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Are these 305's or 315's?

ChevyHDGert

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d2alio Enthusiast

d2alio

Posted
Posted

i think they are 285's as well.... 305's at the largest... no way are they 315's... you'd need a lift for those and that looks like a stock 2500HD

J-rod Enthusiast

J-rod

Posted
Posted

Lol ... just to keep things even, I'll say 305's! :uhoh:

 

Actually, a buddy at work just got a set of 285's on an identical truck and, while the height looks about the same, his don't look as wide as the ones on the truck in the pic. And that should be about right since the 285's are a bit taller but not as wide as the 305's.

 

$.02

Mr Mojo Enthusiast

Mr Mojo

Posted
Posted

Remember 305 refers to section width, not tread width and the height comes into play with the aspect ratio.

 

1 inch=approx 25.4 mm

 

So a 305 would be 12 inches from sidewall to sidewall, then with an aspect ratio of 75 on a 15 inch rim, you get a height of about 33".

J-rod Enthusiast

J-rod

Posted
Posted

Well, the 305's that I've seen (for instance, Goodyear's MTRs) have an aspect ratio of 70 ... which makes em just a tad smaller (in diameter) than the 285/75's. However, if the aspect ratio is 75, then you're definitely correct ... they'd be taller.

 

ChevyHDGert, if ya find out what size they are, let us know! :uhoh:

Big Boy Enthusiast

Big Boy

Posted
Posted

Close but no banana folks

 

305/70/16 is a 33 inch tire x 12 wide

285/75/16 is also a 33 inch tire x 12.5 wide

 

Yes these are approximate. Different manufacturers differ a bit.

J-rod Enthusiast

J-rod

Posted
Posted
Close but no banana folks

 

305/70/16 is a 33 inch tire x 12 wide

285/75/16 is also a 33 inch tire x 12.5 wide

 

Yes these are approximate. Different manufacturers differ a bit.

 

:cheers::cool::smash:

 

The first number (305 and 285 respectively in this case) is the section width (in millimeters. And since 285<305 ... it can't be wider. Given 25.4 mm in an inch

 

285 mm = ~11.2"

305 mm = ~12.0"

 

The second number is a percentage and is used to calculate section height (distance from the bead to the outside of the tread). Once you have section height, double it (once for the top of the tire and once for the bottom), add the wheel diameter and you have the overall diameter of the tire. So in this case that would be 32.8" for the 305 and the same on the 285. So I was wrong in saying the 305 was shorter. I'd never done the calculation myself until now, I based that on a tire size chart for Wrangler MTRs or some other tire I looked at in the past. Sorry for the misinformation. But the 305 is definitely wider! :rolleyes:

 

PS - I just did the "Ask Seller a Question" thing on ebay so hopefully he'll tell me what size tires those are ... I'm all curious now! hehe.

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