NBW

Early next year I was planning to go to Scoobysport to get a DP fitted, and to Powerstation for bumpsteer removal and Eibach's.

Now occurs to me that I could go to TSL to get Eibachs and DP, but has anyone had bumpsteer removed at TSL? Can they do this?

Most importantly, is Trouser's tea as good as he claims?

Trouser

... he he....errr... You'll have to come and see!

On a slightly more serious note, lets get back to bumpsteer..

Our Beissbarth jig allows real-time live adjustment of bumpsteer, so as supension is moved all changing parameters can be checked, measured and adjusted as the strut and wheels desribe their related movement.

We NEVER shim the rack... I still struggle to see after all that development time how it is in the wrong place. we never shimmed it on the tarmac settings for the Rally car, and i run my rack in stock position with 19" wheels and NO bumpsteer. The trick is the method of adjustment and the settings you run to. If everything is as precise as humanly possible the exact degree and minute, and the chassis of the car itself is straight and true then bump steer can be totally eliminated with adjustment alone

We can of course fit you a TSL down pipe at the same time, constucted by the same craftsmen that hand fabricate our Group N systems

..... and.... i might let you have some biccies as well

Cheers

Trouser

[Edited by Trouser - 12/20/2001 9:59:49 AM]

RichiB

Trouser

Do you actually understand what bumpsteer is?????????

Sorry about the question but it is not "humanly possible" to adjust the bumpsteer by any method apart from changing the relationship between the rack , steering arms and the track control arms!!!!!!!

Best stick to making the tea!!!!!!

Rich

NBW

LOL !

I think you may have a sale, see you in the New Year....

Tim

Trouser

.....biscuit anyone??? ......

chuckster

Yep. Sorry to say but the steering rack isn't in the 'wrong' place. It's in the right place to generate the amount of bumpsteer Subaru's designers/boffins deemed correct in a road going mass produced car. Bumpsteer = safety for the average driver who can cope with mild understeer alot easier than he can cope with oversteer.
Chuck

IWatkins

Trouser,

Doesn't sound right to me. I can't see how you can remove bumpsteer through adjustment only. You have to move something surely ?

Cheers

Ian

Trouser

Ok , i think i may , through my lack of technical knowledge expressed my point poorly there.

Speaking to Glenn and Lindsay ( those talented technical type chaps) their view is that the chassis designers at Subaru do not deliberately set out to build a Chassis with that element of bumpsteer there in the first place. In an ideal world where the chassis designers exact parameters are all adhered to, Ie KPI, camber, caster, ride height, steering arm angle etc, then in theory there should no no discernable bumpsteer at the steering wheel. There is always an arc of movement at the road wheel as the suspension is compressed as the relative postions of the rack and the outer track rod end changes, moving the wheel very slightly. A big factor here is the ride height at rest, and therefore the arm angle.

In the real World of car mass production there is no way on Earth that the designers settings are going to be in any way adhered to. Every Impreza is checked for geometry both before and after spanner twirling here, and the before figures can be pretty amazing!.... always within tolerances of course, but those tolerances are immense. Our 02 car had rear toe in on one side and rear toe out on the other! I have driven many standard cars that suffer from "bumpsteer" that can be felt through the steering wheel. This includes our own '02 WRX on the return journey from Holland. This car now has no bumpsteer, yet the rack has not been touched ... what it has had however is a set of Eibachs and lots of very precise geometry adjustment.

With the Eibach's only gently lowering the car the track rods are very close to the horizontal, therefore the track change is minimal with suspension deflection.

another factor is camber, of which there is more adjustment than you would realise in the slightly oversized bolt holes. By getting the camber PRECISELY the same side to side we can minimalise bump steer due to camber change. The car will tend to steer to the side with the least negative camber, if both sides are exactly the same then this characteristic is diminished.

The final nail in the bumpsteer coffin and found through much experimentation that by elinating ALL tracking tolerance, particularly side to side then again, bumpsteer at the steering wheel is undiscernable.

The very easy way for me to show these adjustments and their deeply profound effects is to invite you all en masse, wherever you see us, on track day, on run or here at the garage to drive either mine or Dad's car and see for yourself! .. one of those things that is very easy to prove isn't it?! try it for yerself!!

sorry for "war and Peace" there BTW

Cheers

Trouser

Paul

RichiB

Trouser

Yep! as I thought. You don't actually know what bumpsteer is.

