Hi All

Been awhile since I posted on the Forum. Last time was a few years ago and I was asking suspension questions about my 1998 Classic Impreza (GC8). In the end I decided I didn't have the money to get what I really wanted, so I didn't do anything.

The suspension I currently have on the car is the original Prodrive fast road kit, installed in 1999. Needless to say it's old and very tired!

Things have changed a bit financially and I'm ready to move ahead. I remember hearing really good things about the AST suspension when it originally came out. So I'm considering getting an AST kit or, possibly, a Bilstein B16 Series PSS9 kit. We're talking £1,295.00 (AST 4100), £1,660.00 (AST 5100) or £1273.00 (Bilstein PSS9).

Does anyone have experience with any of these on a Classic? Do you think spending this kind of money is worth it or should I just get a set of KYB AGX struts and Eibach springs and call it a day?

Thanks a lot!

 

I have the 3-way adjustable AST on my gc8 and perform brilliantly, I have done circuit and sprints and they performed brilliantly on either and with enough adjustment for different weather/grip conditions.
I know the 3-way adjustable is more expensive than the sets your looking at (just shy of 5k with VAT) so I can't really say what the ones you are looking at would be like, however if they are anything like mine then it's worth the investment! Plus they can be serviced/rebuilt etc in the uk with ease not like tein etc where it cost more than buying a new set of dampers.
To sum up in my opinion one of the best mods I have done and one of the best places to spend money (if you have it) on the car. Also take into concideration what your planning on doing with the car?
Cheers
CJ

 

Had bilstein b16s fitted to my previous 650bhp plus classic type r, awesome suspension was head and shoulders above the ASTs that were on the car before I switched.

If you are sticking to mid 300s power wise I would not bother with coilover suspension, just get the KYB AGX shocks and Eibach springs and it should suffice at that level of power and give a good road setup.

 

Which Prodrive Bilstein kit have you got:
wr97/98 kit - blue springs, sits low at the rear as the damper body is shorter.
wr99 kit - grey springs

What about P11L or WR15R/T springs with matching bump stops/dust boots?

https://www.scoobynet.com/991887-pro...tunity-14.html

http://www.rs25.com/forums/f114/t222...1-impreza.html

 

I have an EXETC fast road track kit for sale at sensible money, fully adjustable, remote reservoirs job lot. Covered 1200miles 1000 of which were running in miles

 

Thanks very much for the replies!

Just to clarify: I'm looking for a fast road setup (think British B-roads). Unfortunately, living where I do in Canada, there isn't any opportunity for "track days" (And I'm not even approaching 300+ bhp)

The Prodrive kit I have is the original one with blue springs. I measured the rates when I bought the kit: 180 lbs/in FR and 149 lbs/in RR. Not very stiff, I grant you, and I wouldn't mind going up a bit, but not too much. I don't want a bone shaker!

 

One last question. Any thoughts on the KW Variant 1 coilovers?

 

How much sugar?

What are the adjusters on top like too?

 

 

Thanks for the video, 2Pot.

Yeah, I seem to remember that the Prodrive P1 used 215 lbs/in front and 185 lbs/in rear (someone with a better memory may want to correct me!). Someone who should know what they're talking about told me that the P1 setup gave an Impreza "go cart" handling.

AST recommends 285 front and 170 rear. I've seen a lot of kits with much higher rates - I don't want to go there, because it's handling I'm after not "the look" and, as I said, I don't do track days.

 

The much quoted 215/195, for P1's, is incorrect.

They were 194/157 - a match made by Prodrive, for the stiff kyb inverted reds, when used on UK b-roads.
The Eibach P11L's + matching bump stops + agx's on setting 2/4(same as excel-g's) or 3/5, work well on undulating/uneven roads.

I don't know why AST would recommend those spring rates? The difference in front and rear rates means 'flat ride' would never be attained.

 

Excellent information, 2pot! Thanks again. It seems the magic ratio (at least according to Prodrive) F/R is ~1.2

 

Hmmm.... thinking ....

All things considered, what currently available dampers would you recommend with the P11L's - the AGX's or something else? I'm using 19mm F and 21mm R ARB's. I assume the stance of the car would change (currently WR97/98 kit - Blue springs - low at the rear)?

 

With everything else being equal, the ast's would need a rear spring rate at 250lb/in-ish, to achieve flat ride at similar speeds.

 

Against wr97/98's, the front ride height should be the same. I'd expect the rear height to rise 15mm: +/- 5mm, depending on fuel load.
On a saloon, wheel centre to arch, maybe 335mm front, 340: +/- 5mm rear.

Damper-wise:
Koni inserts - but, you'll need to find some struts to put them in.
Excel-g's - equivalent to 2/4 on the agx, I'd use a 20mm max rear bar.
agx - 2/4 or 3/5. In your case, if you like the 21mm rear bar, you might use 2/5 or 3/6.

 

Thanks again, 2pot. Are the spring rates for the P11Ls exactly the same as the P1s? Are they still available through you?

 

Yes & yes.

The spring free lengths are longer, to accommodate struts other than the red kyb inverted - which are still available new.

Can Bilstein not rebuild your wr97/98 struts? I could give you some specs and the bump stops you'd need.

 

Re: rebuilding my existing struts - I know you wouldn't have suggested it if it wouldn't work, so sorry if this is a stupid question, but I'll ask anyway: wouldn't there be a problem with the short rear strut and the new springs?

And what about the red KYB inverted struts? I didn't realize they were still available. Wouldn't they be a better choice than the AGXs or does the adjustability of the latter give them the nod? Or are there other reasons?

