Best tire pressure for racing tonight?

[HardcoreZ28]

Taking the IROC out tonight and haven't been to the track in over a year. I'm running my BFG G-Force tires. What would you guys suggest for pressure front and rear?

[Little G]

35-rear, 50-front

[HardcoreZ28]

Hmmmm.....I always though you wanted to drop the pressure in the rear tires to get a better contact patch??

[Tru2Chevy]

Hmmmm.....I always though you wanted to drop the pressure in the rear tires to get a better contact patch??

That's only true to a point for street tires. Lowering the pressure will be better for launching, but it will hurt you at the 2nd half of the track, cos the lower pressure causes more rolling resistance. I would start at 30-32 lbs in the rear tires, and see how the launches work out for ya.

Pump the fronts up as high as you feel comfortable with....remember that during a 1/4 mile pass, the fronts don't have time to heat up and raise the pressure much. You shouldn't have any problems with the tires if you run the fronts between 50 and 60 lbs. Just remember to air them down before you leave the track.

Good Luck!

- Justin

[HardcoreZ28]

I forget....does E-Town have air or will I have to lug my compressor and inverter with me?

[Tru2Chevy]

I forget....does E-Town have air or will I have to lug my compressor and inverter with me?

They have air, but I don't remember where it is.....

- Justin

[The Fixer]

I forget....does E-Town have air or will I have to lug my compressor and inverter with me?

They have air, but I don't remember where it is.....

- Justin

It's down by the little Tech outhouse, IIRC.

[foff667]

Hmmmm.....I always though you wanted to drop the pressure in the rear tires to get a better contact patch??

That's only true to a point for street tires. Lowering the pressure will be better for launching, but it will hurt you at the 2nd half of the track, cos the lower pressure causes more rolling resistance. I would start at 30-32 lbs in the rear tires, and see how the launches work out for ya.

Pump the fronts up as high as you feel comfortable with....remember that during a 1/4 mile pass, the fronts don't have time to heat up and raise the pressure much. You shouldn't have any problems with the tires if you run the fronts between 50 and 60 lbs. Just remember to air them down before you leave the track.

Good Luck!

- Justin

i heard if you let out too much air in street tires they bow in the middle meaning you only get the outside of the tire contacting ground and thats why not to air them down.

[Squirrel]

do a nice street launch, if the contact patch looks the same thickness all the way through you got a good pressure....dark in the middle, too much pressure, light in the middle too little

[Jersey_TA]

I went with the max psi in the fronts and 20-22 in the rears. I had 19 psi in my hoosier qtps when I ran my 11.93 with a 1.799 60'

[foff667]

I went with the max psi in the fronts and 20-22 in the rears. I had 19 psi in my hoosier qtps when I ran my 11.93 with a 1.799 60'

qtp's are a great bias ply/street tire :)

[89 Trans Am WS6]

When i ran at etown for slp day james told me drop the rears down to about 27psi..i did that and it worked well for me..but i may experiment a bit more on friday//

[transamws686]

hey are the g-forces the drag radial or do they have the minimal tread?

[HardcoreZ28]

The G-Forces are not drag radials...they are regular performance tires. I ran them at 28lbs tonight and they sucked. They spun past the 60' mark. I'm going to drop them down to like 18lbs next time I run.

[foff667]

The G-Forces are not drag radials...they are regular performance tires. I ran them at 28lbs tonight and they sucked. They spun past the 60' mark. I'm going to drop them down to like 18lbs next time I run.

dude they're a street radial tire...you could drop them to 2 psi and if you have the power to overpower them at 27psi you'll have the power to overpower them at 18. Learn to baby it otherwise buy some real tires.

[Fasterthanyou]

So he ran a 14.0 at 97mph... yeah, well it's sick but not NEARLY as bad as it was.
Paul, we gotta get in touch and get that idle fixed first, then do some more tuning. We NEED to start looking at the plugs. You should be trapping higher than me with your heads/displacement/cam advantage. And my trans is sick so I expect another mph just from that. I'd say trapping at around 106-108 should be the goal with that motor.
The only other thing that I can think of that might be your problem is the torque converter. I was talking to RBob from thirdgen and he thinks your problem might be a bad torque converter. I'd say it's worth a shot since you've already got a cam looking for ~2600rpm stall as is.
Next go around we're going to do a lot of fuel tuning. I have a feeling that those 24lb injectors are a tad too small. When Jesse tuned your chip he had tons of fuel dumping in way early (he messed with the maf tables like a moron). That was pegging your injector pulse width to 10ms from like 2500rpm and up. Definatly a fuel problem from here on out. I'd really like to get a way of measuring the performance before we start or it might just be a waste of time. Tim's got a Tazzo which would work nicely. I need to head down that way anyways to do some more tuning with Matts 454ss and HOPEFULLY a 93Z now that I got the bin for it ;) .

[ar0ck]

Ive always tried to play around with psi's and my best result was 25psi on the passenger side tire, and 27 on drivers side. Good Ol' Peg-Leg. Ran 14.97 @ 90mph w/ 27psi

On the street I was normally doing 50' And I had an odd wear pattern. They were over-inflated and only the center ballooned out.

I would start @ 30psi, and work your way down untill the point where you loose time.

[HardcoreZ28]

Prevo more tuning sounds good to me. Let me know when you're available....I'll be available saturday afternoon/early evening for a while and sunday evening. Otherwise next week. I'm planning on fixing my trans crossmember tonight so I can get back into it hard. The torque converter probably isn't helping, but I'd like to use that as a last resort since the car sees mostly street driving. But yeah I was thinking I should be trapping around 107-112 also.

If you can get a hold of Tim's tazzo that would be cool...if not I have my G-Tech, but that thing is a pain to get leveled out.

The sooner the better cause I want to get back to the track before it closes!

[Tru2Chevy]

The sooner the better cause I want to get back to the track before it closes!

Atco is open all winter.....good air :D

- Justin

[Squirrel]

HOPEFULLY a 93Z now that I got the bin for it ;) .coughTAcough :P....im free tonight if youre ready :twisted:

[Fasterthanyou]

HOPEFULLY a 93Z now that I got the bin for it ;) .coughTAcough :P....im free tonight if youre ready :twisted:
I'm free tomorrow afternoon/evening. I found out why you're car wasn't idling right with that bin I burned. It was on a 512 sized flash prom where your calibration belongs on a 256 sized flash prom. In other words it was running it backup mode as if the eprom wasn't even there. I've got an extra 256 chip that we can use for ya.

[Squirrel]

gotta go to work at 4 on Sat., anytime before that is good...dont know if i told you or not, but i read the codes on tues. and got DTC 26 Quad Driver Module #1 Circuit, which by way of shoebox said it has something to do with the air pump, which IIRC isnt there anymore :D.....ill see if matt can reverse his fan job and have you just electronically control the fans instead of them keeping my car below 100 in the winter, it'll make my heater actually blow hot air, extend my fan life, and of course give me more power for the system :P

[84HOtransam]

Taking the IROC out tonight and haven't been to the track in over a year. I'm running my BFG G-Force tires. What would you guys suggest for pressure front and rear?

i put like 18-20 in the back tires and leave the fronts alont..but i have 255/60/15 radial t/a's on 15x7 rims so they widen out a bit with less air..