215/60-15 Tire Selection

[RTincher]

I'm expecting delivery of my newly refinished Weidman deep six and "widened" 7's in December, and am trying to decide on the shoes for them. The car is a '71T with a fresh 2.7RS spec engine and factory 80% LSD. Plans are 70% street, 15% autoX and 15% DE events.

My preference is to go with a combination of 195/65-15 fronts and 215/60-15 rears for the compromise of control, ride quality, original appearance and proximity to original height.

Seems like the most likely choices are the Pirelli P6000's and Bridgestone Potenza RE960AS Pole Position.

http://www.tirerack.com/tires/Compar...None&x=60&y=12

Any comments on these two tires, or recommendations on another in these sizes?

Thanks for the help.

[dvkk]

Yokohama ES-100s. The grip is unreal!

[LKreg]

Your preference sounds good. Harvey reco'd the Dunlops to me and we both liked them. Here they are on 1970S, but in 205 on 6&7's. Don't know why they cost so much less.

[Paul Schooley]

They're made 10 minutes away from me (Dunlops that is)

[nickd]

Porsche Post

Tyres
A month or so ago we looked at seats and harnesses – the things that secure the driver to the car. This month we are taking a look at tyres – the black things at each corner that secure the car to the road.

Background
The 2.7RS was one of the first production cars to be fitted with different sized wheels and tyres, front to rear. At this time, low profile tyres were still in their infancy and the choice of sizes were very limited. The standard configuration was:
1 Front - 6x15 Fuch wheels with 185/70VR15 tyres
2 Rear - 7x15 Fuch wheels with 215/60VR15 tyres
Although different in size, these tyres were of identical diameter and rolling radius.
The vast majority of RS’s left the factory with Dunlop SP Sports, although Pirelli CN36 were fitted to a small percentage of cars. 7”&8” Fuchs rims, when they were homologated later in 1973, were a popular upgrade and these were the widest rims allowed with the original tyre sizes. They provided a slightly flatter ‘footprint’ a slightly wider track and significantly stiffened the sidewalls to give sharper handling.

Spacesaver Spare
Obviously, different size wheels and tyres and, for non-UK cars, the larger 85 litre plastic fuel tank, presented a dilemma regarding the spare. This was resolved only by TUV (the German department of Transport) road homologating an innovative, deflated ‘spacesaver’ spare which was legal for sizes including those of the RS. for the two sizes in, with a compressor. The space saver came either as a 5.5x15 steel or 6x15 forged alloy Fuchs type. Generally the former with its compressor was supplied to Tourings (M472) and the latter with a rechargeable air bottle to Sport (M471). UK-spec cars had to comply with the 1922 Fuel Act(!) and retained the standard 65 litre steel fuel tank and fully-inflated spare.

Developments
Tyre technology moved swiftly and, in 1974 the 911 3.0 Turbo could be had fitted with the newly developed, and lower profile, Pirelli P7 (front – 205/55VR15; rear – 225/50VR15) as a DM 850 optional extra. These tyres could be fitted to the RS, although better suited to 7s&8s, but the lower aspect ratios reduced the overall diameter, which affected gearing and required a recalibrated speedo. Also, the tyres did not fill the arches quite so convincingly, unless the suspension was lowered. This and maintenance of the rolling radius was addressed in the Turbo by going to 16" wheels in 1977. Later series RS’s were fitted with shorter rear suspension trailing arms to homologate them for the 2.8 RSR. This allowed the wider, flatter race car tyres to retain better contact with the road surface and was only really appropriate for the racing width tyres..

Developments have continued apace with wheel sizes increasing and tyre profiles decreasing. Porsche continued to specify 15” wheels (6s&7s) for base 911s and 944s, with the original size tyres, until the mid-1980s. However, over the last 20 years, these tyre sizes have been progressively phased out and there is now a fairly limited choice. The biggest difficulty is finding matching sets, front to rear, in terms of size, brand, speed rating, loading etc.

Tyres obviously play a crucial role in the performance of any car and the latest technology should enhance the steering, braking, lateral adhesion, stability and comfort of the RS even further. Remember that current rubber, even in the original sizes, is almost certainly able to out-perform the 1973 product by a considerable margin in all respects. This includes adhesion, durability and aquaplaning resistance. So, don’t forget that today’s tyres on the original sizes will put significantly higher mechanical loading on your 30 year-old suspension and chassis, especially when on the track. Low profile tyres may not be necessary! In fact you may find that these are so sticky that you may be in danger of loosing a lot of the fun of driving the RS as it was meant to be driven. That is one reason the rounder-shouldered BF Goodrich Comp-TA’s were the ‘demon’ racers’ tyre in the ‘80’s, especially in the wet.