All these are irrelevant to bumpsteer-

Toe
Camber
Ride height
Steering wheel?????

Hope this helps to further your knowledge of suspension geometry.

Rich

PeterPerfect

Blimey, Trouser has opened a can of worms...sounds like we need a response from Derk and Rich @ PowerStation.
They removed my 'bumpsteer' and fitted an ALK last year. The car felt way sharper...more go-kart like...which I love. Even my mates commented on the improvement after driving it !

This could be an interesting thread......

Pete
(still procrastinating about Eibachs...but only because it will cost £45 extra on my insurance )

NBW

Errrr.....sorry Trouser, I was just wondering that it would be easier for me to make one trip to TSL from instead of one to Cheltenham and then another to Essex......

Let's be fair, both TSL and Powerstation have had great endorsements on here (which says as much as any technical explanation of camber, toe-ins, toes-out).

I didn't mean to cause a spat of the 'my laser alignment rig is better than your laser alignment rig' variety or even one of the 'my dad knows more about geometry than your dad' variety.

Chill guys.

Tim
(Training for a career in the diplomatic service)

NBW

PS Chuckster, your theory on mass produced cars tending understeer for safety reasons only goes so far.... my old 306 GTi-6 had not one iota of understeer, and oversteer was easily provoked (and controlled, even by a numbnut like me).

[Edited by NBW - 12/20/2001 8:41:03 PM]

mutant_matt

Peter ,Err, RichiB *is* Rich @ Powerstation....hence the slighty terse response to Trouser's comments about the Bump Steer Mod.

Play nicely now guys

Matt

P.S. Eibachs - do it, you know you want too (and go to Powerstation to get it done (Rich, when are you going to start paying me commission m8 ))

NBW

Oh dear I'm feeling really guilty now.....

So, anyone know where I can get my geometry done, now that I've p155ed off TSL & Powerstation?

Tim

IWatkins

Tim,

I doubt you have pished off either of them. If you in business and on the 'net, you have to expect to get involved now and then

But make sure you go to the people who actually know what they are talking about when it comes to bumpsteer.

Cheers

Ian

mutant_matt

...not that you're at all biased Ian

Matt

P.S. Wireless LAN up and running and it's

Trouser

LOL @NBW.. don't be daft... you are more than welcome

Richi... .. I would reiterate my offer to you mate, you come and drive our car, and tell me just how much bump steer you feel! .. We obviously go about the job in different ways but the end result is just the same isn't it?... the only difference is, I am not the one calling your work for no good reason. I have driven cars that you have set up and have been very impressed. can you say you have driven one of ours?.... i guess not. Try one if you get the chance, you might even enjoy it!

(all typed in the spirit of peace and goodwill to all men!! )

Cheers

trouser

chuckster

HEHEH NBW mate, I was referring to Subaru's. Thats as far as it was supposed to extend LOL
As you said, you got oversteer in a FWD car with no bumpsteer. Oversteer in AWD is much trickier to handle as the dynamics are vastly different, FWD oversteer you just point the wheels where you want to go and nail it, not too much drama as the rear wheels aren't doing anything, in AWD you can have some very nasty moments trying the same thing, and even nastier if you decide to lift off whilst in the middle of correcting oversteer
Peace indeed guys!
However, to balance the arguement, Scoobysport say that whilst fitting and setting up Leda they effectively remove bumpsteer effects....hell I was happy with just Prodrive geometry, my cars tail happy enough as is.
Merry chrimbo everybodypeeps!
Chuck

EvilBevel

Chuck,

>>However, to balance the arguement, Scoobysport say that whilst fitting and setting up Leda they effectively remove bumpsteer effects

Could it be that if you reduce the suspension travel/have a stiffer setup, you reduce the effects of bumpsteer to a certain extent, but that you don't actually "remove" it at all ?

Or am I wrong in thinking that the bump steer will be highest at full compression/decompression ?

I can understand your "tail happy" comment, but on my car the setup is now very neutral actually (including bumpsteer mod). Maybe sudden lift offs may have more effect, but whilst cornering under power/neutral power the car is certainly not more tail happy.

chuckster

You need a more aggressive rear diff mate, rip one out of a type R LOL.
Eat some Leonidas over christmas for me Theo.
Chuck

NBW

Keeping very quiet now.... have a good Christmas everybody, with or without bumpsteer.....

