Club 80-90 Forums

I'm not sure this subject has been broached in the last couple of years (maybe never?) so here goes:

Vehicle suspension/body lifting and the infamous "Elk Swerve Test" or, to put it another way:

The undesirable side-effects of raising an independantly-suspended vehicle to or beyond the limits of the factory adjustment range i.e. the effects on static and instantaneous roll-centres and their implications for good handling especially in emergency situations.

Engineers, get your "Staniforths" out

Nice one mate! baffle 'em with science

silverbullet wrote:I'm not sure this subject has been broached in the last couple of years (maybe never?) so here goes:

Vehicle suspension/body lifting and the infamous "Elk Swerve Test" or, to put it another way:

The undesirable side-effects of raising an independantly-suspended vehicle to or beyond the limits of the factory adjustment range i.e. the effects on static and instantaneous roll-centres and their implications for good handling especially in emergency situations.

Engineers, get your "Staniforths" out

The Elk Swerve Test was first done by a German car magazine on a very early Mercedes A class doing a reverse flip which went a little wrong but publicised anyway. This 'stunt' was childishly copied by Autocar using a Daewoo Matiz about two weeks later which did more to damage the magazine that the Daewoo.

I think to effect handling the vehicle has to handle in the first place which the T25 doesn't do very well, one of a few reasons the Hiace outsold it all over the place. If you were around with a pulse in those days you would know that to be true!

But yes, lowering cars till they almost scrape the ground to my mind is worse than jacking them up, an opinion formed by owning a jacked up Syncro and 'caretaking' my sons slammed 4motion Passat (hit a bump mid corner in that yoke could send you over the nearest hedge)

Any vehicle riding on the bump-stops will be a danger to all, no question . My silver bus was like a go-kart until I got stuck into the suspension, now it's nice and comfy even on a full H&R Cup kit. Lowering also does strange things to effective lever lengths on anti-roll bar links, if they are not replaced with adjustable units.

Suspension works as a system, not a collection of individual components. Change one parameter, it affects all the others.

Excessive jacking will put the wishbones/track arms into full-droop angles:

Draw imaginary lines through them to the vehicle centreline, then back down to the steering axis at ground level (this should also ideally be within the tyre contact patch) and then compare the same to a standard ride-height vehicle. The jacked vehicle has raised it's roll centre.

This is always bad news for handling.

silverbullet wrote: Suspension works as a system, not a collection of individual components. Change one parameter, it affects all the others.

You cant say that on here .... you'll upset those people .....

i got a chance a few years ago to go out on a race track with vw and try out the ESP systems on a couple of passats ,one that was rigged at the factory and could be totally turned off and the other that was standard (just the ESP button that makes you think that its turned off when it really isn`t)
it was mad how much you had to throw these cars around before the esp kicked in and then it was like two huge hands just slapped the rear end back into shape!!
its a good job that we all jack up our syncro`s so we don`t have to avoid things cause i don`t think that the elk swerve test is really an option, not without a couple of outriggers

That may all be true, but by that token you shouldn't add pop-tops or high-tops (never high-tops for lots of reasons! ) or remove seats & add heavy cupboards down one side.
Anyhow, I used 20mm spacers on a old saggy syncro & according to the wheel alignment chappy just returned it to standard settings, with a slightly firmer ride, but I guess you talking about more extreme lifts.

Silverbullet said "raising an independantly-suspended vehicle to or beyond the limits of the factory adjustment range".

What is the factory adjustment range for a syncro? Is it the hub-to-wheel arch figures listed in the tracking adjustment table (483-513mm)? How much do standard springs deflect between empty and fully laden conditions?

It's my guess that most if not all syncros (20+ years old) that have not had modifications or new springs are now well down that table range (490 ish?) - I know mine is. On that basis, are most of those which have had spacers fitted now at or around the top end of the table (500-510 ish?). What difference do new standard springs make to the ride height?

How many vehicles are actually running at greater hub-arch heights than this? What do their drivers feel about the handling? Maybe a pointer is that there has been a recent post by a driver seeking to go back from raised springs to standard in the expectation of better on road handling.

Whilst the higher driving position of the T25 gives us a better view of what the traffic around us is doing, there will always be the risk of a totally unpredictable sequence of incidents that leads to the need for a dramatic avoidance manoeuvre, so I suggest the elk test in some form is of some relevance. This may even be increasing with the number of conversions being done to more powerful engines that could well lead to faster, (more aggressive?) driving.

