Camber\toe specs

[kavadarci]

Hi,
Car goes for alignment today.
I know my mechanic will ask me what settings "I" want.
I know the back is -1.1 but no idea for the front.
Can someone advise what is the best setting for city driving, no track. the car is lowered slightly lower than euro specs with 16" rims

Thank you.

[Bill Verburg]

Originally Posted by kavadarci

Hi,
Car goes for alignment today.
I know my mechanic will ask me what settings "I" want.
I know the back is -1.1 but no idea for the front.
Can someone advise what is the best setting for city driving, no track. the car is lowered slightly lower than euro specs with 16" rims

Thank you.

use the factory specs

[DRACO A5OG]

my 2 cents,

Mine is modified euro height with a slight forward rake.

Front:
Camber -0.75 ( to keep from scrapping fenders due to lowering )
Toe In 1/32
Caster +6.5

Rear:
Camber -1.50
Toe In 1/16

More important is a proper Corner Balance with your weight in the car.

She is my daily but I drive aggressively on the street and can go AX/DE if I choose to. But she loves the canyons

Caveat, you will need to be careful of ramps/driveways. Also you will need a minimum a bump steer kit to lower the steering rack due to lowering or better yet re-position the spindles.

[Trackrash]

There are two things to consider, assuming only street driving.

You don't mention what tire size you have.

Also you will probably find that with a lowered car you will not be able to get the front camber where you want it.

For a street only car I would want zero to about -.5* in the front.

[kavadarci]

I have 16" 205/55/16 front and 225/50/16 back, 8"

[WP0ZZZ]

Originally Posted by Bill Verburg

use the factory specs

I find it quite interesting that the RSs have less rear camber than the standard models. Any clue as to why this might be?

[manbridge 74]

Possibly for better braking? I imagine they were pretty stiff so it’s likely they didn’t have excessive body roll.

[WP0ZZZ]

Originally Posted by manbridge 74

Possibly for better braking? I imagine they were pretty stiff so it’s likely they didn’t have excessive body roll.

Maybe but the race setup (which will presumably be very stiff) on the rightmost column in the table has 1.5 deg front camber and 2.5 deg rear camber.

[Bill Verburg]

Originally Posted by WP0ZZZ

I find it quite interesting that the RSs have less rear camber than the standard models. Any clue as to why this might be?

I don't know for sure but based on what they still do today when delivering factory Cup or race cars like the RSRs, the cars are delivered w/ a very mild alignment w/ the expectation that the owners team will realign to their taste.

I know that on my track car I like a different alignment at different tracks.

[WP0ZZZ]

Originally Posted by Bill Verburg

I don't know for sure but based on what they still do today when delivering factory Cup or race cars like the RSRs, the cars are delivered w/ a very mild alignment w/ the expectation that the owners team will realign to their taste.

Ah, that could certainly be the reason!

Originally Posted by Bill Verburg

I know that on my track car I like a different alignment at different tracks.

I've seen that it is quite common to recommend 1 extra degree of camber at the rear than at the front (same difference as the factory settings). However, a local rally driver told me that he was running lots of front camber and only -0.5 deg rear camber... Since I don't really know how stiff he was running front and rear, it's hard to get much insight from his settings.

I think that rather than obsessing with alignment settings now it will be better if I start with something not very extreme (e.g. -0.5 deg front/-1.5 deg rear) and decide where to move next based on car behavior.

[Bill Verburg]

decreasing camber at a given end or decreasing toe has the effect of speeding up the reaction at that end, by running less camber in back you speed up that end, ie increase over steer. You can totally change the dynamic behavior of a car by tuning the ends differently.

from the 964 up there is an additional tuning component, Kinetic Toe which is controlled by bushings in the rear suspension. Most race cars will eliminate this by using mono-balls, On a 993 w/ mono-balls the KT effect is eliminated but you can still adjust the bump toe curves w/ dramatic effect.

