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Discussion Starter #1
Ran across a tire size conversion table and decided to see what the difference is between the 195-55 than many of us are running and the 175-60 that Darksider # 1 is using and the tire that several others (including me) will be trying sometime in the future.

The 175-60 compared to the 195-55 is:

Sidewall: .1 inch shorter
Radius: .1 inch less
Diameter: .1 inch less
Circumf: .6 inch less
Revolutions: 6 more per mile

Speedometer will be .7 % too fast. In other words (assuming your speedo was correct to begin with:roll:) a registered 60mph would actually be 59.6mph.

I found it on the Internet, so it must be gospel.;)
 

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Trialsman,

Help me with my physics:
If the diameter of the 175/60 is less than the 195/55 how can the speedo be more correct with the 175/60? Am I understanding this correctly?

It seems to me I use more rpm on the 55 than even on the 60 moto tire.

And how can the sidewall be shorter on a 60 than on a 55?

...must be earth warming turning everything around on me...


Ah! after re-reading this I think you mean the 55 is shorter, lesser than the 60...correct? Well that's why we are on this forum, according to KA7W, to sharpen our writing skills
 

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Thanks Frosty,
I guess I understood correctly and thus, I am more confused that ever.

I thought a 60 would have a higher wall than a 55,
And the proportionality of the diameters and circumference has me baffled.

How can the overall diameter be smaller and the circumference larger at the same time--comparatively speaking.

...hey, dont mind me, I am on medications
 

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Circumference = around
Diameter = across

They have a direct relationship so if one goes down so does the other.
I know you know this..just repeating it for myself. ;)
 

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195 175
Overall Diameter: 24.44 * 24.27 * -0.17
Circumference: 76.8 * 76.24 * -0.56

right! come on Geometry, work with me. How can the overall diameter of the 175 be smaller than the 195, AND, at the same time, the Circumference of the 175 be larger than the 195...

....hey, I 'm just asking...stranger things than these are documented in blackholes and dark matter...after all, this is the darkside, ain't it?

But if we use standard logic:

C=(2)(pi)(r)
and thus, D=2(r)
meaning C=D(pi)... since this is a direct variation function of C in terms of D, that would mean that as D increases so will C. Comparatively speaking then, the function depicting the 195 shows the overall diameter being larger than the 175, while at the same time, the data depicts the circumference of the 195 being smaller than the 175.

If one uses Euclidean geometry theories, and both of the tires are subjected to the algorythm of the formula for the Circumference of a round shape, then there is something wrong with this picture. Albeit, there are other multidimensional geometric theories that may solve this euclidean discrepancy were the position of both tires exist in a unique place in the universe. Unfortunately, I am not well versed with these theories...
:popcorn:
 

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Discussion Starter #10
I, too, defer to the smart sounding guy:lol: I told you I just got it off the internet. Maybe I shouldn't have used the word: facts.:oops:

Hell, I never passed algebra.:oops: I just ride em.:shrug:
 

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I as those before me (trialsman, mjmesserli, & hunzee) shall defer to the wise one, the great Nando:superman1:.

For it is through his wisdom that we shall turn the world to the darkside.

All hail to Nando.:bow::bow::bow:
 

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195 175
Overall Diameter: 24.44 * 24.27 * -0.17
Circumference: 76.8 * 76.24 * -0.56

right! come on Geometry, work with me. How can the overall diameter of the 175 be smaller than the 195, AND, at the same time, the Circumference of the 175 be larger than the 195...
24.44>24.27
76.80 >76.24

I am confused. What am I not seeing?
 

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The 195/55 has a larger diameter because 55% of the 195’s tread width is larger than 60% of the 175’s tread width.
Here is my shot at explaining it.

195/55-16

Tread Width: 195 mm or 7.68”
Sidewall Height: 4.22 inches. That’s 55% of the 7.68 inches of tread width.
Overall Diam: 4.22” sidewall height x 2 = 8.44” plus 16” wheel dia. = 24.44”


170/60-16

Tread Width: 170 mm or 6.89”
Sidewall Height: 4.134 inches. That’s 60% of the 6.89 inches of tread width.
Overall Diam: 4.134” sidewall height x 2 = 8.268” plus 16” wheel dia. = 24.27” (rounded off)


I think that’s correct :popcorn: ?
 

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Nando

The ratio 55 or 60 is actually the height (in percentage) of the tire to its width. So a 195/55 has a width of 195mm and a height (55% of 195) of 107.25mm. And a 175/60 has a width of 175mm and a height (60% of 175) of 105mm.
 

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Towerhog,

Does that mean the 175 is shorter than the 190...calculations appear to have gone awry here...give me the meaning!!!

If you can extend yourself beyond the tires, I 'll take the meaning of life also...I 've kind of perplexed by that as well for many years.
 

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Towerhog,

Does that mean the 175 is shorter than the 190...calculations appear to have gone awry here...give me the meaning!!!
Yes. That is what that means. The 175 is shorter than the 195. But only by 2.25mm.

55% of 195 = 107.25

60% of 175 = 105

Grab a calculator and do the math.

And as for the meaning of life? Same formula. :thumbup:
 

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Well Nando, Towerhog had to bring math into this.. but at least for me this one is easy.... The 55 or 60 expression used in a tire size is the ratio of the width of the tire to the height of the tire. But you asked about the width of two different tire, one that is 190mm wide and the other that is 175mm wide. Then wondered which one was shorter... hmmm are you trolling???;) So a 195/55 tire has a height of 55% of the tire width 195.... a 175/60 has a tire height of 60% of the tire width 175... now my head hurts....:lol:
 

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Larry,

Exactly my point...I think I am throwing in the towel....105 is the magical number...I think in cm units the tire would come up to my chest....in which case I might as well use my bulldozer's spare...about same size. If these are in mm then I suspect one of those midget bike tires may be cheaper...in inches, well, yea, I see what you mean...headache! HONEY CAN YOU GET ME AN ADVIL AND A BEER.


....at least, we could have calculated the meaning of life in solidarity...but no! Whatta country!
 

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Height of tire is 2 times the section height plus the wheel diameter. Decode the tire nomenclature as follows:

The 175 is the unloaded WIDTH of the tire (at the widest point) in millimeters when the tire is viewed in cross section.



To get the section height



multiply the section width times the aspect ratio number as a percentage. In this case the aspect is 60, so multiply 175mm * 60% to get 105mm.


To calculate the height of the tire, add the wheel diameter, in our case, 16 inches, to the unloaded heights of both the top and bottom sidewalls.



To get the circumference, multiply the height (diameter) of the tire times pi or 3.14.

Numbers are approximate here. All the tire measurements change when the tire is placed under load.
 

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I love it when a picture appears. It makes things so clear to me.
 
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