Spring Rates Question

[sab]

What would be the maximum spring rates you'd use for road use?

Car is lowered with Koni coil overs, so must be stiff, but not too harsh. Don't mind a slightly hard ride.

Thanks

[Matty]

I currently have 5kg front, 4kg rear (280, 224 lb respectively).

Even with the extra travel of the TEIN shocks and their good damping abilities, I'm finding the rear a little stiff for "real world", Australian conditions.

I found the same thing with Steve's FM springs, which were 342/228 lb (but very low too)

I am happy with the feel of the front end, but planning on backing off the rear springs to 3kg (168 lb) for a bit more ride comfort. (Then I'll up the rear sway to 14mm to compensate for the handling).

At 5/3kg, the rates will be about 70% higher than OEM on both ends.

my 2.2c incl GST.

[Ted]

Best to first check the valving on the Koni coilovers (are they the 28xx series bodies, if so I think its easy to add/remove shims) and see where they work best. The TeinSS on DCMau's car is at 330F/280R, ride is fantastic on the road. I think its almost at the limit of the shock rates though. I've currently got 210/150 on Bilsteins with much more rebound put in, quite nice on the street.

[Brad]

I'm looking at the 335/280 Tein SS whic by all accounts are great on the road. Does anyone know what rate the Clubman springs are?

[CT]

The Tein SS rates are pretty good. I'm farily impressed with them on the road. That said, I wouldn't want anything stiffer in either spring or valving. Track wise, 350/250 is popular, but I have heard of guys playing around in the 600lb zone. The Clubman's problem is the bilstein valving moreso than the springs from what I have been told. They too can be re-valved softer.

[sab]

Thanks for the replies so far guys.

How would the 350/250's that CT mentioned affect the koni coil overs and a spiritly dríven road car?

[Matty]

If you were going that high, I'd get 375/250, which is the "standard" rates that Ground Control use for their coilover conversion kits.

If you want to hurt your brain getting to know more about Konis shocks and their damping performance, there are some excellent threads on the big forum currently (particularly the "Damper Porn" one)

Though Sab, I will say one more thing about your car: it's so bloody low that it probably doesn't matter what the spring rate is. You're using the bumpstops and they're much stiffer in comparison to anything.

I guess my point is: please answer the question of WHY you want stiffer springs rates than you currently have...

[sab]

I guess my point is: please answer the question of WHY you want stiffer springs rates than you currently have...

With my car being as low as it is, the current springs are over coiled, meaning the coils are compressing on top of each other. I'm considdering some FM ones!

[Ted]

When you said coilovers, I assumed that you had the bodies that can take small ID springs. If that was the case, you can just get small ID springs in shorter free lengths. But if its the std Koni yellow with circlip'd perches, then you will need springs that are designed for the car. I haven't looked at a std Koni yellow dyno graph, but I ended getting mine revalved on my old car when I went to a 250/200 setup. From what I felt though, the std Koni yellow works OK from stock rates to about 50% more.

On the Charade, I have Koni yellow bodies but with a coilover collar, so can take small ID springs. At $70/collar, its quite cheap when you consider small ID springs are only about $80.

Clubman springs are the same rate.

[CT]

I have a set of threaded tubes, perches and lock nuts to convert Koni yellows to custom springs. Let me know if you are interested Sab. Converts to a 70mm inside diameter coil which kings or other can make into any length/rate you could require.

[sab]

The original springs that came with the coilovers have a tapered base. Found the Koni springs to be not much stiffer than the oem ones.

I got some alloy bases made up to fit over the adjustable perches, and refitted the whiteline springs I got with my original car.

I can now fit standard size springs without worrying about the tapered base.

[Matty]

Sab - the other option is to get some top perch adaptors made up, then you could fit standard 65mm springs as Ted said (assuming the Koni lower perch is 65mm, check your old springs to be sure....)

Might need some non-standard bumpstops too, but that can be a good thing.

[sab]

Thanks for the info guys. I've decided to give the 350 front, 250 rear's a go as I can get a second hand set at "the right" price and see how they go. I might try some of the other options if my ride is too harsh!

Here's a pic of the original Koni setup, and one with the modified base.