Lib Gen 4 STI Pink Springs and Billies

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Lib Gen 4 STI Pink Springs and Billies

Postby GTB25T » Tue Mar 14, 2023 11:46 am

I tested a change in rear strut assembly on a gen 4 lib sedan because the shocks seemed a bit tired.
I compared the STI rear set with pink STI springs and the Bilstein tuned for STI vs the GTB black springs and GTB Bilsteins

For REAR The Pink STI spring vs Black had same no. of coils, same height, same spring coil diameter.
The actual Bilstein was softer for the STI than the GTB.

When installed the ride height was identical however the GTB rear was a little stiffer in the shock dampening. Using same 20mm solid rear sway bar.
This seems unusual but is it possible the rear STI springs only received a colour change but are essentially identical?

The FRONT I can confirm are different but still only lower the front end by 7mm. The lower portion of the coils are closer together for the STI spring but the ride is significantly more harsh. The handling is more controlled by the sway bar and a 22mm upgrade does it's part. The Bilstein's are supposed to be tuned for the STI suspension however there is no change in feel in practice if retaining the STI spring.

Reports from some drivers are coil overs tend to be stiffer (although adjustable). With the condition of all our roads, I wouldn't dare going stiffer or even more than a 18 rim and less than 40 profile.

In conclusion, think hard and research if deviating from the GTB setup with Bilsteins and black springs. Suspension needs to do its job. Perhaps PINK is not worth the change unless you do plenty of track work.

It also seriously hurts when you see a tyre stuffed because of poor road surface or even worse a rim
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Re: Lib Gen 4 STI Pink Springs and Billies

Postby bigBADbenny » Tue Mar 14, 2023 8:07 pm

Postfl tbSTi pinks rode somewhat higher than prefl tbSTi springs.

Iirc it was slightly more than a horizontal finger gap on a low km tbSTi wagon I was familiar with.

There’s various master lists including part numbers and spring weights eg to be found on legacy GT forum etc.

One might also take into account spring sag with age and or km… This generally affects the rears more than front springs.

As such, and in consideration of spring sag, I’m also interested in the uncompressed length of the springs, especially compared to other examples.

As with coilovers, it’s a delicate balancing act between spring type and weight versus damping type and force range.

Generally the effect of increased damper force is to make the car follow the road to a closer degree.

Bumpstops are an additional tuneable factor, both internal and external type, especially since the gen4 suspension geometry is somewhat limited in comparison with other cars, meaning they’re a very important aspect if the car is used in extremis.

With a model specific custom dampers, one can propose a use case and specify components to suit, and hopefully still be within acceptable damping range, or have the damper washer stack and bumpstops changed to suit.

So your choice might reflect the cost benefit relationship between buying new struts every 100kkm or so vs coilover damper service every 60+kkm.

My SW setup is all about compliance and all conditions grip, so I have stock sways, 8kg springs and damping set to soft.

Some, eg Borsche have a more track/performance setup with heavy rear bar, 14kg springs and a completely revised damper stack, adjustable, but still streetable.

The point being ultimately less compromises, and the car is liberated to another level of enjoyment.

So from personal experience with SW & Koni, the main point is an, as advertised, digressive damper plus warranty and service support are the two main points to consider when investing in your suspension setup.
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