A few of my personal thoughts on tire and wheel sizes FOR THE STREET; all have been tested by myself and my wife over 39 yrs of ownership with no crashes.

If you're attempting to maximize tread width and cornering, 225-50 x 15" fronts on 8" wide Campys seem a bit stretched. I don't use the 7" Campy version, I use 245-50x 15"s- about the widest front tread size one can run on an unflared Pantera body regardless of wheel diameter. Even then, some minor hammer-contouring must be done on the inner fender panels and fender lips rolled, for clearance in tight turns. More so if the U.S DOT bumper-height/headlight height spring spacers are removed and extra caster added. 8" Campy front wheels also correct the poor scrub-radius produced by 7" Campys. I suspect Dallara's first recommendation for the Pantera was for 8" fronts.... or else the excellent fit is pleasantly coincidental.

The first instance of 10" x 15" 'DeTomaso' Campy 5-window wheels were on the Euro Pantera GTS/Gr-3, noted in the 1972 GTS/Gr-3 Supplemental Pantera Parts Catalogue. Along with those wheels were listed 225-50 x15" P-7 front tires and 285-50x 15" P-7 rear tires. The rears were about the widest street tires available at the time and were used in club-racing & hill-climbs. 295-50 street sizes were not yet available or go-fasters would have snapped them up! GR-4 and GT-4 racers, of course used even wider slick 'gumball' racing tires with relocated a-arm points and flares.

 The 245-50 front/295-50 rear tire combination works well on the street on our '72, but to maximize big tire benefits, I use stock OD HOLLOW front antisway bars and HOLLOW 1" OD rear antisway bars. Hollow bars cold-bent of thickwall 4130 tubing are slightly less stiff than replacement solid bars of the same OD. The softer hollow-bar action works well with an otherwise stock Pantera chassis and drops about 50% of the unsprung weight of the bars. I also found it necessary to add Koni adjustable shocks front & rear with different springs (available in the '72 Gr-3 catalogue).

All this, along with all-custom alignment specs, a 2 degree nose-down attitude and a minimal Peter Revson front spoiler (the Gr-3 catalogue lists an equivalent front blade spoiler but I like Revson's curvy design), allows us to take full advantage of the remarkable handling and high speed stability Dallara gave the Pantera. Above 170 mph, a blade rear spoiler (or wing) might be needed for added anti-lift, according to regular SS runners. And if you're running way up there on the speedo on the street, you don't need MY suggestions! You may need a Viet Nam era 'get-out-of-jail-free' card, though...YMMV.

J DeRyke

Jack, good historical info.

There is also a benefit to going smaller on a given wheel width, stretching the tire a small amount. This promotes better sidewall action especially with modern performance tires using stiff sidewall construction.

My experiment with a 235/50-15 Toyo R888R on a 15”x10” wheel yielded some good benefits in transition speed due to the stiff sidewalls being at a more desirable angle in relation to the wheel bead.

Is ultimate overall lateral grip lower? Possibly. Is the reduced overall grip offset by more transition speed in mid corner performance? Possibly.

I have yet to perform instrumented testing back to back with a wider tire. That would prove challenging since same model tires in different, but appropriate tires sizes aren’t easy to come by in the 15” diameter.

I can only comment on track testing which proved to be excellent. The 235 R888R performed superbly on the 10” wheel. Ultimate lateral grip was stupendous and transitioning was much better than a “too wide” tire would have provided.

Another thing to consider is that published tire sizes are often guides rather than actual measurements. Case in point, the 235 R888R is actually 9.7” in width, which predicted its favourable performance and fit on an otherwise unadvisable 10” wide wheel.

Other 225 or 245 mm tires are often much narrower than their published widths may suggest.

However, for looks on the street, it may not be an aesthetic choice for most.

I was hoping to hear from someone who is running these new P7s at higher speed (over 100mph) extended to get their impressions versus the existing TB5/15, P7 Corsa Classic, P Zero, Avon and Yokohama AVS options that have been available.

The Get Out Of Jail Free card sure sounds good!

LS

 

GO TO JAIL

Lash apparently Dougal isn't following this topic. To get an answer to your question it may be more expedient to contact him via the Longstone Tyre website.

Jack, it is true the 15x10 Campy wheels came on the scene in late 1972 or 1973, but the 225mm & 285mm Pirelli P7s came on the scene in late 1977 or 1978. The 15x10 Campys where manufactured for a different tire which came on the scene in the summer of 1972 … the H60V15 Goodyear Arriva. It followed De Tomaso's convention of fitting tires on the widest wheel possible. The 15x10 wheel offset makes much better sense with a 255mm wide tire, which is set about 15mm inside the fender edge.

