Alignment - Fully Laden vs. Driver-only?

[maxm50]

Hi all,
I'm taking my Fiat to a trusted local mechanic for an alignment on Monday. I know that all of the alignment specs for our Spiders are specified "fully laden", which for my 1981 is listed as Driver + Passenger + 130lbs in trunk.

I came from the Miata world, which shares a double-A-arm suspension design in the front. The passionate Miata folks align their cars "how they are driven" - meaning if you typically drive alone, you align it with just your weight in the driver seat. If you typically ride with a passenger, then align it with a passenger's weight also.

I'm struggling to understand why this methodology isn't used in Fiat land. Why should I load the car with 2 people + 130lbs in the trunk if I rarely ever drive it like that? 90% of the time, I'm the only one in the car and with barely anything in the trunk. And if I do have a passenger, I'm not gonna huck it around corners like a madman.

My plan is to ask for the following:
180lbs in the driver's seat
Toe: 1/8” (3.2mm) or 0.30° total (1/16” (1.6mm) or 0.15° per side) (this is double what I used on Miatas)
Camber: -0.5° (Why oh why does the Fiat factory spec call for POSITIVE camber?!)
Caster: +3.5° (same as factory spec, would be fine with a half degree less to get lighter steering)

Anyone see a problem with this thinking?

[18Fiatsandcounting]

I'm struggling to understand why this methodology isn't used in Fiat land. Why should I load the car with 2 people + 130lbs in the trunk if I rarely ever drive it like that?

Fiat did some strange things, and the alignment spec is one of them. I guess the issue is that we know what the alignment should be for 2 specs and 130lbs in the trunk, but we don't really know what it should be for just the driver. What would you set the alignment to?

For what it's worth, and I believe this to be accurate, below is what I found for the unladen specs for a '78 spider. Perhaps your 1981 is similar. It's also fairly close to your plan, although I think your plan is for less toe-in. Due to the design of the spider front suspension, the tires "toe out" when the front end is loaded. You can demonstrate this by taping a yardstick to your front tire, level to the ground, and then sitting (maybe with some gentle bouncing) on the fender for that wheel. The front tip of the yardstick will move outward.

Anyway, here are unladen specs:

TOE: +.157 to +.314 (+4 to +8mm)
CAMBER: -0*20' to +0*40'
CASTER: +2*40' to +3*40'

Hope this helps.

-Bryan

[Nut124]

Does one need to diet down to -60's Italian male weight of 150lbs before sitting in the car for the alignment?

[18Fiatsandcounting]

Ideally, yes. The fully laden weight of a spider is two 150 lb occupants plus 130 lbs of luggage, or 430 lbs total.

Sigh.... I haven't been that weight since I was 15 years old or so.

-Bryan

[Nut124]

I did the front end alignment myself some years ago when rebuilding the front suspension. I did it with the car on blocks, no springs in the front and steering arm disconnected so the hub assy could move up/down and turn easy. I had a digital angle meter on the hub and I would move the hub up/down L/R to examine the caster, camber. I have no notes on this, quite a few years back, but I think I went with a bit more camber trying to predict how actual load would affect the slack, free play at each connection.

I did the toe-in with the string method. This worked fine for me for the last 15+ years. Never had a shop alignment.

[maxm50]

Hey Bryan and Nut,
Thanks for the replies! This is helpful, especially the unladen spec. I think I'll stick with my plan on the toe and camber, but will drop my caster request to 3deg so that it sits in the middle of that spec. I wonder if caster increases as suspension compresses?

I think I'll like being at the lower end of the toe spec - I typically like cars that turn in quickly, especially a "toy" car like this that barely ever sees freeway usage, and is more typically used on 35-55mph windy roads.

Will report back and let you know how it feels after the alignment!

[Nut124]

If you ever think of doing auto-cross or running on a track, more camber would help traction, speed in the corners.