Is camber gain really beneficial?

[Jersey Tom]

Bias-ply tires have been found to generate more camber thrust than radial tires

http://en.wikipedia.org/wiki/Camber_thrust

There is a HUGE difference between the phrase "bias-ply tires tend to generate more camber thrust than radial tires," and the phrase "radial tires don't benefit much from camber thrust."

Besides, camber thrust is not what gives these tires extra limit grip. Two totally different concepts.

Racing tires aren't really radial tires.

Absolutely true, but not not particularly relevant... as even street radial tires "benefit" from camber.

Negative static camber helps keep the tire RELATIVELY vertical during body roll.
And yes during body roll F1s run very little or even no net negative camber, specially for the inner wheel.

Just not true. The intent of static negative camber is to land your dynamic camber wherever you want it, which is a non-zero value - several degrees or much more to get the additional cornering force, depending on how much you can get away with given your tire manufacturer.

Besides, with kinematics... inside wheel will get extra negative camber - outside wheel loses some. With how stiffly sprung such cars are for platform control, your body roll angle and maximum camber gain through cornering is quite small.

[olefud]

A lot of good points made without getting into proprietary info. A few more points of possible interest include the downside of camber gain, i.e. braking. With dive under braking, camber gain kicks in and compromises the tire contact patch. Also, camber gain is generally obtained by l/s arm suspension, but even equal length arms differently angled can provide camber gain.

IMO camber thrust does tend to turn the tire but does not add to cornering thrust –only the contact patch generates cornering thrust. Camber helps because, as mentioned, the vehicle rolls and tends to change the tire camber. Less recognized is the distortion of the tire contact patch (slip angle) and sidewalls under hard cornering which smears and rotates the contact patch towards effective positive camber.

Finally, as a bit of a stretch, I did a bit of work with a lower level NASCAR team (West Series) to address the problem of heat gain and resulting tire pressure increase. Cold tires wanted rather more camber gain which tended to be favored since handling was so bad on cold tires. However, this compromise hot tire handling though not in a dangerous way. Never got a chance to try my theory for enhanced leak-down (no time, no testing), but it probably would be illegal now – and maybe then

[itdontgo]

You need to look at tyre data. Here is some for my race car:

http://www.adventcontrols.co.uk/ACB10Michael.xls

Clearly the camber thrust at least offsets the point at which the lateral force is zero meaning you need some slip angle to have zero force. Ultimately for a race car we're really interested in the uW (coefficient of friction x weight) force which comes from a combination of slip angle generated lateral force and camber thrust. Looking at the numbers you can see this increases noticeably with increasing camber. Whatever the reason for this (tyre deflection?) there is an increase and this is found at a tyre pressure which I would consider on the high side (so you would expect more of an effect at a lower pressure).

However the problem with this is that looking at the force in the same direction generated by the inside tyre at the same slip angle - where the camber thrust is now in the opposite direction! - the total potential for this tyre is reduced.

With my car I have a droop stop on the front suspension so I know there is almost no load (wheel will lift) on the inside front wheel which gives you great traction. It also means you can pretty easily apply the numbers in that data to a real life situation as I know the rear will have a split of about 84/234kg and the front will have about 169kg totalling 487kg which is about right. Doing this you will find the maximum lateral force generated in the rear axle comes at 0 camber. If you camber the tyres the outside generates more but the inside drops significantly more than the gain from the outside. At zero camber you get less on the outside tyre at 9deg slip with 234kg on it but more on the inside tyre from its load of 84kg at the same slip angle. .

In NASCAR they only go left so this is why it works for them. With that in mind on clockwise tracks with right handers leading on to long straights I've wondered whether it would be worth sacrificing some left hand performance to ultimately gain lap time but have never got around to testing it.

The other benefit of camber thrust at lower slip angles is the instantaneous turn it it gives.

On the front axle it is a different story at least for my car as I run it in the dry with droop stops and very stiffly so the inside tyre does not contribute much at all. And of course the reason for that you can see above (the front to rear weight distribution means the car has a tendency to oversteer)

[marcush.]

if you have a rule stating 4°negative is the absolute maximum for your static camber but you know performance peaks at 7degrees some camber gain in bump might come in handy...

[strad]

When I add a little to the front of the Mustang it seems to help on turn in but on the rear IRS it seems to add to the oversteer which I don't need. Why is that?

[Greg Locock]

strad to some extent static negative camber acts like static positive toe in, so your results aren't all that surprising. However, often rear axle toe in is a good thing (and toe out is definitiely bad), which goes against the rules of thumb

[marcush.]

When I add a little to the front of the Mustang it seems to help on turn in but on the rear IRS it seems to add to the oversteer which I don't need. Why is that?

because you have raised the front lateral capacity it seems more than logical that your balance is now shifting towards the front...front and rear is connected by something which is called chassis...
if you start with something of a balance every little improvement or drop in capacity will alter the cars behavior significantly and so a front improvement may welll lead to an overall loss in performance...next step would be to look for improvements at the rear to regain your preferred balance.
of course this is oversimplifying things -you could as well have a situation where the extra grip generated on the front would lift the inside rear .. so you would not work necesaryly on the rear but try to reduce front roll angle (again the chassis is stiff (or it should be) so this will have an effect at the rear...So if the cure is rollbar front ,spring or rear droop travel is not so obvious without data or evidence ..

[itdontgo]

Just to point out what I was on about earlier the camber on those two inside wheels creates their camber thrust in the wrong direction:

[Jersey Tom]

Just to point out what I was on about earlier the camber on those two inside wheels creates their camber thrust in the wrong direction:

So?