Tire spin vs. mph

500/600

Royal Smart Person
Thread starter
Nov 17, 2018
1,169
113
West Virginia
I removed the front sway bar (23 pounds) and cranked the rebound all the way down yesterday now the left front end comes way up even though it still spins. I’ll have to install one of my airbags in the right rear. I have 30x9 Goodyear slicks to try next time. 30” slicks and 2.94 gears and a 2500 converter just sounds hilarious. I also have everything to move the battery to the trunk.

I talked to the track owner and there will be Test and Tune until weather won’t permit any longer so I’ll get another shot at it.

I will not be happy until it hits 97.5mph with this combination and without any more weight removal. I truly believe that I spun that much away Saturday. We shall see.

BTW, I got 14mpg round trip including the strip passes. Not too bad.
 
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pontiac guy

G-Body Guru
Oct 28, 2016
580
93
Royse City, TX
Tire spin slows you down. Consider this. The coefficient of friction when sliding is about 70% of max. Max is the point on impending slip. That means you are only able to transfer 70% of the power being produced to the ground as when the tires aren't slipping. You can spin them faster but you cannot deliver more than the coefficient of friction allows. Of course your power transfered is a function of time. So in theory if you spin more you deliver lower power faster and you could possibly deliver more than no slip but off the cuff I'm going to say no one here is making that much power
 
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lilbowtie

Comic Book Super Hero
Jan 7, 2006
3,460
113
Canton Mi
My car and launch technique are scattered all over the place so far that I can't even give an answer. I've yet to duplicate my best run ever at 12.11@116. The most consistent day I've had was this summer with some 12.30s around 110-112. The track where I ran the quickest/fastest has closed, so I can't even determine if that was a factor or not.

You need to keep a log book of your runs and the weather. I have a weather station that feed a computer program with all of my passes. The computer will actually tell me what the car will run and I can dial it right off the trailer. One weekend @ Summitt Racway a low front came through over night and the next day the computer told me to dial 2.1 tens slower (hard to believe) but it was spot on so keep an eye on the weather.


I will not be happy until it hits 97.5mph with this combination and without any more weight removal. I truly believe that I spun that much away Saturday. We shall see.

I hope you make it but I would be more inclined to believe it would be because of weather-staging (which can go either way)
 
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Kwik_Cutty88

Moderator
Moderator
Nov 22, 2011
1,165
113
Coastal North Carolina
I saw that one too. Pitiful that he used a 20 second 70 mph example.............a vehicle that couldn't produce tire spin on ice.

Surely somebody has run street radials one pass and slicks the next to say that mph did or did not change significantly.
This is as close of a comparison that I could muster with my data sheet (which has 50+ passes on it.)

I understand they are different tracks, different weather, etc, but again as close of a comparison that I could muster. The only things that changed between these two laps are tires.

8.548 @ 85.08 mph---2.103 60 foot time---275/60/15 Hankook Ventus H101 Street Tires---987ft DA



8.031 @ 86.63 mph---1.838 60 foot time---26"x9" Hoosier D07 Slicks--- -38ft DA


 
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UNGN

Comic Book Super Hero
Sep 6, 2016
3,048
113
Southlake, TX
In the case of a high RPM hp car with too tall gearing, the tire spin acts like a slipping clutch gets the car into the power band sooner & keeps the car in the power band for longer.

A '73 Mustang with a 351 Cleveland with headers/cam but still has the factory torque converter & 2.75:1 rear axle, I would bet a dollar that a spinning leave would have a higher trap speed than a hooked up leave.

Setups like this is where these myths begin.

Any car set up for drag racing, no way.
 
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64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
3,612
113
Upstate NY
I’ve read, somewhere, that 7-8% on a drag radial is about where maximum traction is on a prepped track. I spent a bit of time trying to dial in traction control to 8%. After a bit of frustration I determined there were too many factors for a novice such as I to figure out what worked best without ALOT of trial and error. Tire pressure, tire and track temp, of course traction compound, etc., and then my imprecise method of determining tire revs per mile lead me to determine what worked best was based previous experience.
I have no idea how you would monitor this without wheel speed and drive shaft speed sensors data logged though.

What I’m confident of is that a certain amount of slip is better than not enough. And it’s a struggle to control it with spark and fuel cut rather than an abs module like the OEM’s do lol.
 
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Oct 14, 2008
7,668
113
Melville,Saskatchewan
You have a huge but good problem, getting a 500+ ci hot Cadillac V8, designed to move 5000 pound cars, now way more powerful, down a track. I assume you have one of the wider 20" Nitto Drag radials and lowered tire pressure somewhat? Sounds like removing the front swap bar helped somewhat. The track can be frustrating and my 403 with street tires actually hit a 2.6 60 ft due to wheel spin, felt like I was on glass. What does the converter flash at, behind all that torque?
 
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Rancook

Not-quite-so-new-guy
Sep 25, 2020
11
3
Yes, tire spin will typically result in higher trap speed. If peak HP is much higher than stall speed, then the tire slippage will put the engine in, or closer to, peak HP. The higher rpm and HP will give the engine greater leverage to accelerate the car and result in higher MPH sooner (distance wise), but will not make up for lost ET in the 60' due to tire slippage. I've experienced it 100's of times.
 
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SRD art

G-Body Guru
Jun 16, 2011
528
63
St. George, UT
A different scenario but maybe worth sharing? Pumkinator ran consistent 14.60s @ 100.X at 3000 ft altitude with a mildish 406 SBC, stock converter in a TH350 and 2.41 gears. I swapped in a 3.42 GN rear for the next track visit and went 13.90 at 100.X. I was a bit surprised, the 60' improved a bunch and the E.T. dropped 7/10ths but the MPH pretty much stayed exactly the same within a couple 10ths of a MPH. With the 2.41s I was going through the lights in 2nd gear and with the 3.42s I was in 3rd gear.
 
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500/600

Royal Smart Person
Thread starter
Nov 17, 2018
1,169
113
West Virginia
A different scenario but maybe worth sharing? Pumkinator ran consistent 14.60s @ 100.X at 3000 ft altitude with a mildish 406 SBC, stock converter in a TH350 and 2.41 gears. I swapped in a 3.42 GN rear for the next track visit and went 13.90 at 100.X. I was a bit surprised, the 60' improved a bunch and the E.T. dropped 7/10ths but the MPH pretty much stayed exactly the same within a couple 10ths of a MPH. With the 2.41s I was going through the lights in 2nd gear and with the 3.42s I was in 3rd gear.
No spinning with either gearset?

That is what’s supposed to happen. It’s a horsepower thing. Yours is no exception.
 
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