I have 2 different books at home that deal with car handling one of these books says that to reduce oversteer then you should have the rear wheels set to straight ahead the other one says that to reduce oversteer you should apply toe in to the rear wheels!


Anyone car to shed any light on which one is right?

Anyone had any personal experiences from doing either set of setting?

Darren

 

IMHO toe in reduces understeer and induces oversteer which is why the Prodrive settings make turn in sharper. I've just had these settings put onto my Sti wagon and it definately induced slight oversteer. Before it had slight understeer

Bob

 

Darren, bear in mind that I have the anti-lift kit on my car but with 0 toe on the front the car did NOT understeer, when it was set to 1.5mm toe in it DID understeer. MRT suggest 0 toe on the front and 3mm total toe OUT on the rear. Still waiting to get my car back with it reset to 0 toe to confirm my suspicions though!!!

 

I think the "Prodrive confusion" might spring from the fact that they increase the negative camber on the front, which is probably what contributes most to the understeer removal.

 

When braking or cornering any suspension set up with any movement will move towards toe-out. This is how the passive turning in some cars - like my old Rover 200 or some Citreons - works. On those two front drivers this helps the car turn in but as the understeer will be greater than the resulting oversteer it is hard to get in trouble.

Therefore if the rear wheels are parallel then these forces will produce toe-out on cornering. If the toe-in is set correctly then the resulting forces bring the wheels parallel and hence neutral.

My Sti, when it had the Prodrive settings, would oversteer SLIGHTLY and generally when provoked. On the whole it was neutral. The rear wheels had toe-in.

Darren - if you have too much oversteer on your car then either having more toe-in on the rear or reduce the toe-in at the front.

Mike - my understanding of the camber is that this keeps the tyre 'flat' to the ground when corning to produce better grip.

Alternatively this could all be rubbish as I've just returned from sitting in the sun during a pub lunch.

Andrew

 

I agree with that comment Andrew - increasing -ve camber at the front gives you more grip at that end and reduces understeer to some extent. As many people have noted before, you can quickly wear out the inside shoulders of your tyres if you overdo it.

Decreasing toe-in at the front will make the car turn in more eagerly, but costs you some straight line stability. Once you've actually settled into the corner, I don't think toe-in has much influence on the quantity of grip available.

 

The comments about Camber are correct although one other downside of having too much negative camber is that you braking ability is also decreased as the tyres are not flat to the road when in a straight line.

The situation with Toe in is not quite so clear though particulary as I am taking about the rear end toe in. I have since had a chate with Pete and he has said also that having toe in at the rear will cause the car to be unsettled and this is what I am experiencing. Which reinforces what the second book I have says which is that you should reduce toe in at the rear to reduce oversteer. I can also see how this would make sense because you would then be getting the rear wheels nearer the straight ahead position rather than pointing in towards each other which should mean they are both able to work better by doing this you are also reducing the slip angle at the rear outside wheel which should help the grip at that corner.

Darren

 

Darren,

Now you put it that way, it seems to make sense (about toe-in at the back, that is)

 

Hi all,

So..after all this, what are the ideal geometry settings for a car on 17" rims?

Chamber? Castor (if adjustable)? Toe in/out? on the fronts and backs ?

J.

 

Well my immediate answer is it depends!

If you have standard suspension then the prodrive settings are certainly a very good starting point and seem to suit most people. The reason for the questions was that the car hasnt been handling the way I want it to in that it in my opinion is not as well planted at the rear end as it should be but you should remember that my car doesnt have standard suspension and the settings that are put on the car with Leda suspension are somewhat different to the car with standard suspension.

All suspension settings are a personal thing tied in with you own driving style. My STI V with standard suspension and the PRodrive settings was excellent and I would suggest that to anyone who asks me with the slight warning of potential extra tyre wear.

Darren

 

And the Prodrive settings are ?

is this only available to the select few ?

If it is then i want to be a "Select few"



Dave

[This message has been edited by Sonnyrider (edited 29-06-99).]

 

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