DDK - Die Deutschen Klassiker

Dougal Cawley wrote:

Gary71 wrote:I would have liked to see a modern 195/65 in the group test as a reference point.

It would have been worse on these cars.

I would expect a more modern tyre to give better straight line braking in the dry, and less wheel spin in a straight line, definitely in the dry, but maybe in the wet too. but i would only expect it to improve straight line dry performance. But in every other way i would think the CN36 will be better than a modern tyre.

I don't get it - ignoring wind-up, true straight line grip in the dry is a factor of compound (coefficient of friction) more than anything else, and in the dry cornering is a factor of mostly compound and some effect of sidewall and carcass stiffness.. So if a modern tyre is better in a straight line in the dry (be that braking or accelerating) it should (give or take) offer better cornering grip too

Wet grip is down to tread pattern and to a lesser extent compound - if the CN36 is a classic tread pattern then it's massively compromised vs a modern tyre

The only way I could see a modern tyre loosing out to a classic tyre is in ride and potentially "handling characteristics" which I agree are more complex and multi-faceted

I'm with Gary - it would be good to see how a modern tyre (even if technically "incorrect") stacked up.. My guess is as Pirelli were making an advert, they either didn't test one, or they did but didn't include the results

But surely you 'know' and don't need to bet?

What is it that is different in geo terms that the older style design suits?

Now I don't 'know' as I am an eejit, but I'd bet that a modern 195/60 of eqivalent quality would work on our classics at least as well. It's going to be much cheaper because of the volumes. Now we know that price isn't everything!

Dougal Cawley wrote:I would bet that the geometry of the later cars that fit the 195/65 tyres is slightly adjusted to suit the more modern carcass design.

I agree, a simple modern tyre on an early 911 is fine in my experience.

I have modern Dunlop Blu Response Sports on my 73T with a 3.2 in the back.
Works great to me but I don't loon round wet roundabouts trying to go sideways etc. so maybe I'm missing something.

They are A rated in the wet and as quiet as possible, but I selected them for the wet grip.

£40 + vat fitted and balanced/ corner.

I'll try to explain why a period tyre is more suited to an earlier car than a more modern one, but please do remember i am just a tyre dealer with a grade 4 CSE in English not an eloquent engineer turned journalist.

More modern tyres have a relatively wider foot print compared to the width of the tyre than a classic tyre, the lower the profile the more that happens, which means they are less progressive, ie the brake away of a modern tyre is more violent which makes it more difficult to catch. and a modern tyre is not developed to deal with the car drifting at all. modern cars are meant to have ultimate grip. However, in this period cars moved underneath you when you cornered hard, which is a big part of why they are fun to drive.


a Classic tyre has more rounded shoulders to cope with the roll in corners.



Classic cars (here's where my knowledge of specific Porsche models is limited) have a situation where the tyres stay parallel to the side of the car, where a modern cars have a set up where by when you have heavy cornering forces as the suspension reacts it has the effect of adding adverse camber which makes them more suited to the square shoulder of the tyre, by keeping all the foot print in contact with the road. if you fit a modern square shouldered tyre to a car with no negative camber it climbs onto the shoulder of the tyre when cornering and then brakes away more violently. heres a rubbish picture i drew:-



What that is demonstrating is that in the lower picture you will notice a picture of me smiling as i am enjoying the progressive handling of my over exaggerated rounded tyres. as the car rolls when cornering i maintain a reasonable foot print however the car above with a rather sad gentleman has climbed up onto the over exaggeratedly square shoulders of is modern tyres and will suffer with unpredictable handling and a car that goes round a corner like a 50p piece

When you look at a modern car, that has the type of engineering in it that a modern tyre is designed to suit. if you look at it parked up, with steering lock on, you will notice that it's front wheel is at a funny angle, sort of tilted back, that is called caster and that is put into a modern car to help overcome some of the derogatory effects of modern wide foot prints. Then the derogatory effects of this Caster and wide foot prints gives horribly heavy steering and this is then overcome by modern fangled very clever power steering.

I don't know if i have managed to make any sense here. However may i suggest that, regardless how legible my illiterate explanation is, Porsche them selves have decided that these are the best tyres you can get to suit cars of this period and they have given them the N4 homologation. they should know.

Granted if you are racing or you have modified you car (probably by dialing in some adverse camber) then more modern tyres might suit. But for a proper old car, tyres that are developed to compliment old cars are better.

here is a short film of me in my pre Porsche, Porsche; demonstating that even when you have one of the worlds most progressive handling cars in the world you can still make a complete bollox of it (am i allowed to say bollox?)

https://www.youtube.com/watch?v=dT0Y1wOMnuY

Wonderful Dougal, and drawings even I can understand!

