fishboat

I loop about a 6 foot piece of string over my right arm and tie one end of the string to my outer pants cuff. The other end of the string is tied to the inner pants cuff. Then when my foot spins through the bottom half of its revolution the string pulls my pants up and clear of the chain.

...I'm thinking this might be a trick question.

Steel Charlie

As usual, I'm amazed at how difficult a simple thing can become. A couple bucks on fleabay gets a pack of six velcro reflecting cuff bands. TabA/SlotB.

rsbob 

I would connect a string to your left pedal that goes over the top tube that attaches to your right pant leg cuff. Every left pedal downstroke will pull your right leg cuff up and out of the way. Be sure to always dismount to the left. You’re welcome.

fishboat

Might ponder that a bit more..it won't work. It raises the pant leg when raising isn't needed.

zandoval 

On each of my bikes I keep a few Reflective Snap Bands. Usually on the handle bars or seat post. Very easy to use. They are real cheap if ya get them through the ChiCom outlet AliExpress, but I prefer the Euro ones at 17"/43cm. They last a real long time but have a tendency to walk off with human help...



Amazon

big chainring 

I still have old toeclip straps laying about. They work around your pant leg, or strapping your spare tubular to your seat, or when your frame pump is a bit loose, or......

rsbob 

So busted. Not an engineer. OK tie the string to the top tube and connect to the pant cuff in the top most position. When reaching the maximum downstroke it pulls the cuff up. Ta da!

Camilo

They still sell them. I got some last year, can't remember where. I now have 4. Why? I don't know. They certainly aren't as fool-proof or convenient as simple velcro straps. But I usually just do the natty sock-stuff.
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prj71

I don't wear pants.

Lombard

Please don't post any pics.

rsbob 

I don’t wear underwear!

Lombard

With bike shorts, I hope not.

RChung

I used to do that. Seven years ago I woke in an ambulance on the way to the ER with broken bones in my face and a partially flattened helmet, plus various other incidental injuries. I couldn't remember what happened, but much later when I got a look at my bike I saw it was in good(ish) shape but with a bent chainring. My hypothesis is that the rubber band broke and my pant leg got caught and I went over the handlebar. The pants had been cut off me and my wife threw them out so I couldn't verify it, but that's my best guess. My solution is that now I use two rubber bands so that if ever one breaks there's a backup.

juntjoo

Wow! Glad you're still with us. Maybe I should use three lol. Currently using this velcro strap.

shrtdstncrdr

There are a Lot of good ideas here. Up 'til now I've been using a very large safety pin. I pull my pant leg tight at the ankle, fold the excess over towards the back, and put in the safety pin just above the heavy sewing at the bottom of the pant leg. When not in use I keep the safety pin on the brake line under the seat. Works.

RCMoeur 

My solution is simple.

First, I figure out if the bike will be OK as a 1x or double.

Then I find the most-worn large (typically 48t+, although I've used smaller ones on occasion) chainring in the needed BCD in my Pile O' Rings, say to it in a booming voice "Your time has come", clamp it in a vise, and hacksaw off the worn-out teeth as smoothly as I can (an action which is usually very therapeutic for other life stresses). Then use a file to smooth and even out the edges.

It is then installed in the outboard position on the crank, with the other selected chainring(s) inboard. Note: the then-largest chainring must be smaller than the diameter of the sawed-off one, but these days with my relaxed riding style and readily-available 11-12 tooth small rear cogs it typically isn't an issue. If I think I must have a triple up front, I'll install it outboard of the large chainring using old-school long triple chainring bolts.

An example:

RCMoeur 

"My pump got caught in my trouser leg."