can anybody help with a spring length for h and r rss coilovers,i want to change spring rates and get more camber gain in the front,i measured them myself and it looks like sevens will work back and front.Keep up all the good work everyone

 

7" may be too long in front, depending on your spring rate. If you're anywhere close to 350 lbs/in, 6" will work much better. Unless you really like the monster truck look.

For the record, I've tried both on my car with PSS9s with the above spring rate. 7" sat at roughly stock height with the height adjustment set as low as it would go.

Scott
90SM

 

thanks,90STX,the reason i mentioned the sevens was because i have my threaded spring seat all the way to the top of the shock and when i measured the distance it was give or take six and half inches.Ithought maybe even eights and then lower it,what do you think?The measure was taken with wheel off the ground

 

sorry,forgot to mention this is a track set up but this is the first time i will have changed the springs since i got coilovers,probably going with a +-350fr and 500 rear(time to get serious)

 

Well, you can look for differences between thread locations between Bilstein and H&R damper bodies, but I think you'll be surprised by how much less the 350lbs/in linear rate springs compress under static load.

Like I said, I originally tried 7" springs up front on the PSS9s. With the spring perch all the way down to the bottom of the threads, my ride height was really close to stock. I went to the 6" springs, same rate, and raised the lower perch about a 1/2". I'm lower than stock, but hardly slammed. The drop works pretty well for improved handling. Lower is not necessarily better, except possibly for esthetics if that's your preference.

I've still got the 7" long, 2.5"ID Hypercoil 350lb/in springs on the shelf. If you want to try them we could probably work something out. I could certainly be wrong, but I really don't think you'll be happy with the 7" springs in front.

FYI, I'm still on the original PSS9 rear springs. They're linear 345lb/in, so I haven't had a reason to replace them yet. I haven't measured the free length of those springs.

Scott
90SM

 

i would try 6' springs... i think the RSS spring rates are somewhere near 500 for the front, and 400 in the rear

i can measure the stock spring height for ya tomorrow cuze i have them off for the winter

 

thanks 90STX and kyriian for helping with this.Kyriian ,i would to love to know those spring lengths if you have them off the car,just from memory the spring did seem longer than 6 inches,iwould be interested in those springs 90STX,btw go indy!

 

6' F, 8' R, both are unloaded

also, i have a set of 6' 500 lb eibachs if you are interested... its sitting at my friend's store at the moment

 

Regards to linear rate springs:

Just keep in mind that for a given spring length, the block hieght changes as the rates changes. A 7", 500# spring has a shorter block hieght than a 7" 250# spring. This is so because the coils are thicker.

Take the corner weight of your car - roughly 850lbs - and divide this by the spring rate and you will have a basic idea for how many inches the spring will compress once the 850lbs static load rests on the spring. Then subtract this from the spring length. What is left must be more than block height or the spring will bind - all the coils contact one another.

850lbs divided by 500# spring = 1.7 inches. If the free length of the spring is 4" - not to be confused with the actual length of the spring - subtract 1.7 inches and you get 2.3 inches of spring travel. Free length is a number to keep an eye on when choosing a spring rate and length. The two must be viewed together so that you maintain enough spring travel.

Ultimately, the shortest spring possible is best since a spring weighs a lot. A lighter spring reduces unsprung weight, and, the tendancy of a really long to want to buckle in the middle under load - there is a term for this but I cannot remember it.

THE CORNER WEIGHT EXAMPLE ABOVE IS FOR THE FRONT END

 

thanks again to both you guys,a guy at the club is going to give me a bunch of 2.5s of different rates and lengths to try,ideal situation,what rates do you guys run,kyriian did you find the 2.5 linear spring to perform differently than the progressive barrel spring of the rss

 

i never ran the RSS with 2.5' linear springs... i had the eibachs from my previous coilovers

 

wrxmini - refer to my reply above to find the correct length, and...spring rate should be in the nieghborhood of 1.5-2 Hz for the front end...about 300-450# linear. That's quite a big range. The rear rates will depend upon many things, including the selected front rates.