Dougal Cawley wrote:

The problem there is those wheels are far too big for the car. Unless of course the example is a tractor

You don't look like I thought you would Dougal

good explanation - I guess if the control over camber is not there then you gain a lot from having increased body roll
i'd think a 911 can benefit on the front due to the (sort of) McPherson strut set-up (assuming you can get some negative camber in there and bleed it off during compression) but the rear is very square on the older torsion bar set-up
i'm really surprised how rounded the shoulders of those tyres are - very pronounced!

and sidewall thickness has a lot more to do with how the car/feels handles as well as the profile ratio. Likewise tyre pressures.

Tyres are also part of the suspension give and feel, and weight of a wheel can make a difference to how a car handles, as well as anti roll bars.

I think there is a lot more than just the tyre having a rounded shoulder or flat shoulder to how it responds when cornering.?

If you want to pay £192.00!!

Vertical Load-Deflection Behaviour of a Pneumatic Tire Subjected to Slip and Camber Angles


http://www.tandfonline.com/doi/abs/10.1 ... ode=nvsd20


or this one for free

https://www.google.co.uk/url?sa=t&rct=j ... 1224,d.bGs


http://arizona.openrepository.com/arizo ... sip1_m.pdf

I like the explanation that old cars suspension geometry had less camber control than modern cars but..

I think the 911 had essentially the same basic suspension from the early cars until very late on. Poss inc the 993.

And I'm sure that the tyres for the later cars are what we would recognise as lower profile square shoulder design.

An interesting topic!

It remained identical (apart from thicker anti roll bars and changing their location) until 89. The 964s introduced coil overs at the front (and rear?) and other changes

Also found this on the elephant racing site - on their ASP page

The 911 suspension was designed in the early 1960s for narrow, high-profile, bias ply tires of the day. '60s bias ply tires did not need or like a lot of negative camber.

Fast forward 50+ years to 2013 - tire technology has progressed - we run wide, low-profile, radial tires. Modern tires need a lot of negative camber to grip well. No surprise, the 911 suspension designed nearly 50 years ago doesn't match the needs of modern tires!

All modern Porsches are designed with aggressive camber curves matching radial tires needs beginning with the 1990 911(964) and continuing through the current models. The ASP updates the early 911 suspension to similarly perform with modern radial tires.

The core problem is illustrated by the stock blue 911 pictured, the tires follow the lean of the car in the turn - causing poor contact as the tires roll over onto the outside edge. The rate of camber gain is too slow, grip suffers.

the picture is a really good example - you can also see most of the issue is on the rear, as there's some "tuck" on the front, keeping those tyres closer to upright (the outside front looks like its moved with the body, but I think its probably just pushing the front tyre relative to the rim distorting the view)

Love the sketch but I can't buy into the arguments.

An old 73 911 with a few tweeks will live with modern tyres at £50 a corner and even look 'period'.

When you are motoring through shite rain on the M6 in traffic, 'A' rated for Water tyres beat period look hands down.

When did you last see an early 911 with a cornering attitude that the blue one!?

Yes you can change your car to take modern tyres, as i said before "Granted if you are racing or you have modified you car (probably by dialing in some adverse camber) then more modern tyres might suit."

But i would suggest that some adjustments away from standard often lead to others. but thats up to you. I think porsche probably set these cars up pretty well. after all you guys all bought one so they must be alright. i don't think that saving £ 50 on a tyre is worth faffing with the integrity of your car. It will just look and handle at it's best on the CN36. that is what that German magazine says and that is what Porsche say which is why they gave it the N4 homologation

Roll up, Roll up! get em while they are hot!
http://www.longstonetyres.co.uk/page/pi ... urato-cn36
I shall be getting a fresh delivery middle of next week

the whole in the wet issue:-

It is not all about the tread pattern, that is just part of it. compound is also critical, and if you look at the scoring system in the article the results Pirelli got are astounding. so when you say A rated for water tyres, that is exactly what these are. they have the period look as well not instead.

Also fatter foot prints aquaplane more.

It's not about buying into my argument. These are the facts, Pirelli made the tyres for these 911. they know what they are doing they have been making tyres for 100 years and they are one of the worlds best tyre manufactures. Porsche tested these tyres and say yes these are perfect, they can have the N4 homologation. that German magazine tested these tyres with a modern up to date test and said they are great. And yes you can buy cheaper tyres, if you want to choose your tyres just based on price, which is what some people do, and that is their choice. but they are not better, they are just cheaper. (and they look crap)

Here is a Rubber news i made some time ago, when Pirelli first made the CN36 for us

https://www.youtube.com/watch?v=6oqiP1l ... kh&index=4