The second in our series of articles discussing vehicle setup, this post will be on camber.
Camber is the inclination of the wheel on an axis from the front to the rear of the car and parallel to the road surface. To explain in less technical terms, if you look at the car from the front, its the angle the wheel makes with the vertical – therefore if the wheel is perfectly vertical, that is 0 degrees camber. If the top of the wheel leans in towards the car, that is described as negative camber, and if the top of the wheel leans out from the car, that is described as positive camber. While positive camber had some uses in historic vehicles (it reduces the steering effort, a problem in massive old 1930s blower Bentleys with no power steering….) it is not generally used today, and therefore this article will focus on negative camber.
General awareness of what camber is in the car community is pretty good – this is thanks to recent trends of running enormous amounts of static negative camber (more on why its static later…) in order to achieve a certain look. While this is certainly not for any performance benefit, and in some cases pretty dangerous, it at least helps people understand what camber is.
Camber is a critical part of the setup of the vehicle, and unlike toe (described in the previous article), the setting of camber for ultimate performance is generally less subjective – i.e. there is a perfect setting for a certain vehicle on a certain track in certain conditions to get the best performance. To understand why lets briefly talk about what happens when a car is cornering.
As a car corners, the car will experience some roll to the outside of the corner. There will be significant weight transfer to the outside wheels, the tyre will deform and the suspension will compress. Now lets assume the car is set up with zero static camber – as the car rolls and the tyre deforms, the tyre tread will essentially lift from the road and the car will be driving on the sidewall, or at least definitely with a smaller contact patch (area of the tyre contacting the road and providing grip). All this is happening on the outside tyres – the ones that are most loaded due to the weight transfer and therefore the ones that can provide the most cornering force.
Its quite clear from the description above that we could improve the situation by inclining the top of the wheel towards the inside of the car – add negative camber. This is generally why all road and race cars tend to run varying degrees of negative camber. Race cars will usually all be setup to the ‘magic number’ of camber for ultimate performance I described earlier, but before we talk about how to achieve that, lets discuss a potentially more interesting issue – camber on road cars.
In a road car the manufacturer needs to achieve minimal tyre wear and safe and predictable handling at road speeds and loads in all conditions. Consider the car cornering above – depending on how hard they are cornering, the car will roll a different amount, the tyre and suspension will deflect a different amount, and ultimately you will need a different amount of camber. Imagine its a wet day on a slippy road – you will need far less camber than on a dry day, because you will have less grip and your car will roll less. And we must also consider braking and traction – the more static camber you have the less tyre is on the road when you are travelling in a straight line, which negatively impacts braking and traction. The factory settings for the Civic are below:
Front Static Camber: 0 degrees
Rear Static Camber: 0.75 degrees
This is what you might expect – the manufacturer has prioritised tyre wear and braking performance, with 0 degrees camber at the front. This will also reduce any unwanted bumps and vibrations through the steering wheel which excessive camber can induce. A little negative camber at the rear is tolerable, because a FWD car does not wear its rear tyres much, and the balance of camber front to rear will give understeer, for safe and predictable handling whatever the weather. Many people choose to improve performance and balance by adding a little camber (the fabled ‘Fast Road Setup’) – 1 degree all round is common on the Civic (and also happens to be the factory setup for a Nissan GTR). Much more than that and the negative effects will start to outweigh the positive on the road.
Now for a race car the situation is very different – the camber is set to achieve the maximum cornering force (grip!) on that particular day, and the way this is achieved is through testing. After a base setup has been put on the car (some negative camber, based on experience) the driver is sent out to drive several laps at full race pace. When the tyres are up to temperature and the pressures set correctly, temperatures are taken across the tyre tread from the inside to the outside using a spike pyrometer. The camber is adjusted and the driver is sent out again until the temperatures are even across the tyre – this means you are using the whole tyre evenly and getting the maximum performance, and lap times should reflect this. A good dry camber setup will work well at most circuits unless you are searching for those final hundredths, but a cold day, or a wet day will change things massively! A typical wet and dry setup for the Civic Cup Car are below:
Dry Front Camber: -3 degrees
Dry Rear Camber: -1.75 degrees
Wet Front Camber: -2 degrees
Wet Rear Camber: -1.5 degrees
The Civic needs lots of front static camber, because of the poor front suspension design (see below), and also because the general setup of the vehicle puts huge load on the front end. These levels of camber on the road are absolutely ridiculous – before taking the Civic off the road I drove it with this setup over to the garage where it is now kept, and any bumps on the motorway were almost throwing me into the next lane, with big jerks through the steering wheel. Of course this camber makes your traction and braking performance slightly worse, but on track in a car of this power you have far more to gain from carrying corner speed.
Finally to address the meaning of ‘static’ camber. An important issue with camber is the suspension design of the vehicle. Camber can change dramatically as the suspension of the vehicle moves through its range – the value you set when the car is still is ‘static’, and the actual value when loaded in a corner is ‘dynamic’.
An ideal design gains negative camber as it is compressed – all race cars are designed like this. With some clever design this means they can claw back the traction and braking performance as they don’t have to run lots of static camber.
With certain low cost suspension options such as McPherson Struts (as on front of the Civic Cup Car) the design actually loses camber as the suspension compresses. It is for this reason you tend to see touring cars with lots of camber – they generally have to use OEM suspension pickup points and therefore can’t create an effective camber gaining design. Look out for cars with double wishbones all round – these give the best camber control. We have them on the back of the Civic, and you will also find them on almost every high performance car, from a road going supercar to every car on the F1 grid.
Feels like a long article, but it is as short as it could be whilst hitting all the important facts. I hope this gives some insight into how you might choose to set your camber whether for the road or the track, and understand how it affects performance.
Any questions just shoot, please check out the Facebook Page where you will find photos and videos, and of course read the other 7 great articles right here on the site.