What it is
Grouping lets you cluster multiple segments that share similar characteristics (e.g., “Flat with headwind”, “False flat climb”, “Steep descent”) so they share one power target in a pacing optimization. You can also think of it as an execution layer on top of segmentation: segments are the physics resolution; groups are the race-plan resolution.
Why it matters
Simpler race plan: fewer targets to remember → better execution on race day.
Intentional trade-off: you sacrifice a little theoretical optimality for a plan you can actually ride.
Technical limitation: A pacing optimization can optimize at most 20 power targets (optimized groups + ungrouped optimized segments). Above that, the run is blocked with “More than 20 groups or segments to optimize”. Group segments or fix the power for some of them, or use Apply default groups to all segments in that message.
Where it lives
Grouping is defined in the Groups & power step inside an optimization, not in your course definition. You can try different groupings across runs (Edit & rerun) without changing the underlying course.
In equipment optimizations, the Groups & power step doesn't optimize anything: all setups are simulated with the fixed Pedalling power [W] you define, so the 20-target limit doesn't apply there.
Automatic grouping
Segments are grouped automatically when you fetch or update the wind forecast or save wind changes. Each segment is assigned one of nine default groups based on its slope and headwind: Steep climb, Climb, False flat climb, Flat with headwind, Flat windless, Flat with tailwind, False flat descent, Descent and Steep descent.
Segments you've assigned to a group yourself keep that group when the wind is updated.
How it interacts with the model
Optimized groups: in the Groups view, a group shows “Will be optimized” and the solver finds one target for all its segments.
Manual power (group): toggle the group power on and enter a Group power [W] to fix it; it's excluded from optimization.
Manual power (segment): in the Segments view, set the segment's Group to No grouping, then toggle Manual power and enter a Pedalling power [W]. That segment won’t be changed by the solver.
In the Segments view, the Group dropdown offers No grouping and the segment's matching default group.
Bulk actions
Regroup all segments: assigns every segment to its default group.
Ungroup all segments: removes all group assignments (each segment is optimized individually — watch the 20-target limit).
Ungrouping isn't available on all plans; in that case you'll see “Ungrouping is not available in this plan.”
When to group
After you’re happy with basic segmentation and wind (forecast updated). Automatic grouping already gives you a sensible starting point.
Try different groupings for different race contexts (e.g., windy vs calm) and compare the runs in View results history.
Good patterns
Terrain-driven: Steep climb, Climb, False flat climb, False flat descent, Descent, Steep descent (this is what is done automatically).
Wind-aware flats: split flats by exposure: Flat with headwind, Flat windless, Flat with tailwind (this is what is done automatically).
Surface-driven sections: where Rough surface warrants distinct targets. This requires custom groups (Add group), which are not available on all plans.
Tips & pitfalls
If you change the segmentation, Update forecast in the Wind step — grouping is refreshed with the new wind data.
Avoid over-grouping huge mixed sections; keep groups internally consistent (terrain + wind + surface).
Changing the segmentation (Coarse / Medium / Fine) removes existing group assignments; finalize segmentation before you fine-tune groups.
Example workflow
Load/trim/segment course → Get forecast in the Wind step (segments are grouped automatically).
Review the groups in Groups & power; use Regroup all segments to start over.
Leave most groups optimized; fix manual power only where you must (e.g., neutral zones).
Run, review, and iterate with Edit & rerun for different grouping ideas.