Baseline setup

[dsmithwc04]

I was going through the baseline setup on the car in preparation for Blackhawk in three weeks. Is the SCCA Baseline sheet out of date or are the lengths correct for pushrods, a-arms, etc...?

[Fred Michael]

Can't speak to the a-arm lengths but pushrod lengths will be different car to car and track to track depending on the ride height you are looking for. That is somewhat track dependent and definitely driver weight dependent.

[dsmithwc04]

Can't speak to the a-arm lengths but pushrod lengths will be different car to car and track to track depending on the ride height you are looking for. That is somewhat track dependent and definitely driver weight dependent.

Thanks Fred. I understand about the pushrod lengths but the front,lower-rear a-arms were off by 3/4".... wtf? Also, the front pushrod lengths were 1/4" from each other... Whoever set this car up for the previous owner didn't know what they were doing that's for sure.

[Fred Michael]

Off 3/4" side to side? If so then yeah, that's wrong.
If equal side to side then maybe just a different setup.
!/4" on the pushrod is not necessarily wrong. Depends on a lot of other factors.

[dsmithwc04]

Off 3/4" side to side? If so then yeah, that's wrong.
If equal side to side then maybe just a different setup.
!/4" on the pushrod is not necessarily wrong. Depends on a lot of other factors.

The front was off 80lbs side to side on my scales. I'm new to setups but when would unequal pushrod lengths be something you would want?

[Fred Michael]

Depends what you are looking for on crossweight. (80 lbs is too much).
Depends on how the spring are pre-loaded (or not).
Depends on the way the weight is distributed on the car.
Depends on the track the car is set up for.

[steve everard]

Where is the baseline info ? have never seen it.

[cmaxwell]

I was going through the baseline setup on the car in preparation for Blackhawk in three weeks. Is the SCCA Baseline sheet out of date or are the lengths correct for pushrods, a-arms, etc...?

For what it is worth, I found the specs you mentioned to be a reasonable starting point, but that is what they are. With known symmetrical suspension components, string system, caster and camber, ride height, and rake measurements, along with scaling at that start point will allow you to deduce something about chassis symmetry (and/or what compromises may have previously been made due to possible lack thereof).

Almost all changes will be interactive and iterative, i.e. a camber change will produce a corner weight change and vice versa.

Presumption is that you have a known flat plane, and are not chasing a three-legged table around the restaurant.

[dsmithwc04]

Here is the baseline document I was speaking of.

[dsmithwc04]

I'm still trying to wrap my head around ever wanting the pushrod lengths to be 1/4" off side to side. How can this do anything but throw off weight distribution on the front of the car which I'm not sure when you would ever want that unless on an oval perhaps which this car has never seen from it's logbook.

Either way, I'm jigging the suspension up according to the document I posted above and then do my setup from there. Hopefully that baseline is accurate as the car has changed slightly from it's early days....

[2BWise]

Do not assume the chassis is 100% symmetric. Racecars built in a production environment (which for all intents and purposes these were) are going to be subject to build variation. It could also be possible that the original fixture wasn't symmetric. Square up the suspension as best you can, but don't be surprised if you have to make some compromises to get the desired output.

I know my VD has an issue with the front upper shock pickup points. I have to account for that in my setup by varying the pushrod lengths. It's something that won't be able to be corrected until the car gets a ground up rebuild.

[SStadel]

So......use a tape measure and set the shock length the same side to side, then set the pushrod length the same side to side and roll it back on the scales. Btw, measure your tire circumference side to side as well. IF everything is equal you should be close on corner weight at least in the front. You'll go Sling Blade crazy if you think you can get equal rear corner weights.

[SStadel]

Almost forgot. Use a spring rate checker to be sure your springs are the same side to side as that will change things as well. You may soon find out why someone had one pushrod length 1/4" longer than the other.

[SStadel]

Almost forgot part deux. Have you jogged the upper and lower control arms? That will also change things. Lastly, like previously mentioned the chassis is not necessarily perfectly square. Ever see a Nova go down the road (Chevy of course with all deference to Jay!).

[dsmithwc04]

Almost forgot part deux. Have you jogged the upper and lower control arms? That will also change things. Lastly, like previously mentioned the chassis is not necessarily perfectly square. Ever see a Nova go down the road (Chevy of course with all deference to Jay!).

Thanks for the input Steve! I'm not really following on the upper and lower control arms though... I adjusted them to be the same side to side but perhaps there is more to this? Do I need to have them adjusted to be the same in reference to the chassis and if so how is this done? I just measured center to center and make the measurements match...

[Fred Michael]

Pretty confident that he meant jig your a-arms to the numbers you have. Same side to side.

Having said that, you may need to adjust the upper or lower slightly to get the caster number you are looking for.

[clint]

The front was off 80lbs side to side on my scales. I'm new to setups but when would unequal pushrod lengths be something you would want?

rovals or tracks predominantly turning in 1 direction. Lime Rock for example. 80lbs might be a bit much but the general concept applies there

[dsmithwc04]

Okay, I did the best baseline I could get but have a little issue. I got the car level and then corner weighted it and it was WAY OFF. The front shocks are off 1/16" in length with the exact same amount of preload (2 turns)

I adjusted the pushrod lengths to bring the weights to within 5 lbs front and just so happened to be within 15lbs rear side to side. This made the front ride height off by 2mm up front and 2mm in the rear.

