Check hood and brake-lever symmetry: height, angle and gap stay separate
Build a repeatable left/right control record with mirrored features, declared angle axes and resting blade gaps. Visual alignment is not a functional or fit certificate.
Published 9 October 2026 · OpenBikeFit
Control reference field guide · not to scale
One matched column is not the whole pair.
Fictional body-height means: L 622 mm · R 619 mm · difference +3 mm.
Resting blade gaps: L 70 mm · R 70 mm · difference 0 mm.
Height, declared angle axis, gap and brake operation remain separate observations.
On this page
- 01Choose a mirrored physical feature
- 02Height needs a common alignment and datum
- 03An angle needs its rotation axis
- 04Blade gap is a third independent observation
- 05Repeat before explaining a difference
- 06Shape and mounting are separate from symmetry
- 07Use the paper baseline to frame the question
- 08Select the existing tool by the quantity
- 09Remeasure without rewriting the earlier baseline
Choose the quantity first
Inspect the separate L/R hood workflow
Existing free tools keep their access and hardware boundaries. Reading a guide does not create a bike, activate a sensor or approve work.
Open toolTwo brake hoods can look level while their chosen body features, orientations or resting blade gaps differ. They can also look different because the photograph is tilted or the observed features are not mirrored. A useful left/right comparison starts by deciding which question is being measured. Keep height, orientation and blade gap separate so a zero difference in one column does not approve the whole cockpit.
This guide prepares a non-destructive baseline on an assembled bicycle. It does not tell you to rotate hoods, loosen clamps or make both sides identical. Component identity, permitted mounting, routing, braking and shifting operation remain independent mechanical checks. The purpose is a record that another person can understand and repeat, not a cosmetic verdict from a single front-view photograph.
Choose a mirrored physical feature
Name a recognisable hard feature on each matching control body rather than an arbitrary spot on a flexible cover. Record exactly how the two features correspond. A left top corner and a right nose are not a mirrored pair, and comparing them can create a false height difference. If different controls are installed, their shapes may not offer an equivalent feature at all.
Preserve each component identity and the existing mounted state. Do not move either hood to make the measurement easier. A non-damaging removable mark can help locate the same reference later, provided it does not interfere with controls or obscure a required manufacturer marking. Unknown correspondence should remain unresolved rather than being filled by a convenient outer silhouette or a point chosen after seeing the result.
Height needs a common alignment and datum
State whether height is measured from a shared level datum or as a vertical coordinate relative to another named point. Keep the bicycle upright under the same axle/alignment method on both observations. A diagonal tape distance to a hood is not automatically vertical height. The selected feature and projection method belong beside the value so the next reading uses the same quantity.
For a fictional fixed reference, left heights of 621 and 623 mm average 622 mm; right heights of 618 and 620 mm average 619 mm. Left minus right is +3 mm. This is arithmetic on declared observations, not a recommendation to raise the right hood by three millimetres. Changing a datum or choosing another body point can change that difference without any mechanical change.
An angle needs its rotation axis
A control can have a side-view inclination, a top-view turn-in direction or a front-view roll description. Label the axis and viewing/reference plane in plain language, with a sketch if helpful. Choose a sign convention and retain it for both sides. A phone resting on two differently shaped surfaces can report angles which do not represent comparable control-body orientations.
A fictional side-view line at +6° and another at +8° differ by −2° when left minus right is used. That subtraction does not describe top-view turn-in or front-view roll. Do not enter an observed yaw value into a workflow prepared for another declared axis. The existing hood tool requires its own exact reference; this guide does not establish a universal control angle or a permitted mounting range.
Blade gap is a third independent observation
With both blades at rest, select mirrored bar or hood-body marks and matching blade points. Record the measurement direction. A gap to the tip and a gap to the middle of a curved blade are different quantities. The controls assistant accepts its named reference definitions; if the left and right definitions do not match, the observation must be repeated before a comparison can be interpreted.
Fictional resting gaps of 70 and 70 mm give zero difference. The same record can still contain the +3 mm body-height difference or a different declared body angle from the preceding examples. None of the three measurements replaces the others. Nor does a zero resting-gap difference test the amount of movement before pad engagement, clearance under load or the operation of either brake.
