This is the most simple size marking. The first part, 3.00, is simply both the width of the tyre and the height of the sidewall of the tyre in inches. The second part, -4, is the rim diameter in inches. So a 3.00-4 tyre would fit a 4" diameter rim, be 3" wide and 3" tall on the sidewall. Therefore, the overall height of the tyre would be 10" (4" plus 3" plus 3"). For even more weight saving, latex tubes are significantly lighter than butyl tubes, plus there’s less friction against the tyre, resulting in lower rolling resistance. This method is widely used on turf and ATV tyres and is probably the easiest to understand. The first part is the overall height (from the ground to the top of the tyre) of the tyre in inches, the second part is the width of the tyre in inches, and the third part is the rim diameter in inches. The load index and speed index is gradually replacing the PR marking for tyres. The load index is given by a number between zero and 159 in our chart, but can be much higher. The speed index is given by a letter (or letter and number in the case of 'A' speed rating) between A and Z. Typical examples for our type of tyres would be 68M, 55N or 38F. Any ATV tyres we list with this marking will also be 'E' marked and fully road legal. Contrary to the PR marking, the LI and SI give unambiguous and comparable information on the load capacity which can be drawn from the tables below; Speed symbol

Please Note: any reference to 'Royal Mail 24 ™' and 'Royal Mail 48 ™' are Official Royal Mail Service names and should not be interpreted as '24 Hour Delivery' and '48 Hour Delivery'. The former are simpler to use, but add a dead space above the valve, making inflation harder, while with the latter you need to make sure that there’s a fully airtight seal to the inner tube’s valve stem, or your tube will leak air. Valves come in different shapes & sizes to accommodate a wide variety of applications & wheel rim configurations. There are four main categories that inner tube valves fall into & within each are a handful of popular valve models to choose from:

Shop Tubes by Valve Type

As well as coming in pretty colours, latex inner tubes offer lower weight and rolling resistance than butyl inner tubes. They’re relatively expensive though and heat build-up can cause issues if you’re using rim brakes on long descents. Simon Bromley/Immediate Media This time there are three parts to the tyre size, all in inches. The first, 4.10, is the approximate width of the tyre when fitted to the recommended wheel. The second, 3.50, is the height of the sidewall, and the third is the rim diameter.

If you have carbon rims on a bike with rim brakes, you also need to be careful not to drag your brakes on long descents because overheating can cause latex tubes to fail. Some wheel makers recommend against using latex tubes with their rims. On bikes, Schrader valves tend to be used on lower pressure tyres, such as kids's bikes and mountain bikes. These are the same valves used on all motor vehicle tyres and are often referred to as ‘car type’ valves. Schrader valves have a core that is sprung loaded, and the central pin can be depressed with a narrow object to release air from the tube. The spring mechanism keeps the valve closed. Valve extenders screw onto the top of the Presta valve. Some are just hollow tubes, others include a valve at the top, which means that you need to remove the valve core from your inner tube before screwing on the extender. On the other hand, they’re much more fragile and more awkward to fit as they’re floppier than butyl tubes.A 260x85 tyre would be 260mm high and 85mm wide. Converting these dimensions to inches gives us a tyre 10" high, 3" wide on a 4" rim. The modern equivalent size would be a 3.00-4. Valve extenders come in a range of sizes, types and even colours. These ones simply screw over the top of an open Presta valve, but you can also get ones that allow you to place the valve core at the top. Simon Bromley/Immediate Media W hen considering rim diameter, please be aware that it is effectively the diameter of the hole in the middle of the tyre. The measurement from edge to edge of the wheel itself includes the tyre retaining rim flanges, and so will be about 1" greater than the actual marked size.

As already mentioned, it is important not to mix tyre sizes or types on motorised machinery as there can be significant variation in heights and widths between different manufacturers. We have even found that sometimes tyres of exactly the same size marking can vary significantly. As with car tyres, we would suggest you replace your tyres in pairs to ensure optimum performance. There are several methods for giving the size of tyres, with measurements sometimes in inches, sometimes in millimetres, sometim es in both! To help you understand a little better, we have examples and explanations of each method below, from which you should hopefully be able to recognise your own size markings. So, a 145R10 is a radial tyre, 145mm wide, sidewall height of 116mm (80% of 145mm) and fits a 10" rim. A 195/50R13 tyre would be 195mm wide, have a sidewall height of 98mm, and fit a 13" rim. The approximate overall height of the tyre can be worked out by converting both dimensions to either mm or inches, and adding the rim diameter to twice the sidewall height. You must make sure you replace your inner tubes with a tube that is the right size according to the diameter and width for your tyre. The size is almost always written somewhere on the sidewall of the tyre. Inner tubes typically state a wheel diameter and width range for which they will work, e.g. 26 x 1.95-2.125", indicating that the tube is intended to fit a 26 inch tyre with a width of between 1.95 inches and 2.125 inches.Originally, tyres were marked with the exact number of canvas layers (plies) built into the tyre. This was an indication of the strength of that particular size of tyre. It's fairly obvious that a 4 ply wheelbarrow tyre will have a different load capacity to a 4 ply car tyre. As stronger materials were developed, the number of layers could be reduced whilst still maintaining the same strength in the tyre. The designation Ply Rating therefore does not indicate the actual number of layers or plies in the tyre, but the number of layers originally required to give the desired load capacity. When working with PR marked tyres, you must use the actual manufacturer's data to determine the load capacity in kg. This value can often be found on the side of the tyre adjacent to the ply rating indication.

There are many different types of inner tube available so it is important that you get the right tube for your bike and to suit the riding that you are doing. How would I choose the best inner tube for my tyres?The following sizes are common for mountain bike tyres, regardless of whether your bike has 26in, 27.5in (650b) or 29in wheels. Straight Rubber Valves - The valve is made of rubber so is inexpensive & durable. The TR13 valve is the most common, used on car, trailer, quads, lawn mowers & some smaller agri machinery. It has a thin and straight valve stem. The TR15 has a wider / fatter valve stem so is used in wheels that have a larger valve hole, typicallylarger agri machinery or landrovers. If your wheels are even deeper than the longest valve you can find, you can buy valve extenders to add length to your valve. There’s a range of lengths available: Zipp for example makes extenders from 27mm up to 98mm long.