Q: What is the circumference of my tire?

<p>In order to accurately program a <strong>bicycle computer</strong> , 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.</p>

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 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 3

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 4

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

Question 5

What causes a tear at the base of my valve?

Accepted Answer

A valve tear off can occur if it was installed under tension.
Another frequent cause is installing a Presta valve tube into a rim with a larger valve hole. The metal edge of the valve hole can shear the valve stem off the tube.
Valve tear damage caused by improper valve selection Caution: Be aware that there are also rims that have the correct valve hole of 6.5 mm on the outside, but a larger hole of 8.5 mm on the inside, which causes the problem. A nut that is excessively tightened just exacerbates the problem of tear off. The major role of the rim nut is to lock the valve in place at the time of inflation.

In most cases valve tear off is due to tire slip. Continual improvement in brake performance and low inflation pressures often cause the tire to slip on the rim. The tire movement then drags the tube and this can lead to the valve shearing off.

Question 6

Wheelchair Tire Diameters

Accepted Answer

From a construction standpoint, there are no differences between Wheelchair and Bicycle Tires. There are certain optimizations for wheelchair tires (such as non-marking compounds), but a bicycle tire could be used on a wheelchair just fine so long as it is the correct size.

Picking out the correctly sized wheelchair tires can be difficult as a result of multiple naming conventions. It is for this reason that we always encourage the use of a tires ETRTO size during size evaluation. More on that here: How are tires measured?

Specfic to to Wheelchairs, the three most common sizes are 24", 25", & 26". Despite their titles, __these sizes do not correlate to the rim's diameter. __ The following image shows the approximate rim diameter for each size: Wheelchair sizes and their respective rim diameter measurements

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