´71 911T - 14" or 15" Cinturato CN36s?

[RetroGuy]

My ´71T came factory equipped with 14" x 5.5" Fuchs "comfort" wheels, which I am currently running, being shod with 185 x 14" Vredestein Sprint Classics.

Since I also have set of 15" x 6" Fuchs deep sixes ready for installation, I asked myself the following:

Since it´s time to change out the 10 yr. old Vredesteins (which always felt a bit too soft for my liking - I think due to the rather high side walls (measuring out to approx. 148 mm) I was wondering whether I would notice a difference between the Pirelli Cinturato CN36 in their 14" size (wheel diameter 614 mm, equalling a side wall measurement of about 130 mm) and these tires in their 15" size (wheel diameter 637 mm, equalling a side wall measurement of about 129 mm)? I am well aware that between my 14" Fuchs and the Deep Sixes there´s also a difference in width of 0.5" which could make a difference?

The 14" combo would save about 1.3 kg/2,85 lbs per wheel.

Many thanks for your expert advice!

Stefan

[hot66]

ignoring any performance differences .. your car IMHO will look visually better on the 15's

[RetroGuy]

ignoring any performance differences .. your car IMHO will look visually better on the 15's

thanks! I am well aware of this , but at this stage I would primarily be interested if the performance is about the same between these too!

[hot66]

ive not driven any early 911 on 14's so cant comment from experience .. but if you consider Porsche themselves decided all their 1971 E's & S's performed better on 15's and also offered the T's with 15's option for me its a no brainer .

[domtoni]

My car came with 14 inch wheels, and I bought a set of 15 x 6 a good 15 years ago. It was a simple choice, getting tyres that were V rated.

We have had some tyre discussions here about CN36s (new production) vs new tyres for modern cars. I've got P1s in 195x65x15 on the car now (V rated) and can't fault their performance).

One chappie here has a very expensive 911, and he's using the CN36 in 185x70x15 and says their performance is (my words) awesome.

Pays your money and takes your chances.

[kitesurfer2]

14's offer a comfortable ride, but that's about it. In the visual and performance departments 15's win easily.

[Darren65]

I once watched Jerry Seinfeld say that you replace tyres on age not mileage, I think the perceived wisdom is about 5 years(?).....

....never quite got my head around that concept but 10 years!!!

[911hillclimber]

That is what I've read too.
Chemical changes in the compounds, maybe UV light effects and such like.

The tyres on my car trailer were about 10 years old and failed one after the other last year!
Should be proper guidance's such as the MoT etc that all can use.

[hot66]

Rubber changes with age ... basically go hard and reduce the tyre performance. I know it wasn’t 100% the Tyres, but the ‘Paul walker’ Carrera GT crash, the Tyres were more than 9 years old and cited as a contributory factor

[Gasoline]

The 14 inch comfort wheels are ‘comfort wheels' because they were fitted with full fat 185 x 14 tyres. If you fit the 185/70 x14 CN36 tyre to the comfort wheel, you’ll lose the comfort aspect because that particular tyre is low profile. The rolling circumference of 14 inch CN36 is about 5.5% smaller than the correct 14 inch tyre. Additionally, this combo might look a bit odd: a tyre of 185x14 has a diameter of 650mm, whereas a CN36 185/70x14 is only 614mm.

OP, I also have both sets of wheels for my T:
14x5.5 fitted with Michelin MXV-P 185x14: https://www.longstonetyres.co.uk/catalo ... egory/8278
and
15x6 fitted with Pirelli CN36 N5 185/70x15: https://www.longstonetyres.co.uk/classi ... 36-n5.html

These combinations have a broadly similar diameter, in fact, the 14 is slightly taller. All the rubber is about a year old.

The handling/grip performance difference in normal road conditions is imperceptible. On track, the 15s should trump. With regard to manufacturing tolerances, the 14 inch Michelins were a doddle to balance whereas the 15 inch Pirellis were pigs. In terms of ride, the 14inch wheels are noticeably better (but remember, I’m talking about non low-profile rubber). If I was going on a long tour, I’d go 14s.

With regard to looks, the 15s are more sporty, but then the 14s are more retro with their big balloon tyres.

My preference is 15s with CN36 but the 14s with Michelin are as good. I’d definitely don’t like the idea of 14s with a low-profile tyre such as the CN36 - I doubt that combo was ever offered by the factory. However, any new tyre is going to be better than your current 10 year old rubber.

[Chris_ABZ]

I run Avon CR6ZZs 185 / 205 staggered set up w 7R wheels on my '71T. Love them!