WA/A2 04-07 GD GG STI Springs
25 May 2020, 05:41 AM
#61
Scooby Newbie
Curious to see the result of this work.Right now im on kyb ultra sr with oem sti black springs and im feeling that this setup lacks rebound because on turns with quick elevation changes I am floating around a bit,but after a tyre change with A052 yokos and a fast road geo this improved and masked the problem.
25 May 2020, 09:30 PM
#62
Scooby Regular
I can't give a timescale at this point. Still waiting for the wagon test mule back from lock down: it needs revised bushings, brakes, gearbox and front and rear diffs 
- I have a test route inc speed bumps. Then, I don't know how far behind Bilstein will be.
I'm happy with the matching bump stops, I now have, for inverted and non-inverted.
The Bilstein inserts might need:
The rear damping to be more digressive.
Maybe another bar, front and rear, off the fill pressures.
Koni inserts and RB320 struts were my baseline, being very picky:
The Koni's may jack down on to the bump stops - need more compression damping/less rebound damping.
The RB320 need to be more digressive - tendency to launch, over some road imperfections.
- I have a test route inc speed bumps. Then, I don't know how far behind Bilstein will be.I'm happy with the matching bump stops, I now have, for inverted and non-inverted.
The Bilstein inserts might need:
The rear damping to be more digressive.
Maybe another bar, front and rear, off the fill pressures.
Koni inserts and RB320 struts were my baseline, being very picky:
The Koni's may jack down on to the bump stops - need more compression damping/less rebound damping.
The RB320 need to be more digressive - tendency to launch, over some road imperfections.
With regard the Koni's I have found them to be pretty good as an all rounder, certainly significantly improved on the BCs I had before, but at the expense of turn in and crispness. Is this where the digressive valving help control the mass better to give more sharpness while still being more supple over the faster, bigger hitting undulations? Unfortunately my background is rebuilding/revalving mtb shocks for downhill and while I am pretty good at understanding setups there where the body moves around, and there are only two wheels, cars are a little more 'black art' to me. I do notice a tendency for the Koni's to pack (jack) down a little when running towards the upper end of the damper settings. Would you suggest something different to the non-inverted WRX bump stops I'm currently using, even as a bit of a crutch in just the rear to help stop that pack down?
Sorry, also, how close are the S05 and RB320 front springs in the real world with rate and progression, 10mm ride height difference aside?
27 May 2020, 09:35 PM
#63
A progressive spring is a spring that is not linear.
A dual-rate spring would still be termed a progressive spring.
You normally hear "It rides at one rate and then stiffens to another". No, could you imagine trying to organise the damping, in that scenario?
There is a soft section, that stops the spring dislodging at full droop - this section should be closed at normal ride height. This closed section should have protective tubing to stop damage from the coils rubbing together = rust.
The remaining open coils are the damped spring rate section. However, depending on the quality of spring design, it might not be accurately linear, from ride height to coil bind.
Only use the first turn of the Koni damping adjustment - the rest is wear compensation. Or, as you say, it will jack down - the excessive rebound damping will stop the damper re-extending, after each subsequent road irregularity, pulling the car onto its bump stops.
Getting the ratio between compression damping and rebound damping at slow, mid and high damper speeds is the key. You often hear that 0.7 critical damping is the thing to have (is it really?).
Say you had linear damping and you extended 0.7 critical damping to the high damper speeds, on poor roads you would be launching after every bump, with that set-up.
Digressive damping would allow a lower damping ratio at higher damper speeds.
Ride height and chassis balance dictate the bump stop durometer and length. Koni rear inserts might ride 20mm lower than a gas-filled strut, with the same spring.
S05 and RB320 front are the same rate.
A dual-rate spring would still be termed a progressive spring.
You normally hear "It rides at one rate and then stiffens to another". No, could you imagine trying to organise the damping, in that scenario?
There is a soft section, that stops the spring dislodging at full droop - this section should be closed at normal ride height. This closed section should have protective tubing to stop damage from the coils rubbing together = rust.
The remaining open coils are the damped spring rate section. However, depending on the quality of spring design, it might not be accurately linear, from ride height to coil bind.
