[yvesmontreal]

First, here is a link to Michelin's historic tires data:
Pneus XAS - Technique

The OD of the 165R14 XAS, a typical OE tire used by Alfa, is 626 mm; its aspect ratio was actually 82, typical of european tires in that period. 185/70R14 is already a little down in diameter at 615; 195/65 goes further down at 609, and both 195/60 or 185/65 go too far down at 590 and 596 respectively.

I'm not sure 185s would work well on a 7"rim, especially if you use them on the track. Maybe somebody who has tried this combination will shed some light.

I'm with those who like to stay close to the original dimension to retain the vintage feel. But one thing I'm planning to do (once my GTV is ready) is to get a second set of mags in an adequate size for 195/60 tires. Two sets of wheels for two different driving styles - like having a second car for very little money.

 

[Alleggerita]

I am running a set of 185/70-14 Avon CR6ZZ (hard mixture) on 7x14 Campagnolos on my GTA. They are very tall w/ stiff sidewall which is great for ground clearance. They work very well and look period. Section width increases slightly when using a wider rim.

Also running another set on 6x14 wheels on a Giulia TI. Either wheel size is fine for the tire size.

No issues with track use though they are slower than wider Hoosier race rubber or some of the latest low profiles soft compound rubber, though faster than Dunlop vintage race rubber.

Apart from being expensive, they are brilliant for road use with very high limits, though probably too sticky for an unmodified suspension. They also last much better than expected, much longer than previous Goodrich Comp TA's and Yokohama 001R's.

I'm not sure 185s would work well on a 7"rim, especially if you use them on the track. Maybe somebody who has tried this combination will shed some light.

 

[alfazagato]

Whilst it might be visually attractive to have some additional width of rubber on the ground, I tend to agree with Alleggerita as far as the look of the higher sidewall tyres...and it is not always the case that performance may be improved.

 

[Subtle]

Post # 14

Subtle does not own the Panamerica Super.

Alleggerita does.

 

[emotf]

Thanks Yvesmontreal
This helps - I was working on the original OD being roughly 615. Your information clarifies this to 626mm so some combinations I had ruled out as over sized are now quite accurate (ie. 205/60 R15 equates to 627mm)

This further underlines my queries on my first post about the trend that many are running small ODs on 105's which in my opinion do look odd.

 

[60sRacer]

609 to 626 is about 2/3 of an inch, or just more than 1/3 inch large or small. Hard to see the difference visually. After all, its less than +/- 2% in speedo.

Robert

 

[eedneco]

panamerica super

Alleggerita - Subtle
Sorry guys, for my mistake above.
Post corrected.
Cheers
Neil

 

[Subtle]

Can add some subjective info:

I bought my first Alfa--a 1300 Spider--in 1965. Equipped with Cinturatos the improvement in handling, braking and traction over the Healey 100 and MGTF I had had as daily drivers was outstanding. A night and day difference.

In 1969 I bought a new Giulia Super and fitted it with Semperits, which were highly regarded. I took drivers training and there was a tendency to throw shoulder tread blocks.

Five years ago I bought my 101 Spider and have run a few track days with Vredesteins. At a meet in July we had three sessions on each of three days and the tires were predictable and while getting hot and sticky did not throw any tread blocks.

On the highways they have been good in the wet and the 80 ratio provides a very plush ride.

The impression is that they have some 30 to 40 percent more traction than the best street tires of 40 years ago. There is little need to use wider tires.

The ability of the car to soak up rough pavement confirms that it was designed to be competitive under most any condition. This was well before R&T developed their slalom and "G" tests on a smooth surface.

But, that is another story.

 

[brad fischer]

Tire diameters

I agree with Yves about the diameter of the tires in question. You can get specs for all of the tire sizes on line or work it out with a calculator. The sizes below show the evolution of Alfas OE tire and rim sizes for Spider and GTV. ( if the GTV was made into the 90s ).

155-80-15 = 629.0 mm on 4.5" rim
165-80-14 = 619.6 mm on 5.5" rim
185-70-14 = 614.6 mm on 5.5" or 6" rim
195-60-15 = 615.0 mm on 6" rim

I also agree with emotf regarding the small diameter of many tires shown or talked about on this forum, in my opinion they do not look correct.
On my GTVs I have had 165-80-14, 185-70-14, 195-70-14,and 205-60-15.
GTs were originally designed to have a tire diameter of about 630 mm or more,(considering Yves info that early tires were 82 series) that's why I have bought larger diameter tires.

