First Autocross

[NC Cobra]

Brad
Finally got my first autocross in yesterday. Gotta say that is about as much fun as you can have with clothes on. I really enjoyed the chance to push the car and see what would happen. Course was quite fast with several decreasing radius, off camber turns to keep your attention. Temps were mid 80’s, with high humidity so the Nitto NT 01’s were super sticky. Coming off a set of 4.5 year old MT Street Comps the difference between the two was dramatically apparent. I found myself intentionally pushing the car beyond where I normally would have and it just kept asking for more. Several times I pushed it too hard into a corner, the car would start start softly understeering, and just I would lay into the throttle to rotate the car through the corner. It was amazing, almost like the car talked me through what it wanted. I am thoroughly impressed with what this car can do.

That having been said the weak link in the system is definitely me and I can clearly see that the tires were covering up a multitude of sins. However Number one for me needs to be recalibrating my focal point as I’m driving. Turns were coming up very quickly and as my focus has always been on being smooth in my driving. As a result, I found myself looking too far down course and aiming for a gate too far down the course. The result was that I had to make very aggressive steering inputs when I saw the upcoming gate or miss it all together. Shocking how quick it comes at you; but also surprising how responsive our cars are.

Next thing I need to work on is accelerating up to the braking point. I spent too much time coasting rather than pushing the car into the next maneuver. Part of that was learning how fast I could negotiate the slalom sections, but honestly I think most of it was the lack of navigational skills discussed earlier. I had several “what the heck is that” moments I’m embarrassed to say.

Finally, once I get my feces consolidated as to where I’m going, I think I need to work on being smoother. I was able to put together one run where I seemed to have a better handle on the course and could focus on connecting the turns. While my lines were a bit “rounder” it was much smoother and I didn’t scrub off as much speed in the turns as a result. Really felt the flow of car around the course and wound up shaving 3 seconds off my time.

Ultimately I think I the car is pretty much where I want it and I’m going to limit the changes for the next event to tire pressure. I intentionally left everything in full street mode as a starting point yesterday and I think that tire pressures were a bit too high, especially given how hot it was.

Thanks very much to all who have shared your thoughts and knowledge here. I’m looking forward to learning more for sure!

Cheers,
Jeff
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[NC Cobra]

981B34B9-CE4C-4F19-B935-EAA4589952C1.jpeg4F9F402E-B974-4465-8D94-8762DD43C9EE.jpeg0703CB45-2DE1-4F32-A477-A2235B085B5D.jpeg

[GTBradley]

Nice! Glad to see someone else new getting into it. That course looks like it might be challenging, how long did it take to get through it?

By the way, the temp thing seems to work. After a long drive yesterday I tried it and at 22 psi and my temps were consistent in all locations across the tire. I'll try at the next autocross this Saturday too.

[CraigS]

A technique I have found useful is to visualize the shape of the entire course. Not always possible because of the layout but I do my best. You walk it as many times as you can looking at individual and small groups of corners. But then go to the start line and overlook all of it. Maybe the course is like a letter 'M'. Starting on the left, running up that side are 3 offset gates, the first set of right turns is pretty tight, the middle left turn is more like a big 'U', the top right turn is a decreasing radius and a slalom to the finish. This helps me get an overall picture so 1, I don't get lost, and 2, I can plan ahead but not too far ahead. A tip on slaloms; As you walk count steps between slalom cones. The number doesn't matter, but you want to know if the distances are the same or possibly decreasing. When you run the slalom, if they are constant spacing, you hold a steady speed w/ constant throttle. If you are on/off the gas you change the tire's loading and hence their traction w/ each pedal move. NC, I once gave a ride to a fellow AXer who did a great job in his Miata. His comment after was something like, OMG, I had no idea how fast things are happening in your car.

[NC Cobra]

Thanks for the insights Craig. This course was so long I think I might have run out of alphabet before the finish trying to memorize all of it. Think one of my favorite sections was a long 50 mph straight with slalom gates. The fast guys looked to be using the turns to reduce speed going through it (no brake lights) which was important because the last 2 gates got shorter, and led into a left offset, hard right turn. The sneakiest part was that the gate opened up into such a long, lovely, & fast sweeping turn. Really hard not to carry too much speed into the trap looking forward to the fun ahead. As they used to say “patience grasshopper.” Tires got me out of that one a couple of times but it certainly will open your eyes in a hurry!

