Measuring a Trailer Tire

trailer tire size

Each trailer tire has a size branded to its sidewall. This size lists valuable information about your tire. The seven pieces of information that a tire size may contain are the following:

  1. Application Type
  2. Section Width
  3. Aspect Ratio
  4. Internal Construction
  5. Wheel Diameter
  6. Load Range
  7. Service Description
    • Includes Load Index and Speed Rating




Writing Tire Sizes

There are three conventions for writing tire sizes. Each method includes some or all of the information mentioned above.

  1. Metric: This way of writing tire sizes contains the most information about the tire; an example is ST175/80-R13 LRD.
    • Includes the application type, section width, aspect ratio, tire construction, rim diameter and load range
  2. Numeric: This is the most common way of writing small trailer tire sizes; an example is 4.80 X 12B.
    • Includes the section width, rim diameter and load range
  3. Alpha Numeric: This method is not used on any of the tires we sell; an example is B80 X 15D.
    • Includes the aspect ratio, rim diameter and load range




1. Application Type

The application type indicates what the tire is intended to be used for.


Note: When replacing trailer tires, we recommend using Special Trailer (ST) tires.





2. Section Width

section width of trailer tire

The section width refers to the distance from the widest point of a tire's outer sidewall to the widest point of its inner sidewall; this distance is measured once the tire is mounted on the wheel it is going to be used with.




3. Aspect Ratio

section height of trailer tire

Sidewall aspect ratio (or section height) is the ratio of the tire height and width that will tell you the tire's section height.




4. Internal Construction

Internal construction refers to how a tire is made. The letters below indicate the possible internal constructions a tire can have.

rim diameter

Note: For everyday use, tires with different internal construction cannot be used together.



5. Wheel Diameter

Wheel (or rim) diameter refers to the diameter of the wheel the tire is mounted on.



6. Load Range

The load range indicates the horizontal and sidewall strength of a tire. It is represented by a letter within each tire size. Each load range letter correlates to a specific number of tire plies and a load pressure in psi units. Sometimes the load range is left off the tire size and is branded on the tire elsewhere.


The information below tells you the ply rating and load pressure (in psi units) for each load range for Special Trailer (ST) and Light-Truck (LT) service tires.


Note: The weight capacity at a certain unit of psi for each tire is branded on each tire. It may be listed under the tire size or somewhere else on the tire.




7. Service Description

The service description includes the load index and speed rating. Only Passenger (P-metric) tire sizes include the service description.





Questions and Comments about this Article

Ajp

I need to replace the tires on my pop-up camper. I don't see 20.5/8.0-10 tires available on this etrailer website. Can I still get this size tire? Or can a different size work? The wheels/rims are fine, i.e. good shape, so just need tires. It is a 5-lug wheel.

Etrailer Expert
Reply from Victoria B.

Tires have undergone a change in the way the sizes are listed since your 20.5x8-10 tires were made. The current sizing that is equivalent is 205/65-10. I have linked all of the available tires in that size that are already mounted on a 5 on 4-1/2 bolt pattern wheel.

Cindy L.

I have a 1993 Coleman/Fleetwood Pioneer Series Arcadia pop up camper. The sticker on it states "GVWR 1995 GAWR 1810 with 20.5 X 8 X 10 tire, 10 X 6 rims". It has 5 lugs. I need to replace the two wheels and the spare. What tire and rim is recommended and appropriate?

Etrailer Expert
Reply from Victoria B.

The comparable current tire size for your 20.5x8-10 tires is the tire size 205/65-10. I have linked our current available tires in that size that are already installed on a wheel. The link will show you the wheels that have a 5 on 4-1/2 bolt pattern, which is the only 5 lug pattern available for the 10 inch rim.

