Bicycle Wheel Dish: What It Means and How to Measure It

Bicycle wheel dish is the sideways position of the rim relative to the hub. A correctly dished wheel has its rim centered between the outer faces of the hub locknuts, which is the hub centerline, even when the two hub flanges sit at different distances from that center. Most rear wheels with a cassette and many disc-brake wheels need dish because one flange is pushed inward to make room for the sprockets or the rotor. You measure dish by comparing the distance from the rim to each locknut, usually with a dishing gauge, calipers, or by flipping the wheel in a truing stand.

Dish describes how the rim relates to the hub. It does not describe the tire. Even so, the tire sidewall tells you which rim size you are working with, so it is a useful place to start before you talk about dish, spoke length and rim centering.

What do the numbers on a bicycle tire sidewall mean?

Most bicycle tire sidewalls show at least one size code, such as 37-622 or 700x35c, and a pressure rating. The ISO/ETRTO code, for example 37-622, is the most precise. The first number is the nominal tire width in millimetres. The second is the bead seat diameter (BSD) in millimetres, which is the diameter of the rim where the tire bead sits.

Dimensions, units and ratings on the sidewall

Sidewall markings mix several kinds of information. Some are measurements of size, some are naming conventions, and some are performance ratings that say nothing about geometry.

Marking example	Type	What it means	Relevance to wheel dish
37-622	Dimensions (mm)	Nominal width 37 mm, bead seat diameter 622 mm	Identifies the rim diameter family. It does not set the amount of dish.
700x35c	Traditional size name	A French-origin designation. 700c tires fit 622 mm BSD rims.	Identifies the rim family only.
29x2.2	Inch-based size name	About 2.2 in wide, for a 622 mm BSD rim. The ISO equivalent is roughly 55-622.	Identifies the rim family only.
Max 5 bar / 75 psi	Pressure rating	The inflation limit or range set by the manufacturer	None. This is a rating, not a dimension.
120 TPI	Casing specification	Threads per inch in the casing fabric	None.

Common bead seat diameters include 622 mm (700c and 29 in), 584 mm (27.5 in and 650B), 559 mm (26 in mountain bike) and 406 mm (a common 20 in size). Inch names can be ambiguous, which is why the millimetre BSD is the reliable value when you match tires, rims and spokes.

How width and rim diameter affect tire height and circumference

Bicycle tires rarely carry an aspect ratio, because their cross-section is close to round. As a rough approximation, the tire's height above the rim is similar to its width. That gives a simple calculation:

• Approximate overall diameter = BSD + 2 × tire height
• Approximate circumference = π × overall diameter

Example for a 37-622 tire: 622 + 2 × 37 = 696 mm in diameter, and 3.1416 × 696 ≈ 2,187 mm in circumference. A 28-622 tire on the same rim works out to about 678 mm in diameter and about 2,130 mm in circumference. Both tires share the same rim diameter. The wider tire adds height, so its overall diameter and circumference are larger.

These are calculated figures, not real measurements. The actual inflated size depends on the rim's internal width, the inflation pressure, the casing construction and the manufacturer's tolerances. Frame and fork clearance is a separate question, and the calculation alone cannot confirm that a tire fits a particular bike.

The tire's width and height have no effect on dish. Dish is set entirely by the hub, the rim and the spokes. The BSD becomes relevant when you calculate spoke length, as explained below.

What is wheel dish?

Wheel dish is the offset between the rim's center plane and the midpoint between the two hub flanges. The goal of dishing is to place the rim on the hub centerline, which is the midpoint between the locknut faces that clamp into the frame or fork dropouts. When the rim sits there, the wheel runs centered in the frame and between the brake pads.

The hub flanges are often asymmetric. On a typical rear hub, the cassette takes up space on the drive side, so the drive-side flange sits closer to the centerline than the non-drive flange. The rim still has to sit on the centerline, so it ends up closer to the drive-side flange. Seen edge-on, the spokes form a lopsided cone, or a "dish", which is where the name comes from.

Why dish changes spoke tension

On a dished wheel, the spokes on the side with the inboard flange stand more upright and carry higher tension than the spokes on the other side. Both sides have to pull the rim sideways with equal force. The more steeply angled spokes contribute less sideways force per unit of tension, so they need more tension to balance the opposite side.

A simplified example with hypothetical hub dimensions: the non-drive flange is 35 mm from the centerline and the drive-side flange is 20 mm from it. The midpoint between the flanges is (35 − 20) ÷ 2 = 7.5 mm from the centerline, so the rim must sit 7.5 mm toward the drive side of the flange midpoint. As an approximation, the side-to-side tension ratio follows the ratio of the flange offsets, here 35 ÷ 20 = 1.75. The drive-side spokes would therefore carry roughly 1.75 times the tension of the non-drive spokes. Real ratios depend on the actual hub, rim and spoke geometry.

Some rims have off-center spoke holes, called asymmetric rims. These move the spoke bed toward the side with the wider flange, which reduces the tension imbalance. The finished wheel must still have its rim centered on the hub centerline.

Which wheels need dish?

