Thread: 20" Nitto Terra Grapplers

Hi Kev, interesting reading. I know someone who aquaplaned in a Nissan 370Z and he claimed the DSC completely spun the vehicle around and straight into a concrete barrier.

From my experiences aquaplaning usually the car loses steering but continues in a straight line. Hence why being turned sounds strange to me.

Originally Posted by catsman

Hi Kev, interesting reading. I know someone who aquaplaned in a Nissan 370Z and he claimed the DSC completely spun the vehicle around and straight into a concrete barrier.

From my experiences aquaplaning usually the car loses steering but continues in a straight line. Hence why being turned sounds strange to me.

I wasn't driving in a straight line, I was on a slight bend, so that I think was the key, as in the car started drifting in a straight line Vs the direction of the road and then when the front bit in, it exacerbated the situation. It may also be possible that not all wheels were aquaplaning or maybe not all uniformly (as in duration) .... It wasn't a huge slick of water.

I'm just guessing but I think there was more of a dynamic at play. 3 tons at almost 100 kph has a lot of momentum but a slight change in directional force caused by maybe one tyre gripping when the others were aquaplaning could be a plausible cause.

I'm pretty sure the aquaplane was brief and then the slide was more uniform and predictable ... Albeit scary.

The DSC would react to an instability or change in direction I imagine and counter the other way, so I don't see why it would have turned your mates car.

I aquaplaned an old (well new at the time) Mitsubishi Scorpion on the way to Cairns, in the middle of a tropical downpour. It had no electronic aids at all and whilst it remained pointing straight, it drifted into the oncoming traffic lane (fortunately nothing was coming). It only turned when I turned the steering wheel. So I guess there are a lot of variables and dynamics at work.

An other that comes to mind too is the force of the drive wheels. Hitting water could cause them to spin or spin and then bite, causing yaw if that force wasn't identical.

Whilst I did physics at school and I'm an engineer of sorts, I am really only surmising.

Cheers.

I have 285/65/18's Terra Grapplers on my Ranger, I really rate the tyres and would happily fit them again when they run out. I will certainly consider them or the Trail grapplers for the Disco when the LTZ's wear out. I paid $310 a tyre not parallel import. Great on the road and great off, a really good compromise tyre that suits my work, lots of rd k's and also offroad on site every day.

Cheers
Rob

When a tyre aquaplanes, it loses all grip and so starts travelling in a straight line tangential to the radius around which it was originally travelling. It will also mean that front will momentarily be travelling in a different direction to the rears.

As you go from a steady rate of turn to moving in a straight line, the acceleration will make you feel like you are turning when you are just going straight ahead.

Sounds like the DSC worked very well. I've only provoked it by getting the rear out and it has brought the car back into line very quickly - although a bit unnerving when you are intending to oversteer through a corner.

Cheers,
Jon

Originally Posted by jon3950

When a tyre aquaplanes, it loses all grip and so starts travelling in a straight line tangential to the radius around which it was originally travelling. It will also mean that front will momentarily be travelling in a different direction to the rears.

As you go from a steady rate of turn to moving in a straight line, the acceleration will make you feel like you are turning when you are just going straight ahead.

Sounds like the DSC worked very well. I've only provoked it by getting the rear out and it has brought the car back into line very quickly - although a bit unnerving when you are intending to oversteer through a corner.

Cheers,
Jon

Hi Jon,


Thanks for your input. I get the gist but the middle part has me flummoxed.


If I'm heading up a road with a slight right hand turn and then I'm suddenly crossing the lane to my right and I'm heading towards a concrete wall on my RHS, I'm pretty sure I didn't feel the car turn, I'm certain it did turn.


Am I missing something?


In reality it's probably one of these situations where the only real answers would be found with sensors and cameras all over the car.....were all 4 wheels aquaplaning or sliding, if not which were....where was power being applied, if any....what did the driver do during his OMG moment, etc?


But .... yes ... the DSC was very impressive ... thank god.


Cheers Mate.

Yeah, not worded very well, I'll try again.

As you travel around a curve at a steady rate you experience a constant acceleration. When the front end loses grip and starts travelling in a straight line the acceleration changes. This change in acceleration is what you feel. Because the change in acceleration is towards the outside of the curve it can make you feel like you are turning in the opposite direction when in fact you have just started travelling in a straight line.

It's the same feeling as being in an aircraft levelling out of a banked turn. If it happens smoothly you don't really notice. If it happens suddenly, it can feel as if you are turning the other way.

Also, that's assuming both front wheels aquaplane. If only one wheel aquaplanes, it will pull you to one side, same as if you only braked using one wheel, so you would turn.

What I was trying get at with the stuff above is that the change in acceleration can make it feel worse than it really is.

Does that make sense?

Cheers,
Jon

Originally Posted by jon3950

Yeah, not worded very well, I'll try again.

As you travel around a curve at a steady rate you experience a constant acceleration. When the front end loses grip and starts travelling in a straight line the acceleration changes. This change in acceleration is what you feel. Because the change in acceleration is towards the outside of the curve it can make you feel like you are turning in the opposite direction when in fact you have just started travelling in a straight line.

It's the same feeling as being in an aircraft levelling out of a banked turn. If it happens smoothly you don't really notice. If it happens suddenly, it can feel as if you are turning the other way.

Also, that's assuming both front wheels aquaplane. If only one wheel aquaplanes, it will pull you to one side, same as if you only braked using one wheel, so you would turn.

What I was trying get at with the stuff above is that the change in acceleration can make it feel worse than it really is.

Does that make sense?

Cheers,
Jon

Jon,


I started processing this and realised that I was thinking about the difference in the two scenarios due to the Longitudinal axis aspects of an aircraft (roll axis), which gives a three dimensional effect Vs a more two dimensional effect in a car (not completely as the body does roll in that same axis but usually as a counter force) ... and then I realised that I was having flash backs from studies almost 30 years ago (which I acknowledge are pretty bloody rusty) ... LOL!!!


STOP, STOP, STOP.


I changed professions for a reason.


Cheers mate.

Come on, I'm just warming up