[WP0ZZZ]

Originally Posted by Bill Verburg

by running less camber in back you speed up that end, ie increase over steer. You can totally change the dynamic behavior of a car by tuning the ends differently.

Agreed. Relative roll stiffness between front/rear axles also plays a key part in the under/over-steering behavior of the car. That's why I think it's hard to consider alignment unless one knows the stiffnesses.

Once I install all my new Elephant Racing parts I'll be running 22/29 mm torsion bars with stock anti-roll bars (1980 Euro SC) and mono-balls everywhere except for polybronze spring plate bushings. I want to drive the car for a bit before deciding on the new anti-roll bars.

Bill, do have an idea about what sort of car balance I should expect from the setup above with stock anti-roll bars?

[Bill Verburg]

Originally Posted by WP0ZZZ

Agreed. Relative roll stiffness between front/rear axles also plays a key part in the under/over-steering behavior of the car. That's why I think it's hard to consider alignment unless one knows the stiffnesses.

Once I install all my new Elephant Racing parts I'll be running 22/29 mm torsion bars with stock anti-roll bars (1980 Euro SC) and mono-balls everywhere except for polybronze spring plate bushings. I want to drive the car for a bit before deciding on the new anti-roll bars.

Bill, do have an idea about what sort of car balance I should expect from the setup above with stock anti-roll bars?

changing from 19/23 to 22/29 all else being equal reduces understeer by ~25%
the wheel rates go from 152/107 lb/in to 273/269 ie a Δ or 45 lb/in goes to a Δ of 4 lb/in

[WP0ZZZ]

Thanks very much Bill!

Originally Posted by Bill Verburg

the wheel rates go from 152/107 lb/in to 273/269

Those rates consider that both wheels in an axle move up/down together, right? Or are they for only one wheel moving while the other is fixed and therefore they take into account the effect of the anti-roll bars?

[Bill Verburg]

Originally Posted by WP0ZZZ

Thanks very much Bill!



Those rates consider that both wheels in an axle move up/down together, right? Or are they for only one wheel moving while the other is fixed and therefore they take into account the effect of the anti-roll bars?

each wheel rate is independent of the other wheels

[WP0ZZZ]

Originally Posted by Bill Verburg

each wheel rate is independent of the other wheels

I assume that this means that the rates you provided are for a car with torsion bars only and no swaybars so that wheel rates are independent, right?

My confusion comes from the fact that for a car with swaybars, if we fix the FrontLeft wheel and measure the rate on the FrontRight wheel we get a different answer than if we let the FrontLeft free to move up & down in the air and measure the rate on the FrontRight wheel.

[Bill Verburg]

Originally Posted by WP0ZZZ

I assume that this means that the rates you provided are for a car with torsion bars only and no swaybars so that wheel rates are independent, right?

My confusion comes from the fact that for a car with swaybars, if we fix the FrontLeft wheel and measure the rate on the FrontRight wheel we get a different answer than if we let the FrontLeft free to move up & down in the air and measure the rate on the FrontRight wheel.

Sway bar effect is not included in the #s I posted

When setting up a car first choose the basic suspension ie spring rates, then adjust w/ wheels, tires, sways and alignment.

[WP0ZZZ]

Originally Posted by Bill Verburg

Sway bar effect is not included in the #s I posted

When setting up a car first choose the basic suspension ie spring rates, then adjust w/ wheels, tires, sways and alignment.

Cool. Thanks for that!

I'm just used to analyze mechanical balance of a car by looking at the roll stiffness of each axle (in Nm/deg or lbft/deg) with everything connected. It's not an easy number to get because it requires to combine several stiffnesses and mechanical advantages: corner torsion bars, sway bars, tires, etc. But it gives a nice summary of how tires load up in a steady state corner!

Do you know the rates of stock swaybars at the wheels?

[Bill Verburg]

Originally Posted by WP0ZZZ

...

Do you know the rates of stock swaybars at the wheels?

Not off hand