Only use the first turn of the Koni damping adjustment - the rest is wear compensation. Or, as you say, it will jack down - the excessive rebound damping will stop the damper re-extending, after each subsequent road irregularity, pulling the car onto its bump stops.
Getting the ratio between compression damping and rebound damping at slow, mid and high damper speeds is the key. You often hear that 0.7 critical damping is the thing to have (is it really?).
Say you had linear damping and you extended 0.7 critical damping to the high damper speeds, on poor roads you would be launching after every bump, with that set-up.
Digressive damping would allow a lower damping ratio at higher damper speeds.
Ride height and chassis balance dictate the bump stop durometer and length. Koni rear inserts might ride 20mm lower than a gas-filled strut, with the same spring.
S05 and RB320 front are the same rate.
Last edited by 2pot; 27 May 2020 at 10:17 PM.
The following users liked this post:
28 May 2020, 11:18 AM
#64
Scooby Regular
That's interesting about the damping being difficult to sort for a progressive spring; many mtb suspension platforms run rising rate leverage curves and in the case of air shocks run quite a small volume air spring to provide 'ramp up', or in other words, progression. But it's a totally different chassis I would have assumed that the damping solution would be similar, for rebound at least. Like I say though, I am very much not a suspension expert in the car world and appreciate the dynamics are very different (no body to move around for a start).
That advice on the Koni adjustment pretty well matches my experience of them; they pack down on rough roads with repeated bigger hits if you go over that. This point was less with the original STI springs I had them installed with, I'm assuming partly down to their being softer and sagging over time.
Good info on the spring rates, thanks. From a looks perspective I'd like the RB320 springs on the front but they're impossible to find so I'll probably stick with what I have at the moment. Daft thought; would it be possible to re-weld the spring perch on 10mm lower to get the reduced ride height without creating any knock-on issues?
I'll confirm the ride heights later but do you think I would get any advantage to swapping the soft OEM bump stops out for something else in your inventory?
That advice on the Koni adjustment pretty well matches my experience of them; they pack down on rough roads with repeated bigger hits if you go over that. This point was less with the original STI springs I had them installed with, I'm assuming partly down to their being softer and sagging over time.
Good info on the spring rates, thanks. From a looks perspective I'd like the RB320 springs on the front but they're impossible to find so I'll probably stick with what I have at the moment. Daft thought; would it be possible to re-weld the spring perch on 10mm lower to get the reduced ride height without creating any knock-on issues?
I'll confirm the ride heights later but do you think I would get any advantage to swapping the soft OEM bump stops out for something else in your inventory?
28 May 2020, 01:06 PM
#65
The progression would be the bump stops, to balance the chassis during manouvers.
A stiffer rear stop would be advantageous, if understeer is an issue.
If the front has been lowered then a shorter/stiffer front stop (or more compression damping) may be in order - as riding on the front stops would cause understeer/poor grip/poor ride.
If you have lowered ride height, you may want a linear strut, as the available compression travel has been reduced.
The RB320 front struts have more compression damping and short/very soft stops - due to the ride height reduction.
Your oem front 60mm, 3-node, stops are soft - but have they been heat cycled to death, by more frequent contact? 355mmish would mean constant contact.
Your 90mm rear oem stops are soft - promoting understeer. Understeer is fine at the limits of handling or emergency breaking mid-corner, especially in poor road conditions.
Lowering the spring perch is possible, but you'd need to retain the required spring preload, to stop the spring dislodging at full droop + you'd need to ensure that the intentionally closed coils remain closed, or you run the risk of the closed coils being open = you'll be constantly swapping between rates.
Suspension design-wise you might have anywhere between 5mm from ride height to bump stop to 25mm.
So, at the shorter gaps you might have a spring rate at normal ride height and a stiffer rate when cornering, as you would be on the bump stops.
The springs set the ride height and required ride frequency. The damper should be controlling the spring oscillations. The bump stops/bars control the handling balance, not the dampers.
A stiffer rear stop would be advantageous, if understeer is an issue.
If the front has been lowered then a shorter/stiffer front stop (or more compression damping) may be in order - as riding on the front stops would cause understeer/poor grip/poor ride.