Chase

I’m looking to upgrade the rims & tires on my pop up camper. Currently the size is 5.30- 12 Duro Class C with a 4 by 4 bolt pattern. I have 2 1/4 inches of clearance in the front and rear of the tires and 1 1/2 inches of clearance on the inner side of the tire by the axle. What tire and rim combo do you suggest if I’m looking to increase the tire size to possibly 13”?

Etrailer Expert
Reply from Jon G.

I wouldn't go any larger than what you have now. We recommend having 4" of clearance to the fender for suspension travel and then at least 2" of clearance to the trailer frame. Since you're already at 1-1/2" of clearance to the frame I would avoid using larger tires.

Reply from Chase

@JonG Thank you Jon for the quick and helpful advice. Which 12” tire would you recommend? I’d like to pair it with the rims shown below. https://www.etrailer.com/Trailer-Tires-and-Wheels/Dexstar/DEX44FR.html

Etrailer Expert
Reply from Jon G.

I would go with either the Kenda Karrier S-Trail # AM10130 or the Taskmaster # TT53012C . The Kenda will be a little smaller and have a speed rating of 65 mph but it has the higher weight rating while the Taskmaster has the lower weight rating but will be the same size that you have now and a speed rating of 81 mph.

Alex P.

I have a venture PWC double trailer and tire size on my spec says 5.3 x 12 LRD 5H. I need a spare and don't see this am I reading it correct . If not what tire would fit this so I can purchase hub and tire for spare.? Thank you.

Etrailer Expert
Reply from Jon G.

Here is the size and load range of tire you need for your application.

Ernie H.

I have a Powered Parachute. I will be towing the front tire. The two tires on the back need to be highway rated. I would love to find 16x6.50x8 Highway rated. If those could not be found, then the other set is 4.00/4.80-8 16" diameter. The item the tires go on weighs 350 pounds. Any information would be appreciated. Thank you

Etrailer Expert
Reply from Jon G.

We have 165/65-8 and 4.80/4.00-8 size tires like what you're looking for - I've attached links to the selections for you to filter through. In addition to the speed and weight ratings, you'll also need to note the bolt patterns of the wheels unless you already have wheels that you plan on having the tires installed on.

Reply from Ernie H.

@JonG Do you have any 165 or 17" x 65 - 8 that will fit a 8" x by about 3 1/2" wheel? The wheel has a 5/8" hole in middle. And once again, it has to be rated for highway use. Thanks

Etrailer Expert
Reply from Jon G.

@ErnieH We have the 165/65-8 tire size you asked about (see above link) but it looks like those are for a wider wheel like 5-3/8".

Lw

I have a 2019 heartland Fuel fifth wheel. It has Sailun s637 St 235/80r16 14pr tires, load range G, 8 bolt holes. I am trying to find a wheel for a spare tire. I have done some measuring on the spare I currently have and these are the numbers, 3.5" back space, 5" center hole, 9/16 studs, metal valve stem. This tire is rated for 110 psi. spare wheel is white and is steel. Do you have a heavy duty wheel that will fit? Thanks.

Etrailer Expert
Reply from Jon G.

We have the part # A16R80GWS which has a white spoke wheel or part # A16R80GWM which has a white mod wheel. The only difference is that it sounds like you have 7" wide wheels where these wheels are 6" wide. The tire size and load range is the same though. You can upgrade the valve stem to a metal valve stem with part # AM20906 .

Reply from Lw

Thanks much Jon, I have a tire and am looking for a wheel only to mount the tire on. Due to the required 110PSi needed for the tire the wheel needs to be a heavy duty and at least 3750 lb rating with the metal valve to take the pressure. Do you have the wheel only... I believe the wheel size is 6.5 inch. Thanks

Etrailer Expert
Reply from Jon G.

We do have some that are close to what you're looking for in the linked selection. These only have the 6" width as well. If you're measuring outside to outside including the little flanges on your wheels then that would be where your larger width is coming from. For wheel width you'll actually measure bead seat to bead seat which sits in a little more.

