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my front tires seam to slip on hard low speed coners,,
 

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so if i am running stock castor.. ....try less castor?
 

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If the tyre is going into positive camber during fast-ish tight turns (which it probably is), then more caster will help as you gain negative camber on the outside wheel with turn. Even more positive caster will give even more negative camber gain.
Reducing caster will increase understeer, reduce the self centering effect and probably steering feel.
 

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No. You need more caster. This produces more negative camber on the outside tire, but only when turning, which should reduce your understeer.

However, there can actually be an opposite effect on tight turns if you have very wide tires. The tighter the turn, the more negative camber, and this can reduce the tire contact patch since the outside of the wide tire lifts off of the pavement. Again, this tends to occur with very wide tires. I use 275/35x15 on my autocross spider, and verified the contact patch loss with a pyrometer (the outside of the tire was much cooler than the inside).

so if i am running stock castor.. ....try less castor?
 

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would caster afffect turn in?

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my front tires seam to slip on hard low speed coners
Think of caster as the same as the rake of a bicycle or motorcycle fork. Which one turns better Schwinn Apple Crate or a Bianci road bike? Here's why: Bicycle and motorcycle geometry - Wikipedia, the free encyclopedia

On the other hand, which one will have better directional stability? Steering and Suspension: Caster

What the guys are talking about is camber gain due to when the front suspension compresses in the turn, the upper control arm "pushes" the top of the spindle upright out causing the top of the wheel to tilt out on the outside wheel and the top tilts in on the inside. This tilting is not good for traction because your tread is no longer parallel in contact with the pavement (duh). This is why they created "unequal length wishbone" suspension. The start angle of the upper "A" arm matters as well (Body roll adds to the equation). Designed right you can maintain negative camber under compression. Initial negative camber helps as the top tilts out (from a negative camber initial stance), you end up with a fairly perpendicular outside front tire which gives you good traction and directional control - what you're looking for. This is why on race cars when you see them coming at you on the straight the front wheels are tilted inwards at the top.

Your problem is probably unrelated to caster and more likely your alignment is not right. Check Toe and Ackerman. Remember, how does a tank steer?

Suspension set-up should change depending on the track. Long straightaways and sweeping turns? Use 3° caster, 1.5-2° Negative camber, zero toe. Short runs w/ sharp turns? Use 1.5° caster (stock value for 116/119 methinks) and 2.5-3° negative camber, 2mm toe out.
 

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I run as much Castor as I can on 105/115 race cars. This makes slow speed steering very heavy (Watch for stressing out and breaking your steering box) and your negative camber gain fast on the outside tire. Fat hard radials will lose grip as George said.

Radials like negative Camber for cornering, but if you put tons of static negative camber without camber gain (from castor or other suspension geometry changes) you will overheat and overwork the inside ribbon of your tires, especially under braking (flat spot city)
 

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Absolutely. However, there's a practical limit to how much caster you can run - esp. on the 119 chassis cars due to the size of the opening in the upper "A" arm 'cause the shock runs through it. If a coil-over is used, even more so.

Chassis and suspension is for engineers. It's rather complicated. There are other aspects to consider as well.
 
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