How to Know What Size Rim You Need for Your Trailer

So you had a blow out, and your rim is absolutely ruined. Luckily you had a spare ( smart! ) , So you throw on your spare and carry on. But now its time to replace that spare. How do you know what size rim you need to buy? I mean the tire is easy ( as long as you can read ) but how on earth are you supposed to know what size rim to get?

Rims have several specifications that make each rim unique. Here is an example of a rim size:

15    x   5      5/4.5 

Diameter  Width  Bolt Pattern

The first part is easy. Look at the tire size, the last number in the tire size indicates the rim diameter.

So for example: 205/75D15

The "15" indicates that you need a 15" rim. 

Well that was easy. Hope I didn't loose anyone yet ;)

Next you need to determine the width of the rim. 

Trailer wheels come if different widths,  Some common widths are 15x5, 15x6, 15x7. My Point being you wouldn't want to mount your 205/75D15 tire on a 15x7 inch rim. Your Tire would be very stretched and wear unevenly. 

View the charts below to see exactly what wheel fits your tire size. Then simply click here to go to RecStuff.com and Shop for your parts!
8" Tires and Wheels

Tire Size	Rim Size
4.80x8	8x3.75
5.70x8	8x3.75
165/65-8	8x5.375
16.5x6.50-8	8x5.375
215/60-8	8x7
18.5x8.50-8	8x7

10" Tires and Wheels

Tire Size	Rim Size
205/65-10	10X7
20.5X8.00-10	10X7

12" Tires and Wheels

Tire Size	Rim Size
4.80x12	12x4, 12x4.5
5.30x12	12x4, 12x4.5
ST145R12	12x4, 12x4.5

13" Tires and Wheels

Tire Size	Rim Size
ST155/80D13	13x4.5
165R13	13x4.5
ST175/80D13	13x4.5, 13x5
ST175/80R13	13x4.5, 13x5
ST185/80D13	13x4.5, 13x5

14" Tires and Wheels

Tire Size	Rim Size
ST195/75D14	14x5.5, 14x6
ST205/75D14	14x5.5, 14x6
ST205/75R14	14x5.5, 14x6
ST215/75D14	14x5.5, 14x6
ST215/75R14	14x5.5, 14x6

15" Tires and Wheels

Tire Size	Rim Size
ST205/75D15	15x5
ST205/75R15	15x5
ST215/75D15	15x5, 15x6
ST225/75D15	15x6, 15x7
ST225/75R15	15x6, 15x7
16" Tires and Wheels Tire Size	Rim Size
LT 7.50x16	16x6, 16x6.5, 16x7
ST235/80R16	16x6, 16x6.5, 16x7
ST235/85R16	16x6, 16x6.5, 16x7

17.5" Tires and Wheels Tire Size	Rim Size
215/75R17.5	17.5x6.75

For Help Determining your bolt pattern refer to one of these posts:

Measuring Trailer Wheel Bolt Patterns


Printable Bolt Pattern Template

Bolt Pattern Printable Template

Click Here to Access a Printable Bolt Pattern Template

At RecStuff.com, we often get questions regarding the bolt pattern of our customer's wheels. While a 5-Bolt on 4.5" is standard and by far the most common among trailer wheel 5-bolt patterns, there are times in which the trailer manufacturer uses a different pattern such as 5 on 5".
 
When purchasing a trailer, you will want to make sure that the bolt pattern on the wheels of the trailer are standard among the industry. This will ensure that in the case of flat tire or damaged wheel, you will be able to find a replacement when you need it.

Standard sizes include 4-bolt on 4", 5-bolt on 4.5", 6-bolt on 5.5", and 8-bolt on 6.5". If you're unsure about your 5-bolt pattern, we've put together a simple 'bolt pattern template' that makes it easy to ensure you purchase the correct trailer wheel for your trailer.

Visit any wheel on RecStuff.com or click the link above to download the template.

Measuring Bolt Patterns on a Trailer Wheel/Rim

Measuring 4-Bolt Trailer Wheels

Measure a four bolt wheel from the center of a bolt hole, skip one bolt hole and then the center of the next hole. Basically your ruler goes across the center of the wheel.

Measuring 5-Bolt Trailer Wheels

Measure a five bolt wheel from the edge of one bolt hole, skip one bolt hole and then the center of the next hole. In this case the ruler is not across the center of the wheel and you measure from the edge of one to the center of the other.

Measuring 6-Bolt Trailer Wheels

Measure a six bolt wheel from the center of the bolt hole, skip 2 bolt holes and then the center of the next hole. Your ruler goes across the center of the wheel.

Measuring 8-Bolt Trailer Wheels

Measure an eight bolt wheel from the center of a bolt hole, skip 3 bolt holes and then the center of the next hole. Your ruler goes across the center of the wheel.

How to Determine The Age of a Trailer Tire

How to Determine The Age of a Trailer Tire: How To Determine The Age Of A Trailer Tire It's easy to identify the age of a tire. All tires sold in the US require a DOT co...

Trailer Tire Specifications

Structure:

The structure of a trailer tire comes in two different forms, bias ply and radial. Each has it's own benefits. Read more about the differences and similarities at our Radial vs. Bias Ply Trailer Tires (What’s The Difference?) information page.

Ply Rating:

The ply rating on trailer tires typically varies between 2(A) and 10(E). This ply rating is intended to indicate the strength of the tires construction relative to other ply ratings. It doesn't necessarily mean that the tire is manufactured with this specific number of plys or layers. The strength or ply rating of the tire is positively correlated with the load capacity each tire can handle. A higher ply rating results in a stronger tire that can handle a higher load capacity.

