A-Body Autocrossing

[Captain]

I recently started autocrossing my car and have a great time doing so but I'd like to improve my times. When I rebuilt the steering/suspension/brakes recently I did so with more of a daily driver theme in mind- so few aftermarket parts. I'm happy with acceleration, braking and corner entry but my corner exit really suffers due to a heavy understeer. I'll give you some stats on the car to show you what I'm working with.

1972 Buick Skylark
361 ci 375hp/4100ftq
th350 (leave in 2nd on course)
Eaton posi 3.23 10 bolt
Right Stuff brakes 4 wheel power disc kit
225x45x17 Cooper Zeon ZPT
Moog center link, tie rods, idler arm
Stock spindles, front control arms, bushings, ball joints
OEM replacement front springs
3 way adjustable front drag shocks (60/40, 70/30, 80/20)
Front 1.25" sway bar
Tubular non-adj trailing arms
OEM replacement rear springs
split valved rear air shocks
1" rear sway bar

I really struggle with setting my air pressure in the tires. For the fronts I've tried everything from 35-44 lbs, and the sidewalls still roll over a ton. The rears I've tried the same 35-44 lbs and they don't roll over like the fronts but the car handles much better with all the tires in the lower 35 range- with the exception of when I feel the fronts rollover. Once the fronts reach their threshold I might as well stop the car, turn it, and take off again.

I know the rear air shocks need to go- that's first on my upgrade list, but what other tweaks can I do to make the car handle better?

[shep]

I would give Marcus at SC&C a call tell him what you want it to do and he will point you in the right direction. I would guess his pro comp kit stage 1, 2, or 2+ and a set of performance lowering springs perhaps Hotchkis with the Bilstein shocks valved to match the springs all around would be a good start.

[UMI Tech]

Give us a call as well. We can help stick that front end.

[Captain]

Give us a call as well. We can help stick that front end.

Thank you UMI, I'm using a very nice set of tubular trailing arms that bare your name.



Having just replaced the entire suspension/steering and braking system I am not in a position to be able to throw more new parts at the car. Other than replacing the shocks- most things are going to be out of my price range. I'm most interested in working with what I have and tweaking it: camber adjustments, toe, air pressure, rear spring rubbers.

[ProTourGSX]

Some pics of car, and/or video would be nice! Sounds like a fun car!

[rockytopper]

Your closer than you know. About 1500$ more and a call to Marcus will get you what you want. You should consider adjustable uppers with tall ball joints along with lowering springs and a good set of performance shocks. Your car will handle night and day ahead of what you have now. Good luck with it.

[Captain]

My baby


The before


The after


^ You can see the beautiful UMI trailing arms peaking out from the wheel arch

Getting ready to head to it's first autocross


Autocross Video:
http://youtu.be/zlQ9gXIHMcU

[Captain]

Also, here is my RF tire at 36# start pressure and 39# hot pressure- significantly more heat on outside of front tires than the middle. The chalk line started up an inch or so into the tread.

[ProTourGSX]

Cool car! Watching the video made me feel like I was in the passengers seat, too cool!

[UMI Tech]

Nice! Thanks for choosing our trailing arms.

From a car standpoint I think you're looking pretty good to run a first season and get some seat time. The nut behind the wheel (Ha!) is actually the most important part of auto-x. At our local events there is a father and son team with Honda CRX Si's. The dad has a stock one where the son has a slick tire blingmobile. The dad wins by three seconds every time.

Smooth inputs go a long way.

Camber can be decided by using a tire pyrometer.
http://www.longacreracing.com/catalo...id=200&catid=7

It's a little different in auto-x than in oval track, however, because your corner radii are quite often all over the map.

1/16 or so Toe out might help turn-in.

A spring rubber in each RR is a good way to get the back end to rotate a bit. Also, with a radial tire, adding air in the rear will add a bit of spring rate. Adding too much air will also help the back end rotate by decreasing rear grip at the expense of reducing overall grip.

At least I think that's how it all goes.

ramey

Thank you UMI, I'm using a very nice set of tubular trailing arms that bare your name.