If you have lowered ride height, you may want a linear strut, as the available compression travel has been reduced.
The RB320 front struts have more compression damping and short/very soft stops - due to the ride height reduction.
Your oem front 60mm, 3-node, stops are soft - but have they been heat cycled to death, by more frequent contact? 355mmish would mean constant contact.
Your 90mm rear oem stops are soft - promoting understeer. Understeer is fine at the limits of handling or emergency breaking mid-corner, especially in poor road conditions.
Lowering the spring perch is possible, but you'd need to retain the required spring preload, to stop the spring dislodging at full droop + you'd need to ensure that the intentionally closed coils remain closed, or you run the risk of the closed coils being open = you'll be constantly swapping between rates.
Suspension design-wise you might have anywhere between 5mm from ride height to bump stop to 25mm.
So, at the shorter gaps you might have a spring rate at normal ride height and a stiffer rate when cornering, as you would be on the bump stops.
The springs set the ride height and required ride frequency. The damper should be controlling the spring oscillations. The bump stops/bars control the handling balance, not the dampers.
Last edited by 2pot; 28 May 2020 at 01:20 PM.
The following users liked this post:
05 June 2020, 05:25 PM
#66
Scooby Regular
Thanks @2pot, good explanation. Despite having a number of textbooks on the subject, most seem to assume more basic knowledge than I have so there are a number of things you said there which tie a lot together!
My heights are 366mm on the front with S05 + Koni, and then 373mm at the back with RB320 + 10mm spacers + Koni. The bump stops haven't actually seen much use as they were only on the car until about 60k with the OEM WRX springs and it really hadn't been driven hard until then from what I could tell. I only refitted them a few years ago with this setup and they've done about 5k miles in that time, max.
With lowering the perch I'm undecided. With the 22mm rear ARB I'm actually pretty happy with how it all ties together at the moment, little aforementioned niggles in damping aside. My thought was to drop the front perch by 10mm, then lower the insert in the strut by 10mm (a combination of enlarging the hole at the bottom of the strut, a 10mm spacer below the strut body and then an internal spacer to take up the gap). However, if I could just find a set of front RB320 springs that would certainly be easier! If I'm being honest the only reason for going this way is looks.
Again, thanks as ever for such clear explanations.
My heights are 366mm on the front with S05 + Koni, and then 373mm at the back with RB320 + 10mm spacers + Koni. The bump stops haven't actually seen much use as they were only on the car until about 60k with the OEM WRX springs and it really hadn't been driven hard until then from what I could tell. I only refitted them a few years ago with this setup and they've done about 5k miles in that time, max.
With lowering the perch I'm undecided. With the 22mm rear ARB I'm actually pretty happy with how it all ties together at the moment, little aforementioned niggles in damping aside. My thought was to drop the front perch by 10mm, then lower the insert in the strut by 10mm (a combination of enlarging the hole at the bottom of the strut, a 10mm spacer below the strut body and then an internal spacer to take up the gap). However, if I could just find a set of front RB320 springs that would certainly be easier! If I'm being honest the only reason for going this way is looks.
Again, thanks as ever for such clear explanations.
05 June 2020, 08:46 PM
#67
You might not achieve what you want with the RB320 spring. It's very short in free length - made for the Bilstein inverted strut.
The Koni insert, at full extension, is significantly longer = the spring will be loose.
I'd check your 60mm front bump stop gaps - with the stop pushed fully up, how much gap have you got to the contact seat on the insert. Or, put a little tie wrap on the shaft, find a bumpy road and see if it gets pushed down the shaft (or it disappears).
Rather than changing the stop, you can cut off the smallest node with a bread knife. If you're worried about nicking the shaft, you can slide a tubular piece of aluminium can between the bump stop and the shaft.
I've made spacers to drop the Koni inserts. Earlier Koni inserts had the same base thread diameter, but a larger OD, so required a different spacer.
If you go too low with the front ride height and use the spacer, you'll contact the cv boot.
I think your ride heights are spot on - particularly with limited compression damping.
If you want to close the gap, what about using 235/45 x 17 tyres? On an 8" wheel like a jdm sti.
