Subaru Forester SG springs... questions

[Porter]

Greetings all,

I have a few questions regarding the new Control and Flatout applications for the Subaru Forester SG chassis.

I assume the Control springs are similar to the factory Forester STi lowering springs sold in the US as a dealer-installed option, i.e. ~1 inch height reduction with an increase in springrate.

Owners in the US have had luck with the standard Impreza STi springs and/or spring/strut combo on the Forester, but the results are lower than what I am seeking.


My question is regarding the new Flatout spring set... 73215 front and 73239 rear. What ride height do these result in compared to stock?

Are these essentially the same as the Control spring set for the GD WRX/STi (80066 front, 73194 rear)? What is the difference in springrate and length between the Forester SG Flatouts and the Impreza GD Controls?


Thanks,

Jason Porter

[Wojtek]

Hi Jason,

I am not sure on the Forester STi springs, but we're happy to advise details for ours.
The static ride heights for our springs for Forester SG are listed in the following fact sheet:
http://www.whiteline.com.au/docs/fact_sheets/CK_Forester_SG_XT.pdf
Based on our test car, the average drop was about 40mm for Control springs and about 60mm for Flatout springs, using our shock absorbers. But, it's always best to measure individual car as original heights may vary.
We are aware of fitting WRX springs and shocks to Foresters, however we strongly recommend against this due to a number of reasons including incorrect shock lengths and insufficient spring carrying capacity.
Our Forester springs are NOT the same as WRX, in fact they have quite different lengths and spring characteristics, rates and load carrying capacities.

Let us know if you have any other questions.

Regards,
Wojtek.

[Porter]

Wojtek,

What are the spring rates of the Forester SG spring kits, compared to the Whiteline Impreza GD springs? This will be good information to pass along to US owners as a way of migrating them away from Impreza fitment parts.

I also feel the majority of Impreza fitment springs are too low for the vehicle, though the handling results can be quite good when paired with Impreza struts. The strut bodies are actually the same length (clevis to spring perch) but the Forester struts have more rod stroke and provide quite a bit more droop travel.

I have had good experiences in fitting Impreza coilover systems to SG chassis vehicles, but obviously the goals are quite different in a motorsport application.

Thanks for your assistance,

Jason Porter


P.S. - Would you recommend switching to Impreza style rear swaybar mounting brackets with the Flatout SG springs? I have had to make this switch on lowered Foresters in the past in order to keep the bar angle within an appropriate range, and it has helped with the Forester SG "bar flip" problem where the endlinks flip over and the bar hangs underneath the lateral links, damaging the endlinks.

[Porter]

One more comment...

An owner in the UK who participates on the US Forester forum had this to say:
I have just measured my stock CWTG and I get 435mm Front & 435mm Rear.

Based on Whitelines figures for Control springs of a CWTG of 375mm Front & 385mm Rear:

This would drop my car 60mm at the Front & 50mm at Rear.
Is this accurate? The '05 Forester is higher in some markets I suppose, I know they raised it slightly for the US in '05, by perhaps 10mm.

What is the Australian standard for "stock" height?

[Wojtek]

Hi Jason,

Spring rate comparison alone would not be relevant in determining the suitability of cross-application springs. There are other factors, such as lengths and load carrying also need to be considered. In this case, they are quite different.

The OEM struts are also different between WRX and Forester, not only the stroke, but also the spring platform height, open and closed (body) lengths and rates. Again, in our opinion not suitable for cross fitment.

Original ride heights can and do vary, that is why we give resultant fitted ride height for our springs, NOT the amount of lowering.

The rear swaybar bracket idea sounds OK to suit cars with extreme lowering, but it may limit the amount of suspension droop. So, this would need to be investigated. I have not heard about a rear swaybar "flip" problem.

Regards,
Wojtek.

[Porter]

Originally posted by Wojtek
Hi Jason,

Spring rate comparison alone would not be relevant in determining the suitability of cross-application springs. There are other factors, such as lengths and load carrying also need to be considered. In this case, they are quite different.

The OEM struts are also different between WRX and Forester, not only the stroke, but also the spring platform height, open and closed (body) lengths and rates. Again, in our opinion not suitable for cross fitment.

Original ride heights can and do vary, that is why we give resultant fitted ride height for our springs, NOT the amount of lowering.

The rear swaybar bracket idea sounds OK to suit cars with extreme lowering, but it may limit the amount of suspension droop. So, this would need to be investigated. I have not heard about a rear swaybar "flip" problem.

Regards,
Wojtek.
Wojtek,

The SG Forester is an Impreza chassis vehicle (G wagon chassis). They share the exact same chassis design and all suspension mounting points are the same. The Forester has the wagon chassis but uses sedan type control arms (and swaybar) in the front. Rear swaybar geometry is shared with the 04+ STi sedan (ball link type).

Forester and Impreza struts have the same spring perch height. The only difference in the suspension is the length and rate of the spring, and the total piston travel (droop travel) available.

There is a long history of using Impreza suspension componentry on the Forester... with Impreza suspension, the Forester sits at Impreza height and literally becomes a boxier Impreza wagon. Springrates are usually appropriate, as the Forester is actually lighter than the Impreza STi sedan.



Your comments and caution are well taken, however, and I understand where you are coming from with regard to an engineered approach. I agree with you that only Forester-fitment springs should be used on Forester struts... thus my questions regarding a comparison between springrates and uncompressed length for the two applications.

If I can fully impress these differences on the US owner group, you will probably see a significant jump in Forester-fitment suspension sales in the US... which will make Glenn a happy man. :D

Some real data would be very much appreciated and will assist me in encouraging other owners to take advantage of the time and effort that Whiteline has put into engineering a solution that is appropriate to the factory suspension dynamics.



The "bar flip" problem is an issue on lowered (and some stock) Foresters with the factory sway bar. In certain situations at full compression or droop the bar can pull the endlink rearward, and when the suspension reverses direction the endlinks flip over and the bar pushes them downward, around and below the lateral link resulting in bent endlinks. It's a common phenomenon.

[Wojtek]

Hi Peter,
Let me assume your good intensions, that our Forester springs are quite different to Impreza. Apart from having a similar shape, where both springs can "fit in the hole" so to speak, that's where the similarities end. In simple terms, the Forester springs could be labeled as "heavy duty" for they are made with thicker gauge spring steel wire, have more turns, and are longer in height and have much higher load carrying capacity. Unfortunately, "real numbers" above are company confidential information.

Regards,
Wojtek.

[Porter]

Wojtek,

Thanks again for your responses.

I can assure you my intentions are nothing but the best. I have sold Whiteline products in positions at several different companies for a number of years here in the US and have been a consistent promoter of the brand.

I know Glenn Dirkse fairly well through our prior dealer arrangements and in fact have spoken to Jim Gurieff on the phone on more than one occasion with regard to product issues.


Having some hard data to go by in terms of spring comparisons in this case is important to me. I understand your concern with regard to confidentiality, so if you are able to do so, please email me off-forum at jasonporter <at> gmail.com


Thanks again,

Jason Porter