Measure to the nearest 1mm or 1/32 inch, or better. Here are the steps to measure a rim using the circumference: If you don't have a narrow tape measure, you could wrap a bicycle cable inner wire around the rim, hooking the ferrule into the valve hole. Number of spoke holes in the rim and hub (counting both sides), Rim outside diameter, and depth from that to a spoke hole, and/or, Rim measured circumference and depth from that to spoke holes, Spacing of right hub flange from centerline, Spacing of left spoke flange from centerline. The rim shown is a double-wall rim with recessed spoke holes and no eyelets. Next, start hooking in spokes into the hub again from below.
Other spoke calculators account for the stretching and seating of spokes and shrinkage of the rim in a tensioned wheel -- about 1 millimeter of spoke length in a typical wheel. Measure a diameter of the rim, or calculate the diameter based on a circumference. It's a problem in trigonometry, in two steps.
Again, if your ruler only measures in inches, you need to convert to millimeters. By using a tape with a special scale, this system calculates the diameter for you -- saving time, and time is money if you build a lot of wheels. Only the short spoke nipple at the right is really suitable for the spokes shown. To find the correct spoke length when building a wheel, you need dimensions of the rim and hub. The threads of all four spokes in the image below extend equally far. High-quality spokes that have to deal with high stresses often have a smaller cross section of 1.8 mm in the straight part and/or a larger cross section in the arc. This time from below. With a radial spoking pattern, spoke length changes at half the rate of the diameter of the hub flange. That means, however, some loss in rigidity and therefore in force transfer, which is why these kinds of spokes are more likely to be used for mountain bike sports. Tubular rims, in which adhesive is used to fix the tire directly on the rim. Make sure that the nipples are screwed on so as to leave around 2 mm of visible thread. Half that is 67.5mm. Hold the spokes and turn the hub as far as you can in clockwise direction to set their pitch angle.
Close enough! Then as shown in the image at the right, transfer this measurement to the ruler, resting your fingernail lightly against its end. Most spokes are round and have a 2 mm cross section with a rolled thread and an arch of around 95° that is hooked into the hub. The larger holes in the wall which faces the tire allow access when building the wheel. A 36-spoke cross 4 pattern pattern is a good choice when the hub's dimensions aren't known or with flanges of different sizes. And then there also are various hubs used in mountain bikes and road bikes. This type of spoking is recommended only for front wheels with rim brakes, because it is less suitable for absorbing forces from disc brakes or drive forces. Damon Rinard has another description of hub measurements on this site. The tape has a tab at the end. For road racing or time trials, high profile or aero rims are used, which have a better rigidity to weight ratio and are supposed to reduce drag – but that doesn’t really work at speeds below 35 km/h. The ends of the spokes of a fully-tensioned wheel come to somewhere between the bottom and top of the slots in the spoke nipples. This is the most accurate way to measure for diameter. If the diameter falls partway between millimeter or 1/32 inch marks on the tape, you could estimate the fraction. Insert the spoke to the bottom of the spoke-hole recess, and slide your hand down the spoke until the fingernail of your index finger rests lightly against the side of the access hole. With both wheels spoked this way, a bicycle tourist would need to carry only one length of spare spokes, despite different flange sizes on the front and rear hub, etc. You can't get a "contact" measurement this way, but inaccuracy of a small fraction of a millimeter isn't going to be important here. As long as your tools are good, selecting the wrong spokes for a wheel is more likely to result from an outright mistake than from a measurement error. Use the metal tape measure as shown in the image below. The tolerance has become smaller in recent years, because short spoke nipples and matching short threads are fashionable to reduce aerodynamic drag.
If you have any questions, comments or concerns, or for any other reason would like to get in touch, When measuring a spoke using a tape measure, a second spoke may be used to hold the elbow of the spoke and the tape measure's tab, as shown. you can contact us here. On the chain side, the spoking is triple-crossed to cushion the higher forces occurring there, and the more lightweight, double-crossed version is used on the opposite side. We have an article about that. Next, turning the hub over and measuring the other end, the left flange is 35mm from the left locknut. An example is shown below, using the same hub. This caclulator should not currently be used to calculate spoke lengths for straight pull hubs.
The first two spokes will be crossed at the top, the third on the bottom. Spoke lengths are given in millimeters, so you need to come up with measurements in millimeters. Now hook more spokes into the free holes on the hub. The answer is quite easy: The add stability to the wheel and are important for the force transfer from the hub to the wheel. There are manufacturers' specifications and lists of rim and hub dimensions online -- including Damon Rinard's list on this site, BUT, only after you have mostly laced up a wheel will you discover whether spoke length is correct. It differs depending on purpose and can be between 13 and 30.5 mm, whereby wider rims are more frequently used for mountain bike sports and are more robustly constructed than road bike rims, which are optimized for weight. If the spokes extend into the screwdriver slots when the wheel is under light tension, you can't use a screwdriver for initial light tensioning of the wheel. Some rims have spoke holes closer to one side than the other, to reduce dishing when the hub has unequal flange spacing. The first step creates a virtual measuring point directly below the spoke holes in the rim. If a spoke does not extend into the head of the spoke nipple, then the weakest part of the spoke nipple is in tension and the nipple is at risk of breaking. If you are good at holding objects steady in your hands, you can even do the depth measurement with a bare bolt or bicycle spoke, as shown in the image at the left. All you need is the right spoke wrench and a little bit of sensitivity. These measurements are not an exact match for the manufacturer's specifications, but are close enough for all practical purposes. The Sutherland system includes a tool to find the effective rim diameter for spoking. spoke lengths for straight pull hubs. Twice that is 22 mm, and so the spoking diameter measures as 508.2 mm. But in case the math interests you, here's how spoke length is calculated. The leftmost nipple is threaded on until the threads start to bind. Lay a measuring tape or ruler across the rim between two points directly opposite one another.
There's nothing to measure directly there, and that's why a second step is needed. The importance of the hub spoke hole circle diameter depends on the spoking pattern. The threaded end of this spoke measures at 11 29/64 inches (halfway between the 11 7/16 and 11 15/32 marks on the measuring tape). The right flange, at 50mm from the right locknut, is 67.5-50mm or 17.5mm from the centerline of the hub and the left flange at 35mm from the left locknut is 67.5-35mm or 32.5mm from the centerline. Please take the time to ensure that your hub and rim measurements are … In case you were sleeping in 6th-grade math class: Ï is a a Greek letter denoting the ratio of the circumference of any circle to its diameter. C = \/A2 + B2 - 2AB cos Î¸. Spoking the other side of the impeller will create several large and small 'V'. The second step gives the spoke length, by accounting for the spacing of the hub flange away from the centerline. Measurements for Spoke Length Calculations, Roger Musson -- wheelbuilding book, spoke calculator. Insert the first spoke on the rim in the hole on the left next to the air valve. Based on 4188 seller reviews at Trusted Shops, Bergfreunde.eu has received an average 4.8 of 5 stars. at the deeper, smaller holes in this double-wall rim. We will show you in six easy steps, how to get a standard triple cross spoking done: Should the impeller run slightly unround, you can try and centre it again by adjusting the spoke tension. Multiplying by 25.4 gives 530.2 mm. The spokes are stresses only under tension and because of their intrinsic rigidity, they hardly change their shape at all. This caclulator should not currently be used to calculate When I got the spokes and trued the wheel, spoke length was to big and surprisingly the spokes … Error becomes worse for small wheels/large flanges. The table below summarizes the effects of measurement errors. C (in red) is the third side, the one you calculate. You should now have no more empty holes to fill. For example, if the left flange of the hub is 35 mm from the centerline, the right flange 20 mm from the centerline and the spoke holes in the rim are offset 3mm to the left, then the effective flange spacing is 32mm on the left and 23mm on the right.
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