Whiteline adjustable rear swaybar - WOW!

[kaanage]

Handling balance
The 9N Polo is set up to have dogged understeer by default to make the handling totally failsafe (you can actually brake while cornering pretty much at the limit without oversteer).
Removing some of the rear grip makes it more neutral but could catch out unwary drivers with liftoff oversteer becoming a possiblity. Bust some of us actually want that capability.

[Tarq57]

I've noticed the understeer tendency. Comes right pretty quick with a bit of a button-off, if needed. (So far.)

So perhaps a better (early in the piece, anyway) mod might be to do something to improve front grip, rather than reducing rear grip?

[pologti18t]

Just curious, pologt18t, why would you (or anyone) want to decrease grip at all, from either end?
What I'm asking is: why would someone provide a mod who's purpose is to decrease grip?
What are the pros to a sway bar?

Reducing the grip at a particular end is what a anti-roll bar does.

If you want to increase the grip at the front you would most likely need to increase front camber a tad. That is not easy to do (cheaply) on the Polo.

Another way of changing the handling balance is to firm up the rear shocks (if available). It doesn't make the rear end firmer in the same way as a stiffer springs or an antiroll bar does. It just makes the initially turn in that bit crisper.

[Tarq57]

Are there any other benefits to the sway bar, such as improved ride?

[kaanage]

None at all - it will increase lurch from side to side with bumps/potholes if anything (happens if overly stiff roll bars are used as in the Ford Territory)

[pologti18t]

None at all - it will increase lurch from side to side with bumps/potholes if anything (happens if overly stiff roll bars are used as in the Ford Territory)

Exactly. Stiffer anti-roll bars make the overall ride worse (all other components being the same)

[Tarq57]

Thanks for addressing the queries, and sorry about any thread drift.

[safetyman]

Exactly. Stiffer anti-roll bars make the overall ride worse (all other components being the same)

Sorry, but in my case, the ride has improved.
I no longer fall into holes the way I used to.

You are correct that fitting too thick a bar to the Polo would have this effect and I think any thicker than the 20mm bar would really be for track use only but this bar gives an excellent result on the road.

As it is, I have it on the middle setting and don't feel the need to move up to the stiffest. The handling is neutral without any "wild" lift off oversteer.
Set the car up, maintain through the corner and if you decide to lift off, it tightens the line ever so slightly.

And a test run around the back of Appin on some fairly rough tracks, similar to the Kangalloon Rd goat track showed the car was no longer the handful it was previously.

I'd be happy to take anyone for a ride

And it's also very easy to disconnect the bar and show the difference of the Polo without.

[kaanage]

Sorry, but in my case, the ride has improved.
I no longer fall into holes the way I used to.

Is your GTi fitted with stiffer suspension than stock? All this talk about falling into holes and flying over bumps suggests this an maybe the front was stiffened up more than the rear, leading to the strange result you have. Maybe the rear bar has just removed the mismatch making the ride and behaviour more consistent. Not doubting you but it is an odd finding you have.
The only reason that anti-roll bars are used at all is to prevent the need for overly stiff suspension.

As it is, I have it on the middle setting and don't feel the need to move up to the stiffest. The handling is neutral without any "wild" lift off oversteer.
Set the car up, maintain through the corner and if you decide to lift off, it tightens the line ever so slightly.

That sounds pretty much perfect. More neutral response without being a handful. Does mid corner braking (not that you should do it but sometimes, something unexpected crop up) provoke the rear end?

And it's also very easy to disconnect the bar and show the difference of the Polo without.

Now THAT is appealing - it's always nice to be able to do a quick and direct comparision.

[safetyman]

Here's my theory on my car.

I have one or more stuffed shocks.

Without the roll bar:
If either front wheel hit a pothole or heavy rut, that side of the car would "lean" into the hole, as the opposite back wheel was free to lift with body lean, and the end result was loose fillings...

With the roll bar:
The back end is tight >.< with the rollbar and now holds the entire body flat.
When I now hit the potholes/ruts, the body remains flat and the front suspension does the work it's supposed to be doing by dropping into the hole and the opposite rear is kept down on the ground.
When the rear wheel encounters the same hole, it "flys" over it, so to speak, as the bar is keeping the end stiff and preventing the wheel from dropping down.
Therefore, I now have an improved ride.

But my shocks are probably still stuffed...

