Thunderdown in the Underdown at Prairie Dells

Location:
Prairie Dells Trail Head
Heineman Road
Merrill, WI

Facebook Event

This is Wisconsin’s Ultimate Lap! The Iron Bull Epic!
Ride the 37 mile lap or a 13 mile adventure from Prairie Dells over 7 daunting hills to Underdown Lake. This WEMS Series event is held in conjunction with the IronBull Underdown Trail Races.

LIVE music, drinks, food and fun!

Event Schedule

Friday, August 14, 2026

• 5:30 – 7:00pm: Packet pickup

Saturday, August 15, 2026

• 7:00 – 11:00am: Packet pickup

WEMS Underdown Mountain Bike Races

8:00 AM (Hundred Down)
Long-distance Solo: Three (37-Mile) laps completed between 8AM and Midnight for the ultimate 111 Mile challenge. Only a handful have ever successfully completed the three lap challenge! Riders completing two laps will be scored after riders completing three laps.

9:00 AM (Thunderdown)
Mid-distance Solo: One 37-Mile lap

Long-distance Duo: One 37-Mile lap completed by each rider both starting at 9AM (NOT a tag team relay!)

9:15 AM (Oktoberfest Summit)
Short-distance Solo: One 13-Mile lap. Finish this and change your shoes by 11:30am and earn a free entry to the Oktoberfest Half-Marathon

Mid-distance Duo: One 13-Mile lap completed by both riders starting at 9:15AM (NOT a tag team relay!)

Long-distance Team: One 13-Mile lap completed by all riders starting at 9:15AM (NOT a tag team relay!)

IRONBULL Underdown Trail Running Races

9:30 AM (IRONBULL Prairie Dells 60K Run Start)

10:15 AM (IRONBULL Heineman Hills Marathon Run Start)

11:30 AM (IRONBULL Oktoberfest Half-Marathon Run Start)

W.E.M.S. Guidelines: All W.E.M.S. guidelines will be followed.