Adjustable Front Suspension

Here is a little progress on something I have been working on for some time. I decided to go to a high travel/low roll front suspension on my 56 Corvette - 4.5 inches of compression with low camber gain, but lots of caster gain which translates to correct camber for both front wheels with turn (negative on the outside front, positive on the inside). Every suspension point and the rack are on "slugs" for adjustment of: Ackermann, bump steer, dynamic toe, camber and camber gain, caster and caster gain, anti-dive, and roll center. I moved "everything" so I could get clearance for up to a 13 inch wide front tire with 27.5 degrees of turn at full compression. I still need to glass in the new inner fender panels. I will use JRi shocks with special rebound valving and bump stops to keep the splitter off the ground. I am having custom, longer control arms built with bearing pivots and Howe low friction ball joints. They will couple to my existing ATS spindles with ZR1 bearings and Stop Tech brakes. It has been a lot of work, but I think the results will be worth it on a road course.

mfain said:

...a high travel/low roll front suspension on my 56 Corvette - 4.5 inches of compression with low camber gain, but lots of caster gain which translates to correct camber for both front wheels with turn (negative on the outside front, positive on the inside). Every suspension point and the rack are on "slugs" for adjustment of: Ackermann, bump steer, dynamic toe, camber and camber gain, caster and caster gain, anti-dive, and roll center. ... It has been a lot of work, but I think the results will be worth it on a road course.

Click to expand...

WOW Pappy!
I don't envy the flight test to sort all those points out! But when you do - you'll really have some variables to optimize.
Are you thinking Track - for - Track setups - much like setting/choosing gear ratios?
You could!

Cheers - Jim

phantomjock said:

mfain said:

...a high travel/low roll front suspension on my 56 Corvette - 4.5 inches of compression with low camber gain, but lots of caster gain which translates to correct camber for both front wheels with turn (negative on the outside front, positive on the inside). Every suspension point and the rack are on "slugs" for adjustment of: Ackermann, bump steer, dynamic toe, camber and camber gain, caster and caster gain, anti-dive, and roll center. ... It has been a lot of work, but I think the results will be worth it on a road course.

Click to expand...

WOW Pappy!
I don't envy the flight test to sort all those points out! But when you do - you'll really have some variables to optimize.
Are you thinking Track - for - Track setups - much like setting/choosing gear ratios?
You could!

Cheers - Jim

Click to expand...

Jim,

I had target values for each of the suspension parameters based on a medium-to-high speed road course, so I built the center position of each pick-up point to accomodate those. That gives me +/- .5 inch of adjustment at each point based on the slugs. That is a LOT of variables. The biggest adjustment, track-to-track will be in the shock rebound rates depending on how long you need to pin the nose down, and for autocross the roll center and speed of turn rates need to change. Should be fun sorting out.

You don't realize how short a C-1 is ahead of the front axle line until you start putting all the required, big stuff up there.

Nicely done. How much caster?

BBShark said:

Nicely done. How much caster?

Click to expand...

I'm starting with 8 degrees static, with 2.5 degrees of caster gain at 4 inches of compression. That puts me at 2.5 degrees of caster over the kingpin inclination angle, which is 8 degrees. The upper control arms are on horizontal slugs, so the static caster is easy to adjust, and by adjusting the angles of either or both the upper and lower control arms, I could change the amount of caster gain. I could decrease the static caster and increase caster gain if the steering effort is too tough at 8 degrees with 335 front tires, but talking with Sweet, they think the rack they provided is right for the combination. I will have to do a lot of test-and-tune to get the tire temps right to make sure I am working the inside tire enought - which is the goal of this set-up.

mfain said:

BBShark said:

Nicely done. How much caster?

Click to expand...

I'm starting with 8 degrees static, with 2.5 degrees of caster gain at 4 inches of compression. That puts me at 2.5 degrees of caster over the kingpin inclination angle, which is 8 degrees. The upper control arms are on horizontal slugs, so the static caster is easy to adjust, and by adjusting the angles of either or both the upper and lower control arms, I could change the amount of caster gain. I could decrease the static caster and increase caster gain if the steering effort is too tough at 8 degrees with 335 front tires, but talking with Sweet, they think the rack they provided is right for the combination. I will have to do a lot of test-and-tune to get the tire temps right to make sure I am working the inside tire enought - which is the goal of this set-up.

Click to expand...

What's your target date for when the car hits the road/track?

69427 said:

mfain said:

BBShark said:

Nicely done. How much caster?

Click to expand...

I'm starting with 8 degrees static, with 2.5 degrees of caster gain at 4 inches of compression. That puts me at 2.5 degrees of caster over the kingpin inclination angle, which is 8 degrees. The upper control arms are on horizontal slugs, so the static caster is easy to adjust, and by adjusting the angles of either or both the upper and lower control arms, I could change the amount of caster gain. I could decrease the static caster and increase caster gain if the steering effort is too tough at 8 degrees with 335 front tires, but talking with Sweet, they think the rack they provided is right for the combination. I will have to do a lot of test-and-tune to get the tire temps right to make sure I am working the inside tire enought - which is the goal of this set-up.

Click to expand...

What's your target date for when the car hits the road/track?

Click to expand...

Hope to be finished with the car (less motor) this year. I am considering a Ron Sutton-built LSNext-based motor he is developing - Dart aluminum SBC block designed to take LS heads and a fabricated FI intake -- pretty trick - 800-900 hp, depending on pump or race gas configuration. That might take until early spring. I still have the Aluminum Dart big block (complete but unassembled), but my chosen engine builder (Tracy at Sunset Racecraft) was killed a few weeks ago, and I have been leaning toward an LS motor for the weight savings.

Pappy