suspension geometry settings

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tiaf124

suspension geometry settings

Post by tiaf124 »

What geometry settings (camber ,caster ,toe ) would you recommend for a daily driven 124 plus a few occasional quick rides?
The car has a revised standard height suspension with only a set of stiffer KYB absorbers.What would the drawbacks of excessive caster or toe .I was suggested for 4 deg positive caster , or should i insist in the factory specs ?
Thanks
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kmead
Posts: 1069
Joined: Sat Aug 02, 2008 9:24 pm
Your car is a: 1969 850 SC 1970 124 SC 85 X19
Location: Grand Rapids, MI

Re: suspension geometry settings

Post by kmead »

.100" toe in
-.5° camber
standard caster value which is 3°30" as I recall.

This is a very different camber setting from the factory, but it will give you much better handling especially with modern tires which tend do better with negative camber versus positive camber. You may have somewhat more tire wear but most of us dry rot our tires before wearing them out.

The negative to this will be somewhat heavier steering when parking.

More caster will reduce the tendency to tramline or follow the rain grooves in roads. This will also feel a bit more stable at speed, again with more effort at low speeds to turn the wheel.
Karl

1969 Fiat 850 Sports Coupe
1970 Fiat 124 Sports Coupe
1985 Bertone X1/9
tiaf124

Re: suspension geometry settings

Post by tiaf124 »

Thank you and happy new year to everyone.Are there any side effects with toe in?
I thought that only excess caster makes steering heavy and that camber affects only understeer.
Hope to eliminate understeer a bit though
So Cal Mark

Re: suspension geometry settings

Post by So Cal Mark »

you don't want or need excessive toe in. Set toe close to zero or about 1/16" in otherwise you're dragging those tires down the road
tiaf124

Re: suspension geometry settings

Post by tiaf124 »

So Cal Mark wrote:you don't want or need excessive toe in. Set toe close to zero or about 1/16" in otherwise you're dragging those tires down the road
You suggest almost zero toe ... 2 124 manuals that i just browsed gives 0.12'' on rim edge with car laden(2 persons +130lb luggage) for stability in straight line
Is it equaly steady with so little toe ?
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azruss
Posts: 3659
Joined: Sun May 30, 2010 12:24 pm
Your car is a: 80 Fiat 2000 FI

Re: suspension geometry settings

Post by azruss »

the last time i rebuilt my suspension, i set all the geometry myself and have set my own toe-in using a homemade device. I set all to factory specs. Ended up with a car that tracked great and predictable as well as got great tire wear. (65k miles). The one thing i like best about my spider was the ability to place the car on the road within +/-6" of my intention, regardless of road grooves or cross winds. When you look at road irregularities and tire movement while driving, i'm not convinced that a .030" difference in toe-in would be noticable.
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kmead
Posts: 1069
Joined: Sat Aug 02, 2008 9:24 pm
Your car is a: 1969 850 SC 1970 124 SC 85 X19
Location: Grand Rapids, MI

Re: suspension geometry settings

Post by kmead »

Regarding the toe setting, keep in mind the actual toe under dynamic use will be considerably less than the .100".

As the car goes down the road, the front wheels each try to turn to the outside due to the rest of the suspension settings/geometry. This compresses the various ball joints in the steering parts. This compression takes up the tolerances in those parts and the result is nearly no toe in as the car goes down the road.

If you have too little toe in, the dynamic toe will actually be toe out and will tend to wear the inside of the front tires.

As to whether it should be .060, .10 or .12 of an inch, I cannot say. Back in the day the Fiat engineers did the calculations of the tolerances of the parts and arrived at their number which delivered a car which was stable, sporting and didn't wear its tires unduly.

I have had good success with the settings I gave, they can certainly be adjusted to what works well for you and your car.

As an aside. Front wheel drive cars are set up with toe out. The reason for this is that the drive of the front wheels causes the wheels to want to turn inward. The inward turning force takes up the tolerances of the steering rack and again tends to deliver a 0 toe condition under actual use.

I hope that was clear.
Karl

1969 Fiat 850 Sports Coupe
1970 Fiat 124 Sports Coupe
1985 Bertone X1/9
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v6spider
Posts: 1035
Joined: Tue Feb 28, 2006 6:57 pm
Your car is a: 4.3L V6 Powered 1972 124 FIAT Spider
Location: Mount Vernon WA

Re: suspension geometry settings

Post by v6spider »

I am with mark go sparing on the toe. Also +3 ° caster is plenty especially with wide tires...

Cheers!
Rob
http://www.v6spider.com
4.3L V6 Powered 1972 124 FIAT Spider
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