Is anybody else having this much side to side ride height difference? I have the car up on perfectly level scale pads with a laser shooting across the tops of the pads to give me dead accurate ride height.


Perhaps the springs are different rates? I will swap them and check to be sure...

[Fred Michael]

Did you adjust the front pushrods for corner weight or the rears?
Get your front ride heights correct and use the rears to move weight.
Example- to move weight onto the RF, go up on the left rear and down on the right rear.
You may have to reset the front ride heights and then re-adjust the crossweight. You can get there. Keep at it.

[dsmithwc04]

Did you adjust the front pushrods for corner weight or the rears?
Get your front ride heights correct and use the rears to move weight.

I did try that but the rear was off 4mm. Is this prefered?

[Fred Michael]

Off 4mm how? If it is too high or low go up or down with both rears accordingly.
If you have tilt in the car then you will have to raise or lower the front and rear on one side and then reset front ride height and then crossweight.

[Fred Michael]

Are you taking one rear height measurement or two?
I prefer one as close to the centerline as practical.

[dsmithwc04]

Are you taking one rear height measurement or two?
I prefer one as close to the centerline as practical.

I was taking a measurement on both sides near the outside of the floor pan.

[Fred Michael]

Then I personally wouldn't worry about 4mm that far off the centerline. You can probably get it closer if you want to though.

[Fred Michael]

By measuring the rear ride height that far forward you may be putting more rake in the car than you want. Just something to factor in.

[dsmithwc04]

Where are you guys measuring rear ride height?

[Fred Michael]

Been a while since I setup an FE but it was off the gearbox
Give Steve Stadel a call to verify

[mblanc]

no reason you cant do all corrections at one shot, then remeasure, a couple rounds should get you there,

foe example:
after completely accurately measuring car you find
not enough rake
car is low on right side
diagonal off RF heavy +18#

write down what you want to do:

increase rake
raise rear
F no chng no chng
R + 2 flat +2 flat,

fix low on right side
F no chng + 2 flat
R no chng + 2 flat

fix diagonal
F +1 flat -2 flat
R no chng no chng

now add them all together
F Left Right
NC NC
NC +2 flat
+1 flat -2 flat

R Left Right
+2flat +2 flat
NC +2 flat
NC NC

= total change to make
Left Right
F +1 flat NC

R +2 flat +4 flat

done figuring, make the changes

making the car level, and correcting the corner weights, and adding rake, all in one shot. remeasure, tweek, confirm.

'how much' to change, you'll learn with feel/experience, or better yet, write it down for next time.

[MAC Racing]

I measure rear ride height along the centerline to the rear of the trans.

I also set the front ride height and then adjust the rear push rods to get corner weights.

Mat

[dsmithwc04]

I was able to get the front to within 3 lbs side to side and the rear only off 25 lbs side to side. The front is off 1.25mm side to side in ride height and the rear is off about 1mm.

What weight distribution front/rear should I be looking for

[Fred Michael]

Don't worry about F/R. Not much you can do about it without physically moving things on the car.
I would get the front ride heights closer than that, but that's just me. My tolerance is about half that. But like I said, that's just me.

[dsmithwc04]

I'm trying to not create another thread since I have become the "King Question Master" at this point.... Don't believe me? Look at the last 10 threads and who created them, ha!

So my question is this, has anybody created an xyz point plot of the FE/DP02 suspension geometry? Is the DP02 the same as the DP08?

Thanks for any thoughts!

[Fred Michael]

No idea if anyone has plotted it out but it is not the same as the DP-08

[gcoffin]

Just a process check did you set tire pressures and disconnect roll bars before you started your set up.

I usually forget and get to do it twice lol

Once camber, castor, toe are set. I get in the car and have the wife check and set front ride height. Then measure rear and raise or lower the appropriate rear corners to set the weights and rake.

I sit in the car....1/2 full of gas, drinking beer while she works. I prop the corner weight read out up so I can see it so I can tell her exactly what to do.....she loves this.

I then bounce to make sure nothing is bound up

She then re connects the bars and we are done (very done). So if setting corner weights is any harder than drinking a beer or two......well

Also seems like 3/4 inch would mess with camber, big time. Did you check bump steer after you changed everything? Not suggesting it would change but worth a check

[dsmithwc04]

Are most using turn plates for caster or is the upright vertical leading edge possible to get the caster angle from?

[MAC Racing]

I use the camber guage and turn the wheel to get castor.

Mat

[Fred Michael]

Camber guage and turning the wheel will get you a true caster number. A guage on the upright will get you a relative caster number, both can be useful but one requires that you know the built in caster of the upright.
Turning the wheels is also probably a bit more accurate as toe will also have an effect on the direct measurement.

[dsmithwc04]

I've got a question on the caster readings. There is apparently only a 17-18 degree maximum turn angle on the FE. My longacre gauge requires 20 degrees to provide accurate readings. Is the caster change linear throughout the turning of the wheel? Can I just multiply what I come up with for the 18 degree by 1.1 to get actual caster in a 20 degree turn?