Garyd

The jacked vehicle has raised it's roll centre.

Actually, not always true, is dependent upon the axle or supension type, partic some types of erar suspension arrangement. The c.g. certianly moves higher, not always the roll-centre

more powerful engines that could well lead to faster, (more aggressive?) driving

Well, the word could is well chosen, as underpowerment sometimes leads to dangerous driving as does trying to pass someone driving too slowly (more selfish?).


What I have noticed is that today's plentiful torque and power under the foot of drivers who have known no different, can lead to absolutely crazy overtaking methods, involving no planning and minimal judgement, thus despite the power, highly dangerous attempts at passing. It is high time that overtaking, as well as other essential driving skills, were actually 'taught', after the initial test, to be allowed a car of greater than 1 litre and a Motorway rating e.g. Advanced Driving Qualification.

Another 'trend' I've noticed in the church of latter day drivers, is the 'assumption' that a right of way (e.g. give way to the right approaching/entering mini-roundabouts) seems to translate to 'charge at anyone in your way and it'll be their fault if you manage to strike them amidships' - often combined with dirty looks or a lot of finger jabbing.
Just because you have right of way, does not confer the right to cause an accident by a) not lifting off a tad b) not giving a touch on the brakes c) changing your speed profile by accelerating deliberately into a gap, or worse into someone already in it, regardless of their right to be there, or yours. Taxi drivers see, to be high on the list, as well as other sterotypical groups I'd better not mention.



...which is going back to Gary's aggressive driving but where speed and power, per se, is not the issue.

Just don't swerve for elks

A T25 does not handle very well at all. Its a plain fact ..... BUT ...... Im comparing it to other vehicles and there are lots of people here who dont drive anything else and therefore are happy with the handling. There are also people on here who wouldnt know handling if it bit them on the bum.

A T25 does not handle as well as an Amorak, an Amorak does not handle as well as a Freelander, a Freelander does not handle as well as an Audi A4, an Audi A4 ....... do you get the drift? I have had all of these vehicles over the last while to play with - and play I did - so I know. If you put a decent engine and box into a T25 and get the same power to weight ratio as an A4 there is no way you'd keep up with the A4 on a country lane whereas I would think a T5 4motion probably would, remembering with fondness a recent few days in Sweden with a T5 4motion.

handled like a go cart " almost " with those wheels and tyres on and if i cant swerve to miss the object the bull bar will sort the rest out.

I realized that I had omitted to qualify my opening statement with "in relation to Centre of Gravity for the vehicle"

I reckon that T3 does in fact have some good suspension design attributes. I'm sure I read in some old VW blurb that the 2wd was designed to have a negative roll centre?

I suppose that the C.O.G. cold be below the roll centre on a 2wd 'velle or panel van and would be desirable for stable cornering and good road manners. It's certainly respectable for a wide-track brick with such a short wheelbase (just over 8 foot in old money) which should be much more twitchy than it really is at speed and I'm talking illegal mph in this case (naughty boy)

Helluva lot better than an original Range Rover with no ARB's, but that never fell over on me even when rolling so much it ground the door mirrors off on the tarmac

Maybe a high-top syncro camper or one with a roof tent/Westy and rack would actually benefit from a suspension lift. The higher COG could be brought closer to the roll centre with steeper wishbone angles but...lots of tyre scrub and track variation under bump/droop which you'd only really notice over fast bumps or humpback bridges taken too quickly

What I was really asking was:
Who has actually bothered to give this any serious thought before changing springs, adding extra spring packers or applying "Elastoplast" solutions like UCA spacers just to stop balljoints going out of working range? Suspension geometry is a very complicated subject and I'm just a curious enthusiast (don't quote me on that...) Even taking accurate measurements from a vehicle to produce working drawings of what should be going on would be a lot of work.

What's got me going recently is this alternative rhd PAS rack I'm considering; I was initially only worried about not spoiling the Ackermann steering!

silverbullet wrote:
What's got me going recently is this alternative rhd PAS rack I'm considering;

I have a brand new NOS one in my box of bits and pieces !!

VW thought of this CoG thing by going for a body lift as opposed to raised suspension on a Syncro. When I was an apprentice in BL back in the 70's I used to do CoG tests on all the cars on the market that the Mini Metro was aimed at - Fiesta, Renault 5 etc and the CoG of nearly all of them was roughly where the drivers seat belt buckle was and didn't change that much with 4 people in it. The CoG only changed significantly when luggage and roof racks were brought into the equation.