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Before using the calculator, please read the first few pages of the spoke length chapter in the wheelbuilding book.

This is a single page application, so do not use your browsers forward and back buttons.

All headings in the data entry form are "clickable" and show help text. The help text is closed by clicking the close link, or click the same heading again, or click a new heading which will close the previous.

Calculate button, click anywhere on the background of the data entry form, it changes colour when a recalculation is necessary, and the coloured region is the 'click' area, think of it as a huge calculate button! If the spoke length table is out of date and doesn't reflect the data inputs then a red Recalculate message is shown (which also works as a calculate button). If a spoke table is in view and the background is white, and there are no recalculate messages, then everything is good!

Always round the spoke lengths up. There's more help on spoke rounding when you calculate a spoke table and click the heading "Spoke lengths".

Do not use your browsers print function, always use print buttons within the calculator because they produce specially formatted prints.

For use with stainless steel spokes. It cannot be used for titanium spokes, or any other spoke material, because those materials have different elongation properties.

Extended wheel data

The information shown in the spoke length table contains the key data items that are important for the wheelbuilder. Click the checkbox and next time you calculate the spoke table some additional items will be shown.

Comments and suggestions

Please get in touch.

v

RM's drawing tools.

Flange offset

The distance from the hub centre line to the centre of the Left and Right flanges. Shown as dimensions L and R in this diagram.

Offset calculator

Always check your offsets. Measure between the hub flanges (dimension F) and it should be the same as the value shown in the form.

The above calculation does this...

L = h - x

R = h - y

F = L + R

Where h = half the hub width.

Hub diameter

For normal hubs, this is the diameter of the hub flange measured spoke hole centre to centre, sometimes referred to as the PCD (pitch circle diameter).

Straight pull hubs

For radial straight pull hubs, the diameter is measured at the position where the spoke seats.

For cross laced straight pull hubs, the measurement is taken at the extended crossing point of two spokes. If the spokes are close to tangent then the diameter can be measured to the centre of the spoke holes. A small error when measuring the diameter on cross laced wheels will not affect the spoke lengths.

Straight pull 20,28,36 utility

As mentioned in the book, an odd number of posts makes it tricky to measure the diameter and that a calculation utility for doing this would be available here...

todo :)

Spoke hole diameter

The diameter of the spoke holes in the hub.

Good quality hubs have a spoke hole diameter of around 2.5mm or 2.6mm. You don't measure this yourself, it's usually available on the hub manufacturers website. If you can't find it (or don't want to bother looking) then use 2.6mm. Let's say you used 2.6 and the value should have been 2.5 or 2.7, the spoke length error would only be 0.05mm.

Eccentric offset

The amount the hub is offset from the centre of the wheel.

Cross reduction

Large eccentric offsets, large hub diameters and small rim diameters can result in spoke head overlap on the hub flange where the shorter spokes are located, so reducing the cross on those spokes will improve things.

Selecting cross reduction will reduce the number of crosses by one at the bottom of the wheel. The number of spokes affected is determined by the number of spokes in the wheel.

Only use cross reduction if it's really necessary (due to spoke head overlap), and if you do decide to use it, study the lacing drawing carefully. The alternate strategy is to not use cross reduction and simply reduce the number of crosses (of the whole wheel), and use the simpler lacing method.

Spoke offset

This is only used on straightpull hubs.

The measurement is taken from the centre line to where the spoke head seats. It can be either positive, negative or zero depending on the hub design. For a negative offset enter the value with a - (minus) sign.

For a radially laced straight pull hub, the offset is zero.

It is important to use an accurate measurement for the spoke offset because it directly influences the spoke length, for example a measuring error of 1mm will result in 1mm error in the spoke length. The offset is difficult to measure yourself and the hub manufacturer should give you this value.

Positive offset

Negative offset

A hub with paired spoke holes

There are two ways of specifying the pair dimension. Units of measure are required.

• Enter the measurement across the paired holes. For example 12mm
• Enter the pair angle. For example 15deg

The same values are used for both left and right sides. If you require different parameters either side then make separate calculations for each side.

todo make some better pictures!

A rim with paired spoke holes

This will close up the rim holes on the same side of the wheel.

The measurements are taken across two rim holes on the same side. The value you enter must make the spoke holes closer, otherwise you'll get an error message.

There are two ways of specifying the pair dimension. Units of measure are required.