 

Rear 335 +/- 5mm depending on fuel load, with wr97/98's and P11L springs - assuming you've got a saloon, not a wagon? Wagon would be 7mmish lower with wr97/98's - so Paranoid Fabrication saggy butt spacers would be in order.

If you're on rough/uneven roads, I'd take the better low speed ride of the, twin-tube, agx's and their life-time warranty.

 

PM sent to you, 2pot.

 

I'd also consider having your original Bilsteins rebuilt (either through FEAL or Bilstein). They were/are a great damper. AST has made some serious changes to their dampers over the last few years. Better/robuster upper seals and the option of double digressive pistons are nice upgrades. I understand they also improved the bleed bolt design with better/more controlled oil flow (something the older design had some issues with). They are on your side of the coast so shipping and service should be quick.

http://usa.ast-suspension.com/websho...a-gc-gf-detail


One thing to consider is durability in the winter time. If the roads are salted often you might want to consider KWs as they do put up with the salt better. The KW V2 would be the comparable single adjustable to the AST 4100s.

 

Hi Arnie

Thanks for the reply. I think you and I discussed KW coilovers a few years back. As I recall you were very happy with yours at the time. Having my existing Bilsteins rebuilt presents a couple of problems, one is having to send them off to Europe and the other being without the car for the duration. I suppose it's worth considering even so.

 

That 20mm Whiteline rear bar is considered 19/20/21 here.
Also, no reason not to try the 19mm setting on the rear. As the bump stop combination you're now running is already reducing understeer.

 

That's interesting, Mark. Theoretically, what should I expect from the 19mm setting? Better ride? If so, would it still make sense to try the AGXs set to 3/5?

 

It's when you mentioned you'd like more confidence in high-speed turns.
You could try the 19mm rear setting, to make the car less sensitive, at higher speeds - to steering inputs and lift-off oversteer.
You'll also gain grip, traction and comfort, on uneven road surfaces, as your rear suspension is more independent: 20mm to 19mm is a 19% reduction in bar stiffness.
Question is, will you prefer the overall balance?

I'd try the 19mm rear bar setting, before increasing the damping.

 

Thanks, Mark. Will do.

 

What is your current alignment looking like?

 

Here you go, Arnie. BTW, thanks for the PM.

These are all "per side"

CAMBER

Front: -1.2 °

Rear: -1.1 °

CASTOR

+3.5 °

TOE

Front: 0.0

Rear: +0.05" (initially -0.05")

 

OK, here's the last word (hopefully!).

As stated previously, I ended up buying the P11L springs from 2pot (Mark) and mounting them on AGXs. I also bought bumpstops and dust boots from him. That all happened in February.

I have an adjustable Whiteline 21/20/19 swaybar on the rear and, on Mark's suggestion, I originally set the dampers to 2/5 - 5 on the rear because I had the bar set to 21mm. The result left a lot to be desired. The car felt way too stiff, the ride didn't feel balanced and the rear would hop on bumpy corners. Not good! I tried 3/5 and, although the car felt better balanced front to rear, the ride was still unacceptably stiff and the rear still hopped.

I reset the dampers to 2/4 and the rear bar to 20mm. What a difference! However, I eventually came to the conclusion that 2 on the front didn't provide enough body control on bumpy or undulating roads.

I left the rears at 4 and reset the fronts to 3. That provided a fairly comfortable ride, but eventually I felt the rear bounced too much! I changed the sway bar to the 19mm setting (Mark's suggestion) and, after some more "testing", set the rear dampers to 5 again.

Then I started working on the tire pressures. I'm running new BF Goodrich G-Force Comp 2 "Ultra High Performance" All Seasons - 205/50-16s.

Now, when using setting 4 on the rear, tire pressures didn't seem too critical as far as ride comfort was concerned - I could run 35psi on the front and 2,3 or 4 psi lower at the rear without a lot of difference in ride comfort. However with setting 5 at the rear, tire pressure became critical. There's no way I could use 35/33, for instance - really stiff, bone jarring ride (like it was in the beginning). I reduced the rear to 31 psi (35/31) and the situation improved somewhat, but there was an uncomfortable pitching movement front to rear. Then I started playing with the front pressures, thinking that if I reduced the front pressure, maybe more of the energy over bumps will be absorbed by the tire and not be transferred to the rear resulting in the pitching. I ended with 32/30 and that took care of the pitching and the ride was quite acceptable, even on bumpy roads.

However (there always seems to be a however!), the car didn't feel "planted" on the highway anymore. 3/5 produced a really jiggly ride at highway speeds and, for some reason I don't understand, the car felt as if it were riding higher and didn't give the sense of cornering confidence it had at lower speeds. Weird.

After all this fiddling with damper settings, I came to realize it was really important to make sure the front adjusters were seated properly - it's really easy to get them between settings if you don't make sure they have popped up all the way. Duh! So I began to think that maybe the lack of body control at the front I had experienced previously with setting 2 was because I hadn't made sure the adjusters were properly seated. Maybe. I reset the fronts to 2 and the rears to 4. Tire pressures remain the same at 32/30.

I'd be remiss if I didn't give a shout out to Mark for all his help throughout this process. He's a great guy to deal with, very knowledgeable and I wouldn't hesitate to recommend him.

 

Hi John
Are these your current set-up?
Is that rear toe correct?
I'd be using toe-in at the rear, so, +0.15mins (+0.25deg), per side - to get plenty of stability under hard braking - rear toe changes significantly under braking and acceleration.