665s