Causes of bad understeer in car ?

Mister Jingles

Besides tyres I'm just wondering what causes bad understeer, even when the ground is dry ?

CiniO

- Incorrect tyre pressure.
- Car design (some vehicles are way more liable to understeer than others)

166man

Can often be the road conditions really, steep slope, greasy conditions etc....

Under steer can be just as unpredictable as oversteer.

CiniO

Obviously driving technique - if you accelerate when approaching the bend, this might cause understeer.

slimjimmc

Crap tyres?

Mister Jingles

Would suspension ware or bushings front or even rear cause it ? Or anything else related to the steering ?

Mister Jingles

slimjimmc wrote: »

Crap tyres?

Pirelli winters on front and two Chinese on the rear but all 4 have at least 5mm on them.

Probably not the best set up but I find it had to believe this to be the cause, especially in the dry.

Cheensbo

Is the car FWD or RWD?


Most of the time it will be either tyres, the road surface (wet SMA asphalt with leaves and crap on it is about as grippy as wet grass) or a combination of both.

Worn suspension components wont affect it too much unless you really launch it into bends & roundabouts.. If you don't have major rattles you can say within reason that its not too loose under there.

Zubeneschamali

Mister Jingles wrote: »

Pirelli winters on front and two Chinese on the rear

More likely to cause oversteer when the Chinese yokes lose grip.

Lack of driver ability?

CiniO

Mister Jingles wrote: »

Pirelli winters on front and two Chinese on the rear but all 4 have at least 5mm on them.

Probably not the best set up but I find it had to believe this to be the cause, especially in the dry.

Well here's your answer.
It's 10 degrees today, and looks like you chineese crap tyres provide better grip than Pirelli winters.

CiniO

Bam Bam Mickey wrote: »

Lack of driver ability?

What has lack of driver ability to do with car understeering?

Mister Jingles

Cheensbo wrote: »

Is the car FWD or RWD?


Most of the time it will be either tyres, the road surface (wet SMA asphalt with leaves and crap on it is about as grippy as wet grass) or a combination of both.

Worn suspension components wont affect it too much unless you really launch it into bends & roundabouts.. If you don't have major rattles you can say within reason that its not too loose under there.

FWD

It's a mk3 mondeo to be more specific which is why I'm more suprised. I ask if steering would be the cause as well as it is in no way chrisp or sharp what so ever.

Mister Jingles

Bam Bam Mickey wrote: »

Lack of driver ability?

I've driven many different type of cars before my friend, so it's nothing to do with lack of driver ability. My query is specific to just my car

Cheensbo

Mister Jingles wrote: »

FWD

It's a mk3 mondeo to be more specific which is why I'm more suprised. I ask if steering would be the cause as well as it is in no way chrisp or sharp what so ever.

Do you get considerably uneven wear on the front tyres? It would be a solid indicator that something's amiss.

Mondeos are very nose heavy as it is & love to understeer, couple that with winter tyres on a warmish dry surface & its probably gonna be exaggerated..

Maybe swap off the winters & throw away the ditchfinders for some reasonably good all seasons?

CiniO

CiniO wrote: »

What has lack of driver ability to do with car understeering?

You posted yourself about technique!
For all we know the driver might be pushing the car past its limits and cannot use a proper technique.

Mister Jingles

Cheensbo wrote: »

Do you get considerably uneven wear on the front tyres? It would be a solid indicator that something's amiss.

Mondeos are very nose heavy as it is & love to understeer, couple that with winter tyres on a warmish dry surface & its probably gonna be exaggerated..

Maybe swap off the winters & throw away the ditchfinders for some reasonably good all seasons?

It's too early to tell but when I got the car a few months back the tyres where worn on the sides (outside to be exact) so I had the tracking done and also the front ball joints then I picked up the two front tyres. I do intend on taking them off sometime in march as the weather should be getting better and get new ones on all 4 corners.

Regarding them been front heavy I would defiantly agree, even from just looking at them its obvious.

Hal1

It was worn front anti roll bar bushings on my focus causing mine to understeer. It can catch you out and is quite scary to say the least. Check you're engine mounts too.

CiniO

Bam Bam Mickey wrote: »

You posted yourself about technique!
For all we know the driver might be pushing the car past its limits and cannot use a proper technique.

If you push car past its limits it's going to skid, and it's either going to be understeer or oversteer (very unlikely to have 4 wheel skid).
If OP is saying car has tendency to understeer, then we should believe he knows what he is doing and what he is talking about.

If you don't drive to the point when car skids, you won't even know if it has a tendency to oversteer or understeer.

CiniO

Cheensbo wrote: »

Mondeos are very nose heavy as it is & love to understeer,

I had Mondeo MK3 once, and to be honest it didn't have tendency to understeer. Rather opposite.
However mine was 1.8 petrol (so fairly light front) and hatchback (so heavier rear).

couple that with winter tyres on a warmish dry surface & its probably gonna be exaggerated..

