?? centering wheel over K.P. axis

[66Runt]

Getting ready to do disk brake conversion (which means new wheels as well). Have a question for the road racing group.

As far as backspacing goes, are you attempting to keep the center of the wheel over the axis line formed by the line that runs vertically through the ball joints, or are you more focused on keeping the wheels within the wheel well?

Have you driven your cars with wheels that are not centered on this axis, and if so did you notice a difference? if so what was it, and how bad?

Thanks, I've been reading posts on here for the past month or so, and have picked up much invaluable information.
Tried a search on this subject, but couldn't get any hits.

Scott

 

[rbohm]

a combination of both actually. ideally the wheel centerline will hit the ground at the same point the line that runs through the balljoints will to eliminate tire scrub when cornering. the more tire scrub you have, the more you feel it mostly in lost cornering speed. that said, some racers these days actually dial in a bit of tire scrub to help burn off speed in the corners to help save the brakes, especially in long races. on a full fendered car, you are trying for the best compromise though.

 

[66Runt]

offset for tire scrub

Thanks for the reply,

Yeah, I'd tried that back in the early 80's on a Datsun 510. I didn't feel as comfortable and my track times suffered from it. For my abilities I feel better with tight front end. Probably due to not hitting the braking points consistentently enough, (or maybe just old age ).

Think I'll pick a brake/wheel combo that centers the wheel.
Thanks again,

Scott

 

[68rustang]

You are going to have a hard time eliminating the scrub radius without going to a large diameter wheel. Even then you might not have enough clearance in the wheel well to turn the wheel.

 

[rbohm]

You are going to have a hard time eliminating the scrub radius without going to a large diameter wheel. Even then you might not have enough clearance in the wheel well to turn the wheel.

i agree. there are tricks you can use to loosen up the rearend and trick the car into thinking it has less scrub radius. use a 3/4" rear bar with a 1" front bar for example. softer springs at one end with stiffer springs at the other, things like that. these days scrub radius is a race only deal that even the pros use as a tuning thing. i wouldnt sweat it for a street or even most race classes.

 

[66Runt]

So what are you guys using?

I've got to buy the stuff anyways. Rather not reinvent the wheel (pun kind of intended).

If there is a package that works well for you, I'd be interested in hearing about it.

This is a weekend toy. Wouldn't bother me to keep a seperate set of wheels/tires swaybars and springs just for "Track days".

About 70% of the time this car will be on the backroads with G.F. and dog.

The other 30% will be at the local auto-x and if I get serious enough maybe a little club racing.

Thanks for the responses, it's nice to hear from people who have "been there and done that"

Scott

 

[68rustang]

I am finishing up installing new arms Uppers and lowers) from www.laurelmountainmustang.com, 620lb 1" drop coils, kyb gas adjust shocks, dr. Gas eccentric eliminator, and wilwood disk brakes. I have to get my wheels figured out then I will set it down and see if everything clears.