Trouser

He he

sorry.... ho ho ho


i like a healthy banter.... just as long as my tea making abilities are not called into question... just remember i'm NOT the technical one!

....but my PG is legendary!!


Cheers


Trouser

Paul Swarbrick

Don't try to kid us Mr Trouser. Everyone knows that you NEVER make the tea!!

Ho ho ho
Paul

NBW

2 sugars please.

Paul Swarbrick

NBW, you will have to show him where the sugar is, and the kettle and cups and........

Paul

sempers

Ho hum, without wishing to pour fuel on flames, I want to run through something, and lead up to a question in my own roundabout way :

As I understand it, bumpsteer is suspension geometry designed such that as a front strut is compressed, *without* changing the angle of the steering wheel, the roadwheel toes out.

How? Presumably (guess) by placing the rack lower in the car than the inboard suspension arm - such that as the suspension compresses, the arc of the track arm and control arm act so as to decrease the (horizontal) distance between the back edge of the roadwheel and car centerline, and increase the front. i.e. track arm is below horizontal, control arm above. (draw arc's on paper)
That's my simplistic understanding - how it's arranged I'm not sure. What is important is the relative rate of track change between the suspension strut (mid wheel) and steering arm (track arm).

Why - as the car loads up in the corner (rolls), for a consistent steering angle, the outside wheel will toe out, and the inside in. mid corner lift moves weight onto the front, suspension compresses, rear tends to move out, BUT, as the suspension compresses, the outside toes out, inside in, automatic countersteer (to some degree). However, you get that countersteer whether the car is understeering or oversteering. Like it or not.

Any change to the suspension will affect the bumpsteer - lowering will move the positions of the arms on their arcs, and likely reduce the arc through which it moves. I don't know how the camber is changed on a scoob -
(Perhaps someone could tell me? I'd like to know!)
- but it's likely to effect the track, and so on.

Now, I'm not going to question anyone's assertion as to whether or not this is necessary, desireable etc. I don't know, and I'm in no position to comment. I am not a suspension engineer for one thing.

I've driven a few scoobs (3) and I'm still trying to decide whether to purchase one or not. Last one I drove was a nail, no question (hiccups, very wierd steering (heavy on centre, went light off ), piston slap etc.) But it understeered like a b***ard on a wet roundybout. Rather put me off a bit.

What is the normal handling balance of a 97/98 car? Do these things handle (in *standard* form), or do they just stick like limpets? And how adjustable is the suspension without resorting to "modifying" the car. (ie, new parts non-stock).

The other option I'm considering is (sorry!) a 200sx - cheaper, rwd (fun, but I'm unsure about whether it's a good idea / going to lead to meeting a hedge/tirewall) No way as practical. Nor does it have the bonnet scoop

- Mark.

EvilBevel

Mark,

To answer part of your question: front camber is easily adjustable, rears are normally fixed.

MRT do a set of camberbolts for the rear (UKP 50 or something like that).

Out of the factory, the Impreza is really tuned to safety instead of fun (which is wise I think). Combine that with the "understeer whilst cornering under power" most AWD cars suffer from, and they may feel like a dog to someone who is used to RWD.

With some tweaking you can really get a very neutral handling car (or oversteery if that is your choice).

HTH,

Theo

Jza

Just an update as its been wet and snowing!!

I had eibachs and geometry sorted at tsl.

Ive nociced on wet and icy roundabout you get a very progressive slide sideways as the car loses grip. The car doesn't seem to understeer or oversteer - you can just feel all four wheels drift at the same time. Its not a case of "jesus!!" its nice and doesnt bite suddenly like a mo fo!!

Intersting to see that powerstation fitted eibachs to someones MY01 and said the bumpsteer didnt need fixing

Jza

DavidRB

The suspension on the MY01 onwards differs from the MY00 and earlier so it's not surprising.

I remember on my trip to Powerstation, they said that not every Impreza needs the mod and they only do the work where it's required.

EvilBevel

I also vaguely remember there used to be a difference ( <MY01 )between the wagons & the sedans in relation to bumpsteer.

As a side note, I wonder - after all this overexposure - when normal bbs course kicks in and the hailed company gets slaughtered by a few posts ...