DeTomaso Mailing List: February 1997, Message #100
     



From: schrader@sugar-land.anadrill.slb.com (Kirby Schrader)

Subject: Re: Pantera Tires

Date: Fri, 14 Feb 1997 08:38:02 -0600



Thought I'd add my 2 cents and limited experience here....



I first ran 8" and 10" Campies on my '71 with 225/50 and 285/50 Pirelli

P7's. It looked stock and didn't handle too bad, but just jump on the

throttle in low gear and smoke would start rolling out of the wheelwells...

;-))



So I then moved to Etoile wheels; 9" on the front, 12" on the back and

moved up to 285/40 and 345/35 P7's. Much better! In fact, that's what was

on the car during the Ferrari drag race I've got on my web site.



The P7's are pretty soft and they didn't last long. When it came time for

new ones, I found that they didn't make them anymore! So, having committed

to the wheels, I found the only brand available in that size were the

Yokohama AVS series.



These, in fact, were much nicer to drive around on and handled better. They

also last a little longer than the P7's. The downside? They are a much more

square tire in profile which means that I have some fender clearance

problems at the front........



Before going to Texas World Speedway again sometime this year, my plan is

to find another set of wheels and put some racing tires on them. The track

ate up the Yokohamas pretty fast.... The advice below on the various type

available is good! Thanks!



One other side effect of big tires and track driving..... Make sure that

the body is in good shape. All that stress will start showing up as small

cracks in the body. Typical areas? Right at the bottom of the windshield

pillar where it meets the fender, in the lower corners of the tailight

inset and sometimes right around the quarter windows at the back.... And

another place you'll see some problems is at the far rear corner of the

rear deck. I've seen so many cars where the rear deck hits the rear fender

and starts chipping away the paint. A couple of people I know use tape to

cover this area while they're on the track. Doesn't look cool, but saves

the paint! I've not had the problem myself. Dennis Quella reinforced the

rear body section while I was having the car rebuilt at his Pantera

Performance shop and it seems to have done the trick.



FWIW,



Kirby



'71 Pantera   http://mwd.sugar-land.anadrill.slb.com:8080/





>1)  Tire compounds/sizes.  Shane says he isn't wild about mixing tire

>compounds.  Actually, I see nothing wrong with this.  The Pantera tends to

>understeer, and this condition is aggravated when wider rubber is fitted at

>the rear.  The fundamental handling limitation of the Pantera is the

>inability to fit enough rubber in the front (ask Jack DeRyke who autocrossed

>his car for years).

>

>Fitting STICKY rubber in the front is a work-around to the problem.  Terry

>Aultman is running old Goodyear 265/50 VR Gatorbacks (no longer made) on his

>10-inch Campys, with Yokohama A-008R super-goopy 225/50's in the front on

>8's.

>

>I have determined that it's possible to fit a 245/50 in front on an 8-inch

>rim, and that's what I've done.  I've never driven my car though, of course.

> P.J. Couillard took my advice and is running the Euro T/A 305/50 on 10-inch

>Campys in the back (this is an H-rated tire, by the way, not V-rated as

>previously reported), and he pitched his Euro T/A fronts and replaced them

>with BFG's Comp T/A Z-rated 245-50 on his 8-inch fronts.  He says the

>difference is like night and day, the car sticks solidly now and gives a very

>secure, confident feeling when he flings it into a corner (and fling he

>does--I've been with him when he tossed it into 45 mph corners at about 100,

>and the car just corners like it's on rails).

>

>So I think that's the hot setup for 8 and 10 inch wheels.

>

>If you're sticking with the stock 7 and 8 inch wheels, I'd run a 225/50 in

>the front, but definitely something larger than 245 in the rear.  BFG makes a

>V-rated Comp T/A in 275/60 which is almost identical in size (just a bit

>wider) than the original Arriva.  Jack DeRyke is running ancient Pirelli

>275/55's in the rear with 245/50's in the front.

>

>Lots of people will tell you you should never mix tires of different aspect

>ratio.  Well, we do it all the time with GT5/Group 4 cars; I think the rules

>are different when you're dealing with mid-engined cars with wider rear

>wheels anyway.

>

>I wouldn't run anything with less than a 50-series in 15 inch, however.

> Besides looking sort of goofy and throwing off your speedometer something

>awful, they might do weird things to your handling.  Better to go with

>something greater than 50-series, although 50-series is probably ideal.

>

>2)  Good point raised about the increased loads transmitted to an

>unsuspecting chassis by stickier tires.  This is in fact that cause of the

>concern raised about Pantera brakes; there's nothing wrong with the brakes,

>folks.  They were simply designed to absorb X amount of energy, any more and

>the skinny OEM tires would lock up.  Now we've got tires capabable of

>transmitting twice as much energy to the brakes, and they're overwhelmed.

> Not a design flaw, but if you're upgrading one part of the chassis (the

>tires) you've got to consider the effects upon the rest of the system.

>

>3)  With all the hand-wringing about the lack of suitable tires for 15-inch

>wheels, I'm surprised nobody has mentioned running treaded race tires.  My

>427 Cobra came with Goodyear Blue Streak Sports Car Specials, bias-ply

>super-sticky roadrace rubber.  They're probably only good for about 2500

>miles of combined street/track driving, but they're cheap, and once warmed up

>they stick like crazy.  Don Welch has been running them for years on his

>427-powered Targa Pantera, and they look like a great alternative.  Being

>bias-ply, they ride a bit harder, they'll flat-spot if you leave the car

>parked on them for any length of time, and they leak air something fierce

>(they'll lose 5-10 lbs per week if you don't run them with innertubes), but

>it's worth considering.

>

>Besides, with that giant "Goodyear" logo, they look bitchin'!

>

>I've got another friend with a 427 Cobra who runs hand-cut Indycar slicks on

>the street.  They're cut by a sprint-car tire specialist, and have quite an

>aggressive tread pattern, and a surprising depth to the tread.  They're only

>good for 2000 miles on the street/track too, but hey, they look tough and

>stick well!

>

>Finally, Hoosier makes a really sticky DOT autocross or roadrace compound

>tire, I think in 275/60.  John Wehrheim used these things on his car and

>knocked a bunch of time off his previous year's record at the Shelby Club

>Virginia City Hillclimb.  Cobra guys dig these things too.  They're only

>about $115 apiece, and again, probably only last for 2-3000 HARD miles.  Bias

>ply, too.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Kirby Schrader              Phone: (281) 285-8850  FAX: (281) 285-8999

Anadrill MWD                mailto:schrader@sugar-land.anadrill.slb.com

200 Gillingham Lane #110    Compuserve: kschrader@compuserve.com

Sugarland, TX 77478-3136                ( 72550,1653 )

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