Gi'us a chance! I'll take the rear ARB off tomorrow (Sunday) and grease it, and then see if it improves.

But, if anything, it's been getting worse in the last week. I still feel it gets better after playing with the adjusters - I last played with them a couple of days before my last trip to PowerStation and, so, they were quiet as a mouse when they drove it. Now, 2 or 3 weeks later, they are really noisy again. Grrr.

Tune in, same channel, same time, for the next exciting episode...

 

got ast on my classic and did have a grinding noise coming from the nsr wheel
but the noise went after i also played with the adjusters(softer)so i will need to speak to powerstation during the week

 

OK - a happy few hours spent on the car today.

Rear ARB was pretty clean, and moving freely in its (bright yellow) bushes, but I cleaned them up and copper greased them anyway.

Rear springs are marked "Racing 250 30" - not 100% sure what it all means, but 250 might be the spring rate in lb/ft? Didn't check the fronts.

I sprayed the nsr spring with WD40 and cleaned it up a bit, and find that it rotates really easily in both the top and bottom spring seats (jacked up and hub "dangling" of course). I recall PowerStation saying it should sit in an indent in the seat, but there was no obvious place that it wanted to sit. Maybe the problem is they rotate and make a noise when they do so?

Anyway, I've only had a chance for a quick drive, and I don't think the grease and WD40 has really made any difference. But I'll drive it for a few days and see before pronouning.

 

I think the 250 refers to the length and the 30 is the spring rate (in Newtons/mm). I'd expect the fronts to be a bit stiffer, like 40 or 50.

30 is actually a bit on the low side I think, even on the rear, so it could be that the noise is due to the longer excursions allowed by that rate.

 

Hmm - interesting. What you suggest makes sense. It does feel quite soft - at a Ben Elliott driver training day, it was commented by the instructor that the car was not as hard as others'.

I should have checked the fronts, but decided to clean the car rather than faff about looking there as well as the back - what are Sundays for, after all

What's the consensus about AST's and spring rates on a newage then? This would be for a compromise of a daily driver and wannabe track day enthusiast.

 

imho:

60/50 N/mm

These are quite hard on a classic, but with the heavier New Age, about right.

 

Mine is 70F/50R and a daily driver, but a Forester so about 50Kg heavier overall. When it had 50's on the front it had trouble with the amount of travel (leading to big bangs !). It might also be that the further the spring has to move the more likely it is that it moves in the mount.

 

OK - maybe we're homing in on the problem here at last. I'll phone PowerStation and see what spring rates they currently recommend these days, and find out if there's some reason this one has softer springs.

Maybe the previous owner wanted it that way ... he now drives a BMW330d, so that could be it...

 

OK - had a good chat with PowerStation. Very helpful - thanks, Curtis

Here's what he said. I found it useful as well as illuminating, and so I thought I'd post it here in case others are interested.

Standard fit for ASTs (and Eibach's, amongst others, he says) is 50 front and 30 rear, so what I have is standard. Can't go blaming the previous owner's choices then. Cheers Andy

He noted that knocking rear left is a very common problem with standard suspension (as UK owners and Subaru UK will atest to of course) and not unique to ASTs. Really? Never! ;-)

Apparantly the Impreza rear suspension design means the spring is not parallel with the shock. This puts undue strain on the shock and leads to premature wear, and the knocking sound. The rear suspension ends up slightly assymmetric, with the extra forces mainly on the - wait for it - left hand side.

As an aside, he says that the new Impreza is moving to a multilink independent suspension system and no longer uses McPherson struts. Interesting.

Other possible causes of rear noise are the spring rotating in its seat when it is extended, but that is more of a twang than a clunk. Also, the spring can hit the shock in some circumstances - there's no sign of that on mine I have to say, and it doesn't sound like it.

There is also no rubber between the top of the shock/spring and the bodyshell - any noise is directly transmitted to the shell, which explains why it is quite so dramatic when something does make a noise!

I asked if it was lack of travel causing the spring to bottom out, but he says they use 250mm springs to ensure that this isn't the case - there's plenty of travel, he says.

They've tried various fixes in the past, including different top mounts, but with limited success.

Currently he fits a new spring, to his own design, that is tapered and this appears to improve things a lot. He recommended that I had these fitted as they are inexpensive and quick to fit, and should improve things.

Bottom line, it is a case of you-get-that, it appears. I am probably being way too fussy, but will take the opportunity of comparing notes with other newage Impreza AST users if I get the opportunity.

Just to to affirm, I have no complants about the handling or ride quality of the set up - it is stonkingly good, and I have no complaints of PowerStation who could not be more helpful.

I will probably invest in the new springs. Since PowerStation is 2 hours away and I'm not planning a trip there in the near future unless I have to, I may well give this a go myself in due course. It doesn't look like it's too hard to change a spring - is it?

Many many thanks to all who have contributed to this thread. If I do get the new springs, I'll let you know if it improves things.

Cheers,

Tim.

 

So I was correct then

Dipster

 

What's it like being a smarta*rse then

Seriously - if it is a bush worn out, then I ought to be able to get a new shock under warranty from Litchfield then But since its only going to happen again, what's the point And, they say (having looked at it) that there's nothing wrong with the shock

Whatever. I'll still go for the different springs and see how it goes.

 

The tapered springs do give a big reduction in harshness, the top sits against the original rubber mount which seems to damp a lot of noise and vibration.

 

Very nice, after a few glasses of wine thank you.
Seriously, the new age suspension will always wear out rear struts. It's a design thing.

 

 

I just wanted to add that I have the Sportline 1's here in the states fitted with 5/3 (no helpers in the rear) springs on my new age STi, and I too experience the "crash" when going over certain bumps. However, mine occurs on the right side of the car, which is the passenger side over here. I'm considering going to a higher spring rate in the rear, or possibly trying to come by the newly designed spring (although it's been impossible to get a response out of powerstation, hey guys, I want to buy stuff!!).

 

The plot thickens!!

In my experience they don't respond to email, but do to phone calls. You'll probably have to bite on the bullet and pick up the phone!

 

They do respond to email just very slowly.

 

I had the AST suspension fitted in 2005 after it's introduction on the Type 25. Whilst impressed with the handling etc etc.. I was haunted by noise form the nearside left which I likened to a ballbearing being fired at the wheel arch. It would happen predominantly when the wheel passed over a recess in the road i.e pothole or the kind of uneven surface you get around drain culverts that have subsided. After removing the coilover and top mount I traced the problem to the fact that the top of the strut wasn't seating fully in the top mount i.e the shoulder wasn't sitting squarely against the aperture of the bottom face of the top mount. Taking the top mount off i realised that the aperture through which the top of the strut passed was not symetrical thus preventing the strut passing fully through. When on the car, whilst everything appeared tight, there was obviously alot of play at that point and with the changes on the loading of the suspension as it passed in and the out of the hole the shoulder of the strut was obviously hitting the underside of the top mount. The shoulder of the strut was showing signs of pitting with the excessive movement. An easy way of proving this is to remove the coilover and top mount and try and fit the top mount over the top of the strut noting whether the strut and top mount fit squarely. if they don't the top mount will rock from side to side. I remember pointing this out to the fitters who agreed there was a problem and would look at refining the design of the strut/top mount. I'd be interested to know what the outcome was but from these postings perhaps there is still an issue with tolerences. I now have the prodrive springs fitted and can't fault the ride quality

 

Quote:

Originally Posted by 911

imho:

Just seen 911's suggestion.

See my response (Post 15) to this thread https://www.scoobynet.com/scoobynet-...ng-issues.html

Still going to try out the various shock settings before making my mind up though.

 

Interesting. Had a read just.

I have tried several combinations on my Sti V3 classic.
1
One way AST on 50/40 and 60/50 rates.
The latter are hard on the road and great on the track (I mean hillclimb track)
The damping was sorted by trial and error and worked really well.
2
Went to 3 way AST with 60/50 and struggled to find a combination of damping that didn't have a high frequency 'bobbing' on the road. Great on track mind.
This year I asked Curtis to fit the 50/40 springs on the 3 ways. I kept the same damper settings. Same bobbing. Same on track too! ie the weaker rates were not showing any ride /performance change.

Eventually rented a private session on a sprint track I know well with an ace suspension tuner, could almost call him a suspension mapper.

After 3 hours and about 25 hard runs on the dry track we found a very sweet spot on geometry/damping/tyre pressures on CROSS PLY racing slicks.
The damping settings were miles different to last year when i had radial Kumho V70A's on the car.(let alone the geometry on the front end)

On the road the ride is supple (the original intent with the 50/40) no bobbing and the car is fantastically chuckable.

Lessons:

AST's do work.
You need help from an expert and the right equipment on the day
You need the right environment to 'map' the system to perfection

You can get a setting that suits radial road tyres AND crossply slicks!

Graham.
ps:
I kept to the golden rule from Whiteline:

rear rates are 80% of the fronts.

 

Only wanted to get a sensible ride quality though. 3 hours on a track with a personal assistant isn't what I was anticpating!

Has anyone with a later spec car (preferably 06/07) tried spring rates higher than 50/30?

My problem appears to be that if I hit a bump (speed bump or pothole) with just one wheel (at normal speeds - and I don't mean Impreza normal), the spring is not man enough to lift the front of the car and so just travels up to the bump stop. It's not enough to cause major jarring like the original suspension, at least not at the speed I was travelling at - just doesn't feel 100%.

Sorry, just realised I'm hijacking the thread although I do have ASTs and the bump is a little bit noisy.

 

I think that's a bit unrealistic for most people

 

Guys,

I think what Graham is suggesting is that to get the best out of these puppies you need to spend ample time setting them up. This is not the kind of kit you can just bang on and it works. If you are just using these on the road, then all is cool, as PowerStation will get it somewhere very close. If you want it for track use, you really have to spend the time setting the car up. My personal view is that there is no compromise setting between road and track settings. Rebound, fast /slow compression should really be set dependant on the application..... thats why you have the ability to adjust, so you should be using it. It's all personal taste though.

Simon drove my car at ScoobyLive last week, but unfortunately we never had the chance to set-up the suspension. I have seen video ( I thought he might be making it up ) that clearly shows the front bobbing, which unsettles the rear. While this bobbing is happening, it caused lack of grip which caused massive understeer... which meant the car was not going around the corners as is should. Had we had time (and I knew what I was doing lol) before the event, we could of dialled this out by adjusting the rebound. Simon suggests this cost him up to 2 secs.

Look.... they do work, but as Graham is suggesting if you are looking to get best out of them you need to spend time setting them up.

Regards,
Shaun.

 

That is EXACTLY what I am saying.

To get the VERY best from them you HAVE to work at it!

This will be the same for Tien/Spax/AVO/EXT etc , all the same situation.

I am trying to wring the very very best from the AST's, and this is what you will need to do.

It took me 2 years to get here and realise 'DIY' sometimes will not work.

Graham.

Graham.

 

Started my own thread now.

https://www.scoobynet.com/suspension...gs-shocks.html

So feel free to comment.

 

Mine are!

KWv3s fitted by MocomRacing.com . Lovely setup.

I think quite a few people have commented about the poor quality of the (non-race) ASTs.

 

Same with my KW3s, no noise over the standard setup, although I am talking about a classic model.

 

Yes, what he said.

When i 1st picked up my car from crossroads subaru (powerstation fitted the AST's), I drove it straight to Donny for a track day. I didn't alter a thing as it felt awesome.

As I've got more confident with it, I've started to adjust the settings, it took me three sessions last time at Cadwell till i was happy with the way it handled, along with altering tyres pressures.

The more you play with it the better you will get at setting it up for each track/hillclimb/road use etc.

 

My AST didn't knock on NSR until PS fitted the new springs - I went from 40/30 to 50/40.