jburge01

I'm drooling over this power steering rack. Just a couple thou! On second thought I don't need the wife demanding a divorce.

There is some good info in the tech area about how to make your car go where you point it. It is biased toward circle track but it applies to anything with 4 wheels. Before I start replacing parts to cure what I think is a steering problem (assuming it's not a "fix the nut behind the wheel" problem) I think doing some basic analysis of my car's steering geometry is in order.

Anybody have any other good links to setting up steering geometry?

--John B.

Spudz

John,
Those steering racks are a work of art.

What do you think is wrong with your steering set up. ? I have a few very experienced suspension and steering set up guys that I have emailed for help from time to time.

BTW.. if I was running the 10 " slicks I would want power steering as well

tube80z

John,

I don't know if this is what you want but take a look at some of the back issues of Racetech and/or look at their site racetechmag.com. They have some software that lets you look at your steering.

I'm currently running 13x10 wheels and have been working on reducing scrub with the front suspension. I've managed to go from somewhere near 6 inches down to around 3 and hope to get it closer to 3/4 to a 1/2 inch in the future. I run a lot of caster and use pin lead to keep the steering effort down.

just a few thoughts,

T

jburge01

Good thoughts. I'll have to measure scrub too. I'm running 16X10 wheels and tires, Wheels have a 5 inch backspace with 1/2 inch spacers for a net backspace of 4 1/2 inches. The front end is lowered significantly but other than that stock.

While autox'ing, steering seems to require incredible effort just to hold on to the wheel as the tires try to rip the steering wheel from my fingers in the corners. It is especially a big problem where the surface is not particuarly clean and grip changes from low to high in a split second. I can't explain it other than that it is hard for me to tell what is going on but it just doesn't seem right. Everything I do to increase grip seems to exaggerate the lack of rightness. I don't think it is a bump steer problem but I could be wrong. Maybe a bigger steering wheel would help but I don't want to slow my steering reaction times down.

I've never so much as measured a thing on the car, so I think it is high time I started putting my 5 years of engineering school to work and see what's what under the front end.



What is "pin lead"? I haven't heard that term before. I'll take a look at racetech too.

Spudz

John,
Other then tires and wheel choices my car is probably similar in set up . I haven't even checked the front end for alignment after lowering it using cut spring and replacing a few things up there. On a tight course I can wear my arms out trying to wrestle the car around .

I was really going to sell both my Z's and mess with something else , but after figuring the cost up .I figure the the Z would do what I wanted .

Here are a few pictures from my last event .





I was planning on going with either 16 x 9's with 245/45/16's or 16 x 10's with 275/45/16 's next year .

Mike

tube80z

Hi John,

Pin lead is when the spindle is moved off the strut centerline and in this case is moved forward when looking at it from the side. If you look at the imaginary lines that project down used to measure caster you'll see that there is a distance from the contact patch to the steering centerline, called the caster trail. When you add more caster this gets bigger and it works against you when you steer. Pin lead helps to get this back to a more "stock" type figure.

For scrub I changed the anlgle of my spindles to struts. While I have increased SIA (kinpin angle) I feel the reduced scrub has more than made up for it. It's all in the tradeoffs.

I've been slowly measuring everything on my car and hope to get some web pages put together once race season is over. Just in case anyone wants to see my beater.

Cary

jburge01

Good explanation on pin lead. How did you move the spindle? Cut it off an reweld it somehow?

I don't have a lift, so I just put a new metal 2X4 floor in my trailer. The trailer floor area between the wheels of the Z is now removeable, and you can leave it open for access when the Z is on it so I can using it as an alignment rack and not have to jack the car up (one of the most tedioius tasks there when a floor jack won't fit under the car anymore IMHO). I put some screw jacks on the corners of the trailer for leveling and cut off a couple feed on the back of the trailer so it fits better in my garage. It should facilitate this kind of work a little better than jacking the car up for access and then back down and roll back and forth for measurements.

I was checking out the cost of turn plates - pretty high. Then I saw a post on a suspension board from a racer who says using a couple of metal plates sandwiched with grease between them works very well so I'll try that approach for measuring ackerman. I'll setup some conduit & strings like Tom shows on his website for checking toe and I just ordered one of those longacre toe/caster gauges.

Then I have no doubt I'll need to fabricate tubular/adjustable suspension arms and T/C rod will be necessary to make any real adjustments. Looks like I won't get to the motor this year like I had planned ......

--john

tube80z

Hi John,

How did you move the spindle? Cut it off an reweld it somehow?


Nope, I made a custom balljoint spacer that moves the bottom pickup point. It's very similar to moving the balljoint backwards when looking at it from the side. I'm using a spherical bearing the bolts to a stud that's in the spacer -- if that makes any sense.

Custom fabbed struts on the plan this winter.

Cary

jburge01

If you are moving the balljoint backwards, isn't that the same thing as changing caster?

I found this link regarding steering and suspensions to be helpful - www.rqriley.com/suspensn.html

--John

tube80z

Sorry, poor explanation. We don't change where the balljoint is as that sets the caster angle. We're changing where the spindle is by moving where the strut hooks to the balljoint.

This is just a lazy way of moving the spindle forward reducing the distance from the caster axis to the tire center point.

T