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Could a gear change induce wheel spin at launch?

Posted By: J_BODY

Could a gear change induce wheel spin at launch? - 03/08/22 02:05 AM

Coming off my dismal showing at March Meet has given me time to ponder the impossible or improbable…. I spun 2 out of three passes. This is something I have not had an issue with at this track. While the temps were cool (50s) we had some sun shine so I can’t imagine the track temp was too bad. 1.34, 1.24, 1.33 were my hits. The only change I’d made was dropping from a 4.56 to a 4.30. In the past I’d basically printed out 1.22/24 slips there. I guess I’m going to have to add track temp to Daves duties (my right hand man) and log that. Either way, I’m putting the .56s back in before Vegas.
Posted By: n20mstr

Re: Could a gear change induce wheel spin at launch? - 03/08/22 02:12 AM

It depends ? IF the car has enough power , less gear will calm launches down , but 60 the same or sometimes better ….. maybe your power/converter works better with more gear ? It’s hard to say for sure , do you any data logging ? An rpm trace would show a lot here
Posted By: J_BODY

Re: Could a gear change induce wheel spin at launch? - 03/08/22 03:10 AM

I have Racepak data from all three and would love to post them but that seems to be quite the task for me anymore. We we’re running 9.2 to 9.4. I’ll go back and see if it affected stall speed. Less power or bigger tire would cure this smile
Posted By: EvilB1Dart

Re: Could a gear change induce wheel spin at launch? - 03/08/22 03:12 AM

The 4.30 has more wheel speed and the converter will be looser which could further cause traction problems early in the runs. Same tire and same or similar condition?
Posted By: CMcAllister

Re: Could a gear change induce wheel spin at launch? - 03/08/22 03:51 AM

You can absolutely spin the tire from not enough SLR if you are not planting the tire.

That said, I find it hard to be convinced that a small step like that gear change is could make a car go from good to junk. Assuming a 3 speed, that's around a half point of gear ratio. Go back to the old set up and see.

I can tell you that running on a track that is prepped for fuel cars, along with the clutch dust and oil they leave behind, is not typically going to be the best situation for 9 and 10 second door cars.
Posted By: Bad340fish

Re: Could a gear change induce wheel spin at launch? - 03/08/22 11:37 AM

I think with a taller gear once you lose the tire it might be harder to get it back, but you didn't make that drastic of a change. It will be interesting to see how it does when you go back.
Posted By: dvw

Re: Could a gear change induce wheel spin at launch? - 03/08/22 12:58 PM

1.22 at that ET level is pretty stout. You are talking good NHRA S/S numbers. How did the 330 times look? Were they off the same amount? You're hitting the tire with less torque, all else being equal. Might need a looser rebound/tighter compression setting in the rear.
Doug
Posted By: pittsburghracer

Re: Could a gear change induce wheel spin at launch? - 03/08/22 02:02 PM



We race in a lot colder temperatures than that around here but my quickest 60 foot was 1.21 in my Daytona and 1.25 in my Duster. I also have a lot more tire than you do. Even at that when the temps did drop I had to do a longer burn out.
Posted By: Al_Alguire

Re: Could a gear change induce wheel spin at launch? - 03/08/22 06:04 PM

I know a guy that's free in a couple weeks that could help at the Vegas race grin

How old are your tires?

Did you change the shocks at all to compensate?

Do you have any good video of the runs?

Can you email the run files?
Posted By: FurryStump

Re: Could a gear change induce wheel spin at launch? - 03/08/22 07:00 PM

Did you heat the tire just a hair more to overcome the cooler temps? Could have made them a bit
greasy.
Posted By: thewolf1970

Re: Could a gear change induce wheel spin at launch? - 03/08/22 07:18 PM

What ignition box do you have?
Posted By: Cab_Burge

Re: Could a gear change induce wheel spin at launch? - 03/09/22 12:28 AM

Do you know the difference in the density altitudes for both tracks?
Did you change the jets to run Famosa ?
I'm wondering if it picked up enough power due to the altitude and better air out there in the groves to make it spin the tires: work:
Posted By: Dduster

Re: Could a gear change induce wheel spin at launch? - 03/09/22 01:39 AM

Check Your Racepak files and see if You are spinning the tires on the 1-2 gearshift as well? I suspect a shock adjustment is in order as well. Keep going. Did You pick up mph with the rear end ratio change?
Posted By: J_BODY

Re: Could a gear change induce wheel spin at launch? - 03/10/22 04:44 AM

Slicks have 22 passes. 14psi as always
Prior to this weekend I hit that test day in Vegas back in December. Was very cold that day and we loosened the front 4 clicks extension, left the rears alone. I put the turns back into the shocks prior to the 1st pass and took 2 out for pass 2.
Burnouts…. yeah probably over did that perhaps…. It was “cold”
Ignition….. old school 6AL timing locked at 32. Been that way forever.
We went up 4 jet sizes since Vegas was the last run. Was 12.4 afr so we let it be.


Starting to wish I’d stayed with my 4150 carb and 727 trans…. Fun consistent combo that definitely ran the number. smile
I’m sure the softer barometer in Vegas might work my way.
Posted By: Guitar Jones

Re: Could a gear change induce wheel spin at launch? - 03/10/22 11:57 PM

I had a nostalgia pro stock racer tell me that if the track was crappy they would add more gear, not less, to reduce the wheel speed. Never tried it myself as I was locked into the one gear ratio I could get in a pro gear.
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