Sidewall (In.):

The sidewall figure specifies the distance between the tire sidewall's outermost point when inflated. This metric is paramount when determining the amount of clearance you will have horizontally once the tire assembly is installed.

Outside Dia. (In.):

The outside diameter figure specifies the height of the tire when inflated. This metric is paramount when determining the amount of clearance needed vertically once the tire assembly is installed.

Load Capacity (65mph):

Unlike automotive tires, all ST tires are tested and rated at 65MPH. This 65MPH test allows the tire to qualify as a high speed tire. Every ST Trailer Tire you see on the highway goes through this exact same test regardless of tire size or manufacturer. The advertised load capacity on the sidewall of the tire is approved at this speed with proper inflation.

Max PSI:

The Max PSI is the maximum amount of air pressure the manufacturer suggests to be used in that particular tire. It is advised not to exceed this number as it can inhibit the structure of your tire and make it unsafe to operate.

Trailer Tire Sizing

The tires on a boat trailer might be labeled: ST175/80D13 C

• *ST - These tires are for a trailer (Specialty Tire for trailer use only)
• *175 - The maximum width of the tire is approximately 175 mm at the widest point
• *80 - Indicates the height of the sidewall is 80% of the width (in this case 140 mm)
• *D - This is a 'Bias' tire (D is for diagonal-the belts run diagonally from bead to bead or at about 45 degree angles to the center line of the tire.
  'R' is for 'Radial' - the belts run radially from bead to bead or at 90 degree angles to the center line)
• *13 - This tire fits 13 inch diameter wheels
• *C - The load index (also tires can be labeled with a ply rating, typically a "C" load range is equivalent to a "6 ply" rated tire, "B" is a 4 ply and "D" is a 8 ply)

Bias Ply Vs Radial Ply

At RecStuff.com, we often get the question ‘What’s the difference between radial and bias ply trailer tires?’. Naturally, the next questions tends to be, ‘Which is better?’, or ‘Which should I put on my trailer?’. The below information is meant to clear up the difference between the two, and assist you to make the best decision for your specific application.
It also must be noted that tires designed for cars, light trucks and trucks, are not meant for use on trailers, therefore not suitable for trailer applications. A radial tire meant for a car or truck is not the same tire in functional design as the tire used on a trailer. Please be sure the size specified on your tire’s sidewall starts with an ‘st’.

What is the difference between a radial and bias ply trailer tire?

The main feature that separates the radial trailer tire from the bias ply trailer tire is the tire’s belt construction. The cord material (often nylon and steel) also often differs between the two. The differences here affect many functional aspects of the tire.
A radial trailer tire is constructed with steel belts of the tire running at a 90 degree angle of the tread center line.

A bias ply trailer tire is constructed with nylon belts of the tire running at a 30-45 degree angle of the tread center line.

What are the benefits of choosing the RADIAL trailer tire construction?

• Runs Cooler
• Steel Belted – Results in tougher overall construction
• Longer Tread Life
• Wider Footprint

What are the benefits of choosing the BIAS PLY trailer tire construction?

• Crosshatch construction provides stronger/tougher sidewalls
• Due to the design of the tire’s construction, bias ply want to roll straight as the trailer itself often does
• Generally Less Expensive

What is the best choice for my application?

Typically a trailer tire needs replacing due to ‘dry rot’ before the tire’s tread is exhausted.  The Department of Transportation (DOT) recommends replacing tires (ALL Tires) at least every six (6) years.  The key piece of information here is that the recommendation is based on ‘Years’ rather than ‘Mileage’.  Please confirm your tires by checking the manufacturer’s date imprinted on the sidewall of every trailer tire.  While we understand that some tires are rated and built for higher mileage, trailer tires are often not mobile, as the trailer doesn’t always come along with you everywhere you drive.  The general rule of thumb for mileage you can get out of your trailer tire is about 25,000 miles.
So, if you’re trailer makes those longer trips with you on a regular basis, you will probably benefit from spending the extra money on a radial trailer tire to take advantage of the longer tread life.   If your trailer spends a lot of time next to the garage, you might want to save yourself some money by going with a bias ply trailer tire.
We offer both Radial and Bias Ply Trailer Tires in our online store, RecStuff.com, at some of the best prices online.  If the information above still leaves you with more questions, please feel free Contact Us or give us a call at (414) 617-5933.  We’ll try to help you out as best we can.

How To Determine The Age Of A Trailer Tire

It's easy to identify the age of a tire. All tires sold in the US require a DOT code which is mandated by the U.S Department of Transportation. The DOT code indicates the tire meets all federal standards, these identification numbers are important if the product is recalled. The DOT code begins with letters followed by numbers and letters; this is the plant code identifying the manufacture of the tire. The last four numbers after the plant code represent the week and the year the tire was manufactured.
The Department of Transportation (DOT) recommends replacing all tires at least every six years. When purchasing new trailer tires discuss the vendors product turn over rate, to ensure the product that you are receiving has been recently manufactured. Below is an example of a DOT code that is found on a trailer tire.

Example:

DOT   K3AP   4309
K3AP is the plant code identifying the manufacture of this tire
4309 is the week and year the tire was manufactured, this tire would have been manufactured the 43rd week of 2009.
Other numbers are marketing codes are used at the manufacturer's discretion.
Please feel free to contact us with any comments, suggestions, or questions.