Milton -
Very nice explanation of steering geometry - this one goes in the archive!
Gary McCormick
San Jose, CA
milton3 wrote:
> Jeff,
>
> I'm guessing/hoping Datsun doesn't list specs because this is a Sports
> Car. If you go to a good shop with techs that understand what they are
> doing/why they are aligning the car - you should have no problem getting
> the car aligned.
>
> Basically, have an alignment done to encourage the car to respond as you
> like, and protect against tire wear to fit your budget.
>
> Here is a little alignment info to get you going:
>
> TOE: This refers to the degree that the tires are parallel. A perfectly
> parrallel pair of tires is said to have zero or neutral toe. Most
> manufacturers spec a slight toe-in (that is to say that they set up tires
> a little pigeon toed versus west-footed). This prevents tramlining (tires
> following grooves in road instead of steering inputs), and generally
> promotes understeer at turn-in. Neutral toe or slight toe-out will
> provide you with faster turn-in, but neutral tends to tramline and toe-out
> wears tires pretty quickly when combined with camber. I prefer neutral
> toe as it turns in fairly quickly, but it is much easier on the tire wear
> (read pocket) than a toe-out setup. I would set up a dedicated track car
> with neutral toe because fast turn-ins at speed can get hairy, or a
> dedicated autoX car with slight toe-out to get the car to turn quickly.
>
> Camber: The degree to which the top of the tires lean in (/_\) or out
> (\_/) relative to the contact patch. When a car is turning, lateral
> forces work in concert with the downward gravitational force. So, by
> setting up a tire to lean in (negative camber), you are placing it in a
> state of readiness to best handle the lateral forces. Negative camber
> costs you tire wear (inside of the tires) when you spend too much time
> traveling straight. If you are attracted to twisties, a negative camber
> setup can actually prolong tire life - but few of us have that many
> twisties available. Manufacturers again tend toward slight positive
> camber to promote understeer.
>
> Caster: This is the most difficult to explain. It is the degree to which
> camber is made more negative as the wheels are turned. Just realize that
> it is rarely adjustable, and the manufacturers set this one up for the
> type of ride. I.e., Mercedes is famous for very high caster. High caster
> is noticed primarily by how much the car tends to return to straight track
> following a turn. Low caster cars just keep turning - high caster cars
> auto center. As you can guess, high caster can substitute for negative
> camber to an extent. It is generally only adjustable by changing the
> suspension geometry radically.
>
> So, the point of an alignment is to set optimal toe and camber given a
> fixed caster setting. And, you can make these determinations yourself.
> Toe figures are generally expressed as plus or minus a couple degrees,
> Camber figures can get a lot more radical and can extend to the tens of
> degrees, but are extremely radical and of questionable benefit past about
> 10 degrees.
>
> My suggestion is zero toe and as much negative camber as is available by
> adjustment (prolly 2 to 5 degrees tops, but I haven't looked at roadster
> alignment yet). Gives a quick, performance oriented response while not
> being too bad on tires as long as you remember to seek out the twisties
> often. If you are consistently heating up the inside of the tires more
> than the outside, you may want to dial the camber back.
>
> Hope this helped. There are many places on the web that do a more
> thorough (i.e., with pictures) job of explaining suspension geometry
> issues. Don't hesitate to search, but if you get caught "stringing" your
> car for a self alignment - plan to spend all day the first time.
>
> Milton
>
> On 28 Aug 2002, at 13:05, maurell@bellsouth.net wrote:
>
> > alignment done. they say they don't have the specs? can anybody help me
> > with that. my clymer manual list some specs, should that be enough?
>
> milton <milton3@pobox.com>
>
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