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  #1  
Old 12-18-2005
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Tire size explaination

I think this has been covered before but I can't find the post.

So what does 285x75x16 mean ? I know the height and width are in there some where. I know 16 is the diamater of the wheel but thats it. Is that 285 cm tall ?

Also why are some tires in the above format and other more simply put 33x10.5x15 ?
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Old 12-18-2005
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285 is the tread width and the side wall is 75% the size of the width
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Old 12-18-2005
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and thats in mm not cm
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Old 12-18-2005
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Quote:
Originally Posted by dsef82
and thats in mm not cm
edit, yea your right

so 285 divided by 25.4mm = 11.2 inches in tread width
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Old 12-18-2005
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you off 1 inch = 2.54 cm or 25.4 mm don't belive me look it up. i have to do this conversion all the time
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Old 12-18-2005
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dang it got a phone call in the middle of that reply and didn't see where you edited sorry
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Old 12-18-2005
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metric versus english measurements
and they are totally different sizes - close is not exact
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  #8  
Old 12-18-2005
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thats the first metric measurement that makes less sense then the english version, (meaning mm sockets make more sense and are easier then english fractions)
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Old 12-18-2005
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in the above example by side wall you mean the height from the wheel to the top of the tire and not the over all diamater of the tire right ?
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Old 12-18-2005
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so if i get this right that tire in the example is about a 32.8x11.2x16
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Old 12-18-2005
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Tire Size & Service Description (e.g. P185/70R13 89T):

P Tires with a P are using a P-Metric designation, which is the American market sizing standard started in 1976. All P-Metric tires are engineered to standards of T&RA (Tire and Rim Association). The "P" stands for "Passenger" vehicle. If there is no "P", the tire is engineered to ETRTO (European Tire and Rim Technical Organization) standards and is considered a metric tire. Standards by ETRTO and T&RA have evolved together, and are virtually interchangable.

185 The first number on the tire size is the cross-section width. This value is the width of the tire from side-wall to side-wall as measured in millimeters. This measurement is usually obtained from the bead of the tire (where the tire mounts to the rim.)

/70 The two digit number just to the right of the slash (/) is what is referred to as the "aspect ratio". Not a 'specific length', this value describes the distance between the bead of the tire to the tread as compared to the cross-section width. This is viewed as a percentage value. (e.g. P185/70R13 has an aspect ratio of 70% of 185mm....or 129.5mm.). Lower apect ratios confer a stiffer ride and increased control than a similar sized tire with a larger aspect ratio. But larger aspect ratios tend to be more absorbant and add to a smooth road ride.

R This letter indicates the type of ply construction in the tire's casing or carcass. "R" means radial. "D" means diagonal, referring to bias tires. "B" means belted for belted-bias tires. Never mix radial tires with any other constru ction on a car.

13 Rim Diameter. It is the diameter of the bead seat in the rim. Most tires are built to inch standards for rim diameters. However, some tires are built to millimetric rim dimensions. Always match the tire's rim diameter to the wheel rim diameter.

89 Load capacity. Refer to the load index chart of a tire guide to find the maximum load carrying capacity of the tire.

T Speed Rating. This designation should be compared to the Speed Rating Chart to view the recommended maximum speed for this tire.


Speed Index Chart:
Speed Rating
MPH KPH
N 86 140
P 93 150
Q 100 160
R 106 170
S 112 180
T 118 190
U 124 200
H 130 210
V 149 240
W* 168 270
Y* 186 300

*ZR classifications for these wheels are for vehicles capable of over 150mph/240 kph but NOT exceeding 168mph/270kph or 185mph/300kph respectively.
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Old 12-18-2005
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Yes and Yes Ben to you above posts
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  #13  
Old 12-18-2005
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Quote:
Originally Posted by Ranger1
about
very important word here.....
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Old 12-18-2005
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If you have a calculator, I "reduced" the formula so you can figure tire diameter easily from metric sizes.

If it's 285-75R16 for example.

Multiply 285 by 75, then divide the result by 1270. Next add the 16. Like this:

285 x 75 = 21375
21375 / 1270 = 16.8 (rounded off)
16.8 + 16 = 32.8 (approximately a 33" tire).

This works for all metric sized tires. It saves some math. If you can remember just to multiply the first two numbers, and remember "1270", and add the rim size, you can always do it -- even on paper, lol.
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  #15  
Old 12-18-2005
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ok so here is why I ask, I really like the look of a 33x12.5 tire very non pizza cutter looking, where my 35x12.5 are sort of pizza cutterish. I was looking around and trying to figure out how wide a 35 would have to be to have the same height to width ratio of a 33x12.5 ?

I am thinking a 35x13.5 would be a great looking tire but I can only find a few tires in that size.
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Old 12-18-2005
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35x13.50 is a very odd size, and for a tire company who loves odd sizes, go with interco, producers of the Super Swamper line.
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  #17  
Old 12-18-2005
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Quote:
Originally Posted by got-dirty
35x13.50 is a very odd size, and for a tire company who loves odd sizes, go with interco, producers of the Super Swamper line.
Still not having much luck, BFG krawlers come in thats size and toyo MT's thats really all i have found, I found a few 35x14.5 but it was x17or x 18 or something I was hoping for a 15 inch rim size, but this is all just out of curiosity
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  #18  
Old 12-19-2005
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Forget all of that, just go here:
http://www.miata.net/garage/tirecalc.html
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  #19  
Old 12-19-2005
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put too wide of a tire on your Ranger Ben and the look goes from pizza cutter to roller skate
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  #20  
Old 12-19-2005
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  #21  
Old 12-25-2005
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Quote:
Originally Posted by LILBLUE04FX4L2
put too wide of a tire on your Ranger Ben and the look goes from pizza cutter to roller skate
thats funny as hell, my boss has that issue with his f350 6.0 ....
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  #22  
Old 12-26-2005
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I saw a truck the other day that had the roller skate look, not too bad looking,
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  #23  
Old 12-26-2005
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I like the rollerskate look I guess, doesn't look like you can push it over, lol. anyway if it does look like a roller skate then you get some big *** fender flares to bring it together.
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