Bwlch y Groes
1213.5 m · net rise 188.2 m · overall 15.5% · confidence: high · Cwm Cerddin · Gwynedd
Shape: sustained — 31% of the climbing sits in a quarter of the distance; longest continuous stretch at 10%+ is 989 m.
Matches: Wikipedia, 100 Greatest Cycling Climbs (Simon Warren) — Bwlch y Groes — articles in English and Welsh; the route passes 9 m from the pass point. Wales's highest public road pass ("Hellfire Pass"). — No. 91 (verified in the official 100 Climbs app, 2026 numbering).
Gradient ladder what do windows mean?
| Window | Maximum | Located at | |
|---|---|---|---|
| 2 m (diagnostic) | 35% | 451–453 m | |
| 3 m (diagnostic) | 32% | 451–454 m | |
| 5 m | 31% | 451–456 m | |
| 10 m | 26% | 447–457 m | |
| 20 m | 24.0% | 364–384 m | |
| 25 m | 23.8% | 366–391 m | |
| 50 m | 22.8% | 353–403 m | |
| 100 m | 21.7% | 357–457 m |
may_start_earliermay_continue_beyond_end Extent detection suggests reviewing where this climb starts/ends.
Map
Check this route yourself: Google Maps route via their router · Street View at the base where coverage exists · geojson.io our exact measured line · OpenTopoMap
This climb's data: OCL JSON — the full gradient ladder, quality flags and provenance in the OpenClimb Ladder format.
Ridden it, or know better? Submit data for this climb no account needed
© OpenStreetMap contributors · topo tiles © OpenTopoMap (CC-BY-SA) · vector tiles OpenFreeMap
Profile
Provenance
{
"analysis_version": "0.1.0",
"sample_interval_m": 1.0,
"interpolation": "bilinear",
"smoothing": "none",
"gradient_windows_m": [
5.0,
10.0,
20.0,
25.0,
50.0,
100.0
],
"diagnostic_windows_m": [
2.0,
3.0
],
"elevation_crs": "EPSG:27700",
"elevation_resolution_m": 1.0,
"elevation_tiles": [
"data/cache/wales/dtm_1m/wg_del_22_291322_20220114dtm.tif",
"data/cache/wales/dtm_1m/wg_del_22_291323_20220114dtm.tif"
],
"calculated_at": "2026-08-12T09:09:05+00:00",
"road_source": "OpenStreetMap (local PBF extract)",
"road_attribution": "\u00a9 OpenStreetMap contributors, ODbL",
"osm_pbf_path": "data/cache/pbf/wales-2026-08-11.osm.pbf",
"osm_snapshot": "2026-08-10T20:21:40Z",
"elevation_provider": "Welsh Government",
"elevation_dataset": "Welsh Government LiDAR 1m DTM (2020-2023)",
"elevation_licence": "Open Government Licence v3 \u2014 \u00a9 Crown copyright Welsh Government",
"elevation_catalogue_layer": "geonode:welsh_government_lidar_tile_catalogue_2020_2023",
"elevation_tile_ids": [
"wg_del_22_291322_20220114dtm.tif",
"wg_del_22_291323_20220114dtm.tif"
],
"elevation_capture_dates": [
"14-01-2022"
],
"climb_origin": "discovered",
"notes": "Coarse pass: max 21.4% over 200 m (Terrain 50), gain 122.4 m over 719 m way. EXTENDED by graph walk: +0 segment(s) at base, +1 at top (stop: base=no_descending_continuation, top=no_ascending_continuation; min_avg=2.0%). Review before adopting. ADOPTED (notable slice 2026-08-11): clean-steep. AUTO-NAMED from gazetteer (hypothesis, unreviewed): was 'Discovered lane (52.7897, -3.6136)'.",
"renamed": "2026-08-13: 'Bwlch y Groes' adopted over auto-name 'Craig Y Pant to Foel Y Groes' \u2014 identification-certain (9 m from Wikidata pass point; en+cy Wikipedia); standing policy per Peter"
}