I have been doing a little research to clarify some confusion I am encountering with spring rates. It is my understanding that you cannot compare spring rates of standard (stock strut size springs) with 2.5" I.D. Race Springs. Is this true?

If so is there a conversion formula to compare "ride feel" on different type springs? For Example would a Racing Beat Front spring of 145# spring compare to a 2.5" ID 7" spring at 250#? THere must be a difference, because standard springs are more than 7" or 8" tall which is a common length for an ID race spring, so the higher spring rate makes sence, because more pounds are required to compress the spring an inch.

Am I making any sence? I am confused? Someone please Help. The reason I am wondering is because I just ordered a set of Ground Control Camber Caster Plates, with the weld in Coil Over Kit. I didn't know which spring rate to get so they recommended a 7" 250# spring, as I told them I had Racing beat 110# springs in the rear.

THanks for any help,

Spinner-D

 

The original springs are progressive. That means that they have a spring rate that changes dependant on the amount of deflection. Generally they're softer initially and then they get stiffer. Coil over springs are linear. They're the same rate regardless of deflection. I just measured my front springs (RE from days gone by) and they measured about 125# once they got into the linear range. I assume that the RB springs measure 145# once they get into the linear range.

I'm right in the middle of a suspension revision on my '84 RX-7 as well. I'm still trying to decide on spring rates myself. A friend is letting me borrow some 275# springs for the front. I still need to figure out what I need to do on the back.

 

For 1st gens generally you want your rear spring rates to be less than half the front. I use 350 front 150 rear on the blue bridgeport.

There are lots of variables. What type of lateral axel locator, bushings, do you like a tail-happy car? etc.

 

ok I got my question answered on the Suspension forum, and thanks for your input also.

My set up is going to be 250# in front and 110# in back with TOkico Illumina 5-ways and my tires are Kumho Ecsta V700 in size 225/45-15 and for auto x I have the same tires at 235/45-13 on 15x8" rims. I usually run about 32lbs-35lbs of tire pressure, and favor a little oversteer rather than understeer.

What do you think of this setup? Common? Good or Bad?

 

ok I got my question answered on the Suspension forum, and thanks for your input also.

My set up is going to be 250# in front and 110# in back with TOkico Illumina 5-ways and my tires are Kumho Ecsta V700 in size 225/45-15 and for auto x I have the same tires at 235/45-13 on 15x8" rims. I usually run about 32l-35lbs of tire pressure, and favor a little oversteer rather than understeer.

What do you think of this setup? Common? Good or Bad?

 

Sounds like a winner. Be prepared to try different rate rear springs. On my 7 125lbs had understeer, scrubbed the tires on corner exit. And 150 was just right; just a hair of oversteer. 25LBS made a world of difference.

 

How much negative camber are you running, and caster if you know it? DO you have any rubbing problems on the front fenders?

 

350# front 150# rear here....

I love the way it handles.. (but I'm still running the stock front bar)

Illumas & CC plates too

 

350# front 150# rear here....

I love the way it handles.. (but I'm still running the stock front bar)

Illumas & CC plates too