• Enter the measurement across the paired holes. For example 65mm
• Enter the pair angle. For example 15deg

Option 1 or 2

There are two ways of lacing a paired rim. Each option requires different spoke lengths and makes a visually different lacing pattern.

Rim ERD

The Effective Rim Diameter.

The most important dimension for accurate spoke lengths.

This calculator requires you to measure the ERD using the tools and procedure shown in the wheelbuilding book.

If you are building a rim with a concealed spoke bed you need to first measure the nipple seat diameter (NSD). See the book for more details on how to measure the NSD and obtain the ERD.

Asymmetric rims

If your rim is an asymmetric design with an offset spoke bed, then specify the amount of offset here. The rim manufacturer will tell you the amount of offset which is typically around 4mm.

The calculator uses the flange offsets to determine which way to orientate the rim to give the best left/right tension ratio. You can see what it does if you look at the calculation Log. When the left/right flange offsets are very similar the Asym rim can make the tension balance worse, so always look at the tension ratio before and after specifying the Asym value, and in some situations a non Asym rim would be better.

Important

You must always follow the advised rim orientation because the left/right spoke lengths are based on this.

Width between holes

If there is a measurable gap between the left and right spoke holes then enter it here.

Most rims are centrally drilled or directionally drilled and for these rims the width between the holes is zero (leave the entry blank). If you can see a left/right hole stagger of 2mm or greater, then enter the value here. If you can't see anything obvious, then the entry is zero (or blank).

Some fatbike rims have a double row of spoke holes. If the wheel is for an offset fatbike frame using just one row of spoke holes you must still enter the full width between the two rows. See the book for more information on spoke lengths for offset fatbike frames.

Lacing pattern

If a spoke hole width is specified, then the spoke length calculation assumes normal lacing where the spokes from the hub flange do not cross over to the opposite side of the rim. The exception is Fatbike wheels for offset frames (eg. Surly Pugsley), where the spokes are laced to the right hand set of rim holes (the calculation output will prompt you what to do).

Frame offset

An offset frame shifts the position of the rear hub outwards towards the right, which affects the spoke lengths. The frame manufacturer will tell you the offset value. An example of an offset frame is the Cannondale AI (Asymmetric Integration) frame, that has an offset of 6mm.

The more common symmetric frame has an offset of zero. If your frame is not offset, then uncheck the Frame offset option (any entered values are saved, but ignored).

If the required offset is not in the list, change the input to User Input in the system menu (Ξ).

Fatbike offset frames

Examples of Fatbike offset frames are the Surly Pugsley (offset 17.5mm) and the Surly Moonlander (offset 28mm). These offset frames use a standard 135mm freehub, and to achieve the correct tension balance you cannot use a rim with centrally drilled holes.

For a 17.5mm offset frame, use either an asym rim (more offset the better) or a fatbike rim with a double row of spoke holes. A 28mm offset frame requires a fatbike rim with a double row of spoke holes. Do some calculations and keep an eye on tension balance, and always read the notes displayed with the calculation.

Fatbike offset forks

Offset frames can have a matching offset fork. For example, the Surly Pugsley has two fork options, a 100mm symmetrical fork, and a 135mm 17.5mm offset fork. With an offset fork you actually build a wheel that is identical to the rear wheel, so for offset Fatbike front wheels, select a rear wheel in the selection list.

Spokes

The number of spokes in your wheel.

If the required number is not in the list, change the input to User Input in the system menu (Ξ).

Lacing cross pattern

If the required number is not in the list, change the input to User Input in the system menu (Ξ).

Radial lacing

For radial lacing select 0 cross.

When radial lacing a hub using J bend spokes, lace the spokes with the heads out (elbows in).

Straight pull hub cross pattern

With a straight pull hub you have no choice with the cross pattern because it's dictated by the hub design.

Shimano straight pull hub cross count

Shimano straight pull hub specifications may list the number of crosses incorrectly. See Shimano straight pull hubs at the end of the spoke length chapter.

Spoke diameter

It is important to specify the correct diameter for the spokes you are using. The diameter (in mm) is used to calculate the elastic elongation of the spoke which improves the spoke length accuracy.

For a butted (swaged) spoke, use the diameter of the central portion.

If the required diameter is not in the list, change the input to User Input in the system menu (Ξ).

Bladed spokes

Bladed spokes are made by flattening a round spoke. For a bladed spoke use the round spoke equivalent. For example:

If your bladed spoke is not listed, then ask the spoke manufacturer what the diameter of the spoke is before being forged (their website doesn't usually specify this, so you need to ask).

Worksheet

This will print a worksheet for use while you build your wheel.

Hub and rim names are incomplete. Add them now, no need to recalculate.

Any text you enter here will appear on the print.

Print worksheet

The spoke lengths

The calculated lengths are the recommended minimum, so always round the fractional spoke lengths up.

You can round up by up to 2mm, which means you can always find an even or odd size spoke length.

Here are some examples of how you would select an even or odd size based on the calculated length.

Radial lacing

You should lace a radial wheel with the spoke heads out (elbows in), doing it the other way (heads in) puts more stress on the hub flange as the spoke is pulled over it. With all the spokes lying on the inside, the hub flange offset distance is reduced, and for radial lacing the calculator will subtract 2mm from your flange offset dimension. You can see this is the calculation log.

Spoke head clearance

The distance between the spoke and the head of the adjacent spoke.

As the number of crosses increases, the spoke moves closer to the head of the adjacent spoke until it touches (clearance zero), then overlaps it (clearance negative). The overlap should be avoided because it puts an unnecessary bend in the spoke close to the elbow, and it also interferes when placing the spokes in the hub.

Touching

Overlap

If the spoke head clearance overlaps by a small amount of around -0.5, then it still should be okay, anything more then it's not advisable.

Rim entry angle

The angle the spoke makes when entering the rim.

Standard nipples can swivel about 6 or 7 degrees. Nipples with a spherical design such as the Sapim Polyax and DT ProHead can swivel more (9 degrees for the Polyax).

For your hub, rim and spoke count, choose a cross pattern that results in a spoke entry angle of no more than 8 degrees, otherwise the stress on the spoke threads can result in fatigue failures (the spoke could snap at the threads).

Some rims are drilled at an angle to allow the spoke to follow the natural spoke line, in which case the spoke entry angle is not an issue. Examples of this are the WTB rims with 4D angled drilling.

Rim entry angle - combined

This is the actual angle the spoke takes when it enters the rim, taking into account the hub flange offset.

The rim spoke holes are usually aligned towards the hub flange giving a natural spoke line, so you should not be concerned about large angles and the nipple not being able to swivel enough.

Tangent angle

The angle the spoke makes at the hub flange. A radial wheel will be zero degrees, and as the cross count increases so does the angle. 90 degrees will be fully tangent.

Lever arm

The measurement in mm, which is 90 degrees from the extended spoke line to the centre of the hub, shown in red.

Bracing angle

Picture required.

Athough I'm sure you know what bracing angle is.

Tension ratio

This is the ratio between the left and right side spoke tensions. For example, if the spoke tension on the 100% side of the wheel is 120kg and the other side is 60%, then the tension in that side would be 72kg.

This is for information only. When you build your wheel, this is how it will turn out. Tension ratio is calculated using the hub flange offsets and the spoke lengths. There is nothing you can do during building that will affect this ratio.

Left / Right

Left and right is from the perspective of the rider.

Left side

Sometimes referred to as the non drive side.

For disc brake wheels, the disc rotor is located on the left side.

Right side

Sometimes referred to as the drive side (where the chain and sprockets are).

Triplet spoke count

The number of spokes in your triplet wheel.

There are twice as many spokes on one side of the wheel than the other. Rear wheels have the greater spoke count on the right side (drive side), and front wheels the greater spoke count is on the left (disc brake side).

The spoke distribution between the left and right side is shown adjacent to the spoke count. If you change the wheel between front and rear, the spoke distribution will change (cross and spoke diameter will also be changed over).

Triplet lace option

There are two ways of lacing a triplet wheel, and each way requires different spoke lengths. Make your calculation, then use the "Draw" menu option to study how to lace it.

Hubs

For hubs that use J bend spokes, you can choose either lacing option.

For straight pull hubs the lacing option is determined by the hub design. See Triplet lacing in the Wheel design chapter which describes how to identify the required lace option.

Rims

If you purchase a rim that is designed for triplet lacing it will have a specific directional left/right spoke hole drilling, for example a 24 spoke triplet rim will have 16 spokes pointing one way and 8 pointing the other. Depending on how the spoke holes are drilled in relation to the valve hole will determine which lacing option to use. A rim drilled for option 1 will have the valve hole between two spokes on the same side, and option 2 will have the valve hole between opposite side spokes. Use the Draw menu option to visualise this, it will help if you use the button Left Green.

Hub rotate

The value is the angle between a spoke hole on one hub flange and the spoke hole on the other flange. In a normal hub, the two holes are rotated half a spoke hole pitch apart.

This is not the same as a conventional paired hub where the angle is between two hub holes on the same side.

The value shown on the right is the number of degrees for a normal hub (360/spokeCount). If the angle is zero then the holes on the hub flanges will be perfectly aligned.

Paired hub built into a normal rim

This is for a hub taken from a paired spoke wheel and you want to lace it into a rim with equally spaced spoke holes.

The pair angle of the hub will be something slightly more than zero, around 5 degrees to match the hole spacing in the paired rim the hub came from. There is no way of determining this without having the paired rim it came from.

See also the notes for the Rotated wheel type (click the heading Type).

Rim rotate

A normal rim has equally spaced spoke holes. This option allows you to rotate each side of the rim relative each other. They still have equally spaced holes per side, but appear paired, and allows a paired spoke lacing pattern with an appropriate hub (with the same rotation angle).

If the rotation angle is zero, then the left and right side holes will be adjacent to each other (which is only possible if the width between the holes is wide enough). The value shown on the right is the number of degrees in an equally spaced rim (360/spokeCount). For paired lacing the angle is somewhere around 6 degrees although without having the paired rim it's only a guess.

If you are lacing a paired hub into a rim with equally spaced holes, leave the angle as indicated on the right.

See also the notes for the Rotated wheel type (click the heading Type).

G3 Rim dimension

The width of the spoke group measured at the nipple seat of the rim.

Calculation Url

Draw

This will draw the result of a successful calculation.

For more information on wheel geometry, understanding lacing patterns and a detailed guide on using the wheel drawing option see Appendix 4 in the wheelbuilding book.

All drawings are looking on the right side of the wheel (drive side), and the wheel is positioned so that the rim valve hole (shown in red) is at the top centre.

You can have multiple menu options active at any time.

Left - Right

Select which side of the wheel to show. When you look at the left side, you are viewing it through the wheel from the right side.

When looking at a single side, the hub outline is removed and the hub changed to light grey to make it easier to identify where the spoke ends touch the circumference (which is actually the PCD of the hub).

Click left then right to quickly toggle between the two sides, and click whatever is highlighted to return to the full view.

Leading - Trailing

Shows either the leading or trailing spokes. Remember, you are looking on the right side of the wheel and in use on the bike it will rotate clockwise and move off to the right.

Click leading then trailing to quickly toggle between the two spoke orientations, and click whatever is highlighted to return to the full view.

Leading and trailing spokes may not show for a radial wheel, this is explained in Appendix 4 in the wheelbuilding book, sub heading Radial Lacing.

Left green

This will show the left side spokes in green.

Guides

This will show guidelines that radiate from the centre through equally spaced hub holes. They are only shown when you are looking at a single side of the wheel except for wheels that include the Zoom option. When Zoom is active the guides will show when viewing both sides of the wheel.

Redraw

This means the form data has changed. Some data changes will not actually affect the drawing, for example hub flange offset, but when you see the Redraw prompt it's always best to recalculate and refresh the drawing.

It doesn't look right!

It is right, it's just that some things aren't obvious until you think logically about what you are looking at. Also, pay attention to which selections you have activated.

Make sure the drawing is accurate, you may have changed some data inputs but forgotten to recalculate (which refreshes the drawing).

The wheel will always be scaled to fit the display area, so reducing the rim erd does not make the drawing smaller because it gets scaled up to fit.

Zoom

This increases the diameter of small diameter hubs to make it easier to see the spoke placements on the hub. It is visual only, and doesn't alter the spoke length table.

Spoke numbers

For a wheel that requires multiple spoke lengths, this will show the spoke numbers on the drawing when a single side is in view. The numbers refer to the spoke length table.

DT Swiss hubs

The spoke length project

This calculator requires a username and password for the new wheelbuilding book (usernames and passwords for the old book will not work).

Before using the calculator for the first time, please read the first few pages of the spoke length chapter in the book. There is additional help in the calculator system menu (Ξ)