CAD Sync

The CAD sync pushes your bike's geometry and linkage pivot points into your CAD environment as named variables. Currently Onshape is supported via a Variable Studio.

Geometry Variables

Geometry values are synced per size. Each variable is named syn_<property>_s<size> where size starts at 1. For example, a bike with three sizes would create syn_reach_s1, syn_reach_s2, and syn_reach_s3.

Variable Description Units
syn_reach Reach mm
syn_stack Stack mm
syn_hta Head tube angle deg
syn_htl Head tube length mm
syn_fork_length Fork length (axle to crown) mm
syn_offset Fork offset (rake) mm
syn_lower_headset Lower headset stack height mm
syn_trail Trail mm
syn_htt Head tube top (virtual) mm
syn_fc Front center mm
syn_rc Rear center (chainstay length) mm
syn_cs Chainstay length mm
syn_wheelbase Wheelbase mm
syn_sta_eff Effective seat tube angle deg
syn_sta_act Actual seat tube angle deg
syn_stl Seat tube length mm
syn_nsh Nominal sag height mm
syn_insertion Seatpost insertion mm
syn_bb_drop Bottom bracket drop mm
syn_bb_height Bottom bracket height mm
syn_bb_offset Bottom bracket offset mm
syn_upper_headset Upper headset stack height mm
syn_stem_length Stem length mm
syn_stem_spacers Stem spacer stack mm
syn_stem_stack Stem stack height mm
syn_bar_height Bar height (rise) mm
syn_seated_fit Seated fit mm

Shock Variables

Variable Description Units
syn_shock_length Base shock eye-to-eye length mm
syn_shock_ext_length Shock extension length (e.g. trunnion offset) mm
syn_shock_compression Current shock compression (user-adjustable, default 0) mm
syn_total_shock_length_active Active total length (synced as shock length + extension length) mm

syn_shock_compression defaults to 0 mm and is intended to be adjusted by the user in the Variable Studio. syn_total_shock_length_active is set as a formula (#syn_shock_length + #syn_shock_ext_length - #syn_shock_compression) and updates automatically as you change the compression value.

Offset Variables

Two offset variables are provided to shift all linkage point coordinates into positive space. Linkage points can have negative coordinates relative to the bottom bracket, which does not work well with CAD length parameters.

Variable Default Description
syn_x_offset 500 mm Added to all point X values
syn_y_offset 100 mm Added to all point Y values

These offsets are baked into the point values — each point's X and Y coordinates have the offset pre-applied. If you need the original coordinate, subtract the offset from the synced value.

Linkage Point Variables

Linkage points are synced as syn_p<index>_x and syn_p<index>_y. All coordinates are relative to the bottom bracket origin, shifted by the offset values above.

Index Variable Description
0 syn_p0_x, syn_p0_y Bottom bracket (BB)
1 syn_p1_x, syn_p1_y Rear wheel
2 syn_p2_x, syn_p2_y Shock mount 1 (frame end)
3 syn_p3_x, syn_p3_y Shock mount 2 (linkage end)
4 syn_p4_x, syn_p4_y Frame – Link 1 pivot
5 syn_p5_x, syn_p5_y Link 1 – Link 2 pivot
6 syn_p6_x, syn_p6_y Link 2 – Link 3 pivot
7 syn_p7_x, syn_p7_y Link 3 – Frame pivot
8 syn_p8_x, syn_p8_y Link 4 start
9 syn_p9_x, syn_p9_y Link 4 – Link 5 pivot
10 syn_p10_x, syn_p10_y Link 5 end
11 syn_p11_x, syn_p11_y Idler
12 syn_p12_x, syn_p12_y Brake mount pivot
13 syn_p13_x, syn_p13_y Brake arm end
14 syn_p14_x, syn_p14_y DAQ sensor 1
15 syn_p15_x, syn_p15_y DAQ sensor 2

Common Linkage Configurations

Not all points are used in every linkage type:

  • Single pivot (2-bar): Points 0, 1, 2, 3
  • 4-bar: Points 0–7 plus shock mounts (2, 3)
  • 6-bar: Points 0–10 plus shock mounts (2, 3)

Unused points will have a value of 0 (plus the offset).

Onshape Setup

When you trigger a sync, a Variable Studio named syn is created automatically in your Onshape document. The variables are immediately available for use in Part Studios and Assemblies.

To reference a variable in a dimension or feature, use the # prefix — for example #syn_reach_s1 or #syn_p4_x.