Reply from Lw

I have the same Sailun tire in the 235 80R16 load range G... I am just looking for a wheel to mount it on. Must take 9/16 studs, 8 bolt hole, 6.25 center to center of stud...

Etrailer Expert
Reply from Jon G.

@LW The wheels that I linked above will work just fine. They all use 9/16" studs and I've never heard of a 8 on 6-1/4" bolt pattern before so you must have an 8 on 6-1/" bolt pattern.

Favid

I have a 5x8 foot trailer with 205/65 R 15 Can I use a 205/70 R15 as a spare tire? Thanks

Etrailer Expert
Reply from Jon G.

@Favid You always want to use the exact same tire all around your trailer - including your spare. You might be able to use it to hobble along for like a mile to an exit or tire shop but I would get the exact same tire because with my luck I'd need to use the spare when I'm out in the middle of nowhere.

Dale M.

I have a small trailer that I fitted with new tires, 4.80-8. I kept one of the old tires to use as a spare, but don't know what to look for in a wheel. The current wheels don't have lug nuts, they're held on by a cotter pin/castle nut. What do I measure on my current rims so I can get something that fits?

Etrailer Expert
Reply from Jon G.

You have an older trailer as that style of spindle/wheel isn't really around anymore. I'd look for places that specialize in replacement parts for old trailers if you want that exact wheel. Otherwise you're looking at replacing the axle on your trailer so that you have a more up to date spindle.

Dryhten C.

I was given a trailer and it's in serious need of tires and rims. One is bent. one of the tire walls reads. "5.30/4.5-12" What does this mean? I measured the distance from center to center of the lug nuts and that's 4".

Etrailer Expert
Reply from Jon G.

That means you need a 5.30-12 size tire. If your wheels have a 4-bolt pattern then I recommend part # AM30850 , otherwise you need the Taskmaster # AT53012R45SM with the 5 bolt pattern.

Maureen

The numbers on my trailer tyre read 5.3-12 so what size spare do I look for?

Etrailer Expert
Reply from Jon G.

You will want to use a 5.30-12 size spare tire. Here is a link to our selection that you can choose from. You'll want to make sure that the bolt pattern on the wheel and the load range on the tire match what you currently have.

Bill P.

So, if I have a ST 205/75 R14 and I'm looking for tire covers, what size do I get (14, 15, 16, etc.)??

Etrailer Expert
Reply from Chris R.

Your ST205/75R14 tires have an overall diameter of JUST barely over 26", so I highly recommend the Classic Accessories # 052963762402 .

Tom M.

have old boat trailer with 6.9-9 n 84 Carlisle USA trail tire 21" in diameter . Believe the rims are 10.5 " in diameter.They are on a 5 on 4 1/2 bolt pattern for a gator Trailer . need help in finding a replacement tire and wheel . Thank you

Etrailer Expert
Reply from Chris R.

The modern 6.90/6.00-9 trailer tire size is the right replacement for your 6.9-9 units. This is essentially the same size - it just went through a change in how its labeled over the years. The Kenda # AM10040 will work perfectly and for the corresponding wheel we have the Americana # AM20038 .

Jay T.

I’ve got a small older boat trailer and what I can read on the tires are E 4.80- 4.70. Is that correct for a tire size.

Etrailer Expert
Reply from Chris R.

I believe you have a 4.80/4.00 tire like the Kenda Loadstar # AM10002 . I haven't seen it printed quite like what you saw on your particular tire, though. A 4.80/4.00 tire has an overall diameter/height of around 16.1" and a width of 4.6". You could compare these dimensions to your existing tire to be sure.

Bob W.

What is the difference between 5on5 and 5on4 1/2? I understand the first 5 stands for 5 lugs. Is the second # the distance apart?

Etrailer Expert
Reply from Chris R.

You got it. The second number has to do with the actual pattern of the bolts in terms of their separation. There are a few different methods you can use to measure the pattern on a 5 bolt wheel and the article linked below does great job of going over them.



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