Section IX Fitting the 2B Front Wishbones

Warning:- Before carrying out any modifications to the standard design seek written approval from the Kit Designer. Use only high quality materials and fasteners and lock all threads. This applies particularly to Safety Critical items such as Brakes, Steering and Suspension Components.

SVA Note. The SVA test requires that AT LEAST 2 full threads are visible beyond any nuts plain or aero. Your car can fail the test if this point ignored. The SVA further requires that the Upper and Lower Front Wishbone Pivots are protected by some form of cover. Wrapping a load of plastic foam on with tape is NOT now acceptable and a more workmanlike, permanent solution is required. I have used 4 steering rack boots suitably cut down. These are a very tight fit on the square tube and seem to be just the job. See photograph below. Getting these on once the front side panels are in place is almost impossible, at least for the top front, as the pivot bolt nut is virtually inaccessible. Give this some thought. I fitted mine right at the end of the build and it took the best part of a day to fit each one. In the end the panels had to come off to gain access to the nuts. See paragraph 6 below. As my car is yet to pass the SVA (Jan 2005) I will report back on this feature and also the Steering Rack Covers.

If the Chassis is still inverted, turn it over and place on 4 axle stands. Before proceeding with the Front Suspension, fit the Rear Coil overs. These simply bolt in to the Swinging Arm holes as per the included instruction notes, and the Upper Trunnions locate into the cut off ends of the Roll Bar. Before fitting these trunnions make sure the 2 drilled holes are in line. The upper ends of the Coil overs are much narrower than the 40mm inside dimension of the trunnions, you can use packing washers if you are not too fussy or better still a pair special 4mm (approx.) washers will be needed. If you have Estate Swinging Arms you will need to fit a bar in the Arms as the existing hole is unsuitable. This bar takes the full weight of the car and must be securely fitted and of substantial construction, i.e. 6mm x 40mm Steel at least. A through bolt is fitted, to retain the trunnions, once the upper location is settled. Note the trunnion pivot axis is in line with the swinging arm pivot axis. Apart from brake pipes etc. this more or less completes the mechanical part of the rear suspension. Note some bolts remain loose at this stage.

RHSC's supply the Rear Coil overs with the Upper Trunnion bolts loose fitted only.

It is suggested that you carry out a complete Front Wishbone Assembly  prior to any painting of these parts as there is drilling in the Lower Wishbones for the Coil overs and in the Hubs for the Cycle wing stays etc. Some builders may wish to fit the Top Wishbones with the Chassis upside down as access to the add on bracket and the drilling is a lot easier.

It should be noted that the Front In-Fill panels CANNOT BE FITTED with the Front Suspension in place. Adjustment of the Front Wheel Camber also requires some disassembly. Do not fit Nylock nuts to the Upper and Lower Wishbone Arm pivots until final assy and work on the assumption it may have to stripped a number of times. Adjustment of Toe-in and Camber can only be done with the full weight of the car on the suspension, and even then it may settle with use.

The fit and alignment of the Wishbone pivot holes is critical and the following method is recommended.

Check the internal bore of the tubes and remove any bad burrs. Then fit the Nylon Bushes, this is fairly straightforward as they are a medium push fit.

The steel bushes were polished with fine emery and the internal and external corners chamfered by about 10/15 thou, run a 10mm reamer through. Wash in petrol and lightly grease.

The 8 steel bushes were then fitted into the arms, again a light to moderate push fit.  Since these must rotate investigate any tightness or slackness. Zero slop required. If you clamp each tube/bush assembly in a vice you can easily check for free motion prior to assembly.

The next bit is most important as an error here will cause lumpy motion of the suspension.

With a piece of 10mm bright mild steel bar about 2 feet long (this is usually a couple of thou undersize) pass the bar through the two bushes in each arm. Any tightness spells misalignment and the cause must investigated. A small error will probably not matter too much but any serious misalignment may need a new arm. Do not attempt to bend the arms etc. Try removing the bushes and refitting. Also check the bar, it may be bent!!

