01 / KNOW THE ROUTE
What the course asks of you
A technical mountain loop
The race starts and finishes in Llanberis and crosses the northern mountains of Eryri. The organiser describes technical ridges, glacial lakes, remote valleys, scree and rocky paths, with some scrambling and only selected runnable sections.
Why we do not list the summits
The organiser had not published a named list of summits or aid stations for 2027 when we checked, and the final GPX is released two weeks before the event. Rather than guess, plan your recce once the route file is out and use the official map, not a generic Snowdon route.
Time on feet, not distance
With 5,800 m of climbing over 108 km and a 05:30 start, this is a day and a night in the mountains for most runners. The fastest 2026 finisher took just under 12 hours over a slightly shorter course.
02 / BUILD THE BLOCK
How to prepare
Build climbing and descending strength
Long, steep climbs and technical descents are the core of this race. Use hill repeats, sustained hikes with poles if you plan to use them, and progressive downhill work so your quads can cope with thousands of metres of descent.
Get comfortable on rock
Scree, rocky paths and some scrambling demand confidence and good footwork. Spend time on similar mountain terrain in spring, ideally in Eryri itself, and practise moving carefully when tired and in poor visibility.
Rehearse the long day
Practise eating real food while hiking, managing layers as weather changes, and moving through the night with a headtorch. Back-to-back mountain days in April are the best rehearsal you can give yourself.
Keep your running and strength work in one place. Explore MaxMile for your Eryri 100K preparation, or compare the levels of personal coaching.
03 / PUT IT INTO PRACTICE
Pace the race you have trained for
Pace by effort and time on feet, not kilometres. Hike the steep climbs from the start, take the technical descents carefully, and save running for the genuinely runnable sections. A conservative first half pays off when you reach the later ridges in fading light.
The organiser had not published cut-off times for 2027 when we checked, only the overall course close. Check the final cut-off table, then build an aid-station plan that includes time to refill and eat. Expect conditions to change quickly in the mountains and adjust your effort to stay safe.
04 / MAKE ROOM FOR TRAINING
When should your block start?
The Eryri 100K is on Saturday 15 May 2027. A 20-week block starts around Saturday 26 December 2026 and a 24-week block around 28 November 2026, which suits runners stepping up from 50K or 50 miles. Use the winter for strength, hill work and consistent volume, then shift to long mountain days from March.
April is the key month: back-to-back days on steep, rocky ground and at least one long day that runs into darkness. Taper over the final two weeks, using the GPX released about two weeks out to finalise your race plan. Registration closes on 2 April 2027 or earlier if the distance sells out.
05 / SORT THE PRACTICAL BITS
Kit and race-weekend planning
Bib and kit collection in Llanberis is on Friday 14 May, 08:00 to 13:00 and 14:30 to 16:00, with drop bags handed in on the Friday evening. Mandatory kit includes hot-weather and cold-weather items; the organiser confirms 24 hours before the start whether any can be left out. The organiser warns that upland weather can change drastically within hours, with heat, heavy rain, hail and even snow possible in May.
Bangor is the nearest railway station, with an event shuttle to Llanberis, and a race-morning Park and Ride runs from 02:30. Parking passes are sold through MyUTMB, and sleeping in vehicles is not allowed. Book accommodation early; the official travel partner is Nirvana.
