Carrera 4 tyres

[Dean Peach]

Can anyone tell me what size and make the original tyres are for a 1990 964 c4?

 

[Dave Wilkinson]

Dean,

Fronts were 205/55 ZR 16 and rears were 225/50ZR16. I'm afraid I can't tell you exactly which brands of tyre were fitted at the time although a huge range of manufacturers were approved at that time.including the usual players like Michelin, Pirelli, Continental etc. Only "N" rated tyres were approved by Porsche. These sizes were for fitment to the standard D90 wheels.

I doubt that any of the tyres manufactured in 1990 are still available as manufacturers seem to update the available models more often than computers these days.

If you haven't done it already you should invest in a copy of Adrian Streather's book - Porsche 911 - Enthusiast's Companion (Auftragsnummer 964). It's an invaluable resource for the 964 owner. I'm sure it will answer man of your questions - and more besides.

Regards

Dave

 

[mwadams]

Or go to John Miles site which has a lot of tech info and there is a section on wheels, tyres, makes, etc, etc

http://www.porsche964.co.uk/technical/964%20wheels%20and%20tyres.pdf

Mark

 

[Dean Peach]

Thanks for the info guys, I know I've got to put some on my new purchase pretty soon so I looked on blackcircles.co.uk. Not too pricey !
I'll ask my Wife for the book for a pressie.

 

[Neil Eldred]

And when you do get the book, have a look at pages 52,64, 312,321,525 and 540 as there is a rather pretty Targa in it [] (Neil blows own trumpet here) !!

Seriously though the book has plenty of things to read up on and most home remedies are available in it

Regards,

Neil Eldred

 

[38F3E1]

So 1990 cars came with 16" wheels only? My car has 17" Cup 1s fitted (7s front and 8s rear) so have they been added afterwards?

Ian.

 

[Neil Eldred]

Sounds like it. AFIAK it was only the turbo that had 17" wheels to cope with the bigger calipers. !7" wheels fill the arches IMHO so thats why plenty of people have optioned that.
Regards,

Neil Eldred

 

[38F3E1]

Cool. Saves me the job and the cost of doing the upgrade myself. Probably done when the cup mirrors were added too. Shame they didn't do the rear calipers :-(

Ian.

 

[Neil Eldred]

Are you sure that the previous owner hasn't just put bigger wheels on and left the calipers standard? Have a closer look to see. If your going to Enysham have a look at mine as it has the brake upgrade aswel as the 17" wheels

Regards,

Neil Eldred

 

[38F3E1]

Yes that's what I said ... I still have the earlier calipers on the rear.

 

[graham harvey]

This may be a dumb question but why does the profile on the front have to be 50 when the rears are 40. What would the effect be if the fronts were 40 also ?

 

[Dave Wilkinson]

ORIGINAL: graham harvey

This may be a dumb question but why does the profile on the front have to be 50 when the rears are 40. What would the effect be if the fronts were 40 also ?

Graham,

It's not a dumb question. It's because the rear wheels are wider than the front - a design requirement because of the weight distribution. The 40 and 50 figures relate to the aspect ratio of the tyre and describe the height of the tyre sidewall. You can see that a 205mm wide tyre with a 50% aspect ratio (i.e. 102.5mm) would give a similar sidewall height to a 255 tyre with a 40% aspect ratio (102mm). If you used the same aspect ratio for both tyres the rolling radius of the tyres would be different and the wheels would rotate at different speeds. This would cause havoc with the ABS system (and PDAS if you have a C4) since the system is designed to cope with a maximum difference of 6%. Hope that explains it.

Regards

Dave

 

[graham harvey]

Thanks Dave - saved me making an expensive error at the tyre shop at the weekend !