Autocross megathread

[Victorofhavoc]

Thanks! It's parked outside more so I see it more often and I agree, it's fun to look at lol.

I think a fire hazard is a stretch, but my concern was just screwing up my tires I just spent $1800 for. Apparently any other tire that aren't Bridgestones should be fine.

On one of my cars I kept ripping out fender liners on slow corners needing more angle when running a 315 in the front . Heat gun and bending the fender liner in/away solves that problem decently well!

Fire isn't a risk with the liner, alone. Much more of a risk when people spill oil inside and some of it lands on the fender liner or oil evap doesn't get noticed and settles in those areas. I've seen a 100k$+ restomod mustang go up in flames because he didn't clean up his fender well after spilling brake fluid and oil. Didn't help he had shitty wildwood brakes that are known to get insanely hot on the caliper. Ultimately brakes got too hot, brake line popped, hot fluid caught the oil spill on fire, oil got the fender liner, and fender liner got the fuel line. 15 seconds later black smoke filled the sky and the safety truck was moving faster than I've ever seen them go. Everyone was okay... Physically...

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[Sinnelizer]

Copilot generated an image of HRC Titan7 TS-5 18x10 +55 and Kumho V730 275/35R18 (I am looking for mid performance tires for my first months of learning FWD, and also Yokohama ones do not stand SoCal heat in summer), and I am completely sold. Brembo brakes just a cherry on top.

Guess, I'll go with that.

 

[mattm]

My Titan 7 on the ITS. p10-18x9-5-53-5x120-64-1-machine-black
Unicorn build.

 

[Sinnelizer]

@mattm Looks solid, I like the black!

***

Post of shame time, honestly. I just got back from an SCCA autocross event, and on my second run, I asked a Honda Racing Team instructor to jump in with me. He literally yelled at me to stop pushing the clutch in while braking, lol. I didn't even realize I had developed that habit—for some reason, my brain just defaults to "two feet in." Stupid mistake, but I'm glad I caught it during only my second AX event. Tomorrow is a PCA event, and I’ll have another instructor co-driving. I just hope it won't be too humiliating!

For perspective, during the instructor runs, that Honda Racing guy laid down a 37.5s in his absolutely not-street-legal Honda, and a 39.5s in my car. My fastest time was a 40.5s. Meanwhile, the fastest driver of the day was in a 2023 GT4RS doing a 35.9s. Honestly, I'm hoping a set of 200 TW tires will close at least 2 seconds of that gap.

On the bright side, I got lucky working as a corner captain at the slalom. Since I didn't have to chase down cones, I just studied how everyone else handled the section. The ITS was absolutely born for this. I used to struggle in the slalom with my Camaro, but I actually think I'm looking really good through there compared to others—even the faster drivers. I can't wait until the other club members upload their RaceBox logs into SoloStorm tonight so I can look at the data.

One question for the group, though: I know racing slicks heat up faster and peak around 200–230°F, while 200 TW street tires peak around 180–200°F. What is the deal with people spraying their tires? It was almost 100°F out today. I measured my fronts after each run, and even at midday, they maxed out at 160°F on the outer wall (and even less on the inside). Why do people spray them? I asked around grid, and everyone just said "it helps grip" without actually explaining how. If my tires aren't even reaching their peak ambient operating temp, why lower the temperature? Why is everyone so obsessed with spraying, and does it actually work? Thanks!

 

[Victorofhavoc]

@mattm Looks solid, I like the black!

***

Post of shame time, honestly. I just got back from an SCCA autocross event, and on my second run, I asked a Honda Racing Team instructor to jump in with me. He literally yelled at me to stop pushing the clutch in while braking, lol. I didn't even realize I had developed that habit—for some reason, my brain just defaults to "two feet in." Stupid mistake, but I'm glad I caught it during only my second AX event. Tomorrow is a PCA event, and I’ll have another instructor co-driving. I just hope it won't be too humiliating!

For perspective, during the instructor runs, that Honda Racing guy laid down a 37.5s in his absolutely not-street-legal Honda, and a 39.5s in my car. My fastest time was a 40.5s. Meanwhile, the fastest driver of the day was in a 2023 GT4RS doing a 35.9s. Honestly, I'm hoping a set of 200 TW tires will close at least 2 seconds of that gap.

On the bright side, I got lucky working as a corner captain at the slalom. Since I didn't have to chase down cones, I just studied how everyone else handled the section. The ITS was absolutely born for this. I used to struggle in the slalom with my Camaro, but I actually think I'm looking really good through there compared to others—even the faster drivers. I can't wait until the other club members upload their RaceBox logs into SoloStorm tonight so I can look at the data.