[NC Cobra]

Brad, My best time was a 81 second lap with most around 84 seconds. Best novice was a Caymen GT4 at 68, top CAM cars were Vettes at 63, and the fastest was a highly modified Lotus Elise at 55 seconds! Clearly I have a lot to learn but on the positive side I am having a lot of fun doing it! Good luck on your next outing and please let us know how it goes.

[J R Jones]

Brad, On temperature: With friction comes heat and with heat comes pressure. Road driving creates relatively little friction or heat, mostly from sidewall flex. The rears experience more friction but less weight.
When we take tire temperature at the track it is as soon as the car gets to the pit. The last turn skews the data with side-friction. Turn 14 at Elkhart (right) would heat the left edges of the tires, so a bit of rationalization was required.
NC, Part of my career was in the marine industry developing jet pumps. Jets are popular for rivers in Australia, New Zealand and the US NW. One racing class is Jet Sprint with 14 foot aluminum hulls and 750-1000hp. I have ridden at events near Boise and on the Rough River. The slalom course and speed is so violent there is a spotter to direct the driver to subsequent turns. Ever see a boat with a roll bar? Hold your beer and watch this:
https://www.youtube.com/watch?v=buaBCmWj_KM
jim

blackhawk farms.jpg

[NC Cobra]

Yup, leave it to an Aussie to put 1k hp in a 14’ boat on a constricted waterway. What could possibly go wrong with that? Pretty sure it would be a hit down here too in the land of NASCAR.....

[svassh]

I haven't read the whole thread yet so maybe this has been suggested already. I do a couple HPDE events a year in my GT350R a car that FAR exceeds my driving abilities. However one of the best recommendations I ever got was Ross Bentley's book 'Speed Secrets'. Its an outstanding resource I recommend to everyone before their first HPDE event. The book covers many of the topics Jeff and JR posted on and does a great job of explaining castor, camber, weight transfer etc so it applies to autocross or any racing for that matter. The number one rule though already discussed is smooth is fast.

I browse thru this book the week before every driving event to refresh my memory.

[GTBradley]

JR, yeah I'll be checking the temps for real this Saturday at my third AX. My tire temps were above 100˚ after a long drive and they were consistent across the tire, I would think that if I had overinflated tires that the middle would be warmer and that's all I was looking for at this stage. I don't really expect to make any big changes from taking temperatures, but it's always good to understand a subject at a deeper level. Thanks for the insight.

svassh, I am headed out for a long road trip in SW Colorado soon so I took your advice on the book. I'll need something to read in the evenings. I found it at thrift books.com for less than 10 bucks. Thanks!

[J R Jones]

sva, I have had street and race Shelbys, and ran the later in Trans Am when they went to the GT specs. It is in CA these days.
Interesting that my old street car is now a vintage racer in TN.
jimSteve shelby.jpgJRJ 350 1.jpgJRJ 350 `76-2A.jpg

[johnpinetree]

Love love love the thread!

Bradley, I'm about to pull the trigger on transmission and rear end. Also plan to run a Coyote. Do you have any thoughts on how the TKO 0.64 and 3.55 combination worked out? Seems like staying in second was an issue, but maybe on just that one course?

[BEAR-AvHistory]

Yup, leave it to an Aussie to put 1k hp in a 14’ boat on a constricted waterway. What could possibly go wrong with that? Pretty sure it would be a hit down here too in the land of NASCAR.....

Who sponsored the event? I did some with THSCC, mostly very tight big box lot courses & difficult with manual steering. All second gear runs. Not active the past year or so. Expect to get back next summer.

[GTBradley]

That’s great, John and good to hear from you. I can’t say enough good things about this eng/trans/diff combo. I love this car and have zero regrets. The .64 OD is perfect for my long drives and you are correct the 1st gear versus 2nd is very course dependent and I’ve had both, but with the huge power band on the Coyote it can handle being used in the high ranges or low.

[NC Cobra]

Who sponsored the event? I did some with THSCC, mostly very tight big box lot courses & difficult with manual steering. All second gear runs. Not active the past year or so. Expect to get back next summer.

