What type of tires were used on Ferrari 250GTO

[peteski]

When they were new, in the '60s.  I found sizes 6.50-16 front, and 7.50-16 rear, but were those bias ply tires?  Ballon?  Probably not radial.  Need a short tutorial on tires.

[Ace-Garageguy]

Michelin X radials were introduced to the public in 1949, but 250 GTOs left the factory on Dunlop cross-ply racing tires.

The answers you seek are here, grasshopper:

https://www.borrani.com/ferrari-wheels/250-gto.html

Radial tire history:   https://www.michelin.com/en/news/the-x-radial-tire-is-70-years-old/

Difference between radial and crossply tires:   https://www.bigtyres.co.uk/blog/whats-the-difference-between-a-radial-or-crossply-tyre.html

Edited June 23, 2023 by Ace-Garageguy
CLARITY and ACCURACY

[peteski]

Thanks Bill!

I know the difference between bias ply and radial. For modeling purposes the visual difference is the sidewall profile, so I wanted to know what was used on this car. Looks like either radial or bias ply are correct to use.

[Ace-Garageguy]

1 hour ago, peteski said:

I know the difference between bias ply and radial. For modeling purposes the visual difference is the sidewall profile...

I can't always tell by looking, and sometimes have to read the sidewall to be sure.

Add that to the fact that several manufacturers now make vintage-looking tires on radial carcasses, you kinda have to be careful in the real-car biz.

[peteski]

Again, this is for a model. I think that back in the day the bias ply tires had a more "full body" rounder sidewall profile than radial tires have.  That is the look I'm hoping for.

[Ace-Garageguy]

42 minutes ago, peteski said:

I think that back in the day the bias ply tires had a more "full body" rounder sidewall profile than radial tires have.

Interesting. My impression was always the opposite...that bias ply tires generally had flatter, more "vertical" and square-shouldered sidewalls...which would be consistent with their construction, below.

The typical radial tire always looks to me as though it's the one with the "full body, rounder" sidewall, as below.

The crossply Dunlop CR65 racing tire that would have been OEM on a 250 GTO looks more like a radial sidewall, but with a blocky square-shouldered tread.

Edited June 24, 2023 by Ace-Garageguy

[peteski]

Looks like I misspoke.  I'm looking for this:

 

I think those are bias ply?

[Ace-Garageguy]

1 hour ago, peteski said:

I think those are bias ply?

If those are all period photos, most likely.

The Dunlop Racing tire in the top photo (Testa Rossa?) has a non-radial size marking, and looks like a crossply.

The two shots on the 250 GTO I couldn't say for certain by looking...which gets back to me stating earlier I can't always tell (and have to read the tire data to be certain), especially with vintage racing tires, as some of the sidewalls look very much like radials...as I also mentioned.

Honestly, the tires on the GTO look much like the sidewall shape and proportions of a radial 245/70-R15, with a fat round sidewall, and square shouldered blocky tread.

Imagine the tire below without the white lettering...very similar in appearance to the tires in your GTO shots.

Edited June 24, 2023 by Ace-Garageguy

[Ace-Garageguy]

This design is what would have been OEM on the 250, crossply CR65 Dunlop Racing, and inflated on a rim, would look like your photos and also the radial shown above.

https://www.borrani.com/550m15-cr65-dunlop-racing.html

 So use what looks like period shots, and call 'em what you want.  

 

 

Edited June 24, 2023 by Ace-Garageguy

[peteski]

Thanks Bill - very helpful.

Actually Bill, than Dunlop tire is a perfect example of what I was looking for.  It is cross (bias) ply, and yet it has a very bulbous profile, and fairly narrow tread area.

Edited June 28, 2023 by peteski

[TonyH]

Bringing this thread back back. I ran across the following webpage while researching this topic as I've been looking for a suitable replacement tire for the Gunze Sangyo 250 GTO. 

https://www.longstonetyres.co.uk/classic-car-tyres/ferrari/250-gto.html?cc=8u01n7vo4o9duarqe6uulcn3vh-1743715744

 

I just received these tires from Jack Modelling today. I currently have them in the sun to finish post curing. I'll pull the wheels off my completed 250 this weekend to see how they fit. They're supposed to be 1/24th scale to fit the Fujimi but my initial reaction leaves me concerned they might be smaller than I had hoped for. 

FYI shipping was surprisingly fast and cost effective from France so I wouldn't hesitate to order from him again.