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my first auto-x....

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RobSelina

RobSelina

Jedi Warrior
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....was a blast!

I didn't do badly either, placed 4th out of 31 cars!

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I think I've found a new hobby...this was a real blast /ubbthreads/images/graemlins/grin.gif

The main thing I need to work on is my driving, but a characteristic of the car was confusing me and I'm hoping someone can explain it and maybe offer a remedy.

The car oversteers as I'm slowing and entering a turn. This doesn't bother me. What was bothering me is I would hit the gas exiting the turn, and the front tires would sort of give out and it would understeer. The feedback on the wheel would change dramatically too, since the wheel would turn towards lock but I would get very little resistance from the steering wheel, like I was on ice or something like that. Looking at some of the photos, it seems the outer rear tire would compress substantially, but I wasn't lifting the front inside tire as I've seen here, but it didn't look particularly well planted either.

I'm wondering if my suspension may need a little work. I'm about 2" lower than stock with uprated front springs and tube shocks, out back I have the lever arms still and my springs are slightly derated since I flipped the main leaf building a lowered (and lower spring rate) pack.

Any thoughts appreciated, if you need more photos of the event to see what was happening with my suspension there are literally thousands here:

https://www.ee.nmt.edu/~offroad/images/index.php?album=20060409-NMTAuto-X/

https://www.ee.nmt.edu/~offroad/images/index.php?album=20060409-NMTAuto-X-Chris/

https://www.ee.nmt.edu/~offroad/images/index.php?album=20060409-NMTAuto-X-Denise/

https://www.ee.nmt.edu/~offroad/images/index.php?album=20060409-NMTAuto-X-Jason/

https://www.ee.nmt.edu/~offroad/images/index.php?album=20060409-NMTAuto-X-WillyK/
 
Congrats! Both for an admirable showing and the discovery of a GREAT way to pour off some excess adrenal secretions!

Have you changed to urethane bushings yet? You could stiffen the dampers a bit with a heavier oil in them or change the valves, and maybe consider a rear swaybar as a beginning.
 
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Have you changed to urethane bushings yet? You could stiffen the dampers a bit with a heavier oil in them or change the valves, and maybe consider a rear swaybar as a beginning.

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Polyurethane bushings on the rear springs, but I have not converted on the front yet. Waiting for enough $$$ to rebuild completely.

Running tube shocks up front, are you suggesting heavier oil in the rear shocks? Rear sway bar sounds about right to me too on an intuitive level, but I've also heard they're completely unecessary on our cars from a few racers, so I'm not sure what to think.....
 
Yup, rears. Looks and sounds like you need to "stiffen up" the rear first. Jeff or Nial will chime in here and likely have better info... I'm an interloper: MGB's and "SuperSpridget" driver, y'see /ubbthreads/images/graemlins/wink.gif
 
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....was a blast!

I didn't do badly either, placed 4th out of 30 cars!

The car oversteers as I'm slowing and entering a turn. This doesn't bother me. What was bothering me is I would hit the gas exiting the turn, and the front tires would sort of give out and it would understeer.
I'm wondering if my suspension may need a little work. I'm about 2" lower than stock with uprated front springs and tube shocks, out back I have the lever arms still and my springs are slightly derated since I flipped the main leaf building a lowered (and lower spring rate) pack.


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Hi Rob,
The conditions you describe are not totally unexpected. Weight transfer to the front & loss of rear traction is a natural result of braking. Weight transfer to the back & loss of front traction on acceleration is also to be expected. Try to get the braking done before you are hard into the turn, make the turn quickly & get straightened out more before accelerating so much. Your suspension rates will need to be adjusted to your driving style or vs. I'm sure that the real experts on the subject will have some good advice.
Good luck & have fun,
D
 
Smoothly is the key, full on the brakes or full on the gas. Nothing in between on these small tight courses. You do all your slowing before you turn, shift if necessary and go for it.
Car should really feel balanced, yep lean a lot but not over or understear. Should never slide the rear end and not break while turning, ever. Should be able to stear with the throtle in bigger turns. A bit of air out of the tires sometimes helps with cornering, try 25 lbs all around first.

Yep, 4th is super for a first run.

Will not go into it but I know.
 
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A bit of air out of the tires sometimes helps with cornering, try 25 lbs all around first.


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That was one thing I couldn't quite decide on. Running Sumitomo HTR 200 175/50R13s, and I ran all day on 40 psi front and rear. Think I might have overdone it on tire pressure?
 
OOOhh yeah.
 
Haha, roller skate city here I come. Front to back and back to front pressures are going to depend upon the car, the driver, and the track. Just keep trying and you will find out what is best for you.

But always remember, SMOOTH. Don't jerk the little car off her stance slows ya down something terific.

Beep beep, Bugeye comming through.
 
I'd say 30's probably fine for such a low profile. With the stiffer sidewalls of my yokohamas (and the light car) I generally run 28 lbs front and rear. On regular (60 aspect ratio) street tires on my BMW, I would run pressures in the vicinity of 38-42 lbs. However, you could probably get away with a lot less and benefit in the traction department. Chalk the sidewalls at 3-4 places next time. You can see how far the tire rolls by where there's still chalk. If you're running off the tread, your pressure is too low.
 
/ubbthreads/images/graemlins/iagree.gif
 
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I'd say 30's probably fine for such a low profile. With the stiffer sidewalls of my yokohamas (and the light car) I generally run 28 lbs front and rear. On regular (60 aspect ratio) street tires on my BMW, I would run pressures in the vicinity of 38-42 lbs. However, you could probably get away with a lot less and benefit in the traction department. Chalk the sidewalls at 3-4 places next time. You can see how far the tire rolls by where there's still chalk. If you're running off the tread, your pressure is too low.