[kaanage]

That doesn't sound right unless your dampers are seized. Stuffed ones normally will have very little (relative to OK dampers) resistance to movement so you would expect the wheel to fall into the hole more easily which would decrease pitching (on the primary response - later oscillations could do anything depending on the subsequent road conditions).

Are your dampers double adjustable? It could be that the rebound damping has been wound up while compression damping is set to soft. This would also lead to the car "packing down" on a bumpy stretch of road.

[seangti]

The problem with a "rear bar only" mod is that they can cause the rear end to step out in situtations that it wouldn't if you didn't have the rear bar fitted. This makes sense as the reason you fit a rear anti-roll bar is to decrease the grip from the rear end. Such conditions may be an emergency swerve or heavy braking (or coming completely off the throttle) mid corner.

It's probably ok in the GTI as you have ESP.

Guys, this suggestion of decreasing grip in the rear is (in my opinion) a totally inaccurate description of what the sway bar does. This is basical but suitably explains how it works. The lowering in grip is typically not real (though may feel that way) due to the increased turn-in you get from the front end, allowing the rear to waggle. It can make the car less stable at speed and more prone to lift off oversteer depending on chassis balance to start with.

Are you dialing out understeer, or trying to increase general balance/grip??? A rear swaybar will assist to dial out understeer by allowing you to tighting up the rear (allowing you to tune depending on sway bar settings), resulting in better front end grip. An already balanced car (i.e. car that isn't understeering and already maximising the inherent grip), will not likely be better with a swaybar as you've just changed the balance. Spring rates going to ****, balance and feel goes out the door.

Before going off to spend money on any suspension component, understand how each change impacts on the cornering and know what you're trying to achieve by doing so.

[kaanage]

Sorry, car suspension isn't interdependant to that degree. What you do at one end has very little effect on the other unless the chassis stiffness is woeful. The geometry changes in most modern, road car suspension setups do not alter radically enough with lift/droop to hugely influence the grip, either, so limiting roll is more about comfort/confidence factor. Plus I SERIOUSLY doubt than anyone with suspension properly set up would have the grip to bottom out their suspension due to body roll.

I recommend "Engineer To Win" by Caroll Smith as a good all around book on how to make chassis work (and last) as well as being an entertaining read.

[vwthunder]

I had a whiteline adjustabe swaybar on my VR6
It made the car turn in so much better, but VR6's are known for not turning in, due to a heavy V6 in the front, it made a big difference.

I think the polo turns in quite well, I haven't even done this mod yet, as i am happy with the way the polo handles. Might do it in the future

[pologti18t]

This is the actual explaination of how increasing roll stiffness at a particular end reduces grip. So if you increase the roll stiffness at the REAR of a FWD car you will reduce understeer to some extent. In the same regard if you increase roll stiffness that the front you will more than likely increase any level of understeer.

So how does one control the balance of a car when armed with this knowledge? It's actually very simple at this point, if you understand that increasing tire loading adds to the total amount of traction available from it, but this relationship is NOT linear. The more load on the tire, the more traction available, but the amount of traction gained diminishes as load increases. So at first it's almost a direct "you add 250lbs of load, you get 250lbs of extra traction", but at 1000lbs of load, you might only get 800lbs of extra traction. Knowing this, look at the example I gave of the sway bar at work. Since it transfers load away from the inside tire, you lose traction there. Although it transfers this load to the outside tire, it is already quite loaded and therefore the 250lbs of load will not increase overall traction by 250lbs. More like maybe 150lbs. Now the inside tire, being much less loaded, could have gained more like 220lbs or traction from the 250lbs of load. So look at what we have in the end: although the outside tires already do most of the work, adding a sway bar actually lowers the total amount of traction available at this end of the car by increasing the difference in load distribution. And the stiffer that sway bar is, the more it will limit the total traction available at that end.

and finally

But for the purposes of this post, we are explaining how sway bar sizing (which directly reflects it's roll stiffness amount) cures an unbalanced car. If a car is understeering, it's because the rear end has more total traction than the front. If you put a big sway bar on the rear suspension to limit the total amount of traction available there (by maximizing the amount of load transfer to the outside wheel), you can dial it in to match the front suspension's total available traction. And when we get really smart, we start to match the front & rear bars to one another to achieve the best balance through the largest possible range of suspension movement.