Autocross for newbies

[SmsDetroit]

I did my first Autocross event last week and learned a lot. Starting with chalking your tires to see how they are wearing then adjusting the air pressure accordingly. Also got a lot of tips on what to bring. I thought it would be good to have a thread where people can post questions and tips.

 

[SmsDetroit]

So here is my first question. After getting the tire pressure right I never had the front end push in a corner but the rear end got a bit loose. I’m not quite sure if I should loosen up the front end or tighten up the rear. Maybe I even have that backwards. I have coil overs all the way around. Any suggestions would be appreciated

 

[Desert Sasqwatch]

A loose rear is indicative of oversteer. Changes to stiffen the front suspension or loosen the rear suspension can help prevent the rear-end breaking loose. But tire pressures and suspension alignment can also cause handling changes too. If you believe you have the tire pressures correct, how is the tire contact patch on front and rear? Adjusting for maximum contact patch would be the next step, but this is also tied to the stiffness of the suspension. As @Rttoys and others have stated, it takes time to find the correct balance for your Goblin.

 

[JBINTX]

Remember we are 1000 lb rear and 600lb front. Or there about. The rear will want to break loose before the front in a balanced turn.
Not sure what tires you are running. My street tires were 15 psi rear / 12 psi front for autoX to get full face contact. The smaller slicks I run now 20 psi rear / 15 psi front. Most people do not believe those pressures are right because they are so low. Plenty of photos to confirm though.
The Goblin was difficult to handle on the street tires. Switching to stickier tires made an amazing improvement. Now even when the rear breaks loose, it is benign, predictable, and manageable.
I run the shocks half stiff rear and full stiff front.
I hope you have the front brake bias valve installed as well?

 

[SmsDetroit]

My fronts were 19 psi and the rears were 20 psi. I had wear edge to edge on the contact pad. I am not sure if stuffing up the front will send more traction to the rear or is it the opposite of that. The one thing I did learn is I have a lot of learning to do.

 

[Scott #321]

Nitto square 255/40ZR17 tires 12 psi front 18 PSI rear warm. 8 clicks on the front shocks 3 on the rear and with the quafie installed it is finally coming into a balanced feel. Need to replace rear tires now but I am a long way from having my car dialed in for the rough autocross track I run on. prior to the quafie LSD the car was terrible snap loose in the rear but I was also running much higher on the shocks as well.

 

[SmsDetroit]

Nitto square 255/40ZR17 tires 12 psi front 18 PSI rear warm. 8 clicks on the front shocks 3 on the rear and with the quafie installed it is finally coming into a balanced feel. Need to replace rear tires now but I am a long way from having my car dialed in for the rough autocross track I run on. prior to the quafie LSD the car was terrible snap loose in the rear but I was also running much higher on the shocks as well.

Are your clicks off of soft or firm

 

[TravMac]

I agree with the general suspension comments - a little more soft rear made a lot of difference planting the tire through the turn rather than just rolling off the outside edge from the weight bias pushing past the limit of the rubber. Tire selection will also make a big change in how the car handles through these turns (literally every driver last year saying I needed the Hoosier investment instead of R888Rs). There is also something to say about having to adjust multiple items to get the feel you want with your driving style.

I think the main focus for any driver starting out should be consistency before major change. You may gain a few tenths in pure confidence when making a change on one run, and then be worse than when you started 2 runs later. When you do change, also go big to see what that difference results in for you. Many of us aren't good enough with weekend cars to recognize 3 clicks from soft on a shock vs 4, but will start to feel 4 vs 10. AutoX is great for this since the speed is relatively low, and hazards are limited. Maybe not evaluate over only one run either: it may be dedicating a whole event to one setting and seeing how it feels after 5 or 6 runs.

 

[Scott #321]

My clicks are from soft. I am not consistent enough to confidently evaluate the settings based on my times but the combination of going excessively soft on the rear and adding the quafie did make a substantial difference in balancing the car from being extremely loose. I'm running 5-6 seconds slower than the top cars and 10 seconds behind a insanely fast electric crosscart.

