Save your calculation

The menu option "Copy" will copy the calculation to the clipboard. Open up a word processing document or spreadsheet and paste the contents into it. When you build the wheel, open the document and add any information that will prove useful if building the same wheel in the future. Do not edit the calculated spoke lengths, you need these as a reference to what the calculator recommended and what you actually used.

At the time of writing, Google Chrome, Opera and the latest version of Microsoft Edge will preserve all the formatting. Other browsers such as Firefox will copy the data, but may use an unformatted layout.

Type
Hub diameter
Flange offset
Spoke hole dia.
Eccentric offset
Spoke offset
Paired hub
Erd Asym
Width between holes
G3 Rim dimension
Hub rotate
Rim rotate
Frame offset
Spokes
Triplet spokes
Lace option
Cross
Cross reduction
Spoke dia.
Spoke numbers
Zoom
Close
Help Drawing guide

Field settings

Spokes Select list
Cross Select list Select list
Spoke dia. Select list Select list
Frame offset Select list

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Help

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 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 (which turns grey when a recalculation is necessary).

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.

Roger Musson

v

RM's drawing tools.

Do not apply ANY rotations Do not rotate valve to top Spoke zero

Normal

A hub using J bend spokes.

The hub and rim have the same number of equally spaced holes.

Option : Paired hub holes

The hub spoke holes are grouped in pairs, but the rim must always have equally spaced spoke holes.

If the option is unchecked the hub is treated as non paired and any previously entered values are ignored.

Straight pull hub

A hub using straight pull spokes.

The geometry of the hub will dictate the cross pattern. Click "Cross" in the data entry form for additional notes on straight pull cross patterns.

The spoke offset is important, do not guess this entry!

Triplet lacing

Also known as 2:1 lacing.

For a detailed description of triplet lacing and compatible hubs, see Triplet lacing in the Wheel design chapter of the book.

The rim must be centrally drilled with no left/right hole stagger or a rim with a triplet specific spoke hole stagger.

For a given cross pattern there are two ways of lacing the side with the larger spoke count. Click "Lace option" in the data form for additional notes on theses lacing patterns.

Front and Rear

For a front wheel, the "2" side is on the left, and a rear wheel it's on the right. If you change between front and rear the calculator will swap the values for spoke distribution, cross and spoke diameter to the other side.

Option: straight pull hub

The straight pull hub must be triplet specific.

This option removes the spoke hole diameter from the data entry form and replaces it with spoke offset. The spoke offset is important, do not guess this entry.

G3 Lacing

This is a triplet lacing pattern used by Campagnolo on their G3 wheelsets.

Any triplet specific J bend hub can be used for G3 lacing.

Straight pull hubs must be G3 specific.

The rim must be G3 specific with the rim holes drilled in groups of 3.

There is an extra rim dimension for G3 lacing, click "G3 Rim dimension" in the data form for additional notes.

Rear wheels

Campagnolo G3 rear disc brake wheels use radial lacing on the disc side, but Campagnolo have designed a stiff hub shell that transmits the brake force to the crossed side of the wheel. You are not obliged to use radial on the rear disc side (left side) and can use a cross lacing pattern, but be aware that G3 rims will be drilled with directional drilling that assumes a radial inner spoke. If you use a cross pattern you will lose the parallel appearance (use the Geometry option to see the effect).

Front and Rear

For a front wheel, the "2" side is on the left, and a rear wheel it's on the right. If you change between front and rear the calculator will swap the values for spoke distribution, cross and spoke diameter to the other side.

Option: straight pull hub

A standard triplet straight pull hub cannot be used, it must be GS specific.

This option removes the spoke hole diameter from the data entry form and replaces it with spoke offset. The spoke offset is important, do not guess this entry.

Eccentric wheel

The hub is offset from the centre of the wheel.

The wheel will require many spoke lengths and these are shown in a table and grouped in the order of lacing.

Lacing guide

To help you lace the wheel you should study the wheel drawing. Start by selecting the right side leading spokes with guides displayed, and note where the valve position is (shown as the red dot). Show the spoke numbers by clicking the checkbox.

For a radial wheel do not select Leading or Trailing, just look at one complete side at a time. If you do select leading or trailing, then the diagram will not be as you expect, but it is correct.

Rotated wheel

In a normal wheel, the left and right side spoke holes in the hub and rim are rotated to give an even distribution of spoke holes.

This rotated wheel type is based on a Normal wheel type, but allows you to specify custom rotations.

The main use of this is to explore wheel geometry and see how paired spoke lacing wheels are created.

You can also use this if you have a hub taken from a paired spoke wheel and want to lace it into a rim with equally spaced spoke holes. The hub must use J bend spokes.

See the notes for "Hub rotate" and "Rim rotate".

A visual explanation

Enter some data for a cross laced wheel, 24 spokes 2 cross. Make the hub and rim rotation angles the same as the value shown to the right. Draw the wheel and select Left green and Guides, and select Zoom view. This will create a normal wheel with equally distributed spoke holes, and the spoke lengths will all be the same. Now start adjusting the rotation angle of the rim making it smaller and see how the left and right spokes get closer, then adjust the hub.

If the hub and rim rotation values are the same, then the spoke lengths on each side will be the same.

When you change the value on a desktop pc by clicking the up and down input arrows with a mouse it will perform an automatic recalculation and the drawing and spoke length table automatically update.

Radial lacing

If the hub and rim rotations are different it will not be possible to lace the wheel radially because all the spokes on one side will be Leading and on the other side Trailing. The net effect will be to twist the hub. Go ahead and try it, look at the drawing and choose Leading then Trailing and see the warning message. Only when your hub and rim rotations are the same will the spokes be pure radial.

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.

Measuring hub flange offsets

Offset calculator

Hub width x y
F L R

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.

Straightpull hub diameter

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.

Straightpull hub positive offset
Positive offset
Straightpull hub negative offset
Negative offset

A hub with paired spoke holes

The rim must have equally spaced 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!

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.

When you calculate a spoke table, there will be a note advising you which way to orientate the rim when building the wheel, and you must follow the advised orientation because the left/right spoke lengths are calculated based on the specified orientation.

Width between holes

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

Dimension between rim holes

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.

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:

SpokeDiameter
Sapim CX-Ray1.5
DT Aerolite1.5
DT Aerocomp1.8

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.

You need to calculate a spoke table first.

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

Any text you enter here will appear on the print.

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.

CalcEvenOdd
260.0260
262
261260 on the even side is the absolute minimum, still okay, but 262 will be easier to build.
260.4262261Do not choose 260 for the even size because it will be too short.
260.8262261
261.0262261
263
261 on the odd side is the absolute minimum, still okay, but 263 will be easier to build.
261.2262263Do not choose 261 for the odd size because it will be too short.

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.

Spoke head clearance touching
Touching
Spoke head clearance overlapping
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.

Spoke line entry angle

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. A rim for paired spoke lacing has the rim holes rotated towards each other.

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

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.

Add data file

DT Swiss hubs

Front :
Rear :

Please read about the DT hubs feature.

The spoke length project

This calculator is for use with the new wheelbuilding book. Get the book and get access to the calculator, for details please see the wheelbuilding book.

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)

Logon help page.

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