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CN36

Discussion in '206/246' started by Longstone Tyres, Oct 28, 2021.

  1. Longstone Tyres

    Longstone Tyres Formula 3
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    Dougal
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  3. malcolmb

    malcolmb Formula 3
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  4. Longstone Tyres

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    I’m assuming you mean 205/70-15 like the later series 3 E-type fitted when it had power steering.

    https://www.longstonetyres.co.uk/classic-car-tyres/jaguar/e-type.html

    for power steering cars we suggest the Pirelli P5, because this is the tyre Jaguar asked Pirelli to make for their power steering luxury cars.

    6 cylinder cars drive better on the 185-15 Cinturato CA67 which we will have back in stock in a couple of months, or the 185VR15 Michelin XVS.
    However some people like a wider 205/70-15 tyre on here because it fills the wheel arches, and they like the look. And for these non power steering cars we’d suggest 205/70–15 Cinturato CN12 or XWX. But really put function in front of fashion and fit a proper period 185
     
  5. Ribolla_67

    Ribolla_67 Rookie

    Sep 6, 2016
    25
    Austria
    Hi Dougal,
    What is the difference between the Pirelli P5 and the Pirelli CN12 in the same dimension?
    I know the story of the P5 J development from the Norman Dewis book and drive the P5 on my Jag, as I have the CN36 on my Dino. Great tires, better than the (beautiful) XWX.
    But why does Pirelli offer 2 tires in the same dimension?

    Thanks for your expertise!
     
  6. Longstone Tyres

    Longstone Tyres Formula 3
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    CN36 is a 1968 tyre that was developed with Porsche and Pirellis first stab at low profile tyres, very much aimed at progressive handling The CN36 was developed for the Fiat Dino and Porsche 911

    The CN12 is a 1972 sportscar tyre, use by Maserati and Lamborghini and Jensen sportscars as a transition from full profile tyres to low profile tyres.

    the P5 was devceloped in conjunction with Jaguars XJ series and their suspention and steering set up of the period, with a bit more emphasis on quietness and comfort, and a slightly later nid to late 1970s tyre
     
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  8. Ribolla_67

    Ribolla_67 Rookie

    Sep 6, 2016
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    Thanks Dougal!
     
  9. Longstone Tyres

    Longstone Tyres Formula 3
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  10. Froggie

    Froggie Formula Junior

    Sep 27, 2017
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    Dougal,
    If I follow you, on a GT car like the Maserati Indy with power steering and 15" wheels, also usually driven gently, would the P5 be more appropriate than the CN12?
    On the contrary, should the CN12 be preferred only when the car is a sports car or when the usual driving is more spirited?

    Actually, the Pirelli site does not say much.
    If you know more of it as both the P5 and CN12 seem to benefit from modern refabrications, could you develop the differences between the P5 and the CN12 in terms of carcass, rubber, rounded profile, tread, etc. and possibly your driving experience on both tyres?
     
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  11. Longstone Tyres

    Longstone Tyres Formula 3
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    oo that is a good question

    most of my books say 205VR14 so in most cases we just say Michelin XWX

    https://www.longstonetyres.co.uk/classic-car-tyres/maserati/indy/205wr14-michelin-xwx.html

    No one else worth considering makes that size so it isn't normally an issue.

    However i beleive some of the later 4.9 cars fitted 15" wheels which does put you into the CN12 or P5 region (or of course XWX)

    are you on 205/70-15 or 215/70-15?

    Any way it is a good question so i have actually pinged it accross to my freinds in the technical department in Pirelli. Fortuately i have a freind there who was around at the time.

    I'll be back
     
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  13. Froggie

    Froggie Formula Junior

    Sep 27, 2017
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    Thank you Dougal,
    Actually the question does relate to 215/70 R15 for a Maserati Indy (late 4900 Indy's were equipped with XWX's or CN12's in that size)

    I see that there are indeed many options: XWX, CN12, P5 or Vred, to name the usual classical tyres (excluding modern tyres).

    As Pirelli is offering both the CN12 and the P5 in that size, and as the Indy is not really a sports car (more of a GT), I was wondering whether the P5 that was tailored for a smooth ride of later Jags (XJ series, XJS, XJ40) would not fit nicely with the Indy, although the rear suspension in the Indy is more basic.

    So If I have understood correctly, the tyres and handling would be smoother going from the XWX, to the CN12 and finally to the P5.
    Right?
     
