In between reviewing the parking and transport options for this city, the Bristol Traffic Project likes to keep everyone abreast of the local mountain biking conditions. Because if there is a reason why Bristol is a popular place for leisure cycling, it isn't the hills, it's the offroad and backroad cycling for leisure -although we think FirstBus also have a lot of contributions in the matter.
We also like to invent/introduce new words, and are looking forward to building up a good vocabularly for mud conditions. Today, Eismud, a mock-German word to describe Mud that freezes at night and may or may not be frozen during the day.
If you see mountain bikers covered in mud mid-afternoon, you know they've been to Ashton Court or Leigh Woods, and now have a bike to wash or ignore, clothes to remove carefully and dry out before reuse. Conditions: claggy, not too wet. If that is what you like, 12:00-15:00 is good as temperatures are at their highest.
What if you don't want to do the bike wash, yet don't want problems with bringing something muddy back into the house? What if those shoes/boots are the same ones you commute on, and don't want them still damp and flaking off chunks of mud all the next days? The answer is: Eismud. Mud that turns back into ice once the air temperature drops enough. Once frozen, it's dry and does not stick to you or the bike.
To ride in Eismud conditions, wait until near sunset; head out to A.C on a clear afternoon with lights just as everyone else is leaving. 4pm is good; the gates are open till about half past five. Then ride the trails in near or absolute darkness. The iced up mud and broken bits of pedal reflectors will show you the route, though watch out for the downhill towards the quarry section where the path appears to fork at a fallen tree. Take the left fork, as the tree blocks the right hand path.
The main problem with these rides is the temperature: it is very cold. Even if you dress warm, your hands, legs and toes will suffer. And because the mud is solid, its a hard ride for a hardtail. Stand, or get used to the bumps. But, no mud to clean off -it's a trade off.
It's also a bet: if the day is too warm, you set out at sunset and still get covered in mud, then get frozen at the end and have to ride home cold with a bike that needs cleaning and damp clothes for the next day. There's more risk on cloudy days here, as their evenings stay warmer. Look for the clear skies and the cold nights will follow. And then -Eismud!
On a more technical note, it is worthwhile to consider where these repeated Melt/Freeze cycles impact the consistency of the mud, making it strong or weaker. Certainly in ski/winter mountaineering circles. the impact of Melt/Freeze Metamorphosis, "M/F Met" is considered far more hazardous than Equitemperature Metamorphosis, "ET Met", that being sublimation from solid to gas and recrystallisation within the snowpack. M/F Met creates a crust layer on the snow which resists bonding to layers of snow above, so creating a high-avalanche risk weak layer, which may remain hidden many metres below the surface [source: Staying Alive in Avalanche Terrain, Bruce Tremper, 2001]. If the Eismud layer were end up below the surface there could be a similar risk. Given the level gradients in Ashton Court and requirement for sustained low temperatures, this risk must be considered minimal