Anyone with a knowledge of swaybars?

Started by PRM, February 26, 2005, 11:50:11 AM

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PRM

I'm hoping someone out there can advise me ... I ordered an Autotech rear swaybar for my Mark 4 golf and received an ABD Racing Swaybar instead.  The PerformaceCafe supplier in the states says that they are from the same manufacturer (ABD) and that the one supplied is the latest etc etc.  However, this bar is big and heavy - and, to my mind, could be far to stiff for normal driving conditions.  Does anyone know what a normal road one should be (as opposed to a racing one)?
Cheers ... PRM

Filx

Hi PRM, What is the diameter of the bar? As a reference Whiteline (http://www.whiteline.com.au/docs/catalogues/WLA_02.pdf) do a 22mm rear bar for the MK4 Golf. I can't say I've got any experience with the Golf item, but I've use(d) their sway bars on other cars and they're perfectly streetable. I'd go as far as to say IMHO an upgraded rear sway bar is the best value suspension upgrade on most cars, certainly most FWD cars anyway.

Cheers
FAIL - First Attempt In Learning

PRM

I've just received a 28mm hollow swaybar - and it's the only suspension alteration I want to make to the car - I just want to stop the flex and to sharpen up the steering.  Thanks for the chart urg20v, I don't know how a hollow one figures on your scale - but the thing I a little (sic) scared off is how stiff it is.  It is adjustable via the hangers but it is one heavy mother!  Hey, Flix - have you used a 28mm one on the street?

Cheers ... PRM

PRM

I've just had a good look at that pdf file (from Whiteline) - wow - they only supply a 22mm for a mark 4 Golf and using that chart - to go to a 28mm (from a 22) means 170% increase in stiffness omg!

cheers ... PRM

vwrally

The effectiveness of a sway bar is as much to do with the surface area as it does the ammount of metal.

Hollow bars have a higher surface area due to the inside surface area in addition to the outside.

What determines the ultimate stiffness is the wall section of the tube used

Hollow bars are much more progressive and "nicer" than solid bars. You will find that all V8 supercars and the NZ V8 tourers use hollow chromoly bars

If you can give the width of the bar, the length of the arms, the outside diameter and the wall section I can give you a rough guide as to what you have got.

It is more than likely that it will only be as stiff as a 22mm solid bar and will probably weigh less

PRM

Thanks for that urq20v - I'm starting to wet myself just thinking about fitting this 28mm bar. My reason to want a bar - I was doing a lot of country driving, with lots of tight corners and I could feel the car flex and the handling was anything but neutral - previous cars being awd - it was unsettling.  I then happened to get a golf 5 2l manual as a loan car and it felt safer (and faster) across the same terrain, so I set about 'stiffening' the car.  That GTI story - down a cliff on a wet road - now that is real scary stuff but I don't understand why - if, with the bar fitted, you get all wheels on the ground for longer and therefore less oversteer and less chance of letting go.  Are you sure there wasn't an 'oversecure' driver - trusting too much in the bar.  But you said it let go low speed - I just hope my wife doesn't see these postings.

vwrally - the walls are 6mm thick  - being a "C" shape it' hard to define the arms - but the top & bottom extensions of the C are ~ 350mm.

SimonS2

#6
I can only comment on the S2: as Rex notes, the stiffer bar gives more oversteer, not less (depending on how 'tight' it is set up). With the stock rear bar the S2 pretty much always understeers when pushed: I guess the're designed that way as the understeer is progressive and predictable.
With the Whiteline rear bar (only a few mm bigger) it's more balanced, but you can 'flick' the rear out at high speeds, or on a wet road. Fun if you intend to do it, a bit scary if you don't.
You may find you want to mess with other components once you try out that new bar. Some S2 owners, for example, end up fitting a bigger front ARB as well to get the handling a bit more balanced. If your aim is to make the car 'stiffer' then strut braces (front and rear, if available) might be a good idea.