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Sounds good, I'll chalk them up next time and go as low as possible with out having the sidwall roll under. Definitely wasn't happening at 40 psi, but that's why I shot so high seeing everyone else having that problem. I'll drop it down and see what it does.
 
Welcome to the fun.......I couldn't believe what I was missing when I started.

I became obsessed with everything racing & amassed an extensive library on the subject.

When I'm not racing I'm reading about racing.

Go faster goodies may be on all your lists & will confound family members.

If you are ever in a situation where you have to choose between going to an Auto-X or buying a new part......Go race instead.......SEAT TIME will help you more than anything.

Oh &........Try 2 negative up front ( Sumitomos like lots of camber )
Also keep yer pressure up...... 40 front & 35 in the back for starters (Sumis have weak sidewalls) Check w/ chalk as recommended above.

BTW.....That's what I'm running on the car in my sig.
 
Great job, Rob!

Spridgets tend to have almost perfect rear spring rates. Your lowering method may create an imbalance, since you have sofened the rear springs (by flipping a leaf).
The best way to lower a car (while retaining the correct spring rate) is to re-arch the existing springs. The second best way would be to use long U-bolts and spacers between the axle and springs. You can use up to about 1.5" thick spacers before causing other problems.
I'd run about 34 to 36 hot in your Sumis....check themn the second you get out of the car (or have a freidn do it right away.
Check your toe-in....should be about 0 to 1/16".
You can get offset upper suspension bushings to create some negative camber (from Winner's Circle). This will help.
Does your car sit a bit "nose-high". You may wish to lower the car in the front a bit more.
You could do without the rear sway bar.
I'm assuming that you have disabled the front lever shocks so that they have no resisitance.....otherwise, they may hold the nose up if combined with the tubes.

By the way, a critical difference in Autoxross is that you may wish to take the *shortest* line rather than the "best" line (in terms of the apex). This is always tough for me, since club racing mostly requires a good apex even if the total distance traveled is longer.

Autocross is a hoot!
 
www.tsimportedautomotive.com also sells the offset bushings. They can also be used in the inner mounts for the lower A-arm to further increase negative camber, but I don't know if it's necessarily the best idea. They might rotate in that position, causing 'variable' camber!

P.S., I have a problem with understeer, but I have a 3/4" front swaybar, no rear bar, and STP in my rear shocks. The front ones are re-valved stock rebuilds and they feel fine, so I suspect that revalved-rears are the way to go. I also have 3/16" toe-in, which may also be excessive.

As another aside, the Moss 1" lowered and 2" lowered rear springs, supposed to fit only '65? to '74 cars will bolt right onto a 1500. Trust me. I have a set of the 1" lowered springs on the car already. However, the spacers are about as good as this option, and generally less expensive. Spring rate does not change with arch, it only changes with material type, thickness/width of leaves, and the number of leaves. I don't think swapping the direction of one leaf (if I've read it correctly) will make any difference, merely changing the arch.
 
I don't think swapping the direction of one leaf (if I've read it correctly) will make any difference, merely changing the arch.

Yeah, I'm not sure if I am reading that correctly either.

But if one leaf (or more) is flipped (in an atempt to "pull down" the car), it will also "pull against" the other leaf spings, thus softening the total spring rate.
 
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But if one leaf (or more) is flipped (in an atempt to "pull down" the car), it will also "pull against" the other leaf spings, thus softening the total spring rate.

[/ QUOTE ]

That's my understanding of it too. Basically I flipped the main leaf, shortened the second leaf by 1.5" on each side so it would fit inside the inverted main leaf, and then reassembled the pack and hose clamped it to replace the used spring clamps.

I think they're probably a little too soft now.

When I have the money I'll get some 2" lowered springs and add a 0.5" aluminum block if necessary too...
 
Fantastic result for a novice! Congratulations!

I won't say anything about suspension or tyre pressures as my car is very different, and there seems to have been a range of opinions offered already.

Most cars will oversteer as you turn into a corner, its called "trailing throttle oversteer" and is quite helpful in getting the car to "turn in" or "rotate" before the apex. You can balance this in a fast corner by smoothly applying throttle to transfer weight to the back tyres, which causes them to grip better.
As you accelerate out of the corner you are removing weight from the front of the car, reducing the grip that end and causing corner exit understeer.

It is difficult to know without being in the car with you whether your car is doing this excessively, or if it just feels like a lot because its a new experience; if the rules allow I would either try to get a ride with an experienced competitor, or have him or her ride with you to comment.
If a circular skid pad is available try putting a circle of cones down then drive round them faster and faster till the front pushes wide, then see how it tucks back in when you ease off the gas. Wail around for a while in each direction making smooth and also sudden transitions to get the feel of things. Once you are used to this try adjusting tyre pressures to see if you can fine tune the car's behaviour.

Oh! and have fun!
Simon.
 
those of you who auto-x, what class do you run in?

They suggested I run in STS2 last weekend, which gave me a very nice PAX, but I wonder where I should best tune the car to fit.

Upon examining the rules, I would have to return my emissions system to stock for example to truly fit in STS2, and the use of tube shocks may not be legal either. I've only browsed the SCCA rule book, but it seems like FSP really opens up my options and specifically allows all the existing modifications I have in addition to many others. The PAX isn't bad either 0.814 for FSP vs .802 for STS2

Thoughts?
 
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