dcostello

I tested with aero last year and feel its now required on my autocross car.  I first put a rear spoiler on and it made the car so planted that I developed a front splitter for balance.  After all that was completed I did not find a need to adjust any spring rate as the way my car is currently setup I can adjust what I need by mostly by rear tire pressure and shock settings.

What I am about to say is my opinion but my opinion does have some experience behind it.  In my opinion a cars alignment, shocks, tire pressures, sway bars, etc… once set are then “perfect/optimal” for one corner only.  For example, if the suspension is set perfectly for a 45 mph sweeper to give near the threshold of tire grip at max G’s then the same set up will be tight/pushing/understeer on a 25 mph sweeper.  Likewise, if the suspension is set perfectly for the same 45 mph sweeper then the same set up will be loose /oversteering on a 75 mph sweeper.

With that theory said.  I found the aero broadens that 45 mph “setting” to a wider range of near perfect for corners from 40 mph to 50 mph.  If the suspension is set up perfectly to throttle steer at 45 mph, with aero providing more downforce at 50 mph I can actually still throttle steer at 50 mph at the same rate without worrying about the car being too loose.  I can actually add some spring rate to the car and widen the range where the car is most optimal making it looser and more drivable at lower speeds like 40 mph.

Lastly, I will say that if you autocross a lot the courses and corners vary dramatically from speeds all the way down to 20 mph up to 75 mph for street prepared.  Therefore, even with aero you will still push/understeer at 20 mph and be loose/oversteer at 75 mph.  On those you just need to be smooth and possibly give it up a little.

Hope that helps.

Everything is back and about 70% back together.  I wanted to throw out there that I am using an HF rear axle which does not have an internal sway bar.  The bar I was and will continue to use is an external old lightspeed bar.  

Just thought I would throw that out there since there was so much discussion between internal and external.

First event is April 2nd.  Need to get moving to make it.  Some reassembly, reset the ride height, corner weight, and alignment.

Would you please describe this statement further:  "Sway bars adjust the balance when you can't run the spring rate you want because of bumps."

I would say my car is relatively balanced.   When I think balance, I think in the middle of a corner if I lift the throttle the car rotates (oversteer) and if I press the throttle to the floor I get understeer.  I think we would all agree if I take that first autocross corner before the start timing light (around 15 mph) if I lift the throttle the car is not going to rotate.   Based off course design I am adjusting rear tire pressures up to a maximum of 4 lbs (increase on tighter/decrease on faster more open).   For the Nationals drivers who drove my car, I did pick up one technique I am going to work on this year but they commented that I was taking corners faster and on the throttle earlier than them.   At the 2016 National’s I lost by 0.204 over two days and when I had the others drive the car mid-year one was 0.003 faster, one 0.3, and one 0.5 but he had two events of runs.   Basically, I am not that far off and am hoping to campaign hard this year. 

Ok, “resume” aside … I was really trying to get into a discussion for car setup and the effects of tire pressure vs spring rate vs sway bar.  They are all capable of contributing to the balance of the car.   I am really trying to figure out the effect of each and how to widen the balance effect based on these across greater speed ranges (i.e. 35 mph – 55 mph instead of 48 mph – 52 mph).

Maybe they are just too dependent on my driving style but knowledge is power and then apply it! 

The only thing I will say is a little bit on opinion here...  It is my belief a person can only set up a car to be "perfectly" balanced at maximum adhesion for one corner, maybe type of corner, at one maximum speed in that corner.  With that said I do my best to set the car for the most similar corners at the most similar speeds on that days autocross course by fine tuning shocks and rear tire pressures for balance.  By the addition of aerodynamics last year and dialing in the car a little bit better with corner weighting, alignments, shock tuning, and most importantly upping my high speed car control skills I have been able to widen the window of one corner/one speed and get very close to winning Nationals in 2016.  

Lastly taking the last few postings to heart... this past year (2016) I had three National champions which, good and bad, they all beat me.  Bad, it sucks getting beaten in your own car.. Good, its not the car its me!  And their times would have won Nationals...

I have my plan for this years changes and then am waiting for the first test n tune to get this years changes dialed in.  

It has been a long journey to get to this level but I feel there is still a ton to learn.  Not sure if this helps but its just some ideas laid out on a post.