reference will now be made in detail to the present invention . fig1 to 3 illustrate a mac pherson suspension strut comprising a shock absorber with a body 1 and a rod 2 . a lower spring retainer 3 is mounted securely on the body of the shock absorber and a spring 4 is mounted between the lower spring retainer 3 and an upper spring retainer , not depicted . the coil spring 4 has a helical part 4 a , a straight part 4 b guided in translation in a configuration 3 a , 3 b forming a channel for translation in the direction t . one end 4 c of the spring , curved transversely with respect to the straight part 4 b , is roughly perpendicular to this straight part 4 b . the end 4 c therefore extends transversely and roughly at right angles to the direction t of translation . the end part 4 c of the coil spring 4 has , at 5 , an indexing arrangement produced in the form of an orifice through which an elastic pin 6 can pass . the elastic pin 6 can be positioned in one of the three orifices 7 , 8 or 9 to position the end 4 c of the spring with respect to the spring retainer 3 . because the coil spring bears on the lower spring retainer 3 along the line 10 , the spring can be shifted into a position corresponding to the orifice 7 or to the orifice 9 while at the same time keeping the line 10 pressing against the lower spring retainer 3 . this first embodiment allows the position of the spring to be adjusted with respect to the axis of the shock absorber in a simple and economical way , for example by shifting the end 4 c using a mallet until it is in the chosen position corresponding to the desired adjustment of the inclination of the spring with respect to the axis of the shock absorber once the elastic pin 6 has been extracted . fig4 to 6 show a mac pherson suspension strut comprising a shock absorber with a body 11 and a rod 12 , a lower spring retainer 13 secured to the shock absorber body 11 , a coil spring 14 bearing on the lower spring retainer 13 and mounted between the lower spring retainer 13 and an upper spring retainer , not depicted . the coil spring 14 has a circular end 14 a , a straight end 14 b and a curved end 14 c roughly perpendicular to the straight end 14 b . the straight end 14 b is guided in translation in the direction t by a channel determined by two raised parts 13 a and 13 b of the lower spring retainer 13 . the end 14 c roughly perpendicular to the direction of translation t has a curved and preferably tapered end 15 . the curved end 15 can be inserted in an indexing orifice 16 chosen from the three orifices 16 , 17 and 18 made in the lower spring retainer 13 . to move the spring 14 from one chosen position to another indexing position , a tool is inserted into the space 19 to lift the curved end 15 of the spring 14 and move it into a chosen position . pressure is then exerted on the outer edge 20 of the bent end 15 to insert this end 15 into an orifice 17 or 18 . with reference to fig7 to 9 , a mac pherson suspension strut comprises a shock absorber with a body 21 and a rod 22 , a lower spring retainer 23 secured to the body of the shock absorber and a coil spring 24 mounted between the lower spring retainer 23 and an upper spring retainer , not depicted . the spring 24 has a helical portion 24 a , a straight portion 24 b and an end 24 c roughly perpendicular to the straight end 24 b . the straight end 24 b is guided in translation in the direction t by a configuration forming a translation channel delimited by a wave shape 13 a and a rim 23 b . all that is required to move the spring 24 is for the end 24 c to be moved in translation in the direction t . the end 24 c is secured to the spring retainer 23 by a means 25 at least partially surrounding the end 24 c . this means 25 preferably has a collar or curved - tab configuration capable of being fixed removably to the lower spring retainer 23 . to do this , use is made , for example , of a screw 26 , or a pin , or a bolt , or any other similar mechanical fastening means such as a rivet . the screw 26 is screwed into an orifice 27 in the end of the curved tab 25 and into a corresponding hole or tapping 28 , 29 or 30 made in the lower spring retainer 23 . adjustment in this embodiment can be carried out in a similar way to the way described with reference to the first embodiment of fig1 to 3 , such as by using a mallet or some other appropriate instrument able to make the spring 24 move . the screw 26 can be partially loosened to allow prior geometric adjustment , before the spring 24 is fastened in position using the curved tab 25 . the spring 4 , 14 or 24 has a configuration that allows it to be moved in translation in a predetermined direction corresponding to it being guided by a corresponding configuration of the lower spring retainer 3 , 13 or 23 . additional advantages and modifications will readily occur to those skilled in the art . therefore , the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein . accordingly , various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents . all of the documents cited throughout the specification are incorporated herein by reference .