69 Charger on the autocross

[SlinktRR]

Any reason not to use the 275/60 for the rear tires? I just saw nitto makes a 60 series too. I like the gearing with a 28" tire. 50 series makes sense in the front for a shorter sidewall.

 

[Rusty knuckles]

Any reason not to use the 275/60 for the rear tires? I just saw nitto makes a 60 series too. I like the gearing with a 28" tire. 50 series makes sense in the front for a shorter sidewall.

My only reason was for the shorter sidewall. The 50s are basically the exact same diameter as my old 245/60-14s so I didn't have to compromise on anything there really. The 60s being a little taller sidewall, higher effective gear, and making a little higher CG all are working against my autocross times. But they would certainly look better.

 

[Rusty knuckles]

New results today. It was very hot at about 100 ambient. Very tough to keep cars cool. Changed tire pressure a bit. Bumped the front from 40 to 45 psi. Pumped the rear down from 40 to 35 psi. Definitely helped balance a bit. Much more neutral and easy to manage. At the end of the heats both front and rear had picked up about 5 psi. My best times in both heats were my 2nd runs. So I think that tells me something about pressure and tire heat.

I also tightened the rear brakes to get more bias there. Probably over did it because I had to be careful about locking the rears up.

Results on an average 66 sec course:
Fast guy: 61.409
Me: 67.632

So I picked up just a bit today. Very happy. Beat a lot of cars and competitive with ones I "shouldn't" be if you listen to conventional wisdom.

 

[j-c-c-62]

What TB"s?
Your KYB's only work because of your tall sidewalls. You should have learned by now tires are everything, and you still have a lot left on the table in that department.
Good news, you seem to be a fast leaner and not afraid to try new things.
Your body roll is overcoming your dialed in 2-3Deg camber looks to me like. Your tire needs to tire temped to indicate your contact patch.
Tires are everything, and ditch that spare, jack, and full tank if you already haven't.
Fronts should always lock up first, as they are approx. 70% of the braking.

 

[Rusty knuckles]

I haven't measured my torsion bars but assume they are .88. Whatever stock 383 bars are. Rear springs are also non-HD leafs. I know the kyb's aren't the right choice but they were the economical one I needed for this season. This whole car is a compromise to keeping it a true to form muscle car and not crossing the pro touring line with bigger wheels and exotic suspension. I beat both modern challengers that showed up yesterday, one being a redeye, a couple miatas that were pretty stock, an 87 fox body, and a handful of other cars. I ran about mid pack.

I took some go pro video of both front and rear suspension during the runs. I'll compile that and put on YouTube. Really curious what I'll see.

 

[j-c-c-62]

IMO, your next upgrade should be TB's, anything will be an improvement, and your first thought after trying bigger ones out will likely, be, "Did I go big enough?"
Start at 1.03", 1.08 might be a stretch, and you are not ready for 1.14". yet

 

[Rusty knuckles]

Yeah I think both torsion bars and leaf springs are on the docket for next season. I want to keep a good ride so I don't want to go too big and would rather jump my sway bar up more. 1.03 is probably what I'll get. And get some HD leafs.

 

[ckessel]

You're getting a great baseline to start with. As you change stuff, log the time differences. Driving skills will be a factor too of course but still, that type of driving is just plain fun.

 

[Rusty knuckles]

I got my wife to ride with me yesterday. She was afraid of dying and kinda being dramatic. I was talking to her the whole first run explaining what I was doing and where we were going. By the end of the day she was having fun. I think she might come back. Even if I did lose control once. I went hard and as I crossed the finish line hit the brake hard, wheel hopped and spun out. She said have you done that before? Nope that was a first. Lol

 

[ckessel]

She'll really love it when she's at the wheel.

 

[Runcharger]

Great thread, thanks for posting and I love your Charger!

 

[j-c-c-62]

Yeah I think both torsion bars and leaf springs are on the docket for next season. I want to keep a good ride so I don't want to go too big and would rather jump my sway bar up more. 1.03 is probably what I'll get. And get some HD leafs.

IMO, do the TB's first, test, and then decide, Do not do both at same time, it will only get you into the weeds.

My thinking is when you make two changes simultaneously, it becomes only a guess what made a difference or how the changes interacted.
This is important in your case, because what you have shared and posted picture wise so far, your fronts are prone to wear outer edge wise, maybe indicating excess roll is lifting/leaning your tire a lot, a stiffer TB then stock, will reduce that, increasing grip by increasing more even tire contact , but a stiffer TB can also reduce that axles grip, so there is a compromise here to be found. Once you increase front axle grip, your rear axle will be perceived to be looser, and making your rear springs stiffer will reduce rear axle grip, what you don't want, putting you maybe figuratively, into the weeds.

 

[Rusty knuckles]

I dunno how these content creators do it. Rendering videos and uploading takes hours! But anyway it's pretty cool watching how the tires work, how the suspension works, axle wrap on the leaf springs. Even sloshing fuel out the vent (I think).

 

[Kern Dog]

Your camera mounting is excellent. I was impressed at how steady the images came out. The rear mount really let us hear the engine. It sounds pretty good.

 

[Rusty knuckles]

Your camera mounting is excellent. I was impressed at how steady the images came out. The rear mount really let us hear the engine. It sounds pretty good.

El cheapo magnetic mount from ebay for $20 lol. I'll try a different spot on the front next time. It was on the valance. Not sure if it's wind shaking it or the valance moving. The rear I stuck it to the gas tank and it looks a lot smoother.

 

[j-c-c-62]

As very informative as the videos shared are, not sure I could spot the braking wheel hop you have mentioned a couple of times. I have already addressed my reluctance to suggest going quickly to heavier Leaf springs.
But on that topic, understand Mopar leaf's are well designed to reduce/prevent wheel hop to a large degree. that is achieved by having asymmetrical leaves, meaning basically front of the leaf is shorter and with rear being longer.
That divides and optimizes the tasks of the leaf's, front being mainly control/location, rear being to spring the load. A solution in this case for brake wheel hop wheel while mostly maintaining a needed spring rate would be the addition of a front half leaf, which would only slightly raise spring rate. BTW, any use of lower blocks promotes wheel hop. The stiffer the front leaf eye bushing and leaves, the more inherent roll resistance the leaf provides.

 

[Rusty knuckles]

Final autocross of the season was today and I did something a little different. The last few autocrosses a supercharged non-hellcat challenger and a hellcat redeye have been coming. Both are relatively new and I have been consistently beating both in my 69 charger by about .5-1.0 seconds. So today I didn't take the charger at all. I took my hellcat challenger.

I got beat by both of those guys by about 1.5 seconds! Yes there's lots of variables there but I think that distinctly disproves that "modern suspension is better". And I've said before the charger handles better than the new challenger. I'm 100% standing by that.

 

[j-c-c-62]

What is the weight and tire comparison?

 

[Rusty knuckles]

I'm sure the hellcat gives up about 700-800lbs. Tires are also all season. I meant to weigh it today but didn't have time to stop at the scale. The challenger also has 2x the hp. If I was to put all seasons on my charger again I'm not convinced the hellcat could beat the charger still. It'd be close.

 

[ckessel]

Chassis rigidity, suspension differences, tires, brakes, weight, power make a difference. You have a weight advantage over the Cat. It would be a great comparison to see how close you could get to the Cat by doing chassis, suspension, brake, tire, power upgrades to your Charger.