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.

Attachments

Photos (1)

Add Reply

Likes (0)
Post
×
×
×
×