Camber Gain Data

[N Roshier]

Does anyone have any data on the amount of camber gian that is in the new GT and in other production sports cars?

[Julian]

Neil - this info wouldn't be required for your Godiva project would it?

Anyways, don't have data on a new Ford GT, but have mapped my suspsension on my GT40 replica.

Front and rear camber curves attached. Don't know how well it works yet on the track. Drives nicely on the road, but won't have any real track testing for a few more months yet till decent motor is built and car is painted. I'm aiming for a total vehicle roll angle of no more than 2 deg at max cornering (say 1.2 - 1.3 g lateral acceleration).

Positive vertical axis = wheel bump travel (Zero point set at chosen ride height)
Horizontal axis = camber

[N Roshier]

Thanks Julian. The data is partly for Godiva, but not really that much of an influence, more that there seems to be a difference between different manufacturers and a difference between different layouts. e.g. Mazda are very conventional in that front camber gain is more than rear, yet Lotus is the reverse with a mid engine car...and there also seems to be a date of change in philosophy too, just like with f/r track ratio's.
Personally I'd like to compile and list this data on my website at Race Magazine - Home as I know there is a lack of this information about the place and Milliken and Dixon do not help much.

[John]

I don't know for sure and someone please correct me if I'm wrong, but I can think of a reasons why the rear of a car may need more camber correction compared to the front... especially on a rear weight bias car. I'm guessing the lotus your talking about is the Elise? The rear of that car carries over 60% of the weight. so the rear tires are going to be more loaded than the front, and the sidewalls of the tries are going to flex more in a turn; especially powering out of a corner. So I wouldn't be surprised if the rear gained more camber.

[N Roshier]

Good points, was not always the case though. The Lotus's tyres are also shorter side wall at rear and print matches weight. I sometimes wonder if they also factor in an amount for chassis etc compliance under load!

[John]

Another thing, the rear tires on an elise are 255's while the fronts are 225's. Wider tires are more sensitive to camber changes, so maybe they are are trying to optimize the rear a little more for cornering, and not put so much camber correction in the front because they don't want to sacrifice braking; though, I don't recall the elise/exige's i have been in to have much body roll or pitch! but at the time, i wasn't really out to analyze the suspension either!
Its hard to analyze just the camber change because thats only one aspect of the system. I bet those lotus's run big caster up front; thats another thing that would lessen the need for a lot of camber correction in the front.

Our Formula SAE car last year had very little camber correction in the rear, and it was quite evident when standing behind the car as it powered out of a corner. in this picture, you can see the rear wheel going a little into positive camber and the tire really starting to be pulled under. I wish i had a better view of this, you don't see it too much from this shot. This year, more correction has been added to the design.

[Julian]

I've only got limited experience with fooling around with camber. My last competition car had strut front end and live rear axle. All I could do was increase static front camber until thermal imaging of front tyre showed even temperatures across tread. Ended up with 4 deg front static camber, but that was only with 205 wide tyres.

GT40 has 235 front and 275 rear tyres, so will have to go easier on static camber. Then again, shouldn't need so much due to dynamic camber of double wishbone setup. Looking at my graphs, if I limit car to 2 deg roll angle, will only need 1/2 degree or so static neg camber in theory to keep wheels upright. Of course, it's not that simple, so my only way forward is to wait till I can test it and see what it feels like (under or oversteer)+ measure tyre temperatures. And then of course it comes down to corner speeds, never mind everything else! GPS analysis software should help there, as of course does the simple stopwatch and lap times!

[Julian West]

Hi All,

If it helps, here is a brilliant tool for calculating camber compensation from a 750 club racer.....

Racing Aspirations - a Formula 750 constructors diary (Fiat FIRE 1108) - Suspension Geometry Calculator

Regds,