195-70-14 = 628.6 mm
205-60-15 = 627.0 mm

 

[emotf]

Thanks Brad,
I agree with evolutionary the line of thinking. Are you currently running 15"? If so which profile and do you have side view pics on a thread?

 

[fangio8c]

I agree with Yves about the diameter of the tires in question. You can get specs for all of the tire sizes on line or work it out with a calculator. The sizes below show the evolution of Alfas OE tire and rim sizes for Spider and GTV. ( if the GTV was made into the 90s ).

155-80-15 = 629.0 mm on 4.5" rim
165-80-14 = 619.6 mm on 5.5" rim
185-70-14 = 614.6 mm on 5.5" or 6" rim
195-60-15 = 615.0 mm on 6" rim

I also agree with emotf regarding the small diameter of many tires shown or talked about on this forum, in my opinion they do not look correct.
On my GTVs I have had 165-80-14, 185-70-14, 195-70-14,and 205-60-15.
GTs were originally designed to have a tire diameter of about 630 mm or more,(considering Yves info that early tires were 82 series) that's why I have bought larger diameter tires.

195-70-14 = 628.6 mm
205-60-15 = 627.0 mm

FWIW... Hi Brad, I also own a 1970 GTV 1750 with Alfaholics GTA replica wheels. I've really enjoyed mine with 195/65/14 tires. Thought I'd throw that out to you since you did not mention that size in your post. Unfortunately the selection in that size is very limited. I'm thinking of going to a 185/70/14 next time. How did you like those when that is what you had on your GTV?

 

[brad fischer]

Tire diameters

My red GTV came with 165-80-14 on steel wheels didn't like them at all. My dads black GTV still has 20 year old 185-70-14 Michelin MXLs they are barely acceptable.
My ochre GTV came with Pirelli P3s 185-70-14 on steel wheels, they were ok. I then bought 195-70-14 they were better, I liked the rpm reduction on the hiway. I now have 205-60-15 on 7" aluminum rims, they were the best in autocross.
To see photos of my wheels,check out my profile photo on my profile page, or look at some of my other posts .

 

[brad fischer]

more Tire diameters

If I were to buy new tires for 14" GTA rims, I would consider the following.

205-60-14 @ 601.6 mm (to small )
195-65-14 @ 609.0 mm (to small )
215-60-14 @ 613.6 mm
185-70-14 @ 614.6 mm
205-65-14 @ 622.1 mm
195-70-14 @ 628.6 mm

If I were buying new tires for 15" GTA rims, I would consider the following.

195-60-15 @ 615.0 mm
185-65-15 @ 621.5 mm
205-60-15 @ 627.0 mm
195-65-15 @ 634.5 mm

 

[brad fischer]

Tire diameters

Or see attached pics of my car with 205-60-15 on " Exotic Italian Alloy " wheels 15" x 7" 22.4 mm offset

 

[Alleggerita]

FWIW

Avon CR6ZZ diameters/section widths/tread widths are as follows:

155-15: 25" or 635mm 6.2" 4.3"
175/70-15: 25" or 635mm 7.2" 5.0"
185/70-15: 25" or 635mm 7.8" 5.3"

185/70-14: 24.6" or 625mm 7.9" 5.7"

 

[emotf]

Yes Brad - the tyres look right to me.
I also came to the same short list for 15x7"

Ride height looks very natural!
- any suspension changes? any clearance issues at full lock?

 

[brad fischer]

Tire diameters

emotf, I lowered the car about an inch. There was slight rubbing at full compression at the rear fender lip, and at the leading edge of the front fenders, when turning. I rectified both easily. If you use 15" Rotas, the offset is 30mm, my rims are 22.4mm so you will have 7.6 mm more clearance on the outward side. I think the 15" GTA rims are 29mm offset, so they will have 6.6 mm more clearance and fit nicely too.

Allegreta, I don't see how Avon CR6ZZ 175 70 15 and 185 70 15 can have the same diameter.

 

[Alleggerita]

All sizes are nominal. Diameter is different for every tire and ultimately what the manufacturer chooses to make them. For OEM tires in the same size - e.g. 165-14 - Pirelli CN36's used to be smaller diameter than Michelin XAS/XVS. Same applies today for any tire out there.

Allegreta, I don't see how 175 70 15 and 185 70 15 can have the same diameter.