  14. Longstone Tyres

    Longstone Tyres Formula 3
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    Do you know what date they moved to 215/70VR15?

    I have obviously historically had trouble defining it for this web page

    https://www.longstonetyres.co.uk/classic-car-tyres/maserati/indy.html

    It seems at one point i also stumbled accross something suggesting 205/70R15. Id like to get it accurate. i love a bit of pictorial evidence on my web site. specially if it covers tyre pressures too.

    Mme! In my mind their is only Pirelli and Michelin worth considering.

    This is what i wanted to pin down from Pirelli to make sure i explained it right. This is what i got:

    "In parallel with performance, an equally important mainstay for the Collezione project is historical accuracy, whenever possible.


    When asked to supply tyres for events, exhibitions and the like, we always prefer to suggest what would have been closest to the original fitment – and if not available, a reasonable time-congruent alternative.


    In this specific case, the available original option for the Maserati Indy was the CN12, and this is what we would recommend; the P5 was developed only some years later, and for slightly different targets: the first was Pirelli’s best option for sporty cars, while the latter better suited those car where comfort was an important requirement."


    I asked if my older freind there had developed the tyre and if he could rember anything about the development. I then teased them slightly by suggesting they had the same carcass just with a different tread pattern for a bit of fun (knowing full well they weren't.) To which he said:

    "I was about to ask ##### to step in, so no problems at all!


    P5 and CN12 do not share the same spec, even today: as you know the P5 was co-developed with Jaguar and Mercedes back then, and also the current version was tested with Jaguar at MIRA in 2019, in order to get their type approval.


    You are correct, CN12 is slightly stiffer, and I confirm P5 is a product better suited for those circumstances where cruising comfort is more important than pure handling – yet we’re still talking of high end cars.


    I’ll be glad if ########## can add his comment too!"


    Then i was very please to get the following answer from my other freind in Pirelli.

    "Dougal, still alive and kicking.

    Getting back to business, I was involved in the Jaguar P5 development as a youngster in Burton and from memory the two targets were ride comfort and steering precision to give them a competitive edge over the German luxury cars at the time. The pattern was designed from scratch to move away from straight longitudinal grooves of it’s predecessors (CN12 & P7) to improve rolling noise. I recall that P5 by standards at the time was discovered to be extremely good in the wet.

    I cannot find any launch material but these two center page ads tell the tale.


    Obviously the comments from ######### are absolutely correct regarding the authenticity of the fitment in the timeframe of the car. "


    I particularly like the "Pirellibility" coment in this advert.

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    So i hope that covers the CN12 V P5 issue. However CN12 is better for an Indy.

    Then when you ask about a XWX "V" CN12 it does put me in a slightly difficult political position, because i personally think Pirelli and Michelin are the best tyre manufacturers. All 3 tyres are great. However they do have different characteristics. I would suggest the XWX is fabulously durable. If i was going to blast accross Europe at 100 mph then spend some time on a race track then drive home i would fit XWX. However if it rained id rather have the Pirelli. However the Pirelli and Michelin are both ace.

    then of course there is fashion
     
  15. Froggie

    Froggie Formula Junior

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    Wowww, Dougal, that is a very impressive post!
    Excellent information and good to think of, thank you.

    I would say fromm all of this that if I use mainly my Indy as a comfortable tourer on smooth roads or highways, P5 with its "Jaguarist" specs would be fine.
    On the other hand, CN12 and further XWX would be more appropriate if I sometimes wanted to drive spiritedly on small roads. Or would be more appropriate on a Ghibli or a Bora.

    Regarding the transition from 14" to 15" wheels for the Indy, I believe it corresponds to when Maserati introduced the 4900 engine on the Indy. That was in 1971.
    It is well reported in the Indy owner manual.
    At that time, the Indy shifted to the Campagnolo Starbust 15" wheels, like in the Ghibli, departing from the bimetallic Borrani 14" wheels.

    Regarding the Tyres, the 205 VR14 tyres were the normal equipment on 4200 and 4700 Indys, either the Pirelli "Cinturato" HS (I think that this was the name before it was called CN12, you may confirm), or Michelin (without a specific name):

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    That then shifted to 15" tyres on the Indy 4900. Some people sometimes argue that 205/70 R15 tyres were fitted to the Indy based on the Maserati owners'manuals.
    Actually there are a number of mistakes in the manual, the low profile /70 tyres not being always accurately reported. For example, the tyres are reported to be 205/70 VR15 in the french and italinan texts but 205 VR15 in the english text nearby !

