Tire spin vs. mph

SRD art

G-Body Guru
Jun 16, 2011
528
63
St. George, UT
No tire spin. This was on 275-50-15 drag radials, plus the motor really started to pull hard at 2800 but it was a near stock 1800 stall converter so the launch was fairly soft. I wish I had kept the time slips to compare 60' times. I suspect flywheel peak torque was maybe 400 ft lbs and peak hp was maybe 300-325 so it wasn't really anything to write home about.

Thinking back, when I first built my Nova I ran the first track day with some old M&H 26-8.50 cheater slicks that in the video we could see they spun one revolution before they hooked and the car ran 12.30s @ 107.xx. I went back a month later with the same combo only this time on some fresh 28x9 slicks. Car ran consistent 12.06-12.07s all night @ 110. The taller tire may have helped pick up the mph (?) or maybe it was because it got going faster? With the slicks it yanked the left front wheel 3" off the track and pulled a 1.63 60' every time. I didn't keep the M&H time slips because I knew the tire spin left them inaccurate to the car's ability. Would've been interesting to compare all the other time specs. BTW the Nova's motor is now in Pumkinator with more compression added and a couple other goodies to help it breathe better on the top end. 😎

New engine 1.jpg
 

64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
3,612
113
Upstate NY
No tire spin. This was on 275-50-15 drag radials, plus the motor really started to pull hard at 2800 but it was a near stock 1800 stall converter so the launch was fairly soft. I wish I had kept the time slips to compare 60' times. I suspect flywheel peak torque was maybe 400 ft lbs and peak hp was maybe 300-325 so it wasn't really anything to write home about.

Thinking back, when I first built my Nova I ran the first track day with some old M&H 26-8.50 cheater slicks that in the video we could see they spun one revolution before they hooked and the car ran 12.30s @ 107.xx. I went back a month later with the same combo only this time on some fresh 28x9 slicks. Car ran consistent 12.06-12.07s all night @ 110. The taller tire may have helped pick up the mph (?) or maybe it was because it got going faster? With the slicks it yanked the left front wheel 3" off the track and pulled a 1.63 60' every time. I didn't keep the M&H time slips because I knew the tire spin left them inaccurate to the car's ability. Would've been interesting to compare all the other time specs. BTW the Nova's motor is now in Pumkinator with more compression added and a couple other goodies to help it breathe better on the top end. 😎

View attachment 167464
My sub entry level skills/experience have indicated that no tire spin means launches that look like they take place in slow motion. And too much makes a prepped track look like black ice lol.

imho there has to be spin. You have to factor track prep with tire compound and tire air pressure. Squat, shocks, anti roll bars , etc. all come into play, but not until you find the point where weight transfer is important. The best way to get off the line faster is decreasing weight - but we are g-body people, so for anything other than a full prepped 25.3 chassis means our cars are going to be in the 3500lb (heavy) range.

Im going to say that your lowered 1/4 time was a direct function if your decreased 60’. The fact that you had the same trap speed indicates a limit of something in your driveline.
My $.02 - not worth much more than $.02
 
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UNGN

Comic Book Super Hero
Sep 6, 2016
3,048
113
Southlake, TX
Gearing that helps low, hurts high, and that evens stuff out over the 1/4 mile, so the trap speed can be about the same, but ET is drastically different.

Due to the low HP and High Torque, Stockish TurboBuicks are quicker with taller gears.

I made this graph of "rear tire force" to show why that is.
26 vs 28 in tire.jpg


The Advantage areas of the 28" tire are slightly larger in the 1/4 mile, especially on a slick track where 26" tires are more likely to break lose than 28" tires.

High RPM low torque motor graphs are reversed, with the taller gear advantage happens right after the shorter gear shifts and the taller geared car is still in a lower gear.
 
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lilbowtie

Comic Book Super Hero
Jan 7, 2006
3,460
113
Canton Mi
As said by 500/600 it's about the Hp & Weight that determines MPH. MPH is measured in the last 66 ft so it's your HP at this time that determines MPH. Different tires, gear will effect RPM which may effect HP in the last 66ft hence MPH change.
 
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bracketchev1221

Royal Smart Person
Jan 18, 2018
1,052
113
I think it needs to be clarified, for me, I am talking when I lose a few hundredths in 60' I see the mph go up. Like was stated before it allows the engine to get into its powerband a little faster. This is not blowing the tires off in a complete spin. But on the flip side, when my car dead hooks, it lugs the motor down. But it also 60's quicker which then translates into quicker ET's.
 
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500/600

Royal Smart Person
Thread starter
Nov 17, 2018
1,169
113
West Virginia
I think it needs to be clarified, for me, I am talking when I lose a few hundredths in 60' I see the mph go up. Like was stated before it allows the engine to get into its powerband a little faster. This is not blowing the tires off in a complete spin. But on the flip side, when my car dead hooks, it lugs the motor down. But it also 60's quicker which then translates into quicker ET's.
Mine was blowing the tires completely off. Two passes at 94+ and one at 91+ makes me wonder where the 3mph went on that pass and how much I lost on the other two.
 
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Vilanus

Not-quite-so-new-guy
Dec 13, 2020
16
3
My regal made its first pass at 14.07 spun all the way through the traps all 4 gears on the 7.5 rear end ,slicks, 9in with 430s ended in a best of 10.35 so I'd say tire spin makes a difference lmao
A 10.35 car with a 7.5 rear end 😵
 
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