Tyre sizes

I don't have a GTC, but I do have some experience in cars where people actually run non-factory tires and wheels. (Perish the thought!)

The 205/70's will be 10mm narrower and 14mm smaller in diameter than what you have.

Visually they will be smaller and fill the wheel well less. This will tend to make the car look less virile or more delicate, depending on how you look at it. The car will be 7mm lower, which probably won't be noticeable.

Functionally you will turn more revs for the same freeway cruising speed and have 7mm less ground clearance. You may or may not notice any loss of cornering ability.

Do your present tires scrape at all at full lock or when going up a driveway? If so, the smaller tires will probably cure that problem.

Those are the pros and cons--it's up to you. But if you're happy with the car as it is the safe thing to do is to stay with what you're happy with.

Jim

 

Are you sure that the factory spec isn't 205 VR 14? That is what the 330 GTC spec is and this tire is quite different from the 70 series. It will fill up the wheelwell as it should and does not look too low profile as the 70 series does in there.

 

Yes, my 330 GTC had the 205 VR 14's. I don't believe that the 70 series tires were introduced until the late 60's. Maybe by the time the 365 came out, the 70 series was stock. In any event, the 215/70 VR 14 should be a bit wider and LOWER than the 205 VR 14s.

 

Be very careful when comparing tire sizes. For my 330 GT, a Michelin XWX 205/70 x 15 (available from Coker) was specified. But I found the Pirelli P4000e 225/65 x 15 was the same dimensionally, except .3" wider.
If I had gone with a modern 205 x 15 it would have been too small.
Look at the diameter/rolling radius and section width when comparing tires. The labeled size now does not appear to be the same as the earlier sizes.

Cheers
Warren

 

Even modern tires vary significantly in diameter and width despite having the same nominal size. I think the XWX's ran on the large size.

 

Or the modern sizes are smaller and more variable who knows. Check the actual dimensions!

 

I agree - 205 VR 14s are the correct size for the 330/365 GTC. I've used both, and the 205/70 VR 14s are just too short, IMHO.

People seem to freely substitute between the two sizes on their 330s, so nowadays, I guess it's more a matter of personal preference. Of course, the 205/70 has the added benefit of not bottoming out on the front air ducts as frequently, so that's a potential plus right there.

 

Dear Colin

I wondered what you did in the end. I am considering putting the taller 205/14 XWX's on my 275 GTB Long Nose, but am uncertain if the spare will fit in the boot.

Mark Shannon

 

the 205VR14 tyre is correct. It's a "78" series tyre. A 205/70 VR 14 will have a much smaller diameter. Owners usually go with a 215/70 VR 14 to get some of the height/diameter back and puts a little more tread on the road.

Steve

 

I just bought a set of XWX 205/14 for my 330GTC. These will go on my newly restored Campagnolos, and the 13 year old (!) XWXs will stay on the Borranis. My understanding (agreed by Tim Stanford) that the 70 series is incorrect for the 330GTC. My inclination would be for you to stay with whatever size the owner's manual specifies for the 365GTC.

Jack