Q: What is the circumference of my tire?

In order to accurately program a bicycle computer , it is generally necessary to enter the exact tire circumference. The tire circumference varies depending on the rim, the inflation pressure and the load on the tire. For these reasons, it is not possible to list an exact tire circumference. <img src="https://storage.crisp.chat/users/helpdesk/website/cff55f369977f800/dimensions-chart-cicumferences_1n2kn2o.png" alt="Approximate tire circumferences" /> In order to accurately program a bicycle computer, we recommend a simple rolling test with the rider on the bicycle where a mark is made on the tire, and the distance between it's contact point with the ground is measured across one full revolution.

Q: What does EPI mean in relation to the carcass?

The density of the carcass fabric is expressed in EPI or TPI (Ends Per Inch, Threads Per Inch). The range of carcasses used, for example, for bicycle tires are 20, 24, 37, 50, 67 and 127 EPI. In principle, the more close-meshed a carcass is woven, the higher the quality of the tire. A dense carcass is important for low rolling resistance and good riding properties. At the same time, puncture protection increases, because carcasses with a high strand density are difficult to puncture. However, this does not apply to the extremely fine 127 EPI carcasses, as each strand is sheer and quite vulnerable. Through extensive testing and research, Schwalbe has found that the best compromise for low weight and resistance is around 67 EPI. In most of our top tires we use a 67 EPI carcass. Weight and rolling resistance can be reduced even further by using a 127 EPI carcass. But at the same time, these tires are more vulnerable to damage. Therefore, we intentionally use the 127 EPI carcasses only for light competition tires, where weight is an important factor. Most bicycle tires worldwide are certainly manufactured with coarse 20 or 24 EPI materials. This material has no longer been used at all by Schwalbe for a couple of years now. Even very low-priced Schwalbe tires already have a state-of-the-art 50 EPI carcass. But be cautious when comparing EPI indications, as often the number of strands of all carcass layers are added together. An indication of 200 TPI results e.

Question 1

What is the circumference of my tire?

Accepted Answer

In order to accurately program a bicycle computer , it is generally necessary to enter the exact tire circumference. The tire circumference varies depending on the rim, the inflation pressure and the load on the tire. For these reasons, it is not possible to list an exact tire circumference. Approximate tire circumferences In order to accurately program a bicycle computer, we recommend a simple rolling test with the rider on the bicycle where a mark is made on the tire, and the distance between it's contact point with the ground is measured across one full revolution.

Question 2

Why are tires sometimes narrower than their listed size?

Accepted Answer

In order to ensure that tires have sufficient frame clearance, tire manufacturers generally prefer to keep production closer to the lower end of the permitted tolerance (+/- 3 mm). Carcass casing materials have become more and more sophisticated over time. That reduces the tire widening after the fitting. Furthermore, inflation pressure also plays a major role. With maximum inflation pressure the tire becomes wider than with low pressure. And a recently fitted tire still widens over time. This can make a difference of 1 to 2 mm. The tire width is measured at the widest point, i.e. outside the lug.

It's Important to note that a tires mounted width is directly affected by the internal rim width of the wheel it is mounted on. A larger internal rim width will yield a flatter cross-sectional tire profile. Conversely, a smaller internal rim width results in a tire that is taller, but less wide. See in the below tire schematics how a 40mm wide tire can be as narrow as 39mm on a 19mm internal width rim, but as wide as 45mm on a 25mm internal width rim: 40mm Tire Schematic on Various Rim Widths When upgrading a tire, one should consider the internal rim width of their wheel as this will dictate if the new tire will be smaller, or larger then the width listed on the sidewall.

In the case of tires with special technology, such as the **Marathon Plus **or ** Radial Tires**, the ti

Question 3

Why are the tires on my trike wearing out so fast?

Accepted Answer

Recumbent cyclists and Trike users have three wheels contacting the ground. Unlike a bicycle with two wheels, the presence of a third contact point largely restricts any tilting during riding, and as such, wear can be concentrated on the top of the tire.

|| The two most common causes of expedited tire wear on three wheeled mobiles is misalignment or over-inflation.

