305 45 17 MT et street R air pressure question
 

With 305 45 17 MT et street R with a 17x10 wheel on a 2021 LT1 with 440 rear wheel horse max and a 10 speed auto trans, what air pressure (warm) should I be running on a average prepped track on a sunny 60 degree day, 70 degree day, 80 degree day ?. I would like to flat foot the car off idle and want it to dead hook. I have removed the front swaybar and have had a 4 wheel alignment to have 0 degrees toe front and rear along with the least amount of negative camber possible in the rear for a flatter rear footprint. On street tires I usually have a full tank of fuel for rear weight, but my thoughts with these MTs I am leaning toward a half tank instead to save 50 or 60 lbs

Start with 18 psi and see how the car responds

:thanks bud

given those circumstances id start at 24 cold. i managed a 1.60 60' in a full weight m6 1LE on a 275/40. i had 24 cold in mine and the track wasnt even prepped. id like to think an auto car setup like yours would have no trouble hooking.

edit: 58*, 900' da. car made 441.

What he said. Don't overdo the burnout. Not a recommendation but what I did: Bought a really good pressure gauge 0-30 with 1/4 lb. graduations. M/T says best results are with tire temp within 15 degrees of track temp (yes, used a infrared thermometer; checked tire temp asap after every run). As for your question of ambient temperature variations; checking tire temp and adjusting psi will account for that. Checked psi in pits after first run, always needed to lower pressure. After first run, started in pits 1-2 psi lower than what I wanted on the line, i.e. 16-17 lbs. in pits (experimented and documented). Recorded both rear tires temp and psi before and after every run. Removed front sway bar and pulled links from rear sway bar. Stabilized the rear sway bar with a 1/4" x 1" x 8" metal strap bolted to the frame and a couple of zip ties. 1" lowering springs in rear took .1-.2 seconds off the 60'. I did everything you did on the alignment (and more) and DID NOT DRIVE THE CAR ON THE STREET. Fuel issue - my thoughts are,for drag racing, remove weight anywhere you can, front, rear, middle, liquid or solid (drain the windshield washer tank -8 lbs). At the track, I start with 1/8 tank and add a gallon or two when the low fuel warning comes on.

I ran 18 to 20 depending on the track and prep. Best 60ft was 1.35.

Certainly appreciate all the critical info. I have taken pits and pieces off the front of the car including the removal of the washer tank total of around 25 to 30lbs. What did you do, zip tie the metal straps to the sway bar itself after you bolted up the straps to the frame on both sides? closest the to each wheel end of the bar as possible? do you think pinching or clamping the rear springs to drop the rear 1/2 inch would help a little ? I realize you lowered the rear a full inch with shorter springs. I am thinking removing the compete rear seat and taking out the pass seat, and will definitely carry less fuel now thanks to you bud.

:thumbup:

This was a dedicated track car for three years so I did a lot to it that I would not do to a street-driven car. Now, most of what I took off is back on and I drive the car on the street and go to the tract from time to time. I pull the seats, change the wheels and tires and disconnect the sway bars for the track. So, when the car was track only, it was considerably lighter (3,320 lbs.) There is a convenient stud or bolt (10mm) on the back corner of the carriage on both sides. Removed the nut and bolted the brace to that on one end. The other end is fairly close to the wheel/tire, 1" -1.5" away. Let the sway bar sit on top of the brace and zip tied just to keep it from bouncing around. I did it on just one side, but both sides wouldn't hurt. I have no idea how pinching or clamping the rear springs would work. Understand the concept; used to drag race motorcycles with a strap on the front that compressed the front suspension to prevent (to some degree) wheelies. I've weighed some of this and some is by consensuses: Pass seat- 55 lb, rear seat - 30 lb. Sway bars 15 lb. each, muffler replaced with straight pipes 30-35 lb. Aluminum belly pan under engine and plastic panels/covers - 15 lb. Engine covers - 11 lb. Trunk panels and floor - 10 lb. Anti-gravity Lithium battery saves 40 lbs. Skinnies save a lot in tire weight plus use light weight wheel ( I used Bogart 14 lb. each). Used Bogart in rear also (21 lb). Hoosier DBR 10.5' X 28' R-17 is 8 lb. lighter (each tire) than M/T 305 Street R, but is a slick not a DOT tire. Probably a lot more can be found and keep it streetable. Happy hunting.

I misunderstood you regarding the rear sway bar, you removed the links and then supported the bar so it wouldnt move around and obviously you feel making the rear sway bar ineffective is beneficial. You lowered the rear of the car with shorter springs, my thoughts on clamping a couple of coils on the rear springs was to lower the rear of the car a half inch, where you lowered the rear of the car 1 inch with shorter rear springs.

Correct. I can't prove it, but I think removing or disconnecting the rear sway bar will help the rear squat at the launch. Likewise on the front, except for lift and transfer of weight to rear.

Yep, what Yosh said , 17 to 18psi at the pits . Remove front swaybar and pan . With the burnout it will go up to 20psi and the car should hook off of idle . Your best 60ft will come off idle as well. Never heard of removing the rear swaybar on an IRS car , but it’s worth a try . I thought you keep to plant the tires better and keep the car launching straight .

I assume you were foot braking it. Did it 60 ft. better in Tour, Sport, or Track?

In every video I've seen, the Camaro driver pulls through the water in manual, stops on the other side, gets the tires spinning in 1st, shifts to 2nd, floors it for a second or two, and rolls forward.

I can't help but believe these big ass OEM tires don't leave a bunch of water on the track. If you burn through it, fine, if not . . . Not sure Bandimere will let me drive around the box and back into it.