Where to start front suspension

[CTK]

I have started measuring and working out options for control arm pivots on my 55 TBird
i am using m11 spindles with 2/12” drop. I can lower the bottom control arm pivot about 1” which brings it to almost level. They are about 17” long
My first question is anti dive? How do I do this correctly?
And lower control arm length, if I can make them and few more inches longer, should I?



I will also be lowering the upper pivot points to match the amount changed at lower pivot, plus 1” for the spindle being 1” closer between joints, compared to original.
I am also trying to work out if I should include 1/2”-1” extra. Shelby mod. Style.
I am yet to measure completely roll centre but read it should be about 2-4” from the ground.

I am a newbie at this and appreciate any help I can get.

[andrewb70]

This is beyond my pay grade, but hopefully someone will chime in.

Andrew

[CTK]

So I measured up some data points
and hoping someone can help with positioning the UCA pivots and length?
LCA length will be 23.6” with the pivot and ball joint being 5.7” from ground. This places the the pivot 1.77” from the chassis centre and ball joint 25.37”
The UCA ball joint is 16.53” from the ground and 23.15” from the centre.
Scrub radius is about 6” over 2” at 2* camber
Wish at this point I started with better spindles
Making the track measure 57.5”

[jetmech442]

You don't sound like a newbie lol, your actually tackling legit design concerns... I love it! I'm following with interest, especially the lengthening of the arms and the anti-dive setup.

My first suggestion would be to see if the experienced racers/chassis fabricators can give their experience with changing different values of anti-dive in front and how it affected the car and where in the turn they saw the most benifit(braking zones, turn in..etc). Then perhaps to find a modern car with similar specs(weight, wheelbase) and maybe get lucky to see if those parameters are known. This would give you the targets you need to determine if the widening, shelby mods..etc are required.

Are you using any software that will track changes with wheel movement or body roll? When I did my rear 3 link, I probably should have, but scoffed at the 150$ price tag of some...and instead slugged it out with excel. It was doable, but looking back would have been worth the price. If you use excel, I would suggest having a known baseline to validate your sheet with so you know you've got a good starting point.

Just my .02, you may be well beyond this. Super cool car to be wrenching on at this level btw, I'm excited to see where this goes. Goodluck.

[CTK]

I will look into some software, good advise. I have been playing with string.
Is there any recommended?
The more I read the less I feel anti dive is used much. I think it is troubled by binding, but unsure. Trying to research as much as possible before diving in. Pardon the pun

[79T/Aman]

start with getting software to plot things out but the reality is there will be physical testing required to gain data to further refine the design.

[CTK]

Looking forward to physical testing.

[Sbeck09]

Glad to see you are really thinking this through up front. I recently finished designing and building my own complete front suspension. It gets super overwhelming especially in the early stages. The targets for things like roll center, camber gain, arm length, etc. are HEAVILY dependent on your individual vehicle. For example, ride height will determine the optimal pivot points for the arms. Working off of stock pivot locations can be a big limit to how much improvement you can obtain, if any. I played around with different measurements in Performance Trends Suspension Analyzer for a few days once I had an idea where my wheel/spindle would be at ride height. I would encourage you to start there since there is even a free trial of the software for a handful of days.

Don't forget to monitor bumpsteer! I personally started out by measuring my steering rack carefully and making sure that my lower arms had the inner pivot at the best location to avoid bumpsteer and were long enough to set the track width I wanted. From there I let the measurements determine everything else. Is mine perfect? Nope. Am I am expert? Not even close, but I seem to have met all my handling goals. Plus it aligned pretty easily and drives straight. The best thing I did was make sure to build in lots of adjustment for pretty much everything.

As for anti-dive, it is there on basically every double wishbone suspension and should be included, but no one really talks about it. I personally run 7.5 degrees on mine with the ability to adjust from 0-9 degrees. It causes zero bind in my full range of motion. This measurement is again mostly specific to your vehicle.