GrandSportC3

This is a question to all people running 15" wheels with bias-ply slick tires.
What is your tire brand/size, what is your vehicles approx. race weight, what tire pressure works best for you and what approx. 60' times and ET's are you running.

I'm asking this because I started wondering if my bad 60' times (1.48 - 1.49 when running 9.40's in the 1/4 mile) are due to the pressure that I'm running.. I don't really spin but there seems to be some tire slip. The car weights approx. 3000 lbs with me in it and I'm using MT ET Drag 28 x 10.5W - 15 tires with 15 psi cold tire pressure..

REDGAR

You will find a very small base of drivers that use 15" slicks.

If you want 16" slick input, I run mine 15 cold as well and will 60' low 1.40s with a best of 1.39

69 N.O.X. RATT

Have you made any passes on engine only ? If I remember right your 60' times were pretty similar whether on or off the juice.

Glensgages

on this Forum


Ollie, you might want to be looking at Forums that are more in-line with your u;tra-loose converter'd / wheel-standing 9-second car, even if they aren't Corvette-related:
http://www.nastyz28.com/forum/index.php might have the type of information you are looking for.


8.64 @ 164.2 1/4 mile
5.65 @ 129.8 1/8 mile
Tagged, Stickered, Insured street car on Radialz...

98Red

Hey. I run the MT ET Drags, 28x10.5x15 with 14 psi. My C-4 weighs 3010 with me in it. My 60' are around 1.43 with et's of 10.10s. I also have a 9" rear with a four link and coilover shocks.

GrandSportC3

I guess that my 15 psi isn't too far off what's ideal - thanks!

GrandSportC3

yes, I ran a best of 9.90 on engine with a 1.45 60' time..
My best 60' time on the juice was 1.48 but I'm trying to figure out why the nitrous is not coming in immediately..
Nitrous is set up to come in once I let go of the transbrake button..

GrandSportC3

Thanks!
Well, I was specifically looking here because I.R.S. cars might have different tire pressure requirements than solid axle cars.. but I'm not sure.. I'm not an expert.

bojangies46

Just watching your video I think you should drop 1lb tire pressure, or two,come out harder, be quicker on the light,you are at the stage that small things are left, just trial and error, your car is running real strong, my 2ct worth, I think your car is catable 8s on a good day.

Glensgages

I'm not an expert, either, nor have I ever run as-quick-as you in a door-car, but you are in the vast-minority of this Forum, Ollie:
maybe you can learn something from 'other' Forums, and adapt it to your individual application.

mackeyred96

Oliver that what my car 60' with the little LT1. with 360 rwhp.
You must have something WRONG

And yes I had 15x11.5x28 ET DRAGS on the car at 12 psi

GrandSportC3

I won't hit 8's unless I solve my problem with the nitrous not coming on at launch.. My 60' times on the spray are the same or worse than on engine
Once I can get the 60' time down into the mid 1.30's, I will hit 8's without a problem..

GrandSportC3

I'll definetely ask on other forums too..

GrandSportC3

I agree! My car has to launch a lot harder and I doubt that it's the tires/suspension that are holding my back. It has something to do with the nitrous setup/tuning that the car either bogs or the nitrous comes in too late.. I do understand that my 60' times on engine will never be great as I do have a tight nitrous converter that is built for a 250 HP nitrous shot. On engine, the converter is way too tight.. Another reason that i'm not coming out of the hole hard is gearing.. 1.80 first gear on the Glide and a 3.73 spool.. I can't go with 4.11's as I'll run out of RPM if I'll spray the full shot.. Car peaks slightly above 6000 RPM and power drops off significantly past 7000 RPM.. Not a high RPM motor, so I need to keep the trap RPM lower. Even with the gearing, I should launch harder with estimated 620+ RWHP off the transbrake on a 150 shot..

Fuzzy Dice

Give me a couple of weeks and I can offer you some info...I presently have 28" ET slicks on the back of my camaro...I have 30" Hoosier radial slicks in the garage waiting to go on the car...unfortunately I will be taking the kit of the car so I won't be able to use that for comparison...only a 200 shot anyway...

GrandSportC3

You'll see much better 60' times with the Radial Slicks. However, tire pressure is a lot higher in those Radial Slicks.. I used to run 24 lbs in mine (HOOSIER RADIAL SLICKS 30 x 10.5 - 15) and got 1.39 - 1.42 60' times)...
I'd like to see how you'll do with the ET Drag slicks..

Fuzzy Dice

I am debating with myself right now on whether to even run the 28" slicks presently on the car...the problem is too much gear...it has 4:56's and this leads to some screaming rpm in the 1/4....I'm looking for the 30" tire to bring that down some...I'll let you now which way I go...

markshaw70redBB

Ollie -

MT Et Drags - 28x11.5x15 gives you an additional inch of contact. You know about my car - IRS with 3.73 spool, TH 400, 511 ci with fogger, etc. Runs in the 8's. I leave at 3600 rpm using the transbrake and run 10 1/2 pounds of pressure consistently. As for the results, try a 1.30 60'. On a bad day I get a 1.32 60'.

GrandSportC3

Thanks

Have you ever tried higher pressure and how were the results?
Your 28 x 11.5 - 15 ET Drags have about the same tread width as my 10.5W's..

I actually had to decide between the ones you are using and the 10.5 W's
Also see tire discussion in this thread...

http://forums.corvetteforum.com/show....php?t=1931104


Even though they are called 28 x 11.5, the tread width is only 11 inches on those tires. My 10.5W's have 10.9 inches tread width and are .1 inches taller than the 28 x 11.5 ET Drags (mine are 28.1 inches tall and yours are 28 inches tall).
One reason that you get much better 60' times is definetely gearing.. Your TH400 probably has approx. a 2.48 first gear which is a lot more gear than my 1.80 first gear
However, I still should get better 60' times. I'll try to lower the pressure next time at the track. What does your car weight? What is your 60' difference when spraying off the line or when launching off engine? One thing that concerns me is that my 60' times are the same on engine and spray.. Something ain't right..

red79vette454

We run Goodyear 28x10.5x15 slicks. Tire pressure cold, 10.5 psi then maintain 12 psi after the first pass. Best 60' times have been on motor foot break launch at 2800 rpm. This is with a TH400 and a big block.

In your case I would probably lower the tire pressure and raise the launch on the two step to 4500 - 5000 and let her eat.