Mr Crud picks your brains

I've had two front guards get something stuck - the first time the guard was of an older design and simply shattered and i came to a rapid halt but managed not to come off. The second time with a new sks design the mudguard stays released as they were designed and the bike came to a much slower halt.

I managed to get a slightly larger object (my foot) jammed between the wheel and the fork of my folding bike, with hilarious consequences.

Yep, that was a C+ contributor's guard - he did it out on his commute home in the rain - we got a few letters off of the back of it recounting similar experiences with close fitting guards, but in all the other cases the stays snapped.

What was interesting was that given the close clearance you wouldn't have thought an acorn could have gotten in.

sounds like we're both remembering the same incident tony. perhaps it only happened once

I wouldn't say it was common but it certainly happens, i remember a pic that did the rounds a few years ago of a salmon guard that had been bent back double after a stone had got lodged underneath. most guards have a push-fit connector at the dropout that releases if something gets stuck but jamming right uner the fork is a potential issue

I've never though heard of a stone lodging in a fork that didn't have mudguards to guide it in.

If the latter I know of it happening with a set of alu guards the stays of which were too strong to snap off when an acorn (I think it was) lodged between it and the wheel – this caused the guard to fold back on itself like a ribbon until the acorn stuck under the fork pitching the rider over the bars. It's a rare occurence but probably not freakishly rare.

As to objects being flipped into a wheel - yes that does happen, and is a lot less rare, they are normally not flipped in by your own tyre but by someone else's and if they are going to do any damage the most likely it broken spokes or a dented rim – which can lead to a sudden puncture and related unpleasantness.