Having just replaced the entire suspension/steering and braking system I am not in a position to be able to throw more new parts at the car. Other than replacing the shocks- most things are going to be out of my price range. I'm most interested in working with what I have and tweaking it: camber adjustments, toe, air pressure, rear spring rubbers.

[Captain]

I have a background in circle track, other than iRacing, turning right is new to me.

I use a digital IR gauge for tire temps. I'm just not sure what camber setting I need, getting my hands on a camber gauge is not a problem..

Thank you. Turn in is good, apex out it understeers heavily.

I race against a gutted Civic with full aftermarket suspension and slicks, he's in the top 3 every race. In a course where the winning car has 55 second time- I struggle to run a low 62. I'm not totally out to lunch- but with a little tweaking I know I can make the car much, much more competitive than it is right now. And that's my goal.

[Captain]

Also- this nut needs plenty of tightening, only been in two events so far.

[bret]

On the road right now myself, but take a look at our Level 2and level 3 systems. I've not run across a faster Chevelle than ours yet...and it's driven to the events.
I'll have britt post a link shortly.

[Captain]

Thank you for your input Bret- beautiful Chevelle by the way. I drive this car all over the place, road trips to Chicago, Indy, back and forth to work most days when the weather is nice... to the events I race. It's no show car or trailer queen, I built it to drive hard- and that's exactly what I do.

I'd like to reiterate to anyone who may not have read everything that I previously posted- that at this time I am not able to spend more money on a bunch of new parts and am currently needing set up advice on how to make what I currently have work better. Spring rubbers, camber adjustment, tire pressures... that kind of thing. Not realizing how much I was going to enjoy throwing the old girl around in corners I spent all my money on mostly stock parts.

[marolf101x]

I realize you don't want to buy new parts, so I'll just post a link to this video demonstrating what can be done with a parts swap.
Should you find some funds in the future please give us some consideration.
http://www.ridetech.com/tv/2010/11/r...nsion-install/

Now, on to tuning. . .
There are a few general rules you'll want to keep in mind (and they typically don't cost a ton):
1-lower center of gravity
2-equal weight distribution: you want the car to react the same when you step on the brakes or the gas, or turn left or right.
3-shock tuning: the idea is to keep the weight on the tires that need it. So when you turn you want more weight on the front tires. When you are on the gas you want more weight on the rear tires. This can be accomplished with shocks by slowing down or speeding up pitch and roll
4-tires: no matter how good the suspension is it won't stick if the tires are rock hard
5-compromise: remember a good handling car is one that compromises the least

[Captain]

Do you guys get paid on commission or something, lol?

Beautiful kit and parts. At the time of the rebuild I didn't plan on getting as involved in autocrossing as I've become. Not to mention I did quite a bit more than upgrading the suspension when I did all the work, and I don't have deep pockets by any means. I'd like to think with new oem style parts that I've put on the car I'm in no where near as bad as shape as the "before" video.

Maybe in the very distant future I'll be able to afford a kit like that, but I don't see it happening for quite a few years. Until then I'll keep tightening the nut behind the wheel and put on a show for the crowd, the car is a crowd favorite for sure.

[marolf101x]

I don't get paid on commission, I just design parts (though selling parts does ensure I have a job when I get up in the morning!)

As others have said the nut behind the wheel is a BIG part of this. I drive quite a bit and the biggest change that made me faster was to "slow down". Calm and smooth is typically faster than a "drift show".

Keep working on the car, changing one thing at a time and it will eventually get quicker!

[Captain]

In thinking over my current suspension, how bad are my front "drag" shocks hurting me? They're designed to transfer weight to the rear wheels upon acceleration. I'm thinking that even on the 60/40 split setting that this could be a major reason for my understeering from the center off... thoughts?

[Captain]

I have 3 events left this year and enough money to change either the rear air shocks or the front drag shocks- which is going to show more improvement?

[UMI Tech]

Can you add a few psi to the rears to help fix the understeer from the center off? Keeping in mind you're actually reducing traction out back in favor of balance.

Can you feel the car transferring a lot even with the shocks on 60/40?

How are the "ages" of each set of shocks? Clapped out or relatively new?