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Looking for alignment spec suggestions

Discussion in 'Technical Q&A' started by Bob308GTS, Jan 15, 2004.

  1. Bob308GTS

    Bob308GTS Formula 3

    Sep 26, 2001
    1,109
    Aurora,IL
    Full Name:
    Bob Campen
    I’m about 3/4 of the way done with my suspension rebuild on my 79 308GTS, time to start thinking about alignment specs. Tires are Dunlop SP8000, 225/50-16 front and 245/45-16 rear, stock sway bars with ES mounts, new Konis set 1.5 turns out with stock springs, new ES inner bushings all around, new ball joints and tie rod ends, front lowered .5”. No track use just spirited road driving, tire wear is not a real concern, looking for suggestions for front and rear settings to make it handle better than new.

    Thanks
     
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  3. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,004
    No track use and stock-ish tire sizes implies use/start-with standard factory settings.

    What aspect of the current handling are you willing to sacrifice for what increment in performance:

    Straight line stability for turn in?
    Turn in for straight line stbility?
    Absolute cornering grip for control into and durring slides?
    turn in rear grip for post apex power application grip?
    stability under brakes versus turn in?

    add in a dose of:

    Should the tire sizes be changed to maximize performance capabilities of modern high performance rubber? (maybe)
    What do wider tires do to older alignment settings? (A lot)
    Does the driver have preferences that alter alignment/geometry settings? (likely)
    Has chassis been strengthened?
    Has power been added?

    and suspension alignment and geometry is a tricky subject.
     
  4. Bob308GTS

    Bob308GTS Formula 3

    Sep 26, 2001
    1,109
    Aurora,IL
    Full Name:
    Bob Campen
    I know there are as many answers to this as there are Fchat users, but to narrow things down a bit

    straight line stabilty is a must
    would like a little better turn in
    a little less understeer
    chassis is stock
    stock carbed engine, no cats, custom exhaust, rejetted carbs

    really just would like to make better use of the semi-modern tires

    gut feel is to leave the rear with stock settings, change the front from +20' camber to -30' with 2mm toe in and see how it works

    looking for ideas
     
  5. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
    2,559
    Chicago
    Full Name:
    Philip
    Stock spec on my GTB is for basically upright (little to no camber), 4 degrees of caster, some toe-in at the front (sorry, I don't have the specs to hand - they are all in the OM and I wanted to illustrate the point that follows). Rear has a little negative camber and quite a lot of toe.

    I have spent two seasons running stock factory spec. This year I am going to more aggressive setting given the amount of track use the car is seeing. For road setting (even with 225/245 tires) I'd follow the stock setting as Mitch advises unless you have a specific set of characteristics you are trying to create.

    FYI, the guys at QV London have recommended the following (track) alignment:
    Front: same toe-in as stock; increase to 3 to 3.5 degrees negative camber (requires modifying the a-arm mounting forks); stock caster.
    Rear, 2 to 2.5 negative camber, keep the stock toe (the flex on the bushings can cause toe-out if the toe is backed down and most of us wouldn't enjoy this chassis characteristic!

    Incidentally, the cars set up by QV finished 1-2-3 in the 2003 Ferrari Classic series launched in the UK for (essentially stock) 308s/328s.
     
  6. Bob308GTS

    Bob308GTS Formula 3

    Sep 26, 2001
    1,109
    Aurora,IL
    Full Name:
    Bob Campen
    Phillip, love your yellow GTB

    I have all the stock specs, the GTS uses + camber on the front and the GTB is a very small amount of - camber as stock. It just seems the stock settings can be improved.

    BTW instead of modifying the stock front yokes, couldn't you use rear ones instead, they are the same except for a longer mount stud, which can be threaded down and cut if needed. By my calculations it takes 4.5mm of shim at the front to change camber by 1 degree, staying with the stock front yokes one could have up to 1 degree - camber, so to achieve -3.5 the mounting stud would need to be about 12mm longer
     
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  8. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
    2,559
    Chicago
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    Philip
    Bob, yes, I did a similar calc the other day and produced a comparable result for the fronts. I'll have the bolt welds cut out of the fork, pull the bolt, and have a longer bolt welded in. From memory, at the front there is no issue on bolt length. At the rear you have to be a bit more careful given the (lack of) clearance to the engine.

    Unfortunately the car is covered in dust (I usually use a cover but have been doing interior and exterior work on it) so doesn't look too pretty right now. It is nice to have it full of fluids though and not a SINGLE drop of fluid be on the floor! It was a lot of work (and a PITA) to remove all the motor mounts, pull the studs, add stat-o-seals on the pan nuts, clean it all up, add permatex and reassemble. And changing the diff seals is a good way to take some skin off your knuckles as you're breaking the axles. Anyway, it is dry and clean. Hopefully it will stay that way!

    Bob, are you going to come to the 2004 track weekend? We are hoping to have some star attractions this year...
     
