There is a story about the ends breaking off as a result of the engine vibrations.
I usually re-use the clips and hadn't had a problem (so far).
Henk
I had once a serious problem with my 1957 Triumph '21'; a new circlip broke and embedded itself in the piston. Result: two scratches (really more trenches....) in the cylinder, rendering it completely useless. I still wonder how this could have happened . Fortunately, the later 3TA cylinder was exactly the same as the damaged one.
If you have a standard type piston with wire clips it is not recommended to use the 'flat' type of clip as a replacement.
The Triumph T140 uses the same clip as the M20 and these are readily available from Triumph parts dealers so there is no need to reuse the old clips or substitute them with a different type.....Ian
You should always use the same clip as if you put a pressed steel circlip into a groove designed for a wire form type it will come out, but if you have a groove for a pressed steel type you can put a wire one in there, but not the other way round, the profile of the groove is such that the pressed steel type won't seat fully and can be pushed out by the pin. Some gudgeon pins are designed to work with the circlip in that if you have a wire type one, sometimes the gudgeon pin has a slight taper on it's end so as the pin tries to exit the hole, it has already covered the circlip with it's tapered end making it impossible for the circlip to come out, in that it locks it into the groove before it exerts any sideways force on it.