WTB: Pirelli Cinturato CN36 185/70/15 tires

[smiles11]

I’ve tried a few local shops & they’re telling me national backorder. Is there a website that stocks this tire?

TIA

[911MRP]

Longstone Tyres but they’re in the UK. Dougal drops in here from time to time.

[friendlyfred]

I've dealt with Longstone and had excellent service. VERY rapid freight. Less expensive than Coker or Lucas. Would repeat order without hesitation.

[RC70SCoupe]

https://lucasclassictires.com/tires/...inturato-cn36/

[smiles11]

Thank you! Just placed order through Lucas

[smiles11]

Lucas has them in stock! They shipped today! Arriving Friday!

[smiles11]

Another question. Do I need to buy the TR415 valve stems for these wheels to run on 6x15 deep six Fuchs wheels?

[911MRP]

Strictly speaking tubeless tyres should not be used on wheels without the safety humps and without area designed to securely seat a tubeless valve (rather than for the stem of an inner tube)

The humpless rim and the tube valve of the earlier Fuchs were not designed for tubeless tyres. Tubeless without hump not in accordance with Porsche and tyre manufacturer’s published technical information — their reference infomation has long been out there.

Vrieth-Pirelli were the German operation of Pirelli that made the Pirelli tyres used in Porsche factory; this is an original west German made 73 dated CN36 removed from an RS I have kept.
IMG_1610.jpeg

This is in a Vrieth-Pirelli publication of 1972 I have in hard copy among my car’s history papers — my car was equipped with Vrieth-Pirelli Cinturato CN36 according to the fahzeug-auftrag in file so was content was pertinent and contemporary when car was new:

IMG_1605.jpeg


This is 1974 information from Michelin who are said to have invented radials it was my technical info document but I sold the original booklet to Longstone Tyres for reference
IMG_1606.jpeg
IMG_1616.jpeg
IMG_1607.jpeg

Porsche themselves issued a technical instruction giving there position on the matter

IMG_1609.jpg

Moreover tubeless tyres should not be used with inner-tubes either — seem to recall that was Pirelli’s position when I last checked their website a few years back?

Taken together this might be rather a dilemma for drivers of Porsche with earlier, so called deep six Fuchs as tube type tyres not so readily available!

May not be what folks want to hear but just restating what I believe might be still the position held by the major tyre makers in response to the OP question regarding valves since their seating is paramount to reduction of rapid deflation. Pretty sure around the time tubeless tyres were first getting fitted to 911. Porsche used a valve stem support on 7 and 8 Fuchs even though the Fuchs by then were designed to accommodate tubeless valves.

I’m no expert and these published examples here are for historical interest only; so may not be the latest position. I recommend to get up to date advice from the actual tyre maker regarding their product fitment requirements as it’s potentially safety critical.

Insurance companies where I live might if fitment flouted the technical position came to light invalidate motor insurance cover in a claim if tyre rim configuration went against official technical instructions of automaker and tyre suppliers — unlikely perhaps, but in unfortunate situation might it become a significant liability?

Once aware of the position of the OEM and major tyre makers it’s up to each car owner and any company that fits covers to rims what they do with the facts.

Steve

PS
anyone have the technical information group 6 no 12 of 10.10.74 as referenced, maybe there are further information ?

[smiles11]

Thank you for the insightful response. The tires are radial & from the looks of the wheel profile. I think I’m in good shape.

I’ll fit the fat TR415 tire stem to the wheels for good measure.

IMG_7122.jpg

[911MRP]

I don’t see the humps?
IMG_1620.jpg
For comparison this is a 1972 dated Fuchs 7inch which would’ve been on an early Carrera RS. Not from RS as they are still original factory finish Mexico blue but it’s a spare black silver otherwise similar example I have.

Note the distinctive humps running all around the circumference —either side near both outer edges. This safety feature is what Porsche are referring to in the technical information bulletin.

This is a translation of that page using a web tool but German speakers here can probably help if the details need to be more precisely understood. The criteria for use of tubeless tyres are set out by Porsche:
IMG_1618.jpg
By the time this technical information bulletin was issued the Fuchs on 911 had been revised again be “hub-centric” most easily distinguished at a distance from the similar flat Fuchs by centre caps that have two small holes. However closer inspection shows the hole at centre being a different size and accepting a different centre cap is another clue. Both these forms are different to the earlier Fuchs that do not have the hump safety feature also being referred to. Also the valve seating of the earlier Fuchs wasn’t designed with tubeless valves in mind; by contrast the ones with the humps have been designed for tubeless valves.

What some folks (even some experts at the suppliers of the modern Pirelli cn36) had not realised is that Porsche used to tube type rayon belted throughout the so called longhood era. The change from tube type to tubeless documented in respected reference sources as December of 1974 for the Carrera 2,7 G-Series. They evidently had moved to using the hump design rim a few year before they introduced tubeless for calendar 1975 . For example the 73 Carrera RS were supplied with tube type tyre but importantly Porsche had already changed design of the Fuchs TES and RS ahead of the coming of tubeless radial by having incorporated the humps/valve seating.

This is a nos Pirelli CN36 I have that is a Vrieth Pirelli it is a rayon belted tube-type radial not the later steel belted to less. The dot code is visible:
IMG_5833.jpg

As mentioned it is up to owners to decide what combination of Fuchs rim and tyre they fit in current times but in sharing this contextual information hopefully it highlights that Porsche and several of its major tyre suppliers at 72-75 published technical information on what is permitted (or not). While some things have changed such as no longer fitting inner-tubes in modern 60 profile there are some criteria on permited combinations which as far as I know still remain their technical viewpoint. While things have changed and upgraded I suspect the reasoning behind this position is it’s the physics/science.

While it might not be something some folks want to read but it’s a consistent view in black and white. Hope this helps.

Steve