I have just bought a 2008 DB9 with full AM service history. I’m the 2nd owner, the car is known , is in a very good condition and there’s never been any crash damage.

I am very happy with the car, however, there is a peculiar handling issue.

There’s seems to be a large tendency for the front of the car to shift to the outside whenever I take (even slightly) my foot off the throttle in a bend. A factual example could be a motorway exit, where if the car is held at a constant speed (80 kmh) and you lift off the throttle slightly – the front end tucks-in at an alarming rate. I say tucks-in, because it feels like this as opposed to the back wanting to step out.
And to be very clear I don't mean in no way over steer, or under steer. The speed is nowhere near enough at a level of having trouble to control the car and loosing grip.
It is more like a steering or a transmission problem.

Did any body else ever experience a similar problem?
If so, is there a fix?


Many thanks.

 

You say the front shifts to the outside but then say the front tucks in a few sentences later, can you clarify?

Just because you do not think you are going fast enough to induce over or understeer, it's not all a function of speed. Your alignment and tire pressure will also have a huge effect on when over / under steer comes into play.

 

Welcome to the forum!

This is completely normal for any car set up for performance. Hopefully this is clear, I just threw it together...

You've got two main forces acting on your tires (forward and lateral) with traction needed to handle each: traction in going forward and traction in turning. Each tire has a finite amount of traction available to use for those forces. traction isn't allocated as "all or nothing" for one or the other. Rather, it's shared (for example, in a constant speed turn your front tires might be using 30% of available traction for going forward and 40% of available traction for turning, and have 30% of its traction still available for use if you want to increase speed). When the collective forces exceed the tire's capacity, you lose traction.

Imagine this being a "map" of a tire's traction being used:



If the circle is a map, then up is forward traction (straight), left and right are turning traction, down is rearward traction (straight, driving in reverse), and any direction in between the cardinal directions is a combination of turning and straight traction. So in the circle above, the arrow shows that the car is in a turn and using traction for both moving forward and turning.

In a straight line, you're using the tire to move you straight ahead so no traction is being used for turning. If you use more than 100% of the tire's available traction, you spin the tires.

In a turn with a constant speed, your rear tires are trying to push you forward and your front tires are trying to steer you. (Keep in mind that BOTH forces are working on all four tires in a turn.) If the fronts exceed their traction before the rears, you get understeer (the fronts lose traction so the car pushes through the corner). If the rears exceed their traction before the fronts, you get oversteer (the rears lose traction so the back slides out). This can easily be induced by increasing speed in a turn.

So what you're describing is the opposite of that - you're lifting off throttle and decreasing speed.

What is happening that you're concerned with is that the fronts were handling traction at a steady state. You lifted off throttle, which made it so the fronts had less forward traction to cope with, giving them more traction to allocate to turning. The increased turning traction is what causes the "tuck in" feeling - it's a notable increase in turning traction.

It's one of the more basic techniques for performance driving - it allows you to take a turn much more sharply than you could if you went through it at a constant speed. You lift off throttle and the front end bites, so when you get back on throttle it turns in more sharply. It happens in normal driving as well. Totally normal.

 

On a perfectly set up performance car, if you are going in a circle at a steady state speed, and then lift, you'll get slight tuck in and adding throttle will cause slight push out.

 

Sounds like a normal response to the road conditions. It he vehicles tracks straight on acceleration, deceleration it's not a tire or alignment issue. How old are the tires and brand? 2008 could have 7 year old tires.

 

just changed the tyres with winter ones.
problem still there.

 

I have the same question as mkzhang: your statements that the front of the car wants to shift to the outside, and that the front end tucks in seem to describe actions that are the exact opposite. Which is it?

If the front of the car moves more towards the direction that you are turning, as others have stated, it is normal, particularly if as you say this action is not causing the car to lose adhesion at normal speeds. This behaviour is called oversteer and it is exactly what you want in a car that handles properly. Not crazy back end out, opposite lock / tire smoking oversteer, but a nice tightening of the cornering line when you come off the throttle.

 

what is actually happening is that once I take your foot of the throttle there is a clear shift in the direction of the car towards the outside of the turn (front actually changes direction) and I actually have to make a small correction with the steering wheel.

one could describe it as understeer but without any loss of grip at all. Nowhere near that. Just a small but sudden shift in direction.

 

No- haven't had that type of experience. I do have two sets of tires/wheels. My Michelin Super Sports do handle differently( much better) than the stock Potenza's did and better than the PS2's I have on my second set. With your cars known good history I would not think the worst. Alignment (when was it last done?) Tires older than 4or5 years get hardened so not as good handling. Tire pressure important. And of course BRAND & QUALITY of tire. Please let us know your findings. This is a great place to be in touch with allot of well informed Aston enthusiast! Welcome

 

OK, that is definitely not normal. As already suggested: alignment, tire pressures. Suspension checks out OK?