Rim - Buying for spare wheel.

Feb 6, 2009
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Hi Grey13,
I don't think there are any particular requirements that solely apply to caravans, but when I was faced with getting a new wheel and tyre( as a spare) 2 or 3 years ago, i had to make sure that the wheel stud placings matched the holes in the wheel! I also wanted the same outset/inset spacing as the other caravan wheels!
Not only was it necessary to get the correct 5 stud hole rim but also the spacing of the holes, I took meticulous measurements as its easy to get things wrong and wheels can be expensive..... if you look up PCD spacings on tintenet it should tell you the details.
and as always
Happy Caravanning
Nov 11, 2009
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Does your Owners Handbook and/or Specification guide give it? Car alloy wheels have the offset and pcd marked on the inside of the rims so you have to crawl underneath to get it. Caravan wheels I've never checked but no reason why they should be different.

A query to the makers tech support would be useful as they should be able to give you the details.

Edit I should add that not all alloys are marked in the same place. My Subaru had the detail viz 100x5 and 48 and rim size on the insides of the spokes. But some have some of the info on the inside of the hub flange which requires wheel removal.
Sep 4, 2017
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Trailer wheel measurements
Towing and Trailers Ltd Worksop Notts near Sheffield General trailer wheel 4.5j x 13 100mm PCD 4 stud 30mm offset

Trailer wheels are very similar or the same in some cases as a car wheel. There are a lot of different wheels available and if you are building a trailer it is handy to have a bit of an understanding for them. Not all of the information on this page is always required but it may help.

Below is a general lay out of a wheel.

Towing and Trailers Ltd Worksop Notts near Sheffield General trailer wheel 4.5j x 13 100mm PCD 4 stud 30mm offset

Markings found on wheels

There can be 4 or 5 pieces of information marked in the centre of a wheel.

Wheel manufacture is marked on all wheels.
Part number to get a direct replacement. This is not always possible but part numbers can be cross referenced to get a wheel that will do the same job.
Wheel size this gives an inside width and a nominal diameter.
Wheel sizes are normally followed by a code to give a bead type.
Other information that can be found is:

Contry of manufacture
Date or date code.
Occasionally the manufacturer will give the PCD of the mounting holes.

The 3 most important measurements are the rim size, the PCD and the offset, if you get these correct then the wheel will fit.

Wheel size
The wheel size cannot be accurately measured from the rim with a tyre fitted. There are special gauges available to do this.
You will not need to measure a wheel accurately if you have an idea on where to measure.
We do have a few people call and give a tyre size and then say that the rim is 1" larger this is because they are measuring the outer extents of the rim.
The actual rim diameter is measured where the tyre fits and is normally approx 1" smaller than the outer of the wheel.
The width is also meaured on the inside of the wheel.
If the markings are still readable the size is marked as the width in inches followed by a J then the diameter.
for example 4.5J13 means thet the inside width is 4.5" and the Diameter is 13".

Below is a Diagram showing where these measurements are taken.

Towing and Trailers Ltd Worksop Notts near Mansfield General trailer wheel 4.5j x 13 100mm PCD 4 stud 30mm offset

Beads for wheels

A bead on a wheel is basically a hump in the wheel to stop the tyre being pushed away from the edge of the wheel and letting the air out.
The diagram below shows a Typical bead on a rim marked H2.

Towing and Trailers Ltd Worksop Notts near Mansfield General trailer wheel 4.5j x 13 100mm PCD 4 stud 30mm offset

Beads are not needed on small wheeled single axle trailers. Most small wheels do not have a bead.
Shown below are the different markings for the different types of beads and a description of the type of bead.

H Denotes 1 rounded bead on the outside of the rim.
H2 Denotes 2 rounded beads as image above.
FH Denotes a flat hump on the outside of the wheel
CH Denotes a combination humps (1 flat on the outside and 1 rounded on the inside.)
SL is used on wide wheels and means Special ledge.

Trailer wheels. As a rule you will get a H, H2 or no bead.

Wheel PCD

The PCD of a Wheel is very important as it is the measurement used to set the wheel studs / bolts out. There is a lot of information required to calculate some PCD's. This is shown on a seperate page, please click on the link below.

Towing and Trailers Ltd Worksop Nottinghamshire near Retford Trailer, Car and caravan wheel PCD measurements

Wheel offset

The offset is another important measurement this is the measurement from the center line of the rim to the face that bolts to the hub or brake drum.
An offset is put on a wheel to distrubute the centre of the load on a wheel to the centre of the bearings in the hub.
Light and heavy duty trailer wheels have what is called a center nave this means that there is no offset. The wheels bolt to a hub with a mounting face central on the bearings. Wheels for middle of the range weights tend to have an offset these go on 160, 200 and 203mm braked suspension as the outer bearing is normally on the outer face of the brake drum. Car wheels also have an offset for the same reason. This means that the unbraked hubs that fit car wheels also have an offset. These hubs are 100mm, 108mm and mini hubs.
The offset is marked on some rims but not all. When it is marked it is marked with the letters ET then a number. The number is a measurement in mm of how far the face is off center.

If the rim is marked ET30 this means that the center plate (face that bolts to the hub) is 30mm outwards of the center line of the wheel.

The diagram below shows a rim with a 30mm offset.

Towing and Trailers Ltd Worksop Nottinghamshire near Chesterfield General trailer wheel 4.5j x 13 100mm PCD 4 stud 30mm offset

The diagram above shows 2 measurements (A)40mm for the measurement from the front of the wheel to the hub face, and (B)100mm for the rear. These measurements can be taken on any wheel to find the offset.
Once you have the measurements you simply take the front measurement from the rear measurement then divide the answer by 2 as shown below.
To calculate the wheel above the sum is.
100 - 40 = 60 / 2 = 30mm offset.

Nov 11, 2009
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That’s useful but is there a problem with this forum site as the link that you provided has printed out all of its text too.
Jul 15, 2008
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Click the link below.........

.............l would be surprised if the rim you need for your van as a spare is not one like this.

............here is the picture.

It is 5.5J x14 5 stud 112 PCD with an offset of 30.......pretty standard fit on a 5 stud axle.

Nov 11, 2009
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No my caravan spare that is an OEM supplied one is steel. My cars full size spare is steel too. It’s also a different rim size and tyre size to the four alloys fitted but it has the same width and rolling diameter so gearing is unaffected.

The tightening torque for the caravan steel wheel is less than for the alloys but the same bolts are used.


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