Note re design problem

There is design fault at the location of the "added" rear bracket on the upper front wishbone. This has been reported by a number of builders so it is not a one off. The bracket is unfortunately pre drilled. When positioned as far outboard as possible (even with material dressed off to clear the weld) the 10mm drilled hole comes very close to the 38mm chassis tube on the inside of the cavity. This means that there is very little room to get the full head of a bolt into position. There is no easy solution to this problem. The head of the bolt needs to be ground off as little as possible so it can be just fitted in and the hole drilled 10.5mm. Leave as much metal on the head as possible, particularly where the head joins the shank. As this bracket may never come off it may be a good idea to fully weld it in place, as well as securing it with the 10mm bolt. Make sure the bolt is as SHORT as POSSIBLE consistent with fitting a nylock nut and washer plus a couple of spare threads. Another solution would be to fabricate a new bracket with the 10mm hole relocated 2-3mm off centre. This would be just sufficient to allow the fitting of a bolt without any modification.

For some unexplained reason the Rear location points for the 10mm top and bottom pivots are approx. 10mm out of position. I machined up some 10.5mm spacers from 30mm dia bright mild steel bar. Check your own thickness as there is bound to be variations.

The next tricky bit is the drilling of the 10mm  holes in the chassis. For perfect alignment these holes need to be positioned very accurately.

Make up a custom centre punch and with the suspension semi assembled use this to spot the 10mm hole on the inside of the square tube. Then using the custom drill bush, drill through 5mm.  Since the drill bush locates in the Front pre-drilled 10m hole and the also the bore of the 10mm tube 100% perfection is assured. Strip the whole lot down and open up the chassis hole to 10mm. Forget grinding off the drill flanks, this is a waste of time. Do not forget to de-burr the inside holes and remove the swarf.

 Do not rush this part of the build.

The next stage is to fit the 4 bolted on brackets and here we need real precision. Once the holes are drilled in the chassis there is no going back. The brackets come as a stick of 4 flame cut blanks. Cut them up into individual units and spend about 5mins on each one with a file until they are as good as you feel necessary. Also check that they are bent at 90 degs. If not, bend to exactly 90 degs. Check by placing a pair of brackets back to back. Open up the flame cut hole to 10mm. It will just about clean up. The upper brackets will need a corner removing. Make a card template and cut the corner off to suit. Note Right and Left handed. Clamp the brackets firmly in the correct position tight up to the Swinging Arm bush. Use the 10mm dia centre punch and mark of the position of the 10mm hole. Take the bracket off and drill 10mm. to the centre popped mark. De-burr and bolt back in the correct position. Tap the above drill jig into the 10mm chassis hole and drill thro 5mm. This should give you a 5mm hole spot in the centre of the 10mm chassis hole. Open up the chassis hole to 10mm. De-burr and fit 10mm bolts with a washer each side, Nylock nuts and Loctite.

Note:- When fitting the Top brackets make sure they are as far Outboard as possible.

For the real perfectionist the 10mm test bar should pass through all four chassis holes which should be in perfect alignment.

All of the above sounds very long winded but it is worth spending as much time as possible to get it right first time. You only have one go. In practice it does not take all that long and the result should be perfection.

If we want to get really picky the 10mm bolts supplied are not much good either. The plain 10mm dia SHOULD be at LEAST AS LONG as the distance across the trunnions plus a bit more. The present plain length means that at one end of ALL 8 bolts the loads are transferred thro’ the thread crests into the trunnions. As the bolts are coarse pitch and the trunnions quite thin this may be as little as a single point contact. This is not good enough. The solution is to make up custom bolts in High Tensile Steel with a 10mm portion slightly longer than the trunnion width and use a thick washer under the nut. In this way the loads are transferred through a 10mm dia. with a good load bearing area. The open ends of these tubes require special attention, mine failed, also all bolt heads, at least those facing forwards will require plastic covers, see Section XXV The SVA Test.

Rubber Boots over pivots	Under the boots (SVA Pass)

This completes the fitting of the wishbones which should swing up and down with no front to back movement and no visible looseness at all.

The next operation is to fit the Front Hubs, Coil-overs, Disc's and the Steering rack etc.

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© Colin Usher 2005