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Raymond Legrand est peintre amateur. Il peind habituellement des avions de chassse. Mais il lui arrive aussi de peindre par passion des automobiles notamment des Alpine. 


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Home arrow Magazine arrow Technics arrow Push Struts for Alpine A110
Push Struts for Alpine A110 Print E-mail
Written by Philippe Loutrel   

The front end of an A110 was directly inherited from the Renault 8 (and that one is very similar to the front end of the Dauphine and 4CV). It is certainly not an example of stiffness: the "Fluidblocs"(rubber bushings that holds the axle of the upper suspension) and "Flexibocs" (the equivalent for the lower suspension) plus the original rubber bushings in the tie rod ends (RTRE) on the steering rack. All this adds up to a very flexible construction, that will even get worse after one has put some miles on the car.

One alternative is the option to change the rubber bushings to bronze (the "Dangel" adjustable front end) or synthetic materials (like Teflon). This will stiffen up the front end in a dramatic way. Great for on track use, but it will make your car practically undriveable on the public roads.

By installing a guiding device, a push strut, between the end of the lower suspension-arm and the frame, you will improve the directional stability on rough surfaces in a dramatic way. Also, the stability under braking will improve in the same fashion.

The push struts will counter the flex in the front end that opens up the front wheels under braking and the car will stay on course a lot better.

Historically the push struts were a Group IV option offered by the factory in Dieppe.

The mounting of the struts on the frame seemed not to be very rational though; the struts were mounted almost parallel to the central (lengthways) axis of the car. The mounting point of the struts on the lower suspension arms make an arch that causes the front end to open, thus defeating the purpose of the objects. One could make a point by saying that the Group IV cars came all equipped with these struts and a stiffer set of springs as well, thus limiting the range of the suspension.

Installation of the brackets

The position of the brackets on the frame should be straight in line with the axis of the lower suspension arm (see also the appendix and the pictures in Mille Miles # 19 of July 2000).
One steel flat tab (3mm thick, see fig.) is welded in that position. It should be positioned in about a 45 degree angle to the cross member of the frame and have a 10 mm hole (D=10mm). Put a RTRE on the inside of this tab. Weld a M10x150 nut on one side of the second tab to accommodate the bold that goes through the RTRE (in this case an M10x150, 45 mm long partially threaded bold with a 15-mm non-treaded section). This installation is basically the same as the brackets for the rear sway arms on the central tube of the frame.
We decided to use a RTRE instead of the Uni ball rod ends to keep some flexibility in the construction and this for two reasons being: the rest of the front end construction is flexible (see below) and also because of the geometrical compromise we had to make (see appendix).

It is easier to weld the brackets to the frame when the frame is apart from the body, but this is, of course, not mandatory.
The other end of the strut will receive a Uni ball rod end (Aurora three piece A series or similar quality) also fixed with a 3mm steel bracket (Fig.B). This bracket is welded to the sidewall of the end of the lower suspension arm. A vertical hole, D=10mm, is drilled to receive a bolt (M10x150, 40mm long preferably non-threaded section of 15 mm). The bracket should be positioned as far to the end of the suspension arm as possible.
The height of this bracket is 30 mm.

The strut should not be able to touch the rectangular tube of the frame that goes from the transversal tube (on which the RTRE-bracket is welded) and the front end. To make sure that the struts won't touch, you should compress the suspension completely before welding the brackets onto the lower suspension arm (see the note in the "Basic front end set-up" article for three ways to compress the suspension).

Construcion of the Struts

A steel round tube (OD=20mm, ID= 16mm, approximately 300mm long depending on the mounting of the brackets) connects the RTRE with the rod end. The RTRE has a right hand pitch of M12x100. If you want the length of the strut to be adjustable after installation on the car, you have no choice but going with a rod end that has the same, but left handed pitch, being a left hand M10x100 pitch.
A simple solution to mount the rod end and the RTRE on the tube is welding a nut on each end of the tube. A more mechanical way to do it is by welding two appropriate threaded tube adapters to each end of the tube.
Use a jam nut to lock the rod end and the RTRE.
To allow the ball in the rod end to exceed the misalignment, use two safety washers or make them according to Fig.C. Ideally the washers are conical, but it's easier to make them cylindrical. That will work as well.

Mounting and Adjusting

After lubricating threads of the rod ends and the RTRE's, those are screwed onto the tube. The axles (non-threaded part of the bolts) are lubricated, and put some red Loctite on the threads. Once the axles are locked, you can adjust the length of the struts by turning the tube. Put the car in its reference position (the regular driver in the car with half a tank of gas + if applicable a co-pilot). The struts should be free to move; meaning there should be no strain at all on the lower suspension arms. Lock with the jam nuts.
At last to finish to project, you'll have to cut a passage for the struts in the glassfiber protective tray that mounts under the car. It is recommended to protect the rod ends with rubber boots.


An ideally positioned strut means an increase of the length of the base of the triangle that the lower suspension arm basically is (Fig.D). This ideal strut would have its swing axle exactly in line with the axle of the lower suspension arm. Meaning, the thread of the RTRE sits in a 90-degree angle with the length axis of the car. This would implicate that one would either have to bend the threaded part of the RTRE, or the tube; neither of them being a mechanical satisfying solution.

We had to make a compromise, and we have chosen to position the bracket in line with the axle of the lower suspension arm, but with the RTRE (and the threaded section of it) under a 45-degree angle. By doing so, the rubber bushing of the RTRE has to deal with traction, compression as well as with clipping movements, but so far the RTRE seems to be up to the job.


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