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lashss posted:

Dougal, I assume these “new” 285 and 345 P7s are fully endorsed (as noted by their official speed rating) for extended, high speed use?

Anyone with first hand experience on these “new” P7s at extended high speed?

Thank you,

LS

these tyres are Y rated 

https://www.longstonetyres.co....li-cinturato-p7.html

https://www.longstonetyres.co....li-cinturato-p7.html

so that is 300kmh (thats about 200mph). the load and speed ratings are listed on these pages

I have a question nevertheless, a tire 285x40x15 is 11.4% smaller than the OE 255x60x15  and the 345x35x15 is 9.4% smaller.

Beyond the problem of technical controls if they are meddlesome,  doesn't it have true problems? 

 

Rene, running slightly larger OD  but narrower rear tires causes no particular problem on a Pantera. All they do is slightly re-gear the final drive to the pavement and, if you have the torque available, maybe a bit more speed in all gears. I ran 275-55x 15" Pirelli P-7Rs on 8" Campys for 15 years , before a pair of 10" Campys fell into my lap. As mentioned in my 1st post, wider wheels & tires are for maximizing traction and handling. If that's not your primary goal, a narrower, taller rear tire will work fine, look OK and can even be 'adjusted' outboard a bit for better appearance with wheel shims.There's plenty of clearance for even giant rear tires with proper wheel backspace. Front tires are a completely different story.

The 285x40-15" tire was the first really wide street-type radial tire available to the public, so thats what wound up on Gr-3s with the optional 10" rear Campys. If 295-50s or 305-50s had been available, DeTomaso and the racers would have gone with those. Many Gr-3s ran gumball race tires on track or during hill climbs, or in some cases they used treaded racing rain tires because with most Gr-3 club-racers, they WERE interested in maxing traction, not necessarily in European street legality or tire longevity.

One 275/55 has almost the same diameter that the OE tires but one 285/40 is much smaller, the back of the car will be 1"1/2 lower and there will be more space  of 1"1/2  between the wheels and the wings, that should not be pretty.


Is anybody running the OEM Size Michelin XWX  used on early pre L cars of 185/70VR15 fronts and 215/70VR15 rears? Coker Tire sells them, but I want to make sure they dont look wimpy, compared to the Avon tires I am used to. Its only used for street driving, no racing. Any photos out there?

Here are some pictures with OEM tires. I have a set on my car. Yes they look wimpy especially from the rear, and they don't feel good on the road. I have decided to take mine off and go with wider tires, and just keep the OEM's as a spare. Good for originality show, but not for GO!

https://www.mecum.com/lots/CA0...72-detomaso-pantera/

Adjustable shocks so the car can be lowered would improve the looks IMO, but then you are breaking from originality again.

I wonder if anyone has tried Mickey Thompson Tires?

The Sportsman S/R are available in 26x10 (255/55) and 26x12 (305/45) in 15 inch. They even have the european E-Label on them, which make them street legal in the EU. the 26x12-15 is just 2% smaller than the 285/50-15, which is closer than the 275/55-15 Avon (3% bigger).

https://www.mickeythompsontire...-tires/sportsman-s-r

The ET Street S/S are available in a number of different sizes but look a bit sporty for the street.

https://www.mickeythompsontire...-tires/et-street-s-s

Does anyone have experience with these tires?

Pirelli has (or had) a 'Special Projects' tire building shop in Izmir (eastern Turkey) where limited market tires have been built for decades. Problem is, I understand that's also the tire shop where all the F-1 and other pro racing tires are built. Guess which takes precedence during the racing season? Nevertheless, a few such tires do trickle out- to be instantly grabbed by Euro dealers who have standing (paid-for) orders.

That's what happened up to about 2015, anyway. You need to talk to someone in the know located in Europe about today's situation. The Swedish Pantera Owners Club has gotten hold of a few dozen tires that way in the past, but the market is limited for 285-50x15 for 10" Campy rears and a few other brands of street cars. While the smaller OD 285-40 x 15s are used for Countache, Porsche & wide-body Pantera fronts; much bigger market. My info is dated- the last tires I got thru the Swedish Club was early '90s and that was a group buy with the European Lambo Owners Club. Good luck-

I was just e-mailing with Dougal (Longstone tyres) about that Pirelli 285 / 50 R 15 tyre. He said, that he has a list of people waiting for that tyre, but that list is unfortunately a very short list. He also said, that he should be meeting some Pirelli people in October and they should be discussing the production of new sizes. So maybe, if you are interested in that size, it just might be good to add your name on that list before that meeting. I have been on that list for a long time, but I doubt that my interest for one set means very much for Pirelli... dougal@longstonetyres.co.uk 

 

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