Original 240 tire diameter

[Richard McDonel]

I'm at the need-tires stage of my Series 2 240 restoration.  I have the stock steel wheels and a set of 6" mags.  What I want to do is fill the wheel well the way it would have been originally, but I can't seem to find the diameter of the stock, now obsolete, 175 HR-14 tires (no aspect ratio) tires.  Anyone have that data handy?

Thanks

[SoCalJim]

Would this help?  Look at Page 9, in the table for XAS and evolutions.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=20&ved=0ahUKEwjvoMfJwabaAhUp2oMKHTF0BKM4ChAWCHQwCQ&url=https%3A%2F%2Fwww.michelin.com%2Feng%2Fcontent%2Fdownload%2F12061%2F137268%2Fversion%2F2%2Ffile%2FPneusCollection_2012_GB_BD.pdf&usg=AOvVaw1JLhJ2DjfkJI0ZC0Kd2wlo

[Captain Obvious]

Old brain cells, but I believe the default (if it's unspecified) aspect ratio back then was about 80 percent. And if you do some calculations on the listed specs in the document linked to above, they come out to be just that.

For example... They indicate the overall diameter for the 175-HR-14 to be 634mm. Using that as a starting point, if the tread width is 175mm, then the aspect ratio calculates out to 79.5%.

= ((634 - (14*25.4)) / 2 ) / 175 = 79.5%    

[Captain Obvious]

Oh, and even though they are old brain cells, they aren't THAT old. I personally wasn't buying tires back then, but I remember hearing old guys talking about it. 

However, I'll admit that the first tires I bought were bias ply.  

[siteunseen]

31 minutes ago, Captain Obvious said:

Oh, and even though they are old brain cells, they aren't THAT old. I personally wasn't buying tires back then, but I remember hearing old guys talking about it. 

However, I'll admit that the first tires I bought were bias ply.  

Bias tires? So that's where black wall and white wall comes from. Prejudice tire manufacturers!

[Richard McDonel]

Thank you gents,

Yes, the Michelin chart gave me what I wanted. I'm going with the 195/70 R14s - less than a third of inch variation from the 175 HR14s.

Getting closer.

[Martzedcars]

I Always found this listing handy when going for another tire ..

Left you see the tire circumference (in blue colomn)  and to the right all the tires that have that circumference    easy peaZy  

Just you know.. this is in millimeters, not in foot,inches or el, thumbs or whatever...  

Edited April 7, 2018 by Martzedcars

[Richard McDonel]

Mart,

Thank for this.  Potentially very handy -I'm going to save it.  And yes, I pretty much figured out that there were no passenger car tires 2,000 inches around!

Cheers,

[JSM]

On 4/6/2018 at 5:37 PM, Captain Obvious said:

Old brain cells, but I believe the default (if it's unspecified) aspect ratio back then was about 80 percent. And if you do some calculations on the listed specs in the document linked to above, they come out to be just that.

For example... They indicate the overall diameter for the 175-HR-14 to be 634mm. Using that as a starting point, if the tread width is 175mm, then the aspect ratio calculates out to 79.5%.

= ((634 - (14*25.4)) / 2 ) / 175 = 79.5%    

So in today’s terminology would that be 175/80/14? 

[Captain Obvious]

Yes. 175/80/14.  And I can provide one more (admittedly circumstantial) piece of evidence to support that theory...

Up until 74, all the FSM's listed the tire size as 175HR-14. Then in 75, they started listing 195/70/14 as an "optional" size. Doing the math, you find the following:

175/80/14 - Theoretical height is 25.0 inches tall
195/70/14 - Theoretical height is 24.75 inches tall

So with a quarter inch difference between the two, you could switch back and forth between those two and only introduce a very small amount of speedometer error. In my little pea-brain, this supports my belief that the earlier size can be most closely duplicated with a 175/80/14. (Because if not, the speedometer would be significantly wrong.)

Not sure I explained that well... Does that make sense?

[JSM]

1 hour ago, Captain Obvious said:

Yes. 175/80/14.  And I can provide one more (admittedly circumstantial) piece of evidence to support that theory...

Up until 74, all the FSM's listed the tire size as 175HR-14. Then in 75, they started listing 195/70/14 as an "optional" size. Doing the math, you find the following:

175/80/14 - Theoretical height is 25.0 inches tall
195/70/14 - Theoretical height is 24.75 inches tall

So with a quarter inch difference between the two, you could switch back and forth between those two and only introduce a very small amount of speedometer error. In my little pea-brain, this supports my belief that the earlier size can be most closely duplicated with a 175/80/14. (Because if not, the speedometer would be significantly wrong.)

Not sure I explained that well... Does that make sense?

Yep you did. Thanks. 

So the side wall size is always represented in % not mm?  

Edited April 12, 2018 by JSM

[Patcon]

3 hours ago, JSM said:

Yep you did. Thanks. 

So the side wall size is always represented in % not mm?  

Yes, that is my understanding. Sidewall height is represented by the percentage of the tread width