Slick tyre growth clearance

dragv6 · Post by **dragv6** » Sun Dec 03, 2006 4:13 pm

What sort of clearance is needed for a 33" x 14" for 180 to 190 mph.
Was told that at least a 39" tub was required , is this correct?
Thanks from Matt

BillyShope · Post by **BillyShope** » Mon Dec 04, 2006 8:22 am

Depends on how much suspension travel you need. A bias ply might grow to nearly 36 at 200. A radial won't grow much at all.

dragv6 · Post by **dragv6** » Mon Dec 04, 2006 3:38 pm

The tyre is a goodyear slick. 33" x 14" .
So 3" clearance for the tub should be ok then.

Baprace · Post by **Baprace** » Mon Dec 04, 2006 8:56 pm

dragv6, If my memory serves me correct, at 145 I used to rub a little with 3 inch's of clearance back in the 70's with Firestones 32 x 15.5 x 15 , but I also ran 132' of trap speed distance versus 66' distance today so I was running a longer track by 66' I think I would call the tire manufacturer and use their recommendation's , 3 inches just seems a little close. JMO

maxracesoftware · Post by **maxracesoftware** » Thu Dec 07, 2006 11:33 pm

dragv6 wrote:The tyre is a goodyear slick. 33" x 14" .
So 3" clearance for the tub should be ok then.

Code: Select all

Dist	Time	Speed	Accel	Engine	Gear	LockUp	Tire	% Rear
Feet	ET	MPH	GForce	RPM	Number	PerCent	RollOut	Weight
-12.0in	-.147	0.000	2.695	7000	1	0.00	103.67	50.0
   0 =	0.000	9.038	2.803	7800	1	15.00	103.69	100.0
  60 =	1.044	65.576	1.585	8476	1	100.00	104.52	82.0
 330 =	2.932	123.871	1.136	7800	4	95.84	106.71	74.3
 660 =	4.525	154.175	0.847	7800	5	97.84	108.55	70.1
1000 =	5.900	179.299	0.664	8602	5	100.00	110.05	67.7
1320 =	7.064	193.278	0.543	9245	5	100.00	111.19	66.2

just a ballpark example,
it looks like around 2.394" inches growth in diameter
but this is 1.196" effective growth at the Tire Contact patch
which could mean the rest of the Tire is bulged out
enough to be 2 inches closer to Body on each side ,
and thats if the Tire stays centered in the wheelwell,
if because of suspension it shifts axle centerline forward
it might contact....so 3" static clearance all around
may just be enough ?

it looks like at least a 39" tub would be needed

BillyShope · Post by **BillyShope** » Fri Dec 08, 2006 5:36 am

Maxracesoftware, that's almost EXACTLY that which I would have predicted for a bias ply tire. Please tell me it was a bias ply. I worked in the Vehicle Performance Lab at Chrysler in the pre-radial days, but I've been told that the growth of radials is negligible. So, if this was a radial, it would indicate that it grows at the same rate as a bias ply and that which I was told is incorrect.

maxracesoftware · Post by **maxracesoftware** » Fri Dec 08, 2006 6:39 am

BillyShope wrote:Maxracesoftware, that's almost EXACTLY that which I would have predicted for a bias ply tire. Please tell me it was a bias ply. I worked in the Vehicle Performance Lab at Chrysler in the pre-radial days, but I've been told that the growth of radials is negligible. So, if this was a radial, it would indicate that it grows at the same rate as a bias ply and that which I was told is incorrect.

i'm assuming it was GoodYear Dragway Specials "Bias-Ply" Slicks ????

i've Modeled a few hundred or so RaceCars and Street Cars
thru ET_Analyst over the years,
and my Tire Growth Algorithm seems to work pretty well ?

i wish i had a lot more DragStrip Onboard Recorder Data
to look at !

