The bike tyre size is defined by two measures being the tyre diameter and the tire width. For Vittoria tyres, both measures are engraved on the tyre sidewall, as well as printed on the tyre hot patch and packaging. The tyre diameter indicates the compatibility of the tyre with a certain rim diameter. The unit of measurement of the diameter of road bike rims are the ETRTO measure and the French measure, and the most common road bike rim/tyre diameter is ETRTO 622, corresponding to the French size 700. The unit of measurement of the diameter of mountain bike rims/tyres is inches, and the most common mountain bike rim/tyre diameters are 26”, 27.5” and 29”. The tyre width helps to identify the compatibility of the tyre with the rim, frame and/or fork it will be used with. The width of road bike tyres is measured in millimetres. Some of the most common road tyre widths are ETRTO 23-622, 25-622, 28-622 corresponding to the French size 700x23, 700x25, 700x28. The unit of measurement of the width of mountain byke tires is inches, and some of the most common sizes are 29”x2.25”, 27.5”x2.4”.

Proper tyre/frame fitment depends on the clearance, and so to the amount of space in between the tyre and the frame or fork of the bicycle. Alignment of the wheel assembly in a bicycle shall allow not less than the clearance values provided in the table below between the tyre and any frame or fork element or a front mudguard and its attachment bolts. Where a bicycle has a frame or a fork with a suspension system, the values in the table above apply to the suspension system in its uncompressed state.

To be sure you are using the proper tyre size for your rim, you can refer to the ETRTO standards. The nominal tyre size, similarly to the size of motor bicycles tyres and car tyres, is based on specific rim widths indicated by the ETRTO standards. As a matter of fact, the tyre size (or section) mounted on a rim is not universal, as it can slightly differ according to the width of the rim on which the bike tyre is mounted. Current trends among users suggest an increased interest in wheels with larger rim widths. This pushed wheel producers and tyre producers to consider larger rim widths for naming the size of bicycle tyres.

When measuring the size of your bike tyre, you can refer to the nominal size, which is the one provided by the manufacturer, engraved on the tyre sidewall as well as printed on the tyre hot patch and packaging. The effective size is the one that you can measure by using a calliper with the tyre inflated and mounted on the rim. The nominal size corresponds to the effective size when the tyre/rim fitment follows the ETRTO standards.

The maximum outer circunference of wheel & tyre combo will depend on the bike frame and front fork/fork suspension. Please check with your bike and fork manufacturer. However, some modern mountain bikes are made to fit either a 27,5" plus tyre (wider, larger volume such as a 2.6" or wider) and also more regular 29" tyres; again, to be sure, please check with your bike manufacturer or local bike shop. Vittoria makes tyres in various sizes and widths, including 27.5" and 29" diameter from 2.1" up to 2.8" widths.

Nowadays wheel circumference is pretty standard with three main sizes: 26", 27.5" (same as 650B) and 29" (same as 700C or 622mm). However some road bikes, especially smaller sized frames, use 650C (571mm). The best way to find the circunference of your wheel is either checking on the rim to see if that is indicated, checking with the wheel manufacturer or at your local bike shop. Vittoria makes tyres for all these 4 main wheel diameters and a few others too!

Frame size on a bike is typically measured as the distance from the center of the bottom-bracket to the intersection of the top-tube and seat-tube. For Vittoria tyres, wheel size will always be molded into the sidewall of the tyre, as well as printed on the hotpatch and on the tyre packaging.

The maximum width of tyre you can use will depend mainly on your wheels and your bike frame/front fork. The wheel manufacturer will provide information about the minimum and maximum width of tyres that should be mounted. The bike frame and front fork/suspension fork will be able to provide you with the maximum clearance and recommended maximum tyre width.