1st gen caster

[dickita15]

In keeping with local lore and my understanding (admittedly weak) of chassis set up I have always run my first gen with as much caster as I can get thinking that the longer wheelbase and the camber change during cornering was beneficial. However while at the ARRC this year looking over the IT7 grid most of the cars seemed to have the front wheels pulled rearward in the fender well. Would anyone like to share their thought on what the better setup is and why?

Dick Patullo
NER ITA Rx7


[This message has been edited by dickita15 (edited December 14, 2004).]

[titanium]

I just went with what was on the Tire Rack's "care and feeding of Kumho v700" page which says:
"Caster settings can enhance straight line stability and cornering traction, and if adjustable, should be set at the maximum positive value for the vehicle. "
So, I have my strut pulled all the way back on my RX7.
*****************************************
Rodney Williamson
#93 IT7
www.titaniummotorsports.com (http://www.titaniummotorsports.com)

[lateapex911]

Interesting....

It has always been my understanding that "positive" caster, (Dick did you write "camber" when you meant "caster"?) increased the kingpin angle,and moved the wheels forward .

This has always had the effect of more steering return, and better self centering for me. When I have driven my car with the struts back, the car can actually self turn. If Kuhmo wants maximum straight line stability, I would have thought that would have meant the bottom of the strut went forward.

I would be interested in hearing of others experiences as well.

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[moto62]

Dick and Jake- You guys already know my take on the subject but I'll quickly go over my experience. After building the third 7, the only thing I didn't change was the stock caster setting. The previous car had a lot of pos caster and yes, there was more feedback in the steering but that didn't mean it was the fastest setup for the car. With the stock caster setting the car was actually easier to drive and the lap times were a little more consistant, and wheel bearings outlived rotors and pads. Also keep in mind, as you crank in more pos caster, you actually transfer more weight to the rear of the car.(Not necessarily the best thing for an already tailhappy car). Here is a good read on the subject.
http://www.ground-control.com/?D=51f2dd6e8...83249c1a2ca81d8 (http://www.ground-control.com/?D=51f2dd6e82fbe390283249c1a2ca81d8)
Ray

[dickita15]

yes jake i mistyped, fixed now. and yes you have more caster if you move the front wheel forward as I understand it.
thanks rodney.
I would love to hear from some of the SE guys as they all seem to agree with ray.
dick

[Andy Bettencourt]

So if the wheel is toward the rear of the front fender (ie: neg caster), you sacrifice straight line stability and gain turning feel and response...as long as you drive with both hands on the wheel http://Forum.ImprovedTouring.com/it/smile.gif why wouldn't you maximize negative caster? On the cars I have raced, the only issue was that it limited the amount of negative camber you could get - but with a nice camber plate setup, you should be fine, no?

On Solo cars with limited camber curves, it is the right thing to do to maximize POS caster in order to gain neg camber.

AB

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Andy Bettencourt
New England Region, R188967
ITA project SM
www.flatout-motorsports.com