Tire sizes 205-75-D15, 205-70-P15, 205-75-R15

The numbers in the tire refer to its width, aspect ratio, and wheel diameter.

So the 70 versus 75 would look lower than the other. And run smaller - since the aspect ratio would make the 70 appear 'flat' or under inflated since the width is the same on the two tires (205).
The D is for Bias ply versus R for Radial ply.  I think P stands for single-ply bias.

15, of course, is rim size or inside diameter of tire.

This link may help:
http://tires.about.com/od/understanding_tires/a/How-To-Read-Your-Tire.htm

The numbers in the tire refer to its width, aspect ratio, and wheel diameter.
So the 70 versus 75 would look lower than the other.


..................Is a 205-75R15      wider than a      205-70R15     ?
Conflicting answers from multiple sources.

I have a 205-75-D15 that is close to rubbing the wheel well.
I need to know if a 205-70-R15 makes it worse or better.
I need to know if a 205-70-P15 makes it worse or better.

note the difference between the three:
75D15 I have.
Choices I have for a replacment are:
70P15
75R15

You will want to keep the aspect ratio the same - 75.  The 70 tire will run a little smaller on the trailer and always look flat with the same amount of air pressure.

So, your replacement should be the 75R15.  This is a radial ply versus a dual bias ply.   This does not affect the size.

The spare will need to be a spare.
My main question, what is the width of a 75 vs. a 70.
If a 70 is "wider" then I need a 75 since my 75 already comes very close to the wheel well.

I'm not at all worried about miles per hour or flat look, only width.

Width being if the inflated tire is laid on the ground on it's side, which is higher off the ground a 75 or 70.

Let me ask it a different way. I'm not concerned with weight capability or tire diameter.

If a 205-75-D15 tire could be placed in a wooden box 2 feet square and exactly 7 inches deep and the tire fit nice and snug. (24 wide x 24 tall x 7 deep wooden box)

Would a 205-70D15 tire fit in that same box, or require a box 24" x 24" x 7 and ? inches?

The 70 tire will be 10 cm smaller inside the box which is about 2 inches more room in the box.

Then since one of my 205-75D15 tires is within 1/2 inch of the wheel well, I could be benefited by replacing it with a 205-70D15 (replacing means to be kept as a spare).

The 70 would actually get me further from the wheel well.
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If my lug bolts have threads outside the nut, I could add a washer to each lug bolt to get the inner side if the tire away from the wheel well. I see no other solution and only 1 of the 4 tires is that close to the wheel well. If that specific axle had slid one side or another, then I'd see the "extra" on the other end but I do not.

Rubber meeting metal on the road is not good and 1/2 inch clearance is slight.

Yes.  

The 70 would actually get me further from the wheel well.

But there is no difference in width (205 is tread width).   The lug bolt issue is not an issue.

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