 

[Ross]

insanely fast electric crosscart... oh, do tell. Any pics?

 

[Desert Sasqwatch]

In case your looking for a comprehensive explanation of suspension set up, this one is one of the better ones I've found that doesn't get too far into the weeds. May or may not help with the understanding of suspension tuning - which is 50% engineering, 40% knowledge and 10% magic.

Definitive Guide to Suspension Tuning – suspensionspot

 

[Stretch2126]

Depending on the surface I’m usually around 8-10 in the front and 10-14 in the back from soft depending on the surface. I also have 400 lb springs up front and 300 in the back. I have the lsd but no sway bar. My tires are 245 rt660s on 15x10 with 17 psi front and 19 rear. Usually tires will have a wear mark to find the right psi for your camber.
This area of setup has been the quickest for me. It leaves the rear loose enough to really rotate the car around tight corners as long as the front is planted and not going to hit in corners.
Also one last thing to add like TravMac was saying tires are huge for autox. My rt660s do not want to work if it isn’t over 70 degrees and sunny. Once you switch to a slick or a different tire you will probably need to adjust accordingly.

 

[Scott #321]

insanely fast electric crosscart... oh, do tell. Any pics?

No pics but looks like these:

Blue Shock Race electric race karts

Blue Shock Race delivers advanced electric rental karting systems and structured championship platforms designed for modern Arrive & Drive racing centers. We provide complete turnkey solutions — from high-performance electric karts and smart fleet management to race software and league...

blueshockrace.com

 

[Desert Sasqwatch]

Interesting these electric go karts are coming from Latvia. Not cheap, but they do look very professionally built.

 

[SmsDetroit]

Just rechecked my alignment. I’m running 2.4deg of camber in the rear. The rear end was very lose at my last event. Wondering if I should ad more camber or remove some. Suggestions?

 

[Rttoys]

There’s still a lot of factors: Weather conditions, track conditions, track layout, the list goes on. I know on my last autocross, I was first heat to run. The track was very dusty, with a lot of humidity, so it killed my traction. Add in I was only doing single runs, so my tires never got hot. You have to analyze all factors.

To reduce Over steer	Reduce rear pressures or increase front pressures
To increase Over steer	Increase rear pressures or reduce front pressures
To reduce Under steer	Reduce front pressures or increase rear pressures
To increase Under steer	Increase front pressures or reduce rear pressures

I’m assuming you mean negative 2.4° Camber. Looking over some tire specs, they are all saying operating range is -1 to -3° camber. I know when mine was -2.x I wasn’t make very good contact across the tire in the rear. I reduced it to -1.0 and have good contact across almost the whole face now. Maybe reduce rear camber a little bit as see how that goes. Of course, keep playing with tire pressures and shock setting till you find what suits you better.

 

[SmsDetroit]

Thank you. Guys in an Exoset keep telling me to increase camber to neg 3+. What you posted makes more sense to me. Maybe this even I’ll drop to -1.5 and see how it goes and go from there.

 

[Desert Sasqwatch]

Think maybe they are trying to keep you slow? There are enough Goblins in autocross that optimal settings are known (at least within a degree) to get the most out of the rear suspension.

 

[Rttoys]

Thank you. Guys in an Exoset keep telling me to increase camber to neg 3+. What you posted makes more sense to me. Maybe this even I’ll drop to -1.5 and see how it goes and go from there.

The Exocet has a custom rear suspension. The goblin uses a strut from a front suspension on the rear. A whole lot of rules get tossed out the window here, especially with how light we are. You have to go back to basics on tire contact and feel.

 

[Stretch2126]

I run around 1.5 to 1.7 degrees in the rear and with my wheel setup it seems to like it. I have 245/40r15 rt660s so keep in mind wheel width/tire pressure might play a factor. This weekend I’m gonna be autoxing and trying my springs 300/400 f/r for fun.