SimonS2

#7
Quote from: PRM on February 27, 2005, 12:16:43 PM
- if, with the bar fitted, you get all wheels on the ground for longer and therefore less oversteer and less chance of letting go.?
Hmmm.. I think that's not quite right. A swaybar works by tying both sides of your suspension together with a flexible bar. That bar tries to lift your inside wheel when cornering, which has the effect of reducing body roll. In an extreme case this will cause your inside rear wheel to leave the ground more quickly with a firmer bar.?
I think that's how the basic physics of an ARB work. Anyway, probably something tunable with some trial and error. Does the bar have adjustable link points?

dubstar

I thought an ARB was there to keep all wheels going in the direction they are meant too.  When you go round a corner the body roll causes weight to be transferred to one side (faiirly obvious), thus releasing downwards pressure on one sides wheels.  This in turn causes each side to take a slightly different direction around the corner.  The sway bar counteracts the weight transfer and tries to keep the downwards pressure on all wheels the same, meaning  all wheels are more likely to go in the same direction.

That's how I had it explained to me when I was younger.

If you are going for a 28mm rear ARB, you should probably upgrade the front (to say 24-25mm) so that the balance between front and back is maintained.  If you just have the rear bar, the rear is going to be 'corrected' through a corner, whereas you will be battling the front.  This would probably mean the rear will have a mind of its own leading to golf + cliff scenario.  I think, if you are doing the rear, do the front as well, after all, suspension is about getting the perfect balance.
"I am so clever that sometimes I don't understand a single word of what I am saying."

SimonS2

At the risk of making this less clear... I thought an ARB works to compress the less loaded wheel (that's what I meant by 'lift' the inside wheel), thus keeping the car flatter. It compresses the springs more evenly, which will stop some body roll and balance the car better (flatter=lower centre of gravity=less weight transfer), but this is at the cost of reducing the 'independence' of the rear wheels. Worst case scenario might be the inside wheel lifting off the track because the ARB is keeping the suspension too compressed.

Other negative result of less 'independence' with a too stiff ARB is the effects of bumps being transfered from one wheel to the other.

I expect the final result is pretty complex due to the interaction of the springs, shocks, ARB, body flex, etc. not to mention front/rear interaction.

PRM

Thanks for all that guys ... I thought the swaybar would keep the inside rear wheel (when cornering) on the ground (and therefore more traction - sorry stable) - a firmer tighter line.  Stress bars, as I understand them only keep the cabin square - better for comfort but mininal effect on the wheels on the ground. 

Thanks again for your help ... I'm not a racer (really I'm not) and I'm thinking that'll get really technical here and toss a coin as to when & if I fit this beast.

Cheers ... PRM

SimonS2

I reckon that there are so many factors involved in sorting suspension that trail and error works best  ;) You can usually search the Web for someone that's BTDT which makes life easier. If in doubt just find a setup that appears to work and copy it.

Strut braces do a good job of keeping the tops of suspension towers at a fixed distance apart, which I think is important, but again that interacts with all the other components.

vwrally


PRM

I fitted the ADB 28mm swaybar and it's ..... wonderful.? An easy extra 20km/hr round corners and no seasickness for the passengers.? The car feels even better than a Mark 5 - it just sits there.? It's even noticable just pulling out of the driveway and specially at roundabouts - much more neutral as seen on the open road.? Now I have to wait for rain to check if it sticks under wet conditions.

In summary, it is a different car - steering is much more positive, body roll stopped and it allows you go faster more safely - what more could you ask for?

;D

RS ZWEI

Quote from: PRM on March 09, 2005, 10:31:38 AM
I fitted the ADB 28mm swaybar and it's ..... wonderful.? An easy extra 20km/hr round corners and no seasickness for the passengers.? The car feels even better than a Mark 5 - it just sits there.? It's even noticable just pulling out of the driveway and specially at roundabouts - much more neutral as seen on the open road.? Now I have to wait for rain to check if it sticks under wet conditions.

In summary, it is a different car - steering is much more positive, body roll stopped and it allows you go faster more safely - what more could you ask for?

;D

Well thats good to hear you are happy.  :)
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