Correct alignment of a trike should be completed by a experienced mechanic. Brand new trikes often require alignment before riding. A quick check for a trikes alignment can be completed by following the below tips: Tricycle Front Wheel Toe Measurement Check

Over-inflation is prevalent among all types of cyclists. The same theory applies for trike users as well.

||| Maximum listed pressure on a tires sidewall should be reserved for maximum load applications.

While each tire has a specfic and tested maximum load rating (as is stated on the sidewall of the tire), many of Schwalbe's tire have a maximum load rating of around 80kg. This load rating is specfic to a single tire. On a trike, the gross vehicle weight is distributed among three tires. For example, if each of the three tires on a trike had a maximum load of 80kg, than the gross maximum load of the system would be over 500lbs!

As is further described in other helpdesk articles, __ a tire is designed to deform__, and it's correspondi

Question 4

What does EPI mean in relation to the carcass?

Accepted Answer

The density of the carcass fabric is expressed in EPI or TPI (Ends Per Inch, Threads Per Inch). The range of carcasses used, for example, for bicycle tires are 20, 24, 37, 50, 67 and 127 EPI.

In principle, the more close-meshed a carcass is woven, the higher the quality of the tire. A dense carcass is important for low rolling resistance and good riding properties. At the same time, puncture protection increases, because carcasses with a high strand density are difficult to puncture.

However, this does not apply to the extremely fine 127 EPI carcasses, as each strand is sheer and quite vulnerable. Through extensive testing and research, Schwalbe has found that the best compromise for low weight and resistance is around 67 EPI.

In most of our top tires we use a 67 EPI carcass. Weight and rolling resistance can be reduced even further by using a 127 EPI carcass. But at the same time, these tires are more vulnerable to damage. Therefore, we intentionally use the 127 EPI carcasses only for light competition tires, where weight is an important factor.

Most bicycle tires worldwide are certainly manufactured with coarse 20 or 24 EPI materials. This material has no longer been used at all by Schwalbe for a couple of years now. Even very low-priced Schwalbe tires already have a state-of-the-art 50 EPI carcass.

But be cautious when comparing EPI indications, as often the number of strands of all carcass layers are added together. An indication of 200 TPI results e.

Question 5

When is a tire worn out?

Accepted Answer

When the puncture protection belt or the carcass threads can be seen through the tread the tire has reached its wear limit and must be replaced. As puncture resistance also depends on the thickness of the tread layer, it may be useful to replace the tire sooner. The sidewalls of tires often fail before the tread is worn out. In most cases, this premature wear is due to prolonged use of the tire with insufficient pressure. Checking and re-pumping the inflation pressure at least once a month with a pressure gauge is most important.

For tires with a deep tread pattern that generate grip in loose terrain, like those used on a mountain bike, a worn out tire can lead to loss of grip and safety concerns. In such instances the user may wish to replace their tire even before the puncture protection belt or carcass threads begin to appear.

Question 6

How are tires measured?

Accepted Answer

Nowadays, bicycle tire sizes are all marked according to ETRTO (European Tire and Rim Technical Organization) standard. Modern Inch size nomenclature is often used. Older English and French tire size dimensions are still used as well. The 3 most common ways of measuring tires are ETRTO, Inch, French The three most common ways of measuring tires are ETRTO, Inch, French

The ETRTO size for a tire is a millimeter based measurement and is the most accurate. Schwalbe always encourages the use of ETRTO measurements during tire identification. In the above example The ETRTO size specification 37-622 indicates the width of 37 mm and the tire inner diameter (bead to bead) of 622 mm. This dimension is clear and allows a precise classification of the rim size.

The inch marking in the above example states the approximate outer diameter (28 inches) and the tire width (1.50 inches). Another inch marking is 28 x 1 5/8 x 1 3/8 (approximate outer diameter x tire height x tire width); it is also common. Inch sizes are not precise and lack accuracy. For example, diameters 559 mm (MTB), 571 mm (Triathlon) and 590 mm (Touring) are all classified as 26 inch. Tires with diameters 622 mm and 635 mm are both classified as 28 inch. Oddly enough, tires with an inner diameter of 630 mm are clas

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