Front alignment question | FerrariChat

Front alignment question

Discussion in 'Technical Q&A' started by brent Lachelt, Apr 13, 2004.

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  1. brent Lachelt

    brent Lachelt Formula 3
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    #1 brent Lachelt, Apr 13, 2004
    On the front suspension of a 308 there are shims that are used on what is called the lower fork. These are the 2 pick up points for the lower front A-arms. I assume these shims are used as part of the alignment for toe out. I know in a previous thread someone gave some inital set up specs on shims for the upper and lower ball joints. My question is does anyone know what the inital setup would be in regard to those lower A-arm shims, to get a ball park. The shims have different widths 2mm, 3mm etc. Also is the toe on the front set by both these shims and the tow links from the steering rack?

    Thanks
    Brent
     
  2. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
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    #2 Mitch Alsup, Apr 13, 2004
    At the front, the shims control camber and caster (to a minor extent) and use use the steering linkage adjustment to control toe.

    At the rear, the shims control camber and toe directly.
     
  3. brent Lachelt

    brent Lachelt Formula 3
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    #3 brent Lachelt, Apr 14, 2004
    One other point. I have never had the car aligned before. Right now the front has obvious toe out and the rear obvious toe in. Have owned it 2 years. This is exactly how we used to set up our formula atlantic cars in the past. However, I'm not sure this is best for a 308. I'm currently running 17x8 fronts 17x9 rears. 225/45 fronts 255/40 rears. Qa1 adjustable coil over shocks 300 lb springs in the front and 250 springs in the rear. Also the car has been lowered about 2 inches in the front and 1.5 inches in the rear The car tends to pull to the right because of too much toe out on the right front compared to the left front.
     
  4. ferrarifixer

    ferrarifixer F1 Veteran
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    #4 ferrarifixer, Apr 14, 2004
    Toe won't CAUSE pulling under any circumstances, but pulling to one side can be a SYMPTOM of uneven caster/camber, or a braking problem.

    Any uneven toe side to side will simply be offset by an "off straight" steering wheel.

    Check your caster to be around 4-6 degrees each side but EVEN. Check camber to be 0.5 to 2.5 each side but EVEN. Then toe it about 0.5 to 3mm total in front and 2 to 6mm total in rear.

    Trim for desired tyre wear and turn in, but this is a totally driver directed area and depends totally on your tyres and driving style.

    The stiffer your springs are, the more important the corner weights are. So check your full set up. Keep the ride height and rake sensible, with the nose lower than the rear at all times.

    Good luck
     
  5. brent Lachelt

    brent Lachelt Formula 3
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    #5 brent Lachelt, Apr 14, 2004
    Phil you bring up a super point. This is what is really happening when I drive the car. To keep the car going straight down the road I need to have the steering wheel postioned at 11 -5 o'clock instead of 12-6 o'clock. If the wheel is at 12- 6 o'clock (as it should be) it begins to angle to the right. After reading your thread I think my description is incorrect. The car isn't really pulling to the right but rather moving there when the steering wheel is at 12- 6 o'clock. Is that what you mean when you say that any uneven toe side to side will simply be offset by an "off straight" steering wheel. That makes perfect sense. Am I correct with that line of thinking? If so is the toe adjusted by the toe links on the steering rack alone?
     
  6. Mitch Alsup

    Mitch Alsup F1 Veteran

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    #6 Mitch Alsup, Apr 14, 2004
    Before attempting an alignment, get the corner weights set in the right ball park, then do a preliminary alignment on the car, then get the cornerweights set right, then check the actual alignment. Repeat as necessary, use shims under the tires to get the car absolutely dead level and place drivers weight in the drivers seat, 1/2 tank of gas, full fluids, tires at 41 PSI (track HOT pressure). 2mm out of level will invalidate the alignment--these cars are sensitive.

    With the amount of lowering you have done, caster is probably more at fault than toe, although differential camber can cause pulls in either direction. However, you should also redo the bump steer calibration (height of steering rack) to prevent the car from following road surface irregualrities due to bump induced steering.

    Toe on these cars is used to deaden the cars response to situations. You can enliven steering response by using positive toe at the front, or calm the car by using negative toe at the front. At the rear you want enough toe that the car does not toe out under extreme conditions of acceleration squat or decelleration extension.

    When you finally set the front toe, have the driver hold the steering wheel where he thinks deal level is, and adjust the steering on both sides so that the wheels are dead straight with the desired toe evenly on both sides. I like to roll the car off the alignment shims after each adjustment to remove side loads on the tires from influencing measurements.
     

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