  9. Bob308GTS

    Bob308GTS Formula 3

    Sep 26, 2001
    1,109
    Aurora,IL
    Full Name:
    Bob Campen
    Going to try to make the track day, as a spectator.

    drivers side rear yoke on the front does have a close clearance, at least on my 79 due to the battery cable and brake line running right behind the nut
     
  10. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,004
    "straight line stabilty is a must
    would like a little better turn in"

    Then you did not understand that you have to choose A) or B) but not both. The adjustments you make to do A) hurt B) and vice versa. The factory found a suitable balance between A) and B). If you want more of both, you need a different suspension geometry (e.g. not feasible).

    "a little less understeer"

    Lower the rear or put more tire on the front or put less tire on the rear or put less pressure in the rear tires.
     
  11. ferrarifixer

    ferrarifixer F1 Veteran
    BANNED

    Jul 22, 2003
    8,520
    Melbourne
    Full Name:
    Phil Hughes
    Try this

    front toe in 1-2mm total if using 16" wheels, less if 14".
    Front castor up to max available, but symmetrical....5 deg is normal
    Front camber to 1.5 deg neg, swing the castor some more while doing the camber, need a good alignment shop to do this.

    Rear toe in 3-3.5 mm total for 16" wheels, less if 14"
    Rear camber 2 deg neg

    Make sure perfect alignment of front to rear....thrust angle 0.10' max, 0.0 ideally

    Make sure weight in drivers seat while doing adjustments, and at least half a tank of fuel.

    Putting more neg on front will lower your ride height even more than you have with springs already, make sure your wheel arch heights are not more than 20mm lower on the ront, than the back...from the bottom edge of the wheel rim is the best way to measure...not the ground.

    The best thing to do would be to fit stiffer front springs....190lb is a good choice, up from the std 155 ish. But their length will need careful calculation, and/or adjustable platforms/spacers.

    Tyre pressures around 33 lbs front, 36 lbs rear .....cold. 10%more hot.
     
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  13. Corsa

    Corsa Karting

    Nov 1, 2003
    109
    Stockholm
    Full Name:
    Peter
    Anyone tried toe OUT front and rear as I have? (328 GTB with ohlins shocks and stiffer springs).
    It gives quick turn-in and some straight line instability on medium gas. During braking and hard acceleration the stability is quite good.

    Ciao
    Peter
     
  14. davehelms

    davehelms F1 Rookie

    Jan 3, 2004
    4,629
    Full Name:
    Dave Helms
    To customers cars, I add neg camber to front and rear. I do it in .5 degree increments and have my customers keep a journal of how the car handles and its changes before I make another attempt. I keep the front caster near stock so the steering returns to straight. To aid in turn in I take out some of the toe in, in the rear. After making the changes, letting the customer drive the car for awhile (days), and reading their feed back in the journal I have them keep in the door pocket (on the race cars, the debriefing was when the driver was still straped in and just off the track), I can then opt to make more agressive changes or keep them small.
    Depends on how agressive you want to get. Going from stock settings to a full race setting seems a bit of a leap. You will be delighted at the change you would feel with all suspension rebuilt and a stock setting. With this in mind my feelings are to make smaller changes and see what suits your driving style best. Easier to adapt the car to your style, than have you change to adapt to the cars style.
    Dave
     
  15. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
    2,559
    Chicago
    Full Name:
    Philip
    Bob et al: an update on (my) alignment

    First, I pulled all the chassis forks (sorry, don't know the correct term for the fork that holds the a-arm into the chassis). Rears can be used on the front, although you are likely to need to cut them down by 15 or 20mm. Stock fronts are 43mm, rears 85mm (underside of bolt head to tip). For 3 to 3.5 degrees negative (see below), you need another 15 - 16mm on the front so the fronts have got to be close to 60mm in length. I cut mine at 65mm (so I cut 20mm from the rears). For the "old" fronts, I had the 43mm studs cut out and used a hardened bolt - I think 100 mm length. We cut the heads down, welded the bolts in and then I had all 8 forks cad plated for longevity. Were I doing it again, I'd probably go for 95 at the rear, that way the car can be returned to stock setting w/o changing anything (one bolt would be a little close to the gearbox cover plate on the passenger side at the current length).

    For specs, I talked to QV London. These guys set up the cars that finished first and second in the UK Ferrari Classic Racing Series (includes Daytonas, 328s, 308s etc) and have set up the Challenge cars that one the Series 4x in the UK. See:

    http://www.ferrariownersclub.co.uk/events/ferrari_classic_03/index.asp

    (Oh why, oh why don't we have something similar over here...almost enough to make me go back to the UK. Ok, joing aside, back to the thread...)

    So, for track use, on the 308, their recommendation:
    Front. Castor, unchanged. Camber, negative 3 to 3.5 degrees; Toe, none;
    Rear: Camber, 2 degrees; Toe, stock.

    On the front, I am going to start with about 2.5 degrees and leave in a little toe (maybe 1mm). To get it close, and to avoid lots of spacers (and images of shims falling all over the place if something "untoward" happens), I found thick washers that can be stacked.

    On the rears I have added another degree.

    We'll align it on the rack when the weather improves. I've also added higher rate (and slightly shorter) springs.

    Once tried at this level, I'll measure tire temps and adjust from there.

    Philip
     

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