The Koni insert, at full extension, is significantly longer = the spring will be loose.
I'd check your 60mm front bump stop gaps - with the stop pushed fully up, how much gap have you got to the contact seat on the insert. Or, put a little tie wrap on the shaft, find a bumpy road and see if it gets pushed down the shaft (or it disappears).
Rather than changing the stop, you can cut off the smallest node with a bread knife. If you're worried about nicking the shaft, you can slide a tubular piece of aluminium can between the bump stop and the shaft.
I've made spacers to drop the Koni inserts. Earlier Koni inserts had the same base thread diameter, but a larger OD, so required a different spacer.
If you go too low with the front ride height and use the spacer, you'll contact the cv boot.
I think your ride heights are spot on - particularly with limited compression damping.
If you want to close the gap, what about using 235/45 x 17 tyres? On an 8" wheel like a jdm sti.
Last edited by 2pot; 06 June 2020 at 12:46 PM.
The following users liked this post:
06 June 2020, 09:00 PM
#68
Scooby Regular
Once again, brilliant! I've measured the free movement on the front stops as somewhere between 10-12mm. Do you believe this should be sufficient, or would you suggest dropping a node from the stop to give closer to 30mm free movement? I'm about to swap the strut bodies out for some freshly powder coated items so that would be an easy point to cut/change the stops if it's deemed worthwhile.
With regard the ride height and say a 10mm drop on the perch, is this likely to be an issue with CV boot contact? I'm not that keen to give myself another project, dealing with the general rust on the body is enough and therefore reinventing multiple parts is beyond where I'm looking at the moment, but if it was as simple as drilling the hole bigger and tracking down some spacers then I'd be interested. Is it really a worthwhile option to drop the car 10mm front and back (or in other words, is it going to make a noticeable difference to the handling all other things being equal)? If you're of the belief the ride heights are on the money and I'm happy with the handling then I'm certainly not about to jump to changing things about unnecessarily. I've got a few pairs of v7 STI wheels which are only 7.5" so the 235mm tyre is probably a bit big for the rim width.
I've got Alan Staniforth's Competition Car Suspension and also SAE Race Car Vehicle Dynamics but they don't really capture tuning like this, and seem to be more along the lines of valving and custom linkage design (or my brain isn't really calibrated to understanding the detail they go into). Are there any books which do the explanations of the basics in the way you've been able to that you'd recommend?
Finally, do you have a PayPal address? I feel I owe you something for all the help you've given so far, and that you've probably just saved me a fair amount of cash in tracking down some LE07 front springs...
Thanks
With regard the ride height and say a 10mm drop on the perch, is this likely to be an issue with CV boot contact? I'm not that keen to give myself another project, dealing with the general rust on the body is enough and therefore reinventing multiple parts is beyond where I'm looking at the moment, but if it was as simple as drilling the hole bigger and tracking down some spacers then I'd be interested. Is it really a worthwhile option to drop the car 10mm front and back (or in other words, is it going to make a noticeable difference to the handling all other things being equal)? If you're of the belief the ride heights are on the money and I'm happy with the handling then I'm certainly not about to jump to changing things about unnecessarily. I've got a few pairs of v7 STI wheels which are only 7.5" so the 235mm tyre is probably a bit big for the rim width.
I've got Alan Staniforth's Competition Car Suspension and also SAE Race Car Vehicle Dynamics but they don't really capture tuning like this, and seem to be more along the lines of valving and custom linkage design (or my brain isn't really calibrated to understanding the detail they go into). Are there any books which do the explanations of the basics in the way you've been able to that you'd recommend?
Finally, do you have a PayPal address? I feel I owe you something for all the help you've given so far, and that you've probably just saved me a fair amount of cash in tracking down some LE07 front springs...
Thanks
06 June 2020, 10:29 PM
#69
I really wouldn't change the ride heights. If you want something to do? I'd remove the alk - swap to group n rear bush and stock rubber bush in the front arm.
No, I don't think that bump stop gap is sufficient. I should have something suitable bump stop wise - is your 22mm rear bar adjustable?
PM me your email, I'll dig out an install/alignment sheet, there might be something helpful in that.
