Regular twang revisited...

[GTI_PAPA]

Hey guys,

I have had a regular twang (sounds like flicking a ruler) under my car since new. Have been back to VW several times, and they can find anything. Have been reading other forums etc, and have stumbled across one that might make sense. The twang/vibration can be felt through the brake pedal, which leaves the question, "Might it be a sticky hand brake cable that suddenly, fully releases causing this?"

Any suggestions would be appreciated,
Con...

[Ben_GTI]

Is it when you first start moving? I think this is an ABS test....

Otherwise, if you car sits for a while, it is the handbrake stuck to the disc... it does it once then goes away...

If you heard a knock when you brake in reverse, its just calipers sliding around and there isn't much you can do about it.

[noone]

Does this only happen when braking?

[danish]

When you say you can feel it in the pedal, does the pedal lose a bit of its resistence as well?

I encounter a similar problem of shuddering brakes accompanied by a scraping sound occasionally when I brake. However I can only make it happen when on very loose surfaces (like gravel) or going down my driveway, which is quite steep.

Seems like an ABS issue to me, although I really don't like the sound of the scraping!

[ACTGTI]

danish - That's just the ABS working isn't it?

Everyone should familiarise themselves with what happens when ABS (and ESP) is working. It's quite dramatic on the brake pedal and it doesn't take much for it to kick in on a gravel road.

Take out all your loose items in the car (important - if you don't, everything in the back will end up in the front), drive out to a country road and at 80km/h hit the brakes as hard as you can (make sure no-one is behind you). You should feel your brake pedal shuddering under your foot. This is normal. You will be surprised how well the Polo pulls up as well.

You'll also feel it if you take a corner too quickly as ESP tries to apply brakes to various wheels to straighten the car up and avoid a spin.

[break]

I have a similar issue with the ESP system.

I find it cuts in far too early on some surfaces, where it comes in at exactly the right time on others.

Do you notice any consistency on which surfaces and what speed this occurs at?

[ACTGTI]

A little inconsistency I guess but I don't think it's the ESP getting it wrong. It's all to do with the angle you approach the corner, the speed, and whether or not there's anything on the road that's making it slippery or not.

If there's anything at all that is making the road slippery, it will come in earlier than if the road is grippy. An example of this is on a drying road after rain where maybe the left of your lane is damp but the right is dry. ESP will try and help you out here when it really doesn't need to.

I don't think ESP has ever really saved me but I don't find it overly intrusive if I can predict it's going to kick in. It's all about reading the road in front and knowing how your car behaves on its tyres. I don't know what speed but I'm talking as quick as I can on tighter bends with recommended speeds of 25-45 km/h. Never really noticed on faster bends as that would be breaking the speed limit and all

[break]

The particular road I have a problem with ESP on is a long right hand bend coming off the motorway nearby, where the inside wheels on the bend have to run through undulations on the road while the outside wheels are on a flatter/smoother area of the road.

The ESP kicks in and makes the car very unstable on the surface, where as turning off ESP vastly improves the ride through the section.

[noone]

I have a similar issue with the ESP system.

I find it cuts in far too early on some surfaces, where it comes in at exactly the right time on others.

This is with stock suspension?
I found with my new coilovers the traction is improved. It was better with the H&Rs and standard shocks for a little while, but when the shocks started to give out, it got worse again.

For the first few weeks with the new kit, the whiteline front swaybar was set to hard. Whilst the handling was a bit twitchy and uncomfortable, the abililty to take corners at speed and accelerate without wheelspin was pretty impressive.

I'd be looking at your suspension, Think the stock setup is pretty basic.

[ACTGTI]

I'd say it's a case of the weight on inside wheels is lighter as they hit the undulation. ESP is probably reading this as just about to lose traction and thus applies a little brake to the inside wheels. When it does this, you would find that when the weight becomes normal again as the wheels leave the undulation it would feel unstable probably because of a split second where the brakes are still slightly being applied when they shouldn't be.

When I say brakes being applied, it's very subtle and lightly applied but less weight on the wheels means this would be less subtle as there is less resistance from the road.

It's hard to explain but I think I know what you mean. Are you sure that when ESP is off it's actually off? I thought that in the Polo, ESP still operates over a certain speed regardless if it's off or on (it does for me and I remember reading it somewhere). Only the Traction Control remains off when ESP is off.

So maybe it's the traction control causing your issue rather than ESP in which case all of the above applies except that instead of the brakes being applied the engine is slightly retarded inder TC?