Understeer and shudder experience

Dauphin · 25-01-2006, 09:29 AM

Hi everyone,

Yesterday I was going around a roundabout that I have gone around many, many times before. I usually take it pretty quickly but last night something unusual happened. The car got into understeer, seemed to actually be sliding forwards while the wheels were turned, and a big shudder / vibration came up and I'm sure it was coming back through the steering wheel, too.

It was still light, no rain all day. When I was coming home, I tried it again out of curiosity, slower, and could feel the car definately starting to "lose it" at the same spot.

I am wondering if anyone knows what that might most likely be? It gave me a bit of a fright when it first happened.

Regards,

Andrew.

cArSiK · 25-01-2006, 09:36 AM

over inflated tyres? Worn Shocks?

kooky · 25-01-2006, 09:37 AM

well the sliding forward is indeed understeer as you have identified, you didnt happen to stab the brakes while understeering? That would be the ABS activation, but it doesnt sound like that's what you are describing?

Could it be worn ball joints, has the car been lowered? and how many Km's travelled?

cArSiK · 25-01-2006, 09:37 AM

ohh was there oil on the road?

Casper · 25-01-2006, 09:41 AM

Shuddering while understeering is pretty normal, I wouldnt worry about the actual shuddering, just what caused the understeer in the first place. I'm suspecting oil on the roundabout to be honest.
Does the car react differently anywhere else or just this one roundabout?

Dauphin · 25-01-2006, 09:45 AM

My tyres seem good and the pressures (34psi) actually haven't changed since getting new tyres and driving thousands of KM's. Don't know if it's any suspension problem because I sense nothing else wrong, it has IRS. 2000 AU2 Fairlane.

My first thought was actually oil or something deposited on the road at that spot. If it is, I hope it doesn't catch anyone else out. I'll walk my dog up there and check it out later. Yes, car is lowered. Kilometres: 105,000.

25-01-2006, 09:49 AM

Yep shuddering during understeer is normal, its tyrewall flexing whilst trying to grip then "springing" back to its original shape, over and over that causes lack of grip.

Dauphin · 25-01-2006, 09:51 AM

I'm pretty sure it's handling fine elsewhere. I'll throw it around a little later and see if anything happens.

One thing that's changed since last week is it now has a big sub in a box and amp in the rear, both up in the well behind the rear seats. I can feel that the extra weight does change things just a little around fast corners, but do you think it would contribute to front-end understeer?

**Polyal** · 25-01-2006, 09:54 AM

yeap I think most people have been there....its a relatively normal thing.

Id be more worried if it didn't shudder...lol

You probably just went in a bit hot and there just happened to be some stuff on the road. Count your self lucky that it didn't end up in tears I guess.

Oversteer is cool when you mean it, understeer is not.

Dauphin · 25-01-2006, 09:55 AM

Hi BlackLS. That's scary. When I was at the defensive driving course, they demonstrated that with a piece of tyre and it is frightening to think of what a tyre really does under stress.

I have a video of a Bentley being thrown around the Top Gear track and its alloy rims definately must be touching the tarmac as the tyre folds underneath the actual wheel around one corner. You can usually see it to some degree with that Suzuki Liana they get celebrities to drive on each episode of their show.

Dauphin · 25-01-2006, 10:01 AM

Polyal, you know how sometimes people say things and it sticks in your head forever and you always think about it? Well, there was this guy on the forums, I cannot remember his name, and he said he was taking a local corner pretty quickly like he always does on the way to work or something, and this day there happened to be gravel on the corner and he lost it and smashed his car.

I often think about that. While I may not have changed, something else may have. You just never know and you keep on doing it, even though you know better. Then it takes something like this to make you think twice for a while until you start doing it again...... coz you can't help it.

**Polyal** · 25-01-2006, 10:14 AM

Quote:

Originally Posted by Dauphin

Polyal, you know how sometimes people say things and it sticks in your head forever and you always think about it? Well, there was this guy on the forums, I cannot remember his name, and he said he was taking a local corner pretty quickly like he always does on the way to work or something, and this day there happened to be gravel on the corner and he lost it and smashed his car.

I often think about that. While I may not have changed, something else may have. You just never know and you keep on doing it, even though you know better. Then it takes something like this to make you think twice for a while until you start doing it again...... coz you can't help it.

Yeah and you lose a little confidence in yourself and the car.

Ive only really badly undertseered once, and it was in the rain; ended up costing me about $2500 in repairs.

Best to learn from it and move on. If you are seriously worried then go get your car quickly checked over.

OLDFORDNUT · 25-01-2006, 10:21 AM

mate ,as for your sub box,it would have to be over 100kg's to effect your handling,
anyway a front end alighnment only costs about $40,worth it just as a precaution and ask mechanic to check ball joints and such while its on hoist.cheap insurance especially when you consider how much tyres cost these days.

25-01-2006, 10:28 AM

Quote:

Originally Posted by Dauphin

Hi BlackLS. That's scary. When I was at the defensive driving course, they demonstrated that with a piece of tyre and it is frightening to think of what a tyre really does under stress.

I have a video of a Bentley being thrown around the Top Gear track and its alloy rims definately must be touching the tarmac as the tyre folds underneath the actual wheel around one corner. You can usually see it to some degree with that Suzuki Liana they get celebrities to drive on each episode of their show.

If you ever download some Japanese illegal street drifting at night video, you'll see most of the cars drifting low profile tyres have their rims causing sparks on the road.

Pedro · 25-01-2006, 01:09 PM

Quote:

Originally Posted by Rollin

you sure its the rims? IMHO its more likely to be the wire hanging out of the delaminating tyre that would cause sparks...alloy doesnt generally spark when its being ground away in my experience...

Yes, I agree, especially when drifting, as the tyres take such a caning.

LTDHO · 25-01-2006, 01:55 PM

What speed are we talking? This should never happen at a safe speed! Alot of accidents happen due to the speed in roundabouts, they aer designed for slow speed. Look at the camber next time. Very bad for speed!!

:

triple8nitro · 25-01-2006, 03:43 PM

Did you have a full tank of fuel, as well as a bit of gravel.
I was hooning at about 3am once it happened to me but i mounted the gutter,
cost alot though to get it back to good.
TIGHT ROUNDABOUTS + SPEED = DEATH.