Spring rate opinions needed please (free candy inside)

[Miko K]

I will post pics of the candy soon

 

Now the business side of the thread- I am looking to buy a set of front lowering springs for my new setup and can't decide what spring rate to go with.

 

For those not familiar with my car- 1996 Cutlass coupe running an L67 that is turboed, Getrag 282 and an aluminum subframe to kinda give idea about the weight. I wish I could weigh it but car is stationary in the garage until it's all assembled so there is some guess work. You guys have the most experience with these so that's why I ask all of you.

 

I see a few sets on ebay (GEN2&3 w body) that are 230, 280 or 450lbs/in.

 

Which ones should I go with?

 

Thanks in advance!

[jman093]

I would go 450. The custom coilovers many of us run in the rear are usually paired with a spring around 300 lbs (although I remember a couple people using 400 lbs). The front would need more than that with the weight of the engine. 450 is probably about right.

 

k, where's the candy now.

[rich_e777]

This has creepy panel van written all over it. Got lured in and I see no candy. :willy-nilly:

[Miko K]

Here is some promised candy:

 

A semi-polished aluminum subframe, a giant turbo with a 4" SS filter on it and a tall stack of sticky sticky rubber ready to burn!

 

 

 

Looks like I am leaning towards the 450 springs, as I read what autocross people are using, these will be soft for that lol

[Psych0matt]

I went 400 up front

[Miko K]

Yeah I might go coilovers on the front too, the height adjustment need to be perfect in my case or it will look terrible. I need to save up a little now, just bought a set of C6 Z06 front brakes (14" rotors and 6 pistons, 6 pad calipers) and that hurt the car budget a bit.

[George]

I remember in one of the treads that for the Cutlass the factory front springs were in the 250lb range and the rear is in the 200lb range. Food for thought. Something to consider is tires, the higher the speed rating, the stiffer the side wall, the stiffer the ride. For a stiffer ride, buy better quality tires. However, in your case of adding more weight you would need to increase the spring rate. Adding 100 lbs divided by two springs should be 50lb increase in spring rate. A lowered car needs a little higher spring rate yet to keep it from bottoming out. With Z rated tires I would like to go up to 275lb on the front of my 94 vert. Intrax says their performance springs are typically 10% stiffer that stock. FWIW

[Miko K]

I remember in one of the treads that for the Cutlass the factory front springs were in the 250lb range and the rear is in the 200lb range. Food for thought. Something to consider is tires, the higher the speed rating, the stiffer the side wall, the stiffer the ride. For a stiffer ride, buy better quality tires. However, in your case of adding more weight you would need to increase the spring rate. Adding 100 lbs divided by two springs should be 50lb increase in spring rate. A lowered car needs a little higher spring rate yet to keep it from bottoming out. With Z rated tires I would like to go up to 275lb on the front of my 94 vert. Intrax says their performance springs are typically 10% stiffer that stock. FWIW

 

Thanks for the info George, I couldn't find any info on the stock spring rate. My front end was crazy stiff when the car was loaded with the previous setup (intercoolers, supercharger, automatic transmission), lots of steel parts that are now going aluminum. I was using chopped stock CS springs and they are VERY stiff. I think I might be lighter now than stock with the 3100 and the automatic- the heads on the 3800 are heavier but the aluminum subframe should compensate and the turbo weight (along with piping and intercooler) should be offset by the manual transmission. The only weight that hurts my setup will be the C6 Z06 brakes: the rotors weigh 27lbs each and the calipers (loaded with 6 freakin' brake pads per caliper)are around 15 each, then you add 4lbs for the wheel adapters. My tire/wheel combo is at 47lbs which is good for a 275 40 18 setup but still heavier than stock and that is unsprung weight, does not affect the springs but does make for a bumpy ride. I think I'm going to go coilovers because it's easier to tune the spring rates than choosing between just 2 lowering springs of 280 or 450lbs. Seems like I would be doing good around 350-375 but I need to do more research.

Edited November 14, 2013 by Miko K