Repeat before explaining a difference
Reset the measuring instrument and locate each named feature again for an independent reading. Retain the original numbers rather than rounding them until the pair looks equal. Note alignment, tool, coverings and any difficulty locating a feature. A repeated series under a changed reference is a new series, not a way to resolve disagreement in the original one.
The existing tools have explicit product repeatability rules. Those checks describe agreement of entered observations, not absolute measurement accuracy or the cause of an asymmetry. A consistent difference can still arise from a consistently chosen wrong reference. If the instrument, feature or axis is unresolved, ask for a better physical observation rather than treating a decimal output as proof of precision.
Shape and mounting are separate from symmetry
Zipp’s bar discussion treats bar shape and the area around the control as separate design considerations. An installed body feature therefore cannot be inferred from a simple bar-size label. Retain the bar model and the exact controls alongside the readings. A moulded curve or different cover shape can make a photograph misleading even before perspective or bicycle tilt is considered.
The cited Shimano dealer manual has separate installation and adjustment sections, with exact component and assembly requirements. SRAM’s Road AXS/XPLR instructions likewise distinguish control mounting from blade adjustments. These references illustrate the boundary, not a generic mounting tutorial. This page intentionally gives no clamp torque, universal turn-in angle, approved bar material, hose procedure or instruction to make two controls visually match.
Use the paper baseline to frame the question
A compact record should keep left/right component identity, mirrored feature, datum/alignment, angle axis/sign, independent heights, independent angles and resting blade gaps. Mark travel and functional inspection separately as unverified if they were not actually checked. Preserve photographs only as supporting context with their viewpoint stated, not as replacements for named physical readings.
Write one precise question for the mechanic or the next tool: for example, whether the same named body points have a repeatable height difference. That is more useful than a general request to fix crooked hoods. It prevents several quantities being changed at once and makes a later comparison interpretable. The existing blank worksheet is an unfilled record aid, not an installation certificate.
Select the existing tool by the quantity
Use the hood-position assistant for its declared left/right body angle or height workflow, and the handlebar-controls assistant for observed width and resting blade-gap comparison. Their separate access, hardware, save and re-check boundaries stay in place. Reading this guide or opening a tool does not create a local bike, accept consent, satisfy a mechanical gate or measure anything automatically.
Do not route a blade-gap question into a hood-height field merely because both use millimetres. Do not compensate for a body-angle discrepancy using a stem model that ends at the bar clamp. Keep the quantity and endpoint attached to every result. A completed browser comparison can help organise a question while physical compatibility, clearance and operation remain outside that result.
Remeasure without rewriting the earlier baseline
After any separately justified and correctly performed work, use the same features, reference planes and rest state to make a new series. Keep the original record rather than relabelling a candidate setting as a measured final state. If the reference changed, describe that change and do not present the two series as directly comparable. A preserved baseline allows an honest account of what was actually observed.
Stop using a dimensional comparison as reassurance when a control moves, routing is strained or braking or shifting is uncertain. Exact manufacturer function checks and qualified inspection are separate requirements. This guide supplies no fit verdict, recommendation to ride, purchase choice or automatic adjustment. Its complete outcome is a reproducible multi-quantity control record and an appropriate next question, not approval of the bicycle.
Practical questions
Frequently asked questions
Should both hoods look perfectly level?
A visual impression does not establish matching body features, alignment, orientation or blade gaps. Record each quantity separately; this guide does not prescribe identical mounting or approve function.
Which hood angle should I measure?
Name the physical reference line, rotation axis, plane and sign for the task. Side inclination, top-view turn-in and front roll are not interchangeable; follow the existing tool’s exact reference.
Does equal lever reach prove hood symmetry?
No. Equal resting blade gaps can coexist with different body heights or orientations. Brake travel and function are separate checks again.
Can I collect a baseline without creating a bike?
Yes. Read the definitions and use the existing unfilled paper worksheet. Opening the guide or worksheet does not save a bike, accept consent or approve a mechanical change.