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    I believe however that the right tyres specs for the 4900 were actually 215/70 VR15, as this tyre would have the same rolling perimeter than the previous 205 VR14 and also well filling the wheel well in design terms.
    215/70 VR15 is also the tyre dimension in the Ghibli and Bora equipped with the 4700 or 4900 engine, as well as the Khamsin.
    Most of the 4900 Indys are equipped today with 215/70 VR15 tyres, 205/70 VR15 being sometimes observed on some cars because maybe of non availability of 215/70 VR15 or lower price.

    To the administrators and/or Dougal: sorry for having hijacked that thread on the CN36. Maybe the title could be changed to Pirelli tyres: CN36, CN12 and P5...
     
  16. Longstone Tyres

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    Tricky sorting fitment like this, because even by 1974 Michelin didnt know what tyres they were fitting on the Indy!

    so the brochure says 205 / 70 VR15 and 205 VR 15 i find very amusing. Made more amusing by everyon choosing to fit a different tyre all together in a 215/70VR15. I like that.

    In my Mind as a basic Maserati fitted 205VR15 CN72. then in around 1972 they fitted 215/70VR15, as a basic rule of thumb. Mind you then of course there is also the Merak where they couldn't decide what to fit. Just to let us know there wasn't a basic rule of thumb.

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  17. Froggie

    Froggie Formula Junior

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    I may add that on the original Fahrzeugbrief of my Indy, both dimensions (and rolling perimeters!) are reported: 205/70 VR15 and 215/70 VR15.
    So it's up to each one to choose, personally I think that the right choice is 215/70 VR15.

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  18. Ribolla_67

    Ribolla_67 Rookie

    Sep 6, 2016
    25
    Austria
    Hi folks,
    great discussion, almost with scientific accuracy :)

    I would like to contribute my experience with XWX, CN36 and P5 - each driven 3000 - 4000 km per year , mostly sportive in the mountains:
    - Had the XWX for 5 years on my XJ6 Series 1. Looks cool. Ok on dry roads, poor in the rain. Massive issues with imbalances and eccentricity. Made in Serbia.
    - Replaced the XWX with Pirelli P5 on my Jag 3 years ago. Better on dry roads, much better in the rain, like a modern tyre. Nevertheless smoother riding comfort . No imbalance issues at all. Very quiet. Nevertheless precise steering and crispy handling.
    - On my Dinos, I drive the CN36 since 2016. Perfect modern sportscar tyre by all means. excellent handling and braking under dry and wet conditions. Slightly softer ride than with the former XWX. A little bit noisy.

    For your Maserati, I would try the P5 even if historically not correct. There is nothing wrong when a Gran Turismo provides handling AND comfort
     
  19. Longstone Tyres

    Longstone Tyres Formula 3
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    On the subject of tyre size

    I know its not a good business model. However when there is a choice like this i always er toward the smaller tyre, because it makes a care nicer and more fun to drive. Bigger tyres are really only about the look, and peoples perception that bigger is always better. I garuntee if you did a blindfold driving test you would enjoy the drive more on the thinner tyre.

    Gearing difference. msk! will you really notice it?

    205/70VR15 XWX rolling circumference 2034mm https://www.longstonetyres.co.uk/tyres/205-70-15.html
    215/7oVR15 XWX rolling circumference 2076mm https://www.longstonetyres.co.uk/tyres/215-70-15.html

    (I have used XWX dimentions because i had that book close to hand)

    42mm out of 2034 is that a 2% increase in gearing?

    nearly all of my books simply list 205VR14. (Although i do have some that say 205/70VR14)

    I do have this insurance book which it isnt actually terribly clear what its trying to say, but it does give the impression that it is a 15" rim and a 215 tyre. I dont think i have anything saying 205/70VR15. My speculation is that for the sake of ease of usage of the car in period they also homologated the car to fit a 205/70VR15 tyre, because they wopuld have been considerably cheaper, and there have been times where the only option in that size has been the XWX, However thsankfully now there is also the Pirelli tyres as well.

    However all things considered. regardless of my earlier pontifications i would like to encourage everyone with 15" wheels to continue to fit 215/70VR15 tyres instead of 205 becuase i have to make a living, and 215 are more expensive.

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