Kevin,
I’m running with the Central Carolina Region of SCCA here in CLT. Events are typically 1 per month, with the next being this coming Saturday, the 17th at the Z-Max dragway parking lot. Looks like about a 2 hour shot across I-85 if you are looking for something to do next weekend….
Cheers,
Jeff

[CraigS]

Johnpinetree, use one of the speed calculators where you input tire OD, eng rpm, trans ratio, diff ratio. Look for a 2nd gear good for 60-65mph. That will get you through 90% of AXs just fine. Shifting out of 2nd is almost always going to be slower either to 1st or 3rd. BTW the 1-2 shift is almost always dictated by making a smooth transition and not effing up a turn rather than going right to engine redline.

[johnpinetree]

Thanks CraigS,

Yeah I spent the better part of the day looking through these speed calculators. My other thought was that you probably don't want the rpm's to drop too low when you're in 2nd at 20 mph. Anyhow, this is what I'm thinking, be curious what your take is.



For reference here is what the mustang GT runs at:



I sort of figured that if I went any shorter on the final drive ratio I'd have a hell of a time getting grip with these light cars...?

[GTBradley]

Do you guys know if this would work for home mechanic alignments?

Longacre Racing Digital Caster/Camber Gauge

[J R Jones]

Brad, Longacre has a long positive history supplying the racing market. I have used their pyrometers and scales.
Review feedback on Summit is positive.
My only concern is secure fastening to the wheel.
jim

[RoadRacer]

FWIW GTBradley, I got one of these (1 gauge+string frame) secondhand, and it does a good enough job and includes toe too.

https://www.wheelalignmenttools.com/...gnment-system/

I imagine that longacre are better quality, but mine works for shadetree mechanics..

[CraigS]

Yes it will GT. Here is another option.
https://www.longacreracing.com/produ...y---NO-ADAPTER
At this price you can buy two. Here is my mount. A piece of shelving so I didn't have to paint it.
Align tool by craig stuard, on Flickr
I used the bungee because it was quick and, at the time I only had one gauge. Later I made up a J bolt and wing nut attachment that hooked to one of the spokes in the wheel. Covered the end w/ some rubber hose so it would not scratch the wheel. The gauge comes w/ a coarse threaded hole so I loctited the short stud in place. A couple of fender washers, nylon washers, and a nylock let me tighten it just right so it doesn't sag but will twist to center the end bubble.
20180606_134740 by craig stuard, on Flickr
The two aluminum pieces are velcroed in place and make it easier to eyeball the 20 degree steering turn needed whne measuring caster.

[CraigS]

Johnpinetree, that graph looks perfect. Getting 76 out of 2nd you will see that speed in very, very few autocrosses so you could probably go to a 373 but your comment about traction is correct. Nice thing about having just a slightly too tall 2nd is you never need to look at the tach.

[GTBradley]

I was planning to do exactly that, Craig, but the gauge is out of stock and I had found the Longacre at half price.

[Rdone585]

I used the Longacre gauge that attaches magnetically to the hub. I did have to remove the center plate on my wheels and fabricate one out of sheet metal. The original was aluminum and not flat, so the gauge wouldn't hold in the proper position. My centers came off easily with 3 screws, some just snap in place.

[GTBradley]

Well, the season is coming up and I'm looking at buying some spare wheels for autocross day and would like to know if any of you autocross guys can tell me if these are okay:

17x9 and 17x10.5 wheels 5x114.3mm/5x4.5" bolt pattern
The rears are 6.53 backspace +20mm offset
fronts are 6.02 backspace +26mm offset

That size works but the backspace and offset are a little different than what I currently have. Will these work?

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For reference, FFR advertises theirs as:

Front Wheel Size (Diameter x width): 17"x 9"
Rear Wheel Size (Diameter x width): 17"x 10.5"
Front Wheel Backspace: 6.00" (24mm Offset)
Rear Wheel Backspace: 6.7" (27mm
Offset Wheel Lug Pattern: Ford style 5 lug x 4.5" bolt circle

For tires I'm probably going to do the Nitto NT01

[Indy Shu]

Fronts nearly identical to FFR specs and rears would be moved inboard just over 1/4”. I think you’d be ok, but check inside the rears to make sure there’s room.

