tire size calculations

205/65-16 = 26.48 combined wheel/tire diameter/height

200/60-16 = 25.44 combined

The first number in tire sizes is tire width, in 200/60-16, 200 mm

The second number it the sidewall height in relation to the width. So the sidewall height is 60% of the 200mm. So 200 x .6 = 120

Now take the 120 and change to inches by multiplying by .03937
120 x .03937 = 4.72

The last number is the rim diameter, 16 inches

Now add 4.72 + 16 + 4.72 = 25.44

You need 2 sidewall heights in there, one for each side of the rim

So, based on the calculations . . . and seeing the two tires next to each other . . . can I get confirmation from y'all that:

A 205/55-16 tire is wider than a 205/65-16 tire ?

If I do the math on paper, it is; if I use one of those online tire comparers, it's not; when I looked at my 205/65 next to another biker's 205/55, his tire looked somewhat wider (I didn't have a ruler to double-check).

A little help to put my mind at ease ?

mytee_hercules wrote:So, based on the calculations . . . and seeing the two tires next to each other . . . can I get confirmation from y'all that:

A 205/55-16 tire is wider than a 205/65-16 tire ?

If I do the math on paper, it is; if I use one of those online tire comparers, it's not; when I looked at my 205/65 next to another biker's 205/55, his tire looked somewhat wider (I didn't have a ruler to double-check).

A little help to put my mind at ease ?

It's NOT wider......the 205 is the width and 205 is 205. The 55 is a shorter tire than a 65. His calculations are for height not width. The middle number is the % of width. In other words...a 205 X .55 will give you one side wall height. Add that one more time plus the rim diameter and it will give you your overall tire size to match it to what you are looking for.

Some tires between brand or sizes of the same brand are made by different machines can be different sizes, just slightly. But they are suppose to be the same.

I hope this helps you understand what he was doing.

.................bobby

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Well, it may be wider, but only due to differences from one brand to another or differences in wheel width. For example a Continental Milestone 170/80R15 bike tire is 3/8" wider and 1/2" taller than the Dunlop 404 in the same exact size. I've seen offroad truck tires vary by as much as two inches on tires with the same exact measurement on them. This is why we can't just pick ANY 205 rear to put on the stock 1300 rim as some are made for a wider rim and some are just plain wider.

It's just one of those things, manufactureres are not held to any standards really on how they size tires. One of the popular dual sport tires (forget which brand) Just renamed it's 130/80-18 to a 120/80-18 and the measurements diud not change, but 120's are more popular so they just renamed an existing tire pretty much.

George

+ 1 George.........you said it better I think!....


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I have a 06 raodliner with a 190/ 60 17 bridgestone. how do i figure out what size c/t to get that will fit without modifying anything.

sfredendall wrote:I have a 06 raodliner with a 190/ 60 17 bridgestone. how do i figure out what size c/t to get that will fit without modifying anything.

Working on it.....I will let you know tomorrow.


...................bobby

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Just to make your life more difficult, the actual Mounted Width of your tire will change depending upon the Rim Width of your wheel.

Manufacturers specify a size like Pirelli 205/75R/15 based on being mounted to a specific Rim Width, in this case 5.5 inches. So when I mount this tire on my 4 inch (4.0/15 stock) rim the tire walls are squeezed together and it becomes 190 (not 205) wide when mounted.

The rule of thumb is 10 mm for every 1 inch difference. So 5.5 inches minus 4.0 inches is 1.5 inches difference or 15 mm narrower. So 205 drops down to 190.

BTW: I tried and failed to mount this Pirelli to my vs1400 Intruder -- it was too Tall. So it is now for sale cheap to get it out of my garage. Never used at all. $25 plus Shipping (whatever we can figure as the cheapest way).

If my calculations are correct you can get almost the same size tire with a 205/55/17 providing you can find someone who makes that size, I haven't looked.
190/16=4.488" (your tire)
205/55=4.43" (best match)
205/60=4.84"
205/65=5.2"
200/65=5.11"
200/60=4.72"
200/55=4.33"
215/55=4.65"
215/50=4.23"

You will probably need to double check these as I was using my phone for a calculator and I need glasses for close and small work :pirat:

Stater61

You have to take into account the width of your rim and the size rim the tire manufacturer uses.

For example: two tires of 200/60/17 but measured on 5 inch and 6 inch rims will actually be different widths when mounted on your 4 inch rim -- 190mm and 180mm.

I am a new member here (I am usually on IntruderAlert.com) but I would assume a site dedicated to DS tires would have already developed a spreadsheet which calculates all this stuff. If not lets do it, so everybody can share.

I have an Excel spreadsheet I developed for my vs1400 Intruder with 4.0/15 rims. This could be modified to deal with other sized wheels.

does anyone know what size car tire will fit on a 2008 electra glide clasic

i have a factory tire now and need to convert a mu 85 b16 to car tire size.

john1961 wrote:i have a factory tire now and need to convert a mu 85 b16 to car tire size.

An MU85B16 translates to a 140/90-16 tire.
If memory serves me I don't think you have more than a 1/2 inch clearance between your tire and the drive belt.
I don't know of a 16 inch car tire that narrow.

this link may help



.http://ejelta.com/tiresize/index.html?ws17=1&tiresize=180/55-b18&minwidth=160&maxwidth=205&minratio=&maxratio=&minwheel=5.5&maxwheel=&maxdelta=2

you guys are making this way more complicated than it needs to be

unless your changing the wheel as well as the tire, the total height is irrelevant.

so long as your keeping the same wheel is as simple as multiplying the width by the aspect ratio and comparing, no need to convert to inches either

for instance my stock tire is 150/70-17 = 105mm
my car tires is 205/50-17 = 102.5mm

my CT is 2.5mm shorter from the axle to the outer diameter of the tire, a 205/55-17 would be 7.75mm taller