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Discussion Starter · #1 ·
We've talked a lot about lowering and other fun stuff in this section of the forum, but I'm most interested in spring rates; here's why: with a ride height adjustable suspension like Tein or some others, you can run pretty much any spring rate you want and get the ride height where you'd like it to be by adjusting the preload collars.

Stiffer springs affect daily ride quality, not necessarily in a good way. Softer springs give a cushier ride, but allow more body roll, and will fully compress with less force than stiffer springs.

My Supra sits on Tein HAs with some pretty stiff springs. Many of the road racers run even stiffer springs. The car is unpleasant over harsh bumps, even on the softest settings, and still hits full compression on mid-corner bumps. I could argue for both softer and stiffer springs for this car, but the truth is, it isn't a pleasant daily driver.

I don't want my tC to become a competitor to my Supra for harsh ride quality, and yet I'd like it to deliver a bit more confidence inspiring performance, especially under transition, because the car gets altogether too light as the suspension unloads and loads up again.

Tein has a table with available spring rates for their products on the tC. What about the other? Anyone have data for TRD, Eibach, Pro Line, or any of the other spring makers? It would really be handy to have a table with all the spring rates listed, and maybe even a comments section for how those springs work for street and track duty. Anybody have data they can contribute?
 

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Tanabe NF210; Drop: 1.1"F/1.7"R; Rates: 3.0kg/mm F, 4.1kg/mm R

Tanabe DF210; Drop: 1.7"F/2.2"R; Rates: 3.4kg/mm F, 4.3kg/mm R

TRD springs; Drop: 1.25"F/1.25"R; Rates: 3.1kg/mm F, 5.6kg/mm R

Now that's what I found online while researching my spring purchase-- I converted the TRD rates from the listed NM, so I may be off by a slight bit. I'm still trying to locate Eibach-- their site is less than helpful. I didn't list Tein because their site is quite helpful.
 

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No data yet but the supplied springs on the Tein SS coilovers I had on my Matrix worked fairly well and rode very very comfortably, far better than stock on mid settins on the shocks.

But, I was going to go with much stiffer rear springs in order to facilitate rotation of the car into turns for autocrossing. I know Hotchkis runs incredibly stiff springs on the rear of their road race Celica and Wes)he owns their project car) and I have talked about stiffer springs for our project car as well but we are going to test the ones supplied by Tein first being this is an independent rear end versus the Matrix twist beam(not all bad;)

Rick
 

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this is something about the TRD springs:
QUOTE
1.25" in drop and spring rate is increased 18% in the front, and 26% in the rear over stock springs.[/b]
as for ride quiality, i think everyone that has them says its not that much worser than stock... noticable, but no so bad that you can't enjoy the ride
 

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Discussion Starter · #5 ·
Sure but drop is pointless when you can adjust the preload on the spring. I could easily use the TRD spring and set the ride height to exactly the same as stock by just increasing the preload on the spring. It would also make the ride 18% stiffer in the front and 26% stiffer in the rear, but there would be no drop. This would also increase the spring pressure at maximum compression, and might cause the spring to coil bind (VERY bad, spring rate goes to infinity suddenly), but that's another discussion.

The idea is to find out what the available rates are, figure out what the suspension travel is, and figure out which springs will provide the best compromise between keeping the car from scraping the ground, keeping the driver's kidneys intact, and still providing acceptable performance. It's actually a lot easier for race cars. You fit the spring that just goes into coil bind over the worst bumps on the track with the ride height set a millimeter or so above scraping on the ground. In some cases, a little scraping is OK as long as it doesn't unload the suspension unexpectedly. Then you adjust the damping to the softest setting that keeps the car stable under racing conditions, because stiff does not equal fast. Keeping the tire in contact with the ground as much as possible equals fast.

That's why I find the tweel so intriguing. A whole new way to think about suspensions...
 

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Discussion Starter · #7 ·
Ride quality is based on spring and damping rates. Dropping has little to do with that if you are able to adjust the amount of preload on the spring.

The good thing about reducing ride height is your center of gravity gets lower to the ground and the car is able to corner faster. The bad thing about reducing ride height is scraping on the ground over high bumps or steep driveways.
 
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