That's what I say.
When I heard that OP has winter tyres in the front and summer on the back, driving in current warm conditions, I'm fairly sure that's the culprit.

ianobrien

OP, are you braking into the corner or braking before the corner. Braking into the corner (as in braking and then turning into the bend) will promote under steer due to the weight transfer to the front overloading the front tyres. You should be taking your foot off the brake pedal before you turn into the bend (brake in a straight line only).

Other items are that the tyre pressures are correct and nothing is worn or broken in the suspension. The roads at the moment are very slippy as its being dry for long that a film of grease forms on the road. A bit of damp turns this into one slippy surface with no grip. For example, on "dry" roads today I got wheelspin in third gear. The road looked dry but was very very greasy.

Mister Jingles

Hal1 wrote: »

It was worn front anti roll bar bushings on my focus causing mine to understeer. It can catch you out and is quite scary to say the least. Check you're engine mounts too.

That was one of the things I had thought first as well and still feel could be what the problem is until I get it checked.

CiniO wrote: »

I had Mondeo MK3 once, and to be honest it didn't have tendency to understeer. Rather opposite.
However mine was 1.8 petrol (so fairly light front) and hatchback (so heavier rear).

That's what I say.
When I heard that OP has winter tyres in the front and summer on the back, driving in current warm conditions, I'm fairly sure that's the culprit.

I hear what your saying about the tyres and hope its just something as simple as that but the temperatures are really only starting to rise above 6/7 degrees the past week or so, this has been happening a while even when its cold out but the roads are dry.

I do drive more then one car often enough, the mondeo is mine though but I don't seem to have this issue in anything else.

ianobrien wrote: »

OP, are you braking into the corner or braking before the corner. Braking into the corner (as in braking and then turning into the bend) will promote under steer due to the weight transfer to the front overloading the front tyres. You should be taking your foot off the brake pedal before you turn into the bend (brake in a straight line only).

No I dont usually brake driving into corners, I'd usually brake, change down a gear and turn ect, that's how I was taught years ago when I starting to drive.

CiniO

Mister Jingles wrote: »

I hear what your saying about the tyres and hope its just something as simple as that but the temperatures are really only starting to rise above 6/7 degrees the past week or so, this has been happening a while even when its cold out but the roads are dry.

The easiest way to check, would be to swap tyres - front/rear.
30 minutes work with your jack.
If car suddenly becomes oversteer, then you will know it was it.

CiniO

ianobrien wrote: »

OP, are you braking into the corner or braking before the corner. Braking into the corner (as in braking and then turning into the bend) will promote under steer due to the weight transfer to the front overloading the front tyres. You should be taking your foot off the brake pedal before you turn into the bend (brake in a straight line only).

I think you are confusing oversteer with understeer.

ianobrien

CiniO wrote: »

I think you are confusing oversteer with understeer.

Nope. Drive a Citroen AX GT hard (or any proper French hot hatch) and you'll learn about under steer and oversteer (lift off kind). Brake into a bend in the AX and its undedsteer all the way. Get on the power (not wide open throttle) and its fantastic grip. Think for 0.05 seconds about lifting off the throttle and its oversteer.

Special Circumstances

Any clatter from anti roll bars?
There are many many tyre outfits that couldn't adjust tracking to save their lives.

Mister Jingles

Special Circumstances wrote: »

Any clatter from anti roll bars?
There are many many tyre outfits that couldn't adjust tracking to save their lives.

I don't know to be honest. Where would I be looking to hear this, ramps ?

And yep I couldn't agree more about the tracking.

Special Circumstances

Mister Jingles wrote: »

I don't know to be honest. Where would I be looking to hear this, ramps ?

And yep I couldn't agree more about the tracking.

Any uneven road surface would show it up if they were bad. We'll assume they are ok so as you would you know about the clunking if they are bad.
Likewise we'll assume that as bad as some tyre outfits are, they would have noticed if any drop links were missing or broken.
Although...

Hal1

When my anti roll bars were bad the clunking was unreal. Any deviation in the road surface would cause it to jump about. When the bushings go you will know.

CiniO

ianobrien wrote: »

Nope. Drive a Citroen AX GT hard (or any proper French hot hatch) and you'll learn about under steer and oversteer (lift off kind). Brake into a bend in the AX and its undedsteer all the way.

Only reason I can think of, is that you are actually locking the front wheels (which won't occur with ABS) or just applying such a big force (but not yet locking) that once you start turning your steering wheel, this bit of extra force on the wheels will loose the grip.
It's fairly hard to achieve I'd say.
And once you release the brake, you loose and tenedency to understeer.

Get on the power (not wide open throttle) and its fantastic grip. Think for 0.05 seconds about lifting off the throttle and its oversteer.

That all makes perfect sense.

joe912

track rod ends tie rods. jack car up hold wheel at quarter to three and shake to check for play

Mister Jingles

I'll probably just end up sending it in to a garage to be checked over as I wouldn't be too clued into all of that.