Welcome to the North American Subaru Impreza Owners Club Tuesday July 17, 2018
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
Click here to visit TireRack
Brakes & Suspension Forum sponsored by The Tire Rack

Losing traction? Need new tires?
Click here to visit the NASIOC Upgrade Garage...
Go Back   NASIOC > NASIOC Technical > Brakes, Steering & Suspension

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads. 
Reply
 
Thread Tools Display Modes
Old 11-20-2017, 08:27 AM   #1
2pot
Scooby Newbie
 
Member#: 301042
Join Date: Nov 2011
Location: UK
Default WA/A2 04-07 GD GG STI Springs

While waiting for Eibach UK to release the WA/A2 springs, I've received a few questions. Hope the following helps.

I grabbed some images off the web, before Photobucket died. If it's your present/previous car? Thanks for the initial inspiration.

OEM STI



Prodrive 05 STI red S05/D5/001


JDM STI pinks


RB320 suspension



Spring tolerances are +/-3mm at ride height and +/- 7lb/in rate.

At ride height, oem sti spring rates measure 217 front, 171 rear.
JDM sti pink front measure 223, at ride height.

Required specs:
Daily driver/occasional track day.
F245lb/in R223lb/in at ride height
Linear spring rates, in their operational range.
Increase spring free length, to ensure no dislodging, at full droop - non-inverted dampers extend further, than inverted. Eg front Koni inserts are 35mm longer.
Revise the bump stops for inverted and non-inverted dampers: front - account for the lower front ride height, and rear - stiffen.
Don't go too low at the front - bump travel (and spoiler lips ).

Widetrack OEM sti front ride heights compared to :
Prodrive 05-07 sti red S05/D5/001 -18mm
WA/A2 -25mm
JDM sti pink -28mm
RB320 -31mm

Consider how the revised spring rates will effect ride frequency.
Take the extra rear weight of the wagon variant into consideration.
Keep the rear ride height close to the stock sti.
As utilised on the RB320 - increased positive rake:
A, relatively, higher rear ride height moves the roll centre rearward, increasing rear roll resistance.
That, in turn, makes the front end roll more - helping turn-in response and reducing understeer, without the use of stiffer bars.
You want the smallest bars possible, on a road car, to avoid 'roll-rock'.
Roll-rock:
If the spring rate is relatively low and the bar is too stiff, a suspension movement, initially, occurring on only one side of the vehicle, will be transmitted to the other side, inducing an unsettling 'roll-rock' motion and destablizing the tyre contact patch.

The bump stop selection also helps mitigate against understeer. On undulating/uneven roads, you may find the use of a bigger rear bar unnecessary/unhelpful.
* Registered users of the site do not see these ads.

Last edited by 2pot; 11-20-2017 at 11:04 AM.
2pot is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 11-24-2017, 05:30 AM   #2
2pot
Scooby Newbie
 
Member#: 301042
Join Date: Nov 2011
Location: UK
Default

RB320 - interesting article, on what Prodrive did with the '07 STI chassis:

https://www.pcadynamics.com/app/down...he+Insider.pdf
2pot is offline   Reply With Quote
Old 12-17-2017, 10:49 AM   #3
2pot
Scooby Newbie
 
Member#: 301042
Join Date: Nov 2011
Location: UK
Default

Currently investigating, whether it's possible to remove 0.7 of a coil at the rear, and 0.2 of a coil at the front - to save weight, by changing wire diameter/materials. Yet still pass the longevity/stress tests.
2pot is offline   Reply With Quote
Old 12-17-2017, 05:00 PM   #4
Vancouver98STi
Scooby Specialist
 
Member#: 459287
Join Date: Dec 2016
Chapter/Region: VIC
Location: Vancouver BC Canada
Vehicle:
1998 JDM Impreza STi
White GF8 wagon

Thumbs up I appreciate the advice you've sent my way

Quote:
Originally Posted by 2pot View Post

I grabbed some images off the web, before Photobucket died.
You've been quite helpful to me on a couple of different Subie forums, so I just wanted to mention the following in case you're unfamiliar with this "fix". Works great!

Quote:
Originally Posted by Vancouver98STi View Post

I installed Photobucket Hotlink Fix 1.3.9 for Chrome two months ago, and since then have had no issues viewing embedded Photobucket images in forum posts.
Vancouver98STi is offline   Reply With Quote
Old 12-18-2017, 04:04 AM   #5
2pot
Scooby Newbie
 
Member#: 301042
Join Date: Nov 2011
Location: UK
Default

Thanks very much. I'll check it out.
2pot is offline   Reply With Quote
Old 01-19-2018, 07:32 AM   #6
2pot
Scooby Newbie
 
Member#: 301042
Join Date: Nov 2011
Location: UK
Default

Quote:
Originally Posted by 2pot View Post
Currently investigating, whether it's possible to remove 0.7 of a coil at the rear, and 0.2 of a coil at the front - to save weight, by changing wire diameter/materials. Yet still pass the longevity/stress tests.
No, it's not possible.