here's a Pic of Kallita's Top Fuel Dragster Simulation
that National Dragster Article had some Run Data on,
ET_Analyst's Tire Growth Formula seems to work well even at 330+ mph

some Data from National Dragster=>
Top Fuel Dragster - Doug Kalitta - { High Wing DownForce model }
April 2003 Houston, Texas 10 Feet Elevation { NHRA specs }
30.04 Sea-Level Corr.Barometer, 66 deg.F, 45 % Rh, 91 F Track surface

60 Ft= .847
330 Ft= 2.150
660 Ft= 3.058 - 279.04 MPH
1000 Ft= 3.822
1320 Ft= 4.486 - 333.91 MPH

2250 Lbs. 496 CID 4.187 Bore x 4.500 Stroke

Peak HP= 7933 @ 6715 RPM Peak TQ=6205 { 8550 RPM limit }

6.8:1 Compression Ratio , 2.400 Intake 1.940 Exhaust valves
39.3 % overdrive on Blower
62 deg BTDC at Starting Line & 58 BTDC at Finish Line

here's an old Pic i used in my Tire Growth research
of Bobby Cross and Bubba Corzine's Dragster
look how distorted the Tire is on backhalf and forward half,
and how much more vertical Tire growth there is above
the axle centerline -vs- below the axle centerline -to- the
Contact Patch

http://www.maxracesoftware.com/Cross_Co ... agster.jpg

if you aren't careful enough with a high growth Tire
providing enough Tub clearance the distorted forward front half
and upper half of the Tire can contact the Wheel Tub and slice it ?

BillyShope · Post by **BillyShope** » Fri Dec 08, 2006 7:13 am

Very interesting, maxracesoftware! Thank you.

At Chrysler, we assumed a reduction in wheel revs per mile of 0.2 wheel revs per mile per mile per hour. And, as I indicated, that couldn't get any closer to your results in your earlier post.

What I'm sure we both would appreciate is wrinkle wall tire traction data of the type so often seen for transverse loading. I'm tired of offhand comments like, "A tire acts in traction essentially as it does in cornering." Of course it does! And, I'm well aware of the use of the "friction circle" in performance analysis, but I'd like some numbers! For almost the last 50 years, I've been stressing the benefits of equal rear tire loading on launch, but, when it comes to calculating the benefits, I'm forced to use the load curves from tire cornering tests. I'm sure such a procedure is valid, for I'm simply assuming the friction circle is a perfect circle, but I'd still like some traction specific data for the tires actually used in competitive dragracing.

maxracesoftware · Post by **maxracesoftware** » Fri Dec 08, 2006 12:50 pm

BillyShope wrote:Very interesting, maxracesoftware! Thank you.

At Chrysler, we assumed a reduction in wheel revs per mile of 0.2 wheel revs per mile per mile per hour. And, as I indicated, that couldn't get any closer to your results in your earlier post.

What I'm sure we both would appreciate is wrinkle wall tire traction data of the type so often seen for transverse loading. I'm tired of offhand comments like, "A tire acts in traction essentially as it does in cornering." Of course it does! And, I'm well aware of the use of the "friction circle" in performance analysis, but I'd like some numbers! For almost the last 50 years, I've been stressing the benefits of equal rear tire loading on launch, but, when it comes to calculating the benefits, I'm forced to use the load curves from tire cornering tests. I'm sure such a procedure is valid, for I'm simply assuming the friction circle is a perfect circle, but I'd still like some traction specific data for the tires actually used in competitive dragracing.

from Memory ....
wasn't Chrysler in their Direct Connection Book , that first stated
Formulas to account for Automatic Trans/Converter Slip effects
in determing Engine RPM at 1/4 Mile Finish Line ?

i also seem to remember either a GoodYear/Chrysler Article
or maybe just 2 different Articles close together in a Magazine
about using GoodYear Tire Growth formula along with Chrysler
formula to determine Engine RPM at Finish Line ??

maybe i can dig up those old Articles ?
and Scan them .