I was at a park today, and there was a steep hill with decent grass.
it looked like it was more than 45, maybe 55 degrees, and I tried to go down on my 24" club and failed miserably.
is that steepness possible? with a very big muni?

It really depends on how long the hill is and how good you are. If you have good cadence (how fast you can spin your legs) and the hill is short you can ‘spin’ down the hill at high speed. If it’s pretty long, however, a brake or just practice may be in order.

I can’t really tell you if it is possible though without seeing the hill.

Possible to ride, prefferably w/ a break but highly unlikely yours was 45. Erosion would likely keep grass from growing on just about anything more than 30 deg. I’ve certainly never seen anything in the US.

Only a few times have I ever seen a grass slope close to 45 deg. Here is Turtle riding down the steep fields in his area.

A slope is seldom as steep as you think. Soil, sand, gravel, etc. have what is called an “angle of repose” which means that there is a limit to the steepness of a gradient that they can make. Too steep and they become unstable.

There are two ways to ride down a hill on a unicycle: slowly and quickly.

It is possible to change from slowly to quickly half way down. The opposite is not usually possible.

Long cranks make a lot of difference to your control on a steep descent. You need to be confident in pulling up on the seat handle.

You also need to lean back into the hill. This is to compensate for the fact that on a steep slope, the contact patch between tyre and ground is further back.

For fast descents, you need to be confident that you can “spin out”. If you UPD on a descent, you will be projected forwards and the ground will suddenly be along way away. Then you will land on a slope and it will be harder for you to regain your balance.

Excellent advice from Mikefuel.