I'd remove the alk - swap to group n rear bush and stock rubber bush in the front arm.No, I don't think that bump stop gap is sufficient. I should have something suitable bump stop wise - is your 22mm rear bar adjustable?
PM me your email, I'll dig out an install/alignment sheet, there might be something helpful in that.
The following users liked this post:
The following users liked this post:
26 September 2020, 01:06 PM
#71
The suspension test mule has returned .
New 6 speed conversion, non-dccd - 12kgf.m/100rpm uprated centre viscous diff, Quaife atb front/rear and better brakes.
Adjustments:
50-60mph motorway 'fidgety'. Above that, everything smoothes out and it just flows - spot on.
B roads - front high-speed compression damping too stiff.
Rears need digressive valving and softening a bit and less gas fill pressure.
Going to try screw on gland nuts, for this version, rather than press on:
.New 6 speed conversion, non-dccd - 12kgf.m/100rpm uprated centre viscous diff, Quaife atb front/rear and better brakes.
Adjustments:
50-60mph motorway 'fidgety'. Above that, everything smoothes out and it just flows - spot on.
B roads - front high-speed compression damping too stiff.
Rears need digressive valving and softening a bit and less gas fill pressure.
Going to try screw on gland nuts, for this version, rather than press on:
Last edited by 2pot; 26 September 2020 at 07:00 PM.
24 November 2020, 10:23 AM
#74
The WRX wagon, in post #71, is using WA/A2 springs/inverted strut housings with Bilstein inserts.
The latest prototype insert - can Bilstein get the 30mm inverted inserts to use a digressive piston at my specifications.
At the moment, I'm only concentrating on that - prototype inserts aren't cheap.
After that - how much in quantities? - they still might not be cost effective.
The latest prototype insert - can Bilstein get the 30mm inverted inserts to use a digressive piston at my specifications.
At the moment, I'm only concentrating on that - prototype inserts aren't cheap.
After that - how much in quantities? - they still might not be cost effective.
Last edited by 2pot; 24 November 2020 at 03:45 PM.
07 March 2021, 01:58 PM
#75
After 1,000 miles - six speed, full tank, new struts, new strut mounts and new bushes settling - well made springs don't settle.
Saloon would be 9mm higher at the front, as the saloon front arch is cut higher. Saloon rear would be 5mm higher, due to less rear weight.
Saloon would be 9mm higher at the front, as the saloon front arch is cut higher. Saloon rear would be 5mm higher, due to less rear weight.
Last edited by 2pot; 07 March 2021 at 04:20 PM.
02 July 2021, 12:32 PM
#76
For those that have asked, who wish to use blob/hawk rear top mounts, rather than bug, and want a lower rear ride height on the WA/A2 springs - I've done this:
WA/A2+A3
Same front spring as the WA/A2. But, 20mm lower at the rear, than WA/A2. Or, 10mm lower than rear Prodrive S05/D5/001.
Not required on Koni's or low pressure dampers. However, KYB Ultra SR inverted rears have high gas pressures - high gas pressures act as a supplementary spring.
Waiting for an Eibach delivery.
WA/A2+A3
Same front spring as the WA/A2. But, 20mm lower at the rear, than WA/A2. Or, 10mm lower than rear Prodrive S05/D5/001.
Not required on Koni's or low pressure dampers. However, KYB Ultra SR inverted rears have high gas pressures - high gas pressures act as a supplementary spring.
Waiting for an Eibach delivery.
Last edited by 2pot; 02 July 2021 at 04:26 PM.
12 November 2021, 08:06 AM
#77
Scooby Newbie
For those that have asked, who wish to use blob/hawk rear top mounts, rather than bug, and want a lower rear ride height on the WA/A2 springs - I've done this:
WA/A2+A3
Same front spring as the WA/A2. But, 20mm lower at the rear, than WA/A2. Or, 10mm lower than rear Prodrive S05/D5/001.
Not required on Koni's or low pressure dampers. However, KYB Ultra SR inverted rears have high gas pressures - high gas pressures act as a supplementary spring.
Waiting for an Eibach delivery.
WA/A2+A3
Same front spring as the WA/A2. But, 20mm lower at the rear, than WA/A2. Or, 10mm lower than rear Prodrive S05/D5/001.
