Yargk

Okay, for information I'm not sure of, I'll add a note and edit this post in the future when the correct information comes

My main questions are (but I'll go into more detail below):
* What are the lengths of the springs used in the Tarett spring set? (these are 5 inches front and 7 inches rear, thanks for the info Joe)
* Does the GT4 clubsport have helper springs in the front? (edit A: yes, same helpers as the front KW 10/60/80)

1. Stock suspension
Front: 257 pounds/inch length 7 inches NO helper
(picture from Tom at TPC)


stock rear: 457 pounds/inch length 7.7 inches with helper spring so the stack height might be around 8.5 inches




Clubsport front: 200-140 I'm guessing this means 200 Newton/mm and 140 mm length, so it's 1142 pounds/inch and a length of 5.5 inches.
It does have helpers, the same 10/60/80 KW helpers as the rear.





Clubsport rear 220-140 1256 pounds/inch 5.5 inch length
Note the helpers on top


Tarett/swift front: 448 pound/inch, 5 inch length because stock is 7, the swift/tarett spring is shorter with a helper spring

(picture from USCTrojan I think)


Tarrett/swift rear: 560 pounds/inch, I'm guessing a 7 inch length because stock is 7.7, the swift/tarett rear spring is shorter with a longer helper spring than stock, and swift springs come only in whole inches (for example 6,7,8). Above we figured the stock rear stack height (main spring + helper) was 8.5 inches. If tarett used a 7 inch main spring and a 1.5 inch helper here, that would be 8.5 inch. It seems to make sense because the swift helper on the rear has 6 coils compared to the 4 coils on the front helper, and we guessed that the front helper is an inch.

Mech33

To compare apples to apples, you need the spring rate and the length of the spring at a known load. Your pictures all have some unknown load (and therefore unknown compression) applied to the spring, so it becomes a bit of a guessing game on choosing a spring that will have the car sit at the same height at the same perch setting.

Best thing to do is have them off the car and measure their heights there. Second best would be to measure their heights fully loaded with the known car weight at each corner.

Yargk

True. I was hoping that because all of the pictures were at full droop, with most showing a not fully compressed helper, then there should be negligible compression on the main (because the helper rate is so small). However, I agree that it's a bit speculative. Just trying to add some data points and get the ball rolling.

Bill Lehman

Don't get too concerned about helper springs. You can run a short main spring with a light helper and the helper just keeps the main spring from coming unseated at full droop. You can also run an "Assist" spring which is heavier than a helper and allows more spring compliance with the road for street driving and is normally fully compressed. My last set-up was put together with Tarett's info and worked very well as a street/track setup. Apparently the initial Clubsport spring set was found to be on the stiff side and a lighter spring was made available for the series.

mooty

^ bingo.
i have non oem shocks short spring and no heper no assist. main spring gets unseated at droop and BOING back in when i hit stuff once i drop car on ground. scare all my passnegers. price less.

CS has more than just spring issues. the shocks need a lot of help too

Yargk

Yeah, that's what I heard and was thinking too. If the damping was really good, the springs wouldn't be so bad and if the springs were softer, the damping doesn't matter quite as much. But super stiff springs + non-ideal dampers = good drivers complaining.

orthojoe

I am still waiting to install my tarret Spring kit, but did measurements for you, fwiw.

The front springs are 5" long and the rear ones are 7" long

Beantown Kman

I'm looking forward to hearing your impressions once you get them installed. You've made enough other tweaks, and have enough seat time in the car, to offer a good evaluation of the difference they make.

orthojoe

Based on changing the front springs on the gt3, I'm predicting not much of a change in feel or performance. However, if I can get even tire wear without having to flip tires on the wheels, it will be WORTH it.

Tom@TPC Racing

^

Yargk

Thanks for the info! Could you post pictures of your helpers? On the tarett website they show 4 of the same helper, but on USCtrojan's car, the fronts look different than the rears.

Assuming compressed length is simply obtained from free length and the weight of the car (close to a 1-1 motion ratio) and the spring rate, this makes sense for both ends.

Front: stock is 257 pounds/inch, corner weight is about 700 pounds, free length 7 inches => compressed length = 4.28

tarett is 448 pounds/inch, corner weight is about 700 pounds, free length 5 inches => compressed length = 3.43, add a 19 mm approx helper and you're at 4.17

Mech33

Good point on the motion ratio. You need to factor in where the spring is mounted and thus how much additional load the spring sees relative to what the tire sees in order to calculate the true compressed length in the car.

Yargk

Exactly, I was thinking that on a strut car the motion ratio is probably between 0.9 and 1.0, so I'd be off at most a quarter inch.

orthojoe

Here you go! Front and rear helpers are the same

Yargk

Thanks again, it's swift's 70mm spring with a 45 pound/inch rate and a 27 mm compressed length. It's also good to note the spring adaptor is 2 mm.

Anyway, the helper on the front in the picture above is definitely different so I wonder if they changed the setup (the picture above is from an early installation) or if the one above was custom ordered.