negative rear camber
Discussion
You don't gain anything by actually going to a neg camber rear suspension. However, what you don't want is ANY positive camber on the rear. So, as a guide, aim for 0 deg rear camber +0, -0.5 degrees.
With wide radial tyres the best roadholding on a true trailing arm suspension, where the plane of the wheel centre moves absolutely vertically, will always be 0 degrees, but a little bit of negative is fine at standard ride heights.
To measure the actual camber, get the car onto a level piece of concrete and get a square piece of board approx 15" x 20". Push the board up against the rear tyre and measure from the vertical edge of the board to the lowesr point on the wheel rim and from the vertical edge to the highest point on the rim. The top dimension should be either the same or greater than the bottom position reading. This is the actual camber which you can translate into degrees if you wish. As a guide anything between zero difference and 1/8" more to the top should be ok. If not, file out the hole in the rad. arm bracket and keep checking until it's correct. then weld a large penny-washer into place to hold the setting.
Remember, the rear suspension MUST toe-in between 1/16" and 1/8" or else it will never handle well. You can set this at the same time as the camber.
The neg camber on the front helps to overcome the different suspension arm lengths and the changes to the basic geometry as the suspension moves up and down.
I hope this helps,
Peter
With wide radial tyres the best roadholding on a true trailing arm suspension, where the plane of the wheel centre moves absolutely vertically, will always be 0 degrees, but a little bit of negative is fine at standard ride heights.
To measure the actual camber, get the car onto a level piece of concrete and get a square piece of board approx 15" x 20". Push the board up against the rear tyre and measure from the vertical edge of the board to the lowesr point on the wheel rim and from the vertical edge to the highest point on the rim. The top dimension should be either the same or greater than the bottom position reading. This is the actual camber which you can translate into degrees if you wish. As a guide anything between zero difference and 1/8" more to the top should be ok. If not, file out the hole in the rad. arm bracket and keep checking until it's correct. then weld a large penny-washer into place to hold the setting.
Remember, the rear suspension MUST toe-in between 1/16" and 1/8" or else it will never handle well. You can set this at the same time as the camber.
The neg camber on the front helps to overcome the different suspension arm lengths and the changes to the basic geometry as the suspension moves up and down.
I hope this helps,
Peter
Cooperman said:
With wide radial tyres the best roadholding on a true trailing arm suspension, where the plane of the wheel centre moves absolutely vertically, will always be 0 degrees, but a little bit of negative is fine at standard ride heights.
Generally, the purpose of adding negative camber is to compensate for body roll so the outer wheel remains close to vertical when the car is loaded up in a corner. This is why people put so much effort into unequal length wishbones, so you can run low static camber but get significant camber correction on roll. Doesn't the same logic apply to minis?
I've always had the best handling by running 0 to 1/2 deg neg on the back. I think the reason for this is that with more neg on the back, when you do want to kill the understeer, say in a tightening corner, and you lift-off to induce some oversteer, too much neg on the back reduces the tendancy for the car to turn-in and spoils, to some extent, the natural good handling transition from power-on to power-off. I'm only guessing here, but it seems logical, especially in view of the way positive rear camber induces terrible oversteer to the point of it being dangerous, especially in the wet.
On all my rally cars I set 0 to 0.5 deg neg and that's with a slightly increased ride height, 10" wheels and 165/70x10 tyres. It always seems very stable and predictable on most surfaces.
Maybe on a race car with lots of neg on the front, very low and with wide racing tyres you would get a benefit from, say 1 to 2 deg neg on the back, but I don't have the experience on this to comment.
On all my rally cars I set 0 to 0.5 deg neg and that's with a slightly increased ride height, 10" wheels and 165/70x10 tyres. It always seems very stable and predictable on most surfaces.
Maybe on a race car with lots of neg on the front, very low and with wide racing tyres you would get a benefit from, say 1 to 2 deg neg on the back, but I don't have the experience on this to comment.
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