Not required on Koni's or low pressure dampers. However, KYB Ultra SR inverted rears have high gas pressures - high gas pressures act as a supplementary spring.
Waiting for an Eibach delivery.
Some news about these from eibach?
15 November 2021, 04:27 PM
#79
Be interesting if these after-market KYB inverted struts, for the GD widetrack, 114.3 pcd, struts ever become available in Europe.
front 5510035
front 5510036
rear 5510029 (UK equivalent 321004)
rear 5510030 (UK equivalent 321005)
front 5510035
front 5510036
rear 5510029 (UK equivalent 321004)
rear 5510030 (UK equivalent 321005)
Last edited by 2pot; 22 November 2021 at 12:59 PM.
18 November 2021, 12:40 PM
#80
While waiting for the WA/A2 + WA/A3 sets to be made up:
Here's a look at an A3 rear, for use with blob/hawk top mounts.
Ride height 10mm lower than the Prodrive S05/D5/001 rear.
39N/mm
Linear from 15mm above ride height to coil bind.
A3 rear is 30% stiffer than STI widetrack rear spring, at static ride height.
Here's a look at an A3 rear, for use with blob/hawk top mounts.
Ride height 10mm lower than the Prodrive S05/D5/001 rear.
39N/mm
Linear from 15mm above ride height to coil bind.
A3 rear is 30% stiffer than STI widetrack rear spring, at static ride height.
Last edited by 2pot; 18 November 2021 at 12:50 PM.
15 December 2021, 12:49 PM
#81
If anyone is OK with colour mismatched front and rear STI springs, let me know
Due to an Eibach miscommunication, I now have some Diamond red WA/A2 fronts and Prodrive red WA/A3 rears!
Eibach have agreed to discount any mismatched sets, that can be sold. As it reduces the quantity returned to Germany, for re-coating.
£260 for a mismatched set, as opposed to £325.
Due to an Eibach miscommunication, I now have some Diamond red WA/A2 fronts and Prodrive red WA/A3 rears!
Eibach have agreed to discount any mismatched sets, that can be sold. As it reduces the quantity returned to Germany, for re-coating.
£260 for a mismatched set, as opposed to £325.
Last edited by 2pot; 15 December 2021 at 01:03 PM.
29 December 2021, 04:34 PM
#83
If anyone is OK with colour mismatched front and rear STI springs, let me know
Due to an Eibach miscommunication, I now have some Diamond red WA/A2 fronts and Prodrive red WA/A3 rears!
Eibach have agreed to discount any mismatched sets, that can be sold. As it reduces the quantity returned to Germany, for re-coating.
£260 for a mismatched set, as opposed to £325.
Due to an Eibach miscommunication, I now have some Diamond red WA/A2 fronts and Prodrive red WA/A3 rears!
Eibach have agreed to discount any mismatched sets, that can be sold. As it reduces the quantity returned to Germany, for re-coating.
£260 for a mismatched set, as opposed to £325.
03 March 2022, 11:36 AM
#84
KYB after-market front struts for 114.3mm pcd Impreza hawkeye STI (Some late model blobeye STI were also 114.3mm pcd).
Contact:
https://www.spring-loaded.co.uk/
Grey:
front 5510035
front 5510036
rear 5510029
rear 5510030
Gold UK rear equivalent 321004 £120 on ebay.
https://www.ebay.co.uk/itm/301496955...UAAOSwt31hCWF4
Gold UK rear equivalent 321005 £120 on ebay)
https://www.ebay.co.uk/itm/291359930...QAAOSwQldhCWGD
Contact:
https://www.spring-loaded.co.uk/
Grey:
front 5510035
front 5510036
rear 5510029
rear 5510030
Gold UK rear equivalent 321004 £120 on ebay.
https://www.ebay.co.uk/itm/301496955...UAAOSwt31hCWF4
Gold UK rear equivalent 321005 £120 on ebay)
https://www.ebay.co.uk/itm/291359930...QAAOSwQldhCWGD
Last edited by 2pot; 17 June 2022 at 11:40 AM.
The following users liked this post:
