RB5_245

Hopefully a set of AST's will be winging their way to me shortly, so I'm after a bit of set up advice. Ride height will be the first of no doubt many questions.. About 5mm Higher at the back? what sort of height should I be going for? Do you measure from the wheel center to the arch?

Cheers
Dave

911

As a rough guide, 20mm down from stock is good. Keeps the driveshafts reasonably in line.

Best go from wheel arch peak to wheel centre though arch to raod easy to measure, but 'road' must be reasonably flat.

If you like I will post the heights off my hill climber.(but I'm at work now)

Expert on this is Fuzz.

Graham

RB5_245

Would be useful but no great rush as I'll be waiting on delivery for some time.

I have no base to go from as std, as the ride height has already been raised by fitting the top mounts. Also I take it that would be 20mm lower than sti height, as uk would be an extra 15-25mm on top of that?

Would you agree with keeping the back slightly higher?

911

Body rake has been highly debated over the years and it's effect on the dynamics.
My 911 is very sensitive to such things and my Sti seems exactly the opposite!

However, the car is great at present so it might give you a starting point.

You are right about the relative heights of Sti /UK, mine is an Sti v3.

Will post the heights later.

Graham

RRH

John Felstead recently spent a day setting mine up at Oulton recently- the geom had already been done but John spent the day fiddling with arb settings and ride height, and increasing / decreasing it by millimeters at a time.

It does feel a lot better now its set up properly- unfortunately I don't have the ability to do it- and the rear end doesn't feel like its falling over itself now, if that makes sense.

911

Makes total sense.
5 or 6 mm will make the car on an impreza, and John is a wizard.
Roll-oversteer is what i guess you mean, and the 911 is mega sensitive to that curse and the rake angle is used to minimise it (and a bit more).
Forgive me if youv'e seen this before, but note the absence of appreciable roll:
http://www.dropshots.com/day.php?use...1&ctime=030140
Graham

cmpequeno

your vids are always welcome graham

don't lower it too much... I raised mine because when I turned the front right wheel rubed somewhere... now it's raised and it's fine. I think 30 mm will be ok...

RB5_245

Is that on 60/50 springs or 50/40?

As for lowering it too much, I actually want to keep it standard but will adjust it for best performance.

Dave

DuncanG

You would probably be running short of droop, with it inclined to catch air, if you setup for standard height.

As a first rough cut set the height so you have about 50:50 bump:droop travel, then fine tune from there.

Whereabouts are you Dave?

RB5_245

I live up in moray, but am in holland for this year actually.

I have no problems being airborne lol

I'm not following with bump, and droop travel. Is this to do with finding a good roll center to start? Or the extremes of loosing spring pre-load/ risking hitting bump stops.

In which case you're saying stick the adjusting collars at a middle height setting and go from there?

Cheers
Dave

DuncanG

Nothing as advanced as roll centre height - simply pointing out (in a roundabout way) that these have shortened struts and are optimised for lower running. So if you set the ride-height near standard you'll have more (potential) bump travel than the springs will provide while losing droop and that will make them more skittish on the crests. More a problem in Moray than Holland I'd guess

50:50 bump:droop is a good _starting_ point from the pov of ride on the back roads. Handling and roll-centres (and aesthetics) etc is a different issue and you might then want to adjust bump/droop to suit.

You cant assume that if you set the collars in the middle of the threaded range that you'll be in the middle of the suspension travel when static (sitting on wheels). An easy way to determine bump & droop:
* measure the shaft's full travel front and rear before fitting
* fit and measure the hub centre to arch heights when at full droop (jacked up, no tension on arb)
* fit wheels drop, to ground, roll back & forth and push each end down, then measure hub to arch again.
* the difference in measurement is droop, and bump = full-travel - droop. With soft top-mounts you need to factor in some squish on those.

The reason for bringing this up is a lot of folk naively think you can set the height to anything you want (since its fully height adjustable init?) without realising they are limitting either bump or droop and not getting the most travel possible which is important on the lumpy stuff.

The helper springs will keep the main springs seated so thats not an issue.

Sorry if thats teaching you to suck eggs, its all common-sense really.

RB5_245

Thanks for the post, I've spent the last 4 years fiddling with the engine and completely ignored the suspension. It's only now I'm getting into it, in a bit of a crash course so all info is welcome. It's a very interesting subject, much more complicated than engines I think

I think I'll take your 50-50 suggestion as a max ride height then as it's going to take some stong compression to hit the bump stop on these I think, and hump backed bridges are everywhere

No problem with top mounts as mine are solid.

I think i'll just pester graham for his ride height one they arrive

Cheers
Dave

911

Here they are!
Sorry for the delay, been a busy week...

Distance from wheel centre to wheel arch 'apex' is 335mm front AND back.

I think this is about where Duncan is, about 50/50 so at static ride, car empty, the travel is at mid-point. Drive shafts arn't too crooked either.

The whole chassis subject is facinating and even better when you are searching for the optimum. I think I've managed to find the sweet spot now, and the car even looks good (to me)



will be fun revamping it all for slicks...

Graham

RB5_245

Thanks. I'll use that as a start point provided my intercooler doesn't scrape on speed bumps

RB5_245

My first guess came out at pretty much 315mm all round, not to far out.

Does anyone know the thread pitch of these? I would like to set the height without taking the wheels off 5 or 6 times

Cheers.

911

iirc: 1 turn = 3mm pitch.

RB5_245

Thanks.. about 10 turns for me then

911

That looks a nice 'stance' to me !

RB5_245

Raised up all round now, 332mm from wheel center to top of arch. I got fed up adjusting after that

It has seemed to have induced masses of toe out though, so that has to be cured. Noticed a lack of willingness for the steering wheel to self center and tire squeel and reasonably sensible cornering speeds.

Very impressed though, I was expecting a much harsher ride. These could almost be called comfertable!

One thing I noticed though was though the adjuster collar is set in the same place on both rear units, the driver side wheel drops down considerably more when jacked up

911

Last sentence confuses me.
Both should be the same to about 5 mm?

Is the one that is showing less droop sticking?
Is the rear roll bar correctly set?

Graham

RB5_245

That was my first thoughts. Disconnected the roll bar on both sides just to be sure.

Measured the distance from the collar to the bottom of the thread. Both the same. Checked the assemblies that I hadn't missed anything out. Both the same. Both sat at the same height before they were installed on the car.

If the damper is stuck it never moved under my weight... What is really odd is both seemed right on there own.

With the weight off they should both go to the full stroke of the damper as long as the roll bar is disconnected, regardless of any other considerations??

Unless the top mount spherical bearing was stuck?

RRH

Just been outside and measured mine, 320mm all round

cmpequeno

from ground to wheel arch, 600mm, 205/45/17 tires