Section X Front Hubs and Disc Brakes

Safety Notice:- Robin Hood Sports Cars Ltd have issued an Important Safety Notice to owners of Robin Hood cars with Wishbone Front Suspension and screw-in lower ball joints. If you have not already been contacted directly by Robin Hood Sports Car's Ltd. You are strongly advised to visit the RHOCaR Web Site where full details have been posted. Otherwise contact Robin Hood on 07976 640 841.

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 & Suspension Components.

Note: The Zemmeride Coil Overs are just about adequate but the Gaz Coilovers are a distinct improvement (but at a much higher price) and give a much superior ride and roadholding. (as one builder said "it's a different car") If money is no object you should consider fitting these at the rear as well. Another example of having bought 4 more or less useless units and then having to purchase 4 more thus paying twice for the same item. I will post the Gaz Part Numbers here when available but the Gaz Coilovers website www.gaz-shocks.com is currently unavailable where you (will) be able to download a .pdf catalogue. (August 2007)

With the two sets of Front Wishbones (temporarily) fitted it is time to make a start on the Hubs etc. Run a 12mm tap through the original MacPherson strut clamp bolt holes and the 2 holes on the Calliper carrier bracket. (this is the only part you do not get with a Disc overhaul kit)

Next fit the Upper ball joint to the so called dummy MacPherson strut. Some trouble seems to have been experienced fitting this, but as mine went in easily I suspect that the walls of the tube are now thinner to allow easier access with a standard 3/8" drive socket. Make sure the internal taper is clean and free of burrs etc. Wipe any grease off the tapers and apply the slightest drip of Loctite Retainer Grade 648. Gently push the taper home, rotate once or twice to spread the Loctite and very very lightly clamp up in a vice, just to nip the parts together. After about 10 mins put 3 or 4 washers over the thread inside the barrel and fit the nut. Tighten up. Remove the nut and washers, put some threadlock on the thread, add a single thin washer then the nut and tighten up as tight as you can. It is unlikely this will ever need to come off again, so get this as tight as possible. The Haynes Sierra Manual gives a figure of 65-85 Nm for a similar application.(upper and lower ball joints) This procedure has been approved by Loctite technical dept.

Paint inside the barrel and leave to dry. Repeat for the second unit. When dry these can be fitted to the hub taking care to note the orientation of the taper as per the video, do not fit the cycle wing brackets at this stage as they will only get in the way. Leave the barrel about a 1/4" proud of the hub top face. (The thickness of the wing brackets)

With the adjustment locknut in position, screw the upper ball joint thread into the threaded portion of the upper wishbone leaving about 1/4" of unused thread. Nip up the locknut. Fit the Lower swinging arm ball joint exactly as the above procedure followed by the tie rod end ball joints. See the Safety Note above and apply the correct torque for this size of thread. Note that the tie rod ends are handed, see video. There is a note issued by RHSC's not to tamper with the castellated ball joint to lower singing arm nut as this is applied with a very high torque under controlled conditions by RH and must not be tampered with. Nuts etc. coming loose in this area can be fatal. The Haynes Sierra Manual gives a figure of 72-88 NM for this application.(tie rod ball joints)

Whilst builders should pay strict attention to the safety notice above, it should be noted that literally tens of millions of these tapered ball joints are in use throughout the world and when correctly fitted are generally regarded as a zero defect item. Indeed once fitted a ball joint removal tool or a press is usually required to get them apart. When poorly fitted they will fall apart very quickly.

Slip the disc brake onto the hub and assemble the disc calliper’s c/w new pads as per the Haynes Manual. Use 4 new Ford securing bolts with a washer and Threadlock.

Most of this will need to come off at least once to:- a) Fit the side panels, b) Adjust the Camber, so build on this basis.

Note:- Before fitting the Steering Rack read Section XIII Pedal Box & Steering assembly Paragraph 2

Set the Steering Rack to mid point, it is 3 full turns lock to lock, so set at 1 1/2 turns. Carefully position the rack