Ultimately, safety has to be the primary consideration, so, if your tread levels are low (less than 4mm) or the tyres are more than 10 years old, perhaps now is the time to consider a change. I have recently explored the options available and listed below are some of the available choices.

Road Tyres
Only Fulda is currently able to supply the original standard sizes in matched sets but the tread pattern is definitely not “period”. (Fulda ‘special order’ code is: 503 153 for the fronts and 502 713 for the rears). The rears remain available in 215/60s from other manufacturers, but the only alternative fronts are now 195/65s. These have a slightly wider footprint and stiffer sidewall, improving front-end grip and steering responses and reducing understeer. There appear to be only two choices from mainstream manufacturers – Pirelli P6000 (N1) or Good Year Eagle NCT5. I run the Pirellis on my 6s&7s and I have just fitted the Good Years to my 7s&8s so, in the future, I should be able to provide some comparisons. Initial impressions favour the Good Years

There is a wider choice in the lower profile 205/55 and 225/50 sizes. These include Michelin Pilot Exalto, Bridgestone SO3, Dunlop SP9000, Good Year F1, plus some other less well-known brands.

Race & Road Legal Track Tyres
If you want a period race tyre, Vintage Tyre Supplies at Beaulieu still do the traditional early ‘70s Dunlop Racing tyres. These would look terrific, but they are cross ply and not covered by the EEC road homologation.
The no longer available Pirelli P-Zero Cs used to be very popular. The Michelin Pilot Sport Cup (205/50 and 225/50) seems to have superseded them. Dunlop Motorsport also offer the D01J in these sizes, or more interestingly, the D84J in 225/55 and 205/60, which would provide a wider footprint whilst still closely matching the correct rolling radius. The D84J has an attractive traditional tread pattern and sidewall featuring the emotive Dunlop-R logo.

Mixing Tyres
Aside from the legal requirements, it is highly inadvisable to mix different tyre makes on the same axle. Most people would also prefer to retain matched tyres front to rear. However, for those in the know, particularly for competition use, there are circumstances where it is necessary to achieve particular characteristics from one end of the car by using different tyres. So, if you know what you are doing, fine. But, for most of us, the engineers designed the car to have matching pairs.

Set Up
Obviously, if you are investing in a new set of tyres it pays to have a full 4-wheel geometry check by an accredited specialist with an intimate understanding of the RS. I had mine done by JZ Machtech and they recommended fitting a Weltmeister strut brace. This contributes to the torsional stiffness at the front of the car, however, it is not acceptable under Appendix K historic regulations.

Porsche originally recommended tyre pressures of 2.0 bar (front and rear), but revised the rears to 2.4 bar in May 1973. Most owners will use these as a guide and experiment to find their preferred settings.

The above is purely intended as an informative guide. Tyre performance is very subjective, but getting the right tyres on a well set-up car can transform the performance, safety and enjoyment. As a final note do not be tempted to run on the road or track on tyres over seven years old. "Original" tyres may look nice for concours - in use they may seriously damage your health and wealth...


I went to Pirelli P6000 a year back and enjoy their handling characteristic's , they roll somewhat more than the low profiles I had on for years. Would love to get hold of some DUNLOP R's though......

I use LES TRONZO - PERFORMANCE TIRES - WILMINGTON DE - HE ATTENDS HERSHEY EVERY YEAR.....

[ljowdy]

Sorry but I don't mean to hijack this thread but, I could use a little help in this department.

Currently, I'm having a 1973.5 911T restored. It's a sunroof coupe with all of the "S" options including Koni's and anti sway bar.

I'm stuck on wheel and tire size. I have the option of having Deep 6" at all 4 corners, flat 6's at all 4 corners, 7" at all 4 corners or Deep 6 front and 7 Rears.

Opinions????? Anyone with sound advice will be appreciated.

Next problem. Regardless of the rim sizes, what tire sizes do your recommend. For example: 205/60/15 front, 215/60/15 rears? etc etc

Final problem: Which tire brand and model seems to be the best for all around street use providing the maximum grip. I don't really care about tire wear, just grip.

thanks in advance
Larry