[Bob Cowan]

The rears should fit fine. You have room there to add a spacer if you need it.

The fronts will fit fine as well.

Have you considered a Hoosier A7 tire? I mean, as long as you're looking at a dedicated tire, must as well go big. Of course, once you experience the Purple Crack, it's tough to go back.

[Jeff Kleiner]

I "think" you'll be OK with those. My fronts are 9" with 5.94" and 24MM. My rears are 10.5" with 6.81" and 27MM however that's on a straight axle, not IRS.

I've run a couple of sets of NT01s (255/40 front and 315/35 rear). Have them heat cycled when you purchase; they'll last longer and you won't have to scuff the mold release off the get them to grip. Start at 20 psi and go up or down 1-2 depending on what you need.

Good luck!

Jeff

[GTBradley]

Thanks, guys. It's always nice to be sure. I may end up needing spacers on the rears, as on the right side the tire is only a ¼" away from the coil-over with my FFRs. Does $500 sound fair for the 4 wheels?

[GTBradley]

Yeah, I looked at those A7s today, but dang they are pricy! You have a source better than $500 for the rears, Bob?

[Bob Cowan]

Yeah, I looked at those A7s today, but dang they are pricy! You have a source better than $500 for the rears, Bob?

yes, they are expensive. And even more expensive this year. But they are the best. A set this is going to cost me about $1,500 this year.

This is where I buy mine: https://trackdaytire.com/

[GTBradley]

You almost have me convinced, but I won’t be trailering, so I need something that’s also a streetable tire.

[CraigS]

$500 for the wheels is OK especially if buying from a person so no shipping or tax. But look here;
https://www.americanmuscle.com/buwh1-9404.html
https://www.americanmuscle.com/dedibuwh.html
Those links are a couple years old but I did do a refresh page. Double check that these are current prices. Also note the year Mustang that they fit and then search for other styles. AM has lots of them.
Depends how far you have to drive. I autocrossed my MkII for 15 yrs on Hoosiers driving to and from the event on them. Yeah that probably isn't the best for the tires
but I enjoyed driving back and forth and had no interest in a truck and trailer. The only problem is rain. I got caught once in a while and it is not fun having to stay under 40 mph but the tires are so phenomenal. OTOH, another option is run in CAM-S on BFGs, or one of the other 200 tread wear tires.

[GTBradley]

Thanks, Craig, those do look to be a good deal especially considering the free shipping and they would have only cost me 60 bucks more, but as it turns out the wheels I got are nearly new and I saved about $300 over their original price. I suppose I could have negotiated, but they were the only local wheels I could find that were the right size and I'm impatient to get the season started.

[GTBradley]

So I've got the wheels, now for the tires. Yes, yes I know, I've been told I shouldn't even be on sticky tires until I've got more experience, but I don't want to wear out my street tires and like I said, I'm impatient. I'm also tired of my Nitto 555g2s squealing all the way around the track.

In doing my research on what I wanted in a dedicated autocross tire I settled on the 100 tread wear category, even though I thought hard on how I could make the R-comp, Hosier work. The 100s are the stickiest AX tires that are also highway legal, barely.
The tires I considered were:
Nitto NT01, Toyo Proxes R888R, Hoosier A7, Nankang AR-1.

Screen Shot 2022-02-02 at 7.56.11 PM.pngScreen Shot 2022-02-02 at 7.57.21 PM.pngScreen Shot 2022-02-02 at 7.58.12 PM.pngScreen Shot 2022-02-02 at 7.58.59 PM.png

Grassroots Motorsports has a really good article, done recently, on Ultimate Track Tires. I used their matrix and suggestions for AX tires to select the Nankang AR-1. I didn't go with the best tire, the Hosier because you can't use them on the highway and I won't be trailering or using a support vehicle, as I'm still just planning on learning/having fun and not competing in AX for the foreseeable future. I didn't go with the Toyo R888Rs simply because they are not available right now. The Nitto 01 reportedly are not as quick to warm up as the Nankang though the Nankang AR-1 suffers from heat tolerance, but I won't be using them in a way that heat build up will be an issue. My thought is the tire that warms the quickest is best because AX runs are usually around 50 seconds long. Realistically, the Toyo, Nitto and Nankang would all work fine for me, but the Nankangs are interesting, so I'm going to try them.

The article suggested for autocross choose A or AA for Warm-up and B or better for Pace:

[Jeff Kleiner]

I'll look forward to hearing what you think of the Nangkangs. I've eyed them but am not ready for tires right now (actually I could stand a set since the current ones are 2 years old and won't be optimal this year but it's hard to justify with <1,000 miles on them). I've run two sets of NT-01s and am currently using R888Rs so it's interesting to see that my observation that the Toyos warm up faster matches the tester's.

Jeff

[GTBradley]

This tire technology is very interesting to me. It's amazing what scientists and engineers can come up with just by reformulating the same ingredients. It does make me wonder if the Nankangs will be more popular in AX because of the gains they made in the warm-up category.

I can see not wanting to replace these every year as the cost was about $1300, however, I couldn't get free shipping and I paid to have them heat cycled.

These tires came with tech data and tire pressure suggestions that kind of surprised me too. Are you seeing those kind of temperatures on your tires?

Nankang AR-1

Competition Tire

175/50R13, 185/60R13, 185/60R14, 195/50R15 - perfect for Vintage / Historic Racing!Also for Vintage we have the 205/60R13 and 235/45R13*** Nankang AR-1 Specs ***

• Special inner angled pattern design to improve performance in wet track conditions.
  
• Special bevel pattern design for improved tire stiffness.
  
• Large block at tire shoulder for improved tire stiffness and traction on curved roads.
  
• Wide center ribs for improved steering performance and precision.
  
• Optimized tread with wider contact patch for the best stability at high speed driving.
  
• Unique semi-slick compound shorter tire warming time which speeds up tires in reaching effective working temperature and improves gripping performance.

Set up tech tipsOptimum operating window 160F degrees to 220F degreesOptimum camber settings between -1.0 to -3.0 degreesHOT Pressure settings - Just a guide - precise pressures should be decided by driving style, ambient temps and car set up23 - 27.5 psi for cars less than 1760 lbs 24 - 32 psi for cars 1760 lbs - 2200 lbs 27.5 - 37 psi for cars 2200 lbs - 3080 lbs34 - 42 psi for cars over 3080 lbs

PTS offers Tire Shaving starting at $40 per tireWe also offer Heat Cycling - Have your competition tires heat cycled today and be race ready!*Caution: The Nankang AR-1 is recommended for competition events only.

[CraigS]

I haven't run Nankangs so my A7 experience may not transfer but here it is anyway. Pressures 18-20. As low as 16 at the beginning and end of each season when weather is cooler. In addition to tire temps across the tread I use white shoe polish at the edge of the tread to see how far they are rolling over. Re-apply after each run. You want to see wear to the top of the small arrow.
Tire triangle by craig stuard, on Flickr
Again these are different tires, but when it gets hot out 80F or more, you may need to spray the tires w/ water so they don't get too hot and greasy. Camber at -3.0 front and -2.0 rear.

[bionicbelly]

I have experience with quite a few of these tires. I'd skip the nankangs if I were you. They are not super durable, and not that quick either. Nitto's are ancient tech. They were great in the day, but there are WAY better tires out there. Toyo's are kind of the same. Both are ok for track days, but slow, and not good autocross tires.
If you want the straight up fastest, it is the Yokahammas, or RE-71R's. (if you can find them) The best all around and best wear are the Hankooks. You can do an entire 24 hour race on a single set. They are also grippy in a very wide heat range, which will work for autocross.
Another one to look at is Cooper RS3. Very fast, very good wear. They require completely different alignment specs that the other 200 tw tires though. They are MUCH stiffer, and will want much less camber, and less toe than the others.
https://www.jbracingtires.net/
This guy has lots of used race tires, if you want to try some stuff out before you buy new stuff. A7's, Toyo R1R's etc. (It's easiest to call him fyi)

[GTBradley]

Ah, “missed by that much!” Just ordered them last night. Thanks for the input, I knew it was a risk someone would say the Nankangs aren’t that good. I’ll let you know what my experience is and, by the way, I was aware of the durability and am willing to deal with that aspect.