If it's a '95 bike the earlier Mavic 231/261's will be a shade too early...it is true that the width is the difference as others have already pointed out. Best option would be something like 231 SUP's a bit later, but joined differently to make a better braking and stronger rim... SUP is some french something or other to do with this
If you haven't seen it the mombat timeline is good for dating some bits and pieces
http://www.mombat.org/Timeline.htm#1995
Also, avoid MA-40's like the plague....they're derived from the road rim with the same model name - i.e super narrow - and anybody who has removed a steel beaded tyre will know what I mean there :evil: