Front Suspension Concerns

[ironworks]

Originally Posted by Track Junky

Great point Roger. Spacers will change your scrub radius. In my experience 5.5" backspace with a 9.5" wide wheel works very well. Although, if your not going to be competing with the car I dont think you will notice.

EDIT: Pad thickness of the wheel will also affect scrub radius.

You have to get the pivot center of the spindle to fall in the middle of the tire. The further off it is the more movement you will get out of the tire. Does the tire pivot around the axis or roll around it. It is rolls your going to need more room meaning a smaller tire.

[eric1967]

Originally Posted by ironworks

You have to get the pivot center of the spindle to fall in the middle of the tire. The further off it is the more movement you will get out of the tire. Does the tire pivot around the axis or roll around it. It is rolls your going to need more room meaning a smaller tire.

If I understand this right the center pivot of the spindle would be the center of the ball joint. Is this correct?

[Vince@Meanstreets]

Originally Posted by eric1967

If I understand this right the center pivot of the spindle would be the center of the ball joint. Is this correct?

Picture a line center of upper ball joint center to lower ball joint center continuing to the ground. Also known as king pin inclination

[bret]

Excellent drawing!
There is LOTS of generic info on scrub radius issues around the forums and suspension type websites...and damn little consensus about what is "right".

My OPINION: I've built some cars with as small a scrub radius as possible...they seemed to be very light on the steering, some to the point they were twitchy. On my 33 Ford, the scrub as originally .568 negative...the centerline of the tire was about 9/16 inboard of the scrub line. Felt ok, but a little light and twitchy...but maybe I was just trying to get used to the car.
I changed to a 2" wider front wheel, with the extra width all to the outside, and from a 275 to a 315mm front tire. This moved the scrub radius to approx. 1.5" positive. Aside from the extra front traction, the car had a more stable and firm feel to it in a straight line, and has no "tramming" effects [following the grooves in the road].
Just my experience.

There are a group of circle track guys who recommend a zero scrub radius to make their cars easier to steer with no power steering. It probably works for them, but within their very narrow parameters.

[Stovebolter]

Kind of reviving this. What was the consensus? I've been following Gaetano's build and like his set up but I too have considered running the 10's on my soon to be 69. I'm not worried about making mods to the inner fender, and/or limiting steering lock to lock. My concern is modifying the fender itself. I'd rather not lose the OEM fender.

Gaetano, you mention you modified the inner and outer fender. Are you talking about rolling the flange or actually pulling the fender out for more flare?

Bret, I am wanting to run the 18x10's 5.75 bs. On your system, are you restricting overall drop to 2"s? I know I can adjust for more drop with spring rates but don't want the same issues Cole is running into. I realize most of his trouble is his back space.

Cole, any new results?

David

[Track Junky]

Inner wheel well was cut out where it rubbed. I used a baseball bat to roll the front fender. I dont recommend doing this if your car is already painted or you want to keep the front fenders looking stock.

So whats the verdict Cole? Those 1/2" spacers I gave you work out?

[Stovebolter]

Thanks Gaetano. I was aware of rolling the fender flange. You've answered my question. All of my worries are gone. I'm not worried about rolling the flange. I just didn't want to get into changing the OEM shape of the outer fender.

David

[Cole]

Originally Posted by ironworks

You have to get the pivot center of the spindle to fall in the middle of the tire. The further off it is the more movement you will get out of the tire. Does the tire pivot around the axis or roll around it. It is rolls your going to need more room meaning a smaller tire.

So the heck with the spacer, go for a re-hoop?

[Cole]

Thanks to all those that replied. Here is picture from either side of the car without a alignment yet. Not sure if its helpful.

[Bryce]

looks like you need some negative camber and all the weight on the front end.