Pre-production machine testing = 0.25mm increase in wire diameter. Slight increase free spring lengths.

Now in Eibach's manufacturing schedule.
2pot is offline   Reply With Quote
Old 02-01-2018, 05:55 AM   #7
2pot
Scooby Newbie
 
Member#: 301042
Join Date: Nov 2011
Location: UK
Default

For those that asked:
Reducing the number of coils does reduce the coil bind/weight. But, increasing the coils, increases elasticity. The spring has to reach coil bind and return to its specified free length.

If the design/material exceeds its elastic limit, then the spring won't reach coil bind, or will take a set, and not return to the specified minimum free length.

The WA/A2 springs have an increased free length, compared to a stock STI spring - to accommodate longer length, non-inverted, struts - koni inserts, AGX etc. As well as inverted struts.

UK delivery - now due week commencing 19 March.

Last edited by 2pot; 02-01-2018 at 07:45 AM.
2pot is offline   Reply With Quote
Old 03-30-2018, 02:36 PM   #8
2pot
Scooby Newbie
 
Member#: 301042
Join Date: Nov 2011
Location: UK
Default

2pot is offline   Reply With Quote
Old 04-12-2018, 03:42 PM   #9
2pot
Scooby Newbie
 
Member#: 301042
Join Date: Nov 2011
Location: UK
Default

The blob/hawk top mount restricted the spring design.
Utilising the bug rear top mount:
No additional sprung weight, as the dead coils are at the top.
The 2 plane angularity of the bug rear top mount is a closer mirror, to the lower strut perch - a more constant/even pressure on the closed/ground top coil.

2pot is offline   Reply With Quote
Old 05-01-2018, 06:35 AM   #10
2pot
Scooby Newbie
 
Member#: 301042
Join Date: Nov 2011
Location: UK
Default

Just waiting for the clip tubing to be fitted - next week.

Anyone buying Feal fixed perch struts?
I'd like to see a set of these springs, in that combination, wagon or sedan (no charge) - PM me.
I need your wheel size and et, tyre size and front + rear bar sizes.

Last edited by 2pot; 05-01-2018 at 07:38 AM.
2pot is offline   Reply With Quote
Old 05-14-2018, 04:03 PM   #11
2pot
Scooby Newbie
 
Member#: 301042
Join Date: Nov 2011
Location: UK
Default

Positioning the clip tubing, at rear ride height. Just the fronts to go now:

2pot is offline   Reply With Quote
Old 05-14-2018, 07:36 PM   #12
A-man07
Scooby Specialist
 
Member#: 271525
Join Date: Jan 2011
Location: BagEnd
Vehicle:
7/2 STi/WRX wagon
SWP/AW

Default

FWIW, I appreciate your efforts here. Nice job.
A-man07 is offline   Reply With Quote
Old 05-15-2018, 05:30 AM   #13
2pot
Scooby Newbie
 
Member#: 301042
Join Date: Nov 2011
Location: UK
Default

Thanks.

The GC/GF/GM springs have been good. Hopefully, the WA/A2 springs will find their niche in the market.

Last edited by 2pot; 05-15-2018 at 05:36 AM.
2pot is offline   Reply With Quote
Old 05-16-2018, 11:48 AM   #14
2pot
Scooby Newbie
 
Member#: 301042
Join Date: Nov 2011
Location: UK
Default

Done:
2pot is offline   Reply With Quote
Old 07-02-2018, 05:32 AM   #15
2pot
Scooby Newbie
 
Member#: 301042
Join Date: Nov 2011
Location: UK
Default

Have some feedback from a US '04STI + WA/A2 + 225/45 17 + Koni's + 6 speed. After 120miles: 364mm front, 360mm average rear.
New oem 04sti listed at 386mm front, 366mm rear.


^ OEM sti springs + 225/45 17: 374mm front, 342mm rear.


^ WA/A2 (just after fitting) + 225/45 17: 364mm front, 364mm rear.

Further height measurement after new alignment + bushes and dampers fully settle.

Last edited by 2pot; 07-02-2018 at 07:47 AM.
2pot is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

All times are GMT -4. The time now is 11:15 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2018 Axivo Inc.
Copyright ©1999 - 2017, North American Subaru Impreza Owners Club, Inc.