One question for the group, though: I know racing slicks heat up faster and peak around 200–230°F, while 200 TW street tires peak around 180–200°F. What is the deal with people spraying their tires? It was almost 100°F out today. I measured my fronts after each run, and even at midday, they maxed out at 160°F on the outer wall (and even less on the inside). Why do people spray them? I asked around grid, and everyone just said "it helps grip" without actually explaining how. If my tires aren't even reaching their peak ambient operating temp, why lower the temperature? Why is everyone so obsessed with spraying, and does it actually work? Thanks!

Because you're oversimplifying operating temps. True endurance slicks are at those temps but autocross type slicks like the a7/a8 peak closer to 170-190F.

The autocross cheater 200s also peak very low now. Often 140F and by 170 they're cooked. The yoko a052 for example are stupid grippy from cold, but at 170F they're absolutely gone and just shredding rubber off as you go. The tires will also quickly cool on the outside by 20-30F with even a 30 second cool down driving around a paddock while still being hot inside.

That said, it's stupid to spray your tires. You're just cooling the outside and the risk of spraying your brakes and cracking pads and rotors is high. It could make you slightly faster if you're chasing thousandths, but you'll drop tenths spending that time tuning tire pressure and using a tire pyrometer.

 

[CANDE5]

You won’t pick up 2 seconds from 200 tw tires but it’s surely gonna help some. The factory tires on these cars are phenomenal but there is some to be gained. Love seeing more people using these cars at events. They’re in their element in AutoX!

Kick some ass out there!

 

[optronix]

Because you're oversimplifying operating temps. True endurance slicks are at those temps but autocross type slicks like the a7/a8 peak closer to 170-190F.

The autocross cheater 200s also peak very low now. Often 140F and by 170 they're cooked. The yoko a052 for example are stupid grippy from cold, but at 170F they're absolutely gone and just shredding rubber off as you go. The tires will also quickly cool on the outside by 20-30F with even a 30 second cool down driving around a paddock while still being hot inside.

That said, it's stupid to spray your tires. You're just cooling the outside and the risk of spraying your brakes and cracking pads and rotors is high. It could make you slightly faster if you're chasing thousandths, but you'll drop tenths spending that time tuning tire pressure and using a tire pyrometer.

There are so many opinions on this topic.

What I've defaulted to is anecdotal experience. I never sprayed my tires before and thought it was stupid. Dude in front of me in grid had FTD (in his Audi TT) and liked to chat. He suggested I try it. I did, and I was faster. The very next week I did the same; I didn't have a sprayer, but someone in the grid always does, and if you know them they will almost certainly encourage you to borrow it. I did- and the car felt better and I ran faster.

I poked around a bit on reddit and Miata forums and what not. Saw the disparity in opinions, and all the attempted arguments for and against trying to back in real science.

Ultimately landed on buying a sprayer the following week.

Also- I don't even see how it's possible to spray your brakes; the nozzle is literally blocked by the entirety of the tire tread. I feel like if you spray your brakes you deserve to crack a pad/rotor lol.

 

[Victorofhavoc]

There are so many opinions on this topic.

What I've defaulted to is anecdotal experience. I never sprayed my tires before and thought it was stupid. Dude in front of me in grid had FTD (in his Audi TT) and liked to chat. He suggested I try it. I did, and I was faster. The very next week I did the same; I didn't have a sprayer, but someone in the grid always does, and if you know them they will almost certainly encourage you to borrow it. I did- and the car felt better and I ran faster.

I poked around a bit on reddit and Miata forums and what not. Saw the disparity in opinions, and all the attempted arguments for and against trying to back in real science.

Ultimately landed on buying a sprayer the following week.

Also- I don't even see how it's possible to spray your brakes; the nozzle is literally blocked by the entirety of the tire tread. I feel like if you spray your brakes you deserve to crack a pad/rotor lol.

People get in a rush and water oversprays. In autox especially I've seen many cars with rotors cracked to hell and people not realizing it. Like I point to the cracks and they go, "oh I didn't think those were cracks"

That said, I've sprayed before and it WAS faster. But then I also dropped tire pressure 2-3 psi instead of spraying and still went faster. It does depend on a lot, mostly tire. If you're running the yoko, then yeah spray them down. If you're running a ps4s, then yea spray them down. If you're running a higher temp compound that actually likes being in the 170-200 range, then spraying won't help.

Fastest guy I've known was actually running tire warmers between runs. He was fastest because his starting setup for every run was exactly the same and most predictable of everyone. He was also running the lowest starting pressure out of anyone in grid.

 

[Sinnelizer]

People get in a rush and water oversprays. In autox especially I've seen many cars with rotors cracked to hell and people not realizing it. Like I point to the cracks and they go, "oh I didn't think those were cracks"

That said, I've sprayed before and it WAS faster. But then I also dropped tire pressure 2-3 psi instead of spraying and still went faster. It does depend on a lot, mostly tire. If you're running the yoko, then yeah spray them down. If you're running a ps4s, then yea spray them down. If you're running a higher temp compound that actually likes being in the 170-200 range, then spraying won't help.

Fastest guy I've known was actually running tire warmers between runs. He was fastest because his starting setup for every run was exactly the same and most predictable of everyone. He was also running the lowest starting pressure out of anyone in grid.

@Victorofhavoc
Just to confirm—warming tires isn't allowed in autocross, right?

***

Anyway, my stellar instructor/codriver took the CC09 class win today at the PCA event. He drove my car for the very first time today and was the only one in class running on OEM tires with me. Second place went to another instructor in his own CTR FK8 on 200TW Bridgestones.

I ended up 4th overall, but don't get me wrong—I was turning 58s in the morning. I made a deal with my codriver: he takes the class win while I focus on my skills. And today, my brain genuinely short-circuited after his assignment. I learned how to left-foot brake in a manual car. Now, I've done left-foot braking in my Camaro, and I learned heel-toe at Skip Barber—but doing it in a stick shift completely overloaded my CPU. I drove most of the day in a manual-override of my brain, constantly fighting the urge to push the clutch in every time I braked. I even stalled at the start and at the finish a few times. I just can't seem to rewire myself... yet.

But if this skill can get someone to 1st place (which my instructor just proved), I'm all in.
We didn't spray the tires. We started at 38 psi square, but then the CTR instructor shared his setup: 33 psi front, 42 psi rear. I couldn't bleed the fronts anymore (I had them chalked), so we bumped the rears up to 42 psi. Worked perfectly.

He's #59, I'm #418. And just to be clear—I'm not usually at the back of the pack; I was leading the FS class at SCCA until today. Today was their competition day, and I got kicked out to 2nd in a class I no longer even have a car for. Kinda sad, but that's life. Can't wait for next year with them—still deciding between BS or BST.

 

[Victorofhavoc]

Tire warmers were legal years ago. Not sure if that's changed recently. I stopped autocrossing in 2018 when I started winning and got bored . Went to high speed stuff and haven't gone back except for occasional rounds with a few friends.

 

[mattm]

Tire warmers were legal years ago. Not sure if that's changed recently. I stopped autocrossing in 2018 when I started winning and got bored . Went to high speed stuff and haven't gone back except for occasional rounds with a few friends.

Passive tire warmers/covers are still legal. Electric or putting them in a a car with the heat blasting (and putting them on a car just before you run) is not legal.
I have a set that can retain heat as they cover the outside of the tires and the tread. They double as bags/carriers, too.

 

[Victorofhavoc]

Passive tire warmers/covers are still legal. Electric or putting them in a a car with the heat blasting (and putting them on a car just before you run) is not legal.
I have a set that can retain heat as they cover the outside of the tires and the tread. They double as bags/carriers, too.

I do know designing them as a solar oven concept can work extremely well.

 

[optronix]

On the tire pressures- that's the main reason I think the PS4S are absolutely trash for autocross. With any additional camber, you WILL destroy them in a few runs. Ask me how I know.

They're just rubber bands strapped around those 19s. You HAVE to run crazy high pressures or you will peel them off the wheel at speed. Probably not at autocross speed but there's video evidence where Zygrene peeled one off at Laguna Seca I've posted multiple times on here.

And yes, higher pressure in the rear will help the car rotate. But so will camber, or a rear bar. I've found I don't really need a rear bar to get the car to rotate but honestly I don't know what I don't know. If I do continue down the path of modding my DE5 rear bar is the next thing to go on, along with suspension geometry correction like an anti-lift kit and roll center adjusters.

If I were to offer a suggestion- either stay in BS or get ready to pour money and energy into BST to stay competitive. Until they move the Supra and M2 out of BST, the odds are stacked against you. BS, same problem but at least you're not dumping money trying to incrementally improve an already excellent platform. It's no small feat.

 

[Sinnelizer]

Thank you! Actually after my co-driver win, who thinks this car is a perfection and I don't need to change a thing about her, I am thinking more about staying in BS. So, I am shopping for forged 18 wheels, and all I can find even on Titan7 site for ITS has offset +45. I am not the smartest, but today I question my intelligence even more. How to stay within the class with +53? I want a spare set of wheels so it's just easier between sets of worn tires to replace them. And I can take a spare set to an event, kill the old one, and replace on site. Anyway, what is this offset thing that is out of range for me to stay at BS class?

 

[mattm]

The 53 offset is a unicorn. Titan only did some limited sets. I got lucky.

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