Aerobar armrest pad width: centre span, edges and each side’s station
Pad width is not extension spacing, pad-shell width or an ideal arm position. Preserve left/right lateral coordinates, endpoint conventions and yaw before comparing spans.
Published 11 October 2026 · OpenBikeFit
Aero contact reference · not to scale
Keep each side, not just a span.
Fictional Z positive toward rider’s left: L +110 mm, R −95 mm → lateral centre span 205 mm; midpoint +7.5 mm.
Separate parallel 80 mm pad shapes: outside span 285 mm; inner gap 125 mm.
Projected references only; not direct 3D distance, contact width or an ideal armrest position.
On this page
- 01Define a lateral reference and each named centre
- 02Read the source before copying a width label
- 03Centre span is not the inner gap or outside span
- 04A common shift preserves span but changes location
- 05Yaw and station change the edge question
- 06Distinguish the lateral projection from direct separation
- 07Preserve a complete pair record
Free blank worksheet
Keep a technical paper reference
Use reference and question spaces for extra armrest fields. Fixed digital slots do not replace these distinct endpoints.
Open toolThe word width can describe an individual pad, a pair of pad centres, the inner opening between armrests or the extensions that hold the hands. These are independent dimensions. A record is comparable only after its two endpoints, direction and side convention have been named. It is not a target based on shoulder breadth or a prediction of comfort, control or aerodynamic performance.
This guide builds a technical width ledger for an existing cockpit. It does not ask you to move the armrests, change a hole pattern or narrow the hands. Manufacturer adjustment tables belong to their exact supported configurations; the fictional arithmetic below does not turn a hole spacing or available range into permission for physical work.
Define a lateral reference and each named centre
Keep the same BB-relative origin used for the side-view record, and introduce a lateral Z direction positive toward the rider’s left. A named left pad station at Z=+110 mm and right station at Z=−95 mm have a lateral centre span of 110−(−95)=205 mm. This is the chosen projection, with units and signs explicit, not a direct distance over unknown fore/aft or vertical differences.
State what centre means: a marked geometric reference, a manufacturer-defined centre or another reproducible station. The centre of a cushion outline need not be the centre of its holder, bolt pattern or a loaded arm-contact region. Preserve those definitions rather than choosing whichever visible feature makes two values agree. Do not estimate a hidden station as zero.
Read the source before copying a width label
The SRAM Vuka Aero manual defines its armrest width between pad centres. The Vuka Clip manual separately names total armrest centre-to-centre width and armrest-centre-to-extension-centre quantities. This is evidence that pad and extension references are not interchangeable, even inside the same manufacturer’s cockpit documentation.
Keep the applicable product and revision with a copied label. A table’s width can depend on a holder, mounting arrangement or wedge state; it is not a universal equation for every armrest. Do not reproduce a manufacturer’s table as a menu of recommended positions or infer unseen geometry from an adjustment code. A named dimension still needs the correct actual assembly.
Centre span is not the inner gap or outside span
For a separate fictional top view, assume both pad reference shapes have 80 mm lateral width, their transverse edges are parallel and their centres are at +110 and −95 mm. The outside span is 205+40+40=285 mm. The inner gap is 205−40−40=125 mm. All three answers describe the same ideal shapes with different endpoints.
The two equal 80 mm widths are explicit assumptions, not a property inferred from the pads’ name. With unequal widths use each actual declared half-width separately, and only if that edge model is justified. Shaped pads, rotated pads and nonparallel edges do not share a single automatic centre-to-edge conversion. The illustration is not a pressure map or an available support-area assessment.
A common shift preserves span but changes location
The fictional stations +110 and −95 have midpoint (110−95)÷2=+7.5 mm relative to the chosen centre plane. Add +20 mm to both stations and they become +130 and −75: the centre span is still 205 mm, but the midpoint is now +27.5 mm. A pair-width number therefore cannot establish that the pair is centred on the bicycle.
Likewise, a matching midpoint does not establish equal individual offsets, matching X/Y coordinates or a physically mirrored assembly. Keep both sides, not just a total and a symmetry badge. The signed midpoint is an educational descriptor under the declared origin, not a direction to shift anything or a judgement about the rider.
Yaw and station change the edge question
An armrest can present different edges at different fore/aft stations, particularly when its plan-view axis is rotated. State the yaw convention and the station used for an inner-gap or outside-span observation. A gap measured near the rear boundary is not automatically the same gap farther forward. Keep any angle reference separate from a cushion surface inclination.
An ideal straight 80 mm transverse segment rotated 10° in plan view has a lateral projection 80 cos10°≈78.8 mm, but that toy segment is not a real pad outline. Its rotation does not define a contact width at every station. If you cannot identify the actual edge relationship, retain a separate physical observation or unknown rather than feeding a catalogue width into that formula.
Distinguish the lateral projection from direct separation
With lateral separation 205 mm, a separately declared fore/aft difference 30 mm and vertical difference 5 mm, the ideal point-to-point distance is √(205²+30²+5²)≈207.2 mm. Calling both distances width without the convention loses information. A top-view lateral projection alone cannot establish the 207.2 value because the other two components are not supplied by it.
Extension-centre spacing is another record. It can be 140 mm in a fictional assembly while pad-centre span is 205 mm; subtracting them does not by itself locate the hands or approve bracket positions. A grip surface, hand contact and arm-contact region have their own endpoints. Do not substitute those anatomical observations for the hardware reference stations.
Preserve a complete pair record
Write left and right exact pad and holder identities, centre definition, lateral coordinates, X/Y where actually observed, raw readings, reference plane, edge station and orientation. Keep source and measured values distinguishable. Retain unmatched or missing data; an unchanged average cannot erase a differing side, and a closest pair of readings does not prove physical accuracy.
Use the free paper worksheet’s notes for this extra technical record; there are no dedicated pad-width slots in its fixed digital sheet. Continue to a separately named grip point and extension record. Do not use a bar-width field for pads or an armrest span as an ideal handlebar width. This learning path ends in clearer questions, not a prescribed cockpit or a compatible assembly.
Practical questions
Frequently asked questions
Is pad width the distance between extensions?
Not by default. Preserve the two pad references and the two extension references as independent quantities.
Does the same centre span mean the pair is centred?
No. A common lateral shift can leave span unchanged while moving the midpoint. Retain each side’s coordinate and the reference plane.
Can I subtract pad-shell widths to find the inner gap?
Only with explicitly resolved edge geometry and station. The fictional parallel 80 mm shapes give a 125 mm gap, not a universal formula for rotated or shaped pads.
Does a projected span establish the direct 3D separation?
No. Direct point distance also needs the fore/aft and vertical differences under the same references; missing components remain unknown.