Spring Rates
 

I had posted these in another thread and thought it may be useful to everyone. In this manner I can edit when new information is made available and keep it up front.

All have been converted to lb/in.

Stock RX8 6spd
F 155.61 lb/in
R 112.86 lb/in

Stock RX8 Automatic
F 144.21 lb/in
R 101.46 lb/in

Mazdaspeed Spring
F 280 lb/in
R 190.4 lb/in

Tein high tech
F 184.8 lb/in
R 134.4 lb/in

Tein S Tech
F 207 lb/in
R 145 lb/in

RS*R
F 181.44 lb/in
R 122.08 lb/in

Tanabe Sustec NF210 (Normal Feel)
F 162.4 lb/in
R 112 lb/in

Tanabe Sustec GF210
F 179.2 lb/in
R 145.6 lb/in

Auto Exe
F 212.8 lb/in
R 145.6 lb/in

Espelir
F 212.8 lb/in
R 151.2 lb/in

Racing Beat
F 187 lb/in (calculated 20% Stiffer than Stock)
R 136 lb/in (calculated 20% Stiffer than Stock)

H&R
F 194~203 lb/in (calculated 25%~30% Stiffer than Stock)
R 141~146 lb/in (calculated 25%~30% Stiffer than Stock)

Eibach
F 180-187 lb/in (calculated progressive rate 15%~20% Stiffer than Stock)
R 130-136 lb/in (calculated progressive rate 15%~20% Stiffer than Stock)


--coilover--
Tein CS
F 280 lb/in
R 168 lb/in

Tein Flex
F 504 lb/in
R 392 lb/in

Tein Basic
F 448 lb/in
R 336 lb/in

HKS Hipermax II
F 448 lb/in
R 280 lb/in

JIC FLTA2S
F 448 lb/in
R 280 lb/in

JIC FLTA2H
F 560 lb/in
R 392 lb/in

Speedsource Grand Am Cup Cars changes from track to track but was
F 800 lb/in
R ??
at one point according to one of the drivers.

Thank you Alex :). Let the suspension tuning begin!!

Very nice, useful info. I'm stickying this for a few days.

The JIC coil-overs are offered in two different spring rates:

• RX8FLTA2S - 8kg/5kg
• RX8FLTA2H - 10kg/7kg

forgot 1 ... tein s-tech

Thanks for this info Alex. It's great to see all the rates in one spot.

anyone get the Eibach, H&R, or RB rates?

Thanks for the info,

It would be great if we good list complete info on the springs for instance:

1. Claimed Drop front and rear

2. Actual Drop front and rear if there are reported discrepencies from the claims.

3. Spring Rate Range for any of the springs that are variable rate

I know it would be some work but it would be a nice one stop buying guide.

Thanks,

-Mr. Wigggles

Racing Beat says that their springs are about 20% stiffer than stock front and rear.

So that would be:

F 187 lb/in (calculated)
R 136 lb/in (calculated)

-Mr. Wigggles

works for me... I'll add it til someone tells me different ;)

Just got off the phone with H&R and they say that the exact spring rate is proprietary. However she then said that it will be 25%-30% stiffer. Note that this is still essentially a linear rate spring.

So H&R is:

F ~194-203 lb/in (estimate)
R ~141-146 lb/in (estimate)

where "~" means roughly

I called Eibach and the guy told me that for the RX-8 it is a progressive spring rate that is between 15% stiffer than stock at the rest position and up to 20% stiffer than stock as the spring contracts.

Eibach is

F 180-187 lb/in (calculated progressive rate)
R 130-136 lb/in (calculated progressive rate)

So wich one / wich spring rate setup that good for street use??

--
Espelir Active GT springs:

Claimed:
On the spec drop 30mm for front & rear w/ 30%+ stiffer than stock.

Actual:
If calculated f/Alex table above.

Stock RX8 6spd : Espelir
F 155.61 lb/in : F 212.8 lb/in (36.75%)
R 112.86 lb/in : R 151.2 lb/in (34%)

Testing on my car w/stock shock-abs:
The drop not equal, rear drop more 5-7mm than the spec. If look from the side, the rear more lower than the front.

Front >> more stiff than stock, short recoil but not bouncing, good grip and handling.
Rear >> although it has higher spring rate but it feels softer than stock, better grip, rebound to slow at bumpy road, more body roll..

Overall, this springs is good. The front are excelent, but rear :confused: need more adjustment.. I fixed the problems by changing the rear shock-abs & swaybar with the harder one.

*sorry 4bad english :D

Oh thanks... that helps me big time.

I am tossing up the future suspension either a Tein Flex with EDFC or MazdaSpeed shock to save money. Looking at the spring rate Flex is quite stiff. I may go for CS or MazdaSpeed then

Just want to say , Tein S-techs drop is perfect , the front is allitle dipped lower than the front , front drop measured was 1.75 inches and rear was around if not less than .5 inches.
Sadly enough they are being removed for tein flex's .... , but it was a great set up , reccomended for anyone who wants to go low , and the steering feel was alot more precise and accurate , it made the stock handling feel flimsey ....

Can someone explain a little bit more how higher or lower spring rates affect the handling of the veh. From reading the post, a higher spring rate means bumpier ride.... What are some suggestion for a nice handle veh in hwy speed?

If the car has a 50-50 weight balance, why are all of the spring rates (stock and aftermarket) so much higher in the front? To keep it from diving during braking?

The engine is in the front. Look at the stock spring rates. They are also stiffer in the front. This can also lead to a push (understeer). Check the difference between the front and rear stock vs. the front and rear aftermarket. The back is stiffer to help promote neutral or oversteer condition usually associated with high performance driving characteristics

the spring rate of the spring itself isnt very informative, it is the rate at-the-wheel that matters. different geometry in the suspension results in different rates front and rear for the spring, but the rate at the wheel for a 50/50 car should be about equal.

now, the roll couple, or percentage of weight transfer for a car will usually be between 75% and 90% front. this is why the front sway bar is stiffer than the rear.

to avoid the car diving under braking (or squatting under acceleration) some cars have geometry called anti-dive and anti-squat. i think the rx8 has little of either (though i dont know for sure), which is prefereable for a sports/race car.

the rx8 is actually a mid-engined car, if you go by the definition that the engine is completely behind the front axle.

james

Will adding a stiffer sway bar or spring cause the vehicle to oversteer or understeer? I know alot of the performance parts were designed for track use. The road condition will be much different than ideal track surface condition..

If anyone has tested their setups it would be useful to see skidpad or slalom results to try and compare the benefits to stock or the other brands. The new Gtech RR model has a skidpad test on it if you can find a parking lot and some spraypaint. Anybody have some data to share?

I know on the Stock 6spd rx8 the ones with the GT package have different springs. Does anyone know the differnce between Stock 6spd and 6spd with GT package?

Bump again.

That's news to me that the GT package has higher spring rates than a Sport or Touring Package 6spd. For that matter, I think all RX-8's with the 18" wheels have the same "sport tuned" suspension upgrade. The only exception to this is the Shinka which supposedly has stiffer shocks.

Kw variant-3 coilover (hpa motosport - part # 35275008) spring rate is a 455 in the front and a progressive in the rear.

I drove the RX-8 with the full Mazdaspeed setup ( springs, shocks, and bars) I have a hard time believing those numbers as posted which seem to be so much stiffer than all the other springs. I don't think the Mazdaspeed car was that much stiffer than any of the performance shocks. I have the H&R's and I would not bet any money that the Mazdaspeeds are that much much stiffer.