The amount of dish depends on the hub design, so the table below describes general tendencies rather than fixed values.

Wheel type	Typical flange layout	Dish	Higher-tension side
Rim-brake front	Flanges usually symmetric	Little or none	Usually equal
Disc-brake front	Rotor-side flange moved inward	Moderate	Rotor side
Rim-brake rear, cassette	Drive-side flange well inboard	Often substantial	Drive side
Disc-brake rear, cassette	Both sides constrained, by the cassette and by the rotor	Varies with hub design	Usually drive side
Single-speed or fixed rear	Often near-symmetric	Little or none	Often similar

How dish affects spoke length

On a dished wheel, the spokes on each side usually need different lengths, because each flange sits at a different distance from the rim plane. Spoke length calculations use the rim's effective rim diameter (ERD), the flange diameter, the center-to-flange distance for each side and the lacing pattern. ERD is related to the rim's BSD from the tire marking, but it is not the same figure, so take it from the rim manufacturer or measure it. On a typical cassette rear wheel, the drive-side spokes come out shorter because that flange is closer to the rim plane.

Wheel dish measurement: how to check whether a wheel is centered

To measure wheel dish, compare the distance from the rim to the left locknut face with the distance from the rim to the right locknut face. If both distances are equal, the rim is centered on the hub centerline. If they differ, the rim is off-center by half the difference.

Method 1: Using a dishing gauge

A dishing gauge is a bridge-shaped tool. Its two arms rest on the rim, and an adjustable center probe reaches toward the axle.

1. Remove the tire and tube if they get in the way of the gauge arms. True the wheel laterally first so that a wobble does not distort the reading.
2. Place the gauge across one side of the wheel with both arms on the rim at the same reference point, such as the brake track or the rim edge.
3. Adjust the probe until it just touches the locknut face, or the end cap on hubs without exposed locknuts, then lock it.
4. Flip the wheel and place the gauge on the other side without changing the probe setting.
5. Check the probe. If it touches the locknut with the arms seated on the rim, the dish is correct. If there is a gap at the probe, or the arms rock because the probe hits first, the rim is off-center.
6. Measure the gap or offset. The rim's centering error is half of that difference. For example, a 2 mm difference means the rim sits 1 mm off the hub centerline.
7. Take readings at several points around the rim and compare them, so that small lateral wobbles do not mislead you.

The direction of the error follows from geometry. If the probe falls short of the second locknut, that locknut is farther from the rim plane than the first one, so the rim needs to move toward the second side.

Method 2: Using calipers or a ruler

Without a dishing gauge, you can lay a straightedge across the rim and measure from it to each locknut face with calipers or a depth gauge. Use the same rim reference point on both sides. The rim is off-center by half the difference between the two readings. This method is slower and less repeatable than a dishing gauge, but the principle is the same.

Method 3: Flipping the wheel in a truing stand

1. Mount the wheel and set the stand's indicator close to one side of the rim.
2. Note the gap at a marked point on the rim.
3. Remove the wheel, flip it, and remount it so the same point lines up with the indicator.
4. Compare the gaps. A change means the rim is off-center by half that change.

This works only if the stand clamps the axle in exactly the same place both times. Some stands are self-centering, but you should not rely on a stand's centering until you have verified it with a known-good wheel or a dishing gauge.

Checking dish by looking at the wheel in the frame is less reliable. Frames, dropouts and axle seating can be slightly asymmetric, so treat it as a rough check only.

How to correct wheel dish

You correct dish by moving the rim toward one hub flange: tighten the spokes that run to that flange, or loosen the spokes that run to the other flange. To move the rim to the left, tighten the left-side spokes, loosen the right-side spokes, or combine both.

1. Find out which way the rim needs to move and by how much, using one of the measurement methods above.
2. Choose your approach based on overall spoke tension. If the wheel is under-tensioned, tighten the side the rim should move toward. If it is already near the rim's maximum tension, loosen the opposite side.
3. Turn every spoke on the chosen side by the same small amount, such as a quarter turn, working all the way around the wheel. Equal adjustments move the rim sideways without introducing wobble or hop.
4. Re-check lateral true, radial true and dish, then repeat in small steps.
5. Stress-relieve the spokes as your usual wheelbuilding practice allows, then check true and dish again.

Keep an eye on spoke tension throughout. On a dished rear wheel the drive side is already the tighter side, so you can quickly push it past the rim manufacturer's tension limit if you keep tightening it to correct dish. Spacing also matters. If you change axle end caps or spacers, or move a hub to a frame with different spacing, the locknut faces move, and the wheel may need to be re-dished.

What dish tells you, and what it does not

A correct dish measurement confirms only that the rim is centered between the hub's locknut faces. It does not tell you whether the wheel is laterally or radially true, whether the spoke tension is adequate or even, or whether a given tire will fit the frame. In the same way, the size code on the tire sidewall tells you the rim diameter family and the nominal tire width. It says nothing about dish, and calculated tire diameters are approximations rather than measured fitment.

Dish, truing, spoke tension and tire size are separate checks. Doing all of them gives you a wheel that is centered, runs straight and suits the bike.