Caster ?'s again

[Cajun Kid]

Willie,

I have Super Bell gropped straight axle set up from Pete and Jakes

[Cajun Kid]

Prior pic had old wider front wheels and tires, here is a shot with new norrower front wheels and tires.  Just before I took it to have front end aligned.



after we set caster to 8 1/4 degrees and toe in at 1/16 it seemed to drive straighter ( I was on the highway so I backed out just over 125)

[Cajun Kid]

More pics on my photobucket

http://s261.photobucket.com/albums/ii43/cajunkid5690/?start=0

[Sumner]

Hey Sumner....any chance that car has negative scrub radius (deep backspace on the front wheels, to get them into the fenders)?  We had a BUNCH of that on the Prius project, in 2004, due to the fender shape and putting the front end on the ground (we actually clocked the transaxle 28 degrees to get the axles at a reasonable angle).

If the scrub is inboard, the car will need toe out to settle the lash in steering pivots/linkage.  I remember seeing that setup on a production RWD car with Vor Lauf (spelling?) geometry, in the late 80's (our joke was that "Vor Lauf" was German for "hold left" because that model pulled right on road crown!   ....old mechanics jokes....makes sense to us!)

Regards, JimL

Thanks, I'll check into that when I get back.  5:30 am and off to WOS and the special meet .

c everyone there,

Sum

[willieworld]

charles---you have a dropped I beam axel --with 4 link--transverse leaf spring--cross steering--panard bar--with late model disc brakes--all of the right stuff--in the pic. with no body it looks like you have about 1 1/2 in of + scrub --you said you changed wheels and tires---all of the adjustments you make (or measurements you take )on your front suspension should be done with all of the weight on the wheels--if you are going to measure or adjust the toe roll the car back 6 ft then roll it forward 6 feet and do your measureing or adjusting  do that each time you measure or adjust---8 degrees should be plenty --and no with 4 bar front suspension your caster wont change as the front suspension works ( as long as all 4 bars are the same length )  if you stand in front of the car and look at the kingpin you will notice that it has an angle it is angled in at the top and out at the bottom--if you draw a line down through the kingpin until it touches the ground it should hit the ground in the middle of the tire if it hits outside the middle you have + scrub if it hits inside the middle you have - scrub---there are some different opinions in lsr but i think most will agree that the closer you get to 0 scrub the better (that line through the kingpin should hit the ground in the middle of the tire= 0 scrub---every thing else you have done is good just remember that your suspension was designed in the 20s for gravel roads with a 50 mph speed limit --the concern then wasnt high speed handleing it was comfort  --if you sort out the scrub and GET A GOOD FRONTEND ALIGNMENT you should be good to go  willie buchta

[Cajun Kid]

Willie,  thanks for the info. Yes you picked up all the details of my suspension from the pics.. man you are good...

The Scrub was - with the old wheels as the line hit inside the middle, that is why I went to narrower wheels and tires and changed the offset...

Best I can see the scrub is at the 0 or very close to the middle , maybe the line is a bit inboard of the middle (but not more than 1 tread block) much better than it was.

Before there was 4 inches of contact patch to the outside of the line 70/30  now looks closer to 50/50

Hope I am explaining myself...

Thanks again

[willieworld]

charles---looks like it dont count --you should measure it --in theory if the scrub is 0 then the wheel wont have any leverage to steer the car on uneven (pothole) ground --but its only theory and can never be perfect because you will always have part of the wheel outside 0 and part inside 0 so the narrower the wheel the better and a narrow wheel is more streamlined  --measure--measure   willie buchta

[Cajun Kid]

Willie, I have measured, but her is the rub,  the line through the king pin is "imaginary" of a "projected path" through it, through the wheel and then through the tire to the ground.   So, with all that is "looks" like I an as close to zero scrub as I can see. If there is any margin of error the "line" is just inside the center of the contact patch of the tire (less than 1/2" from center).

If there is a more precise or scientific way to "measure" this I would sure do that as well,,,,

Either way I now have

1) Narrower wheels (down to 5" from 7")
2) Narrower Tires (down to 5" from 7.3)
3) Less (much less) Scrub
4) More Caster (now 8 1/4 was right at 2)

So I guess the real test will be less than two weeks away when we Run at Maxton,

All theory says that the 4 changes above should help the car run straighter at speed and "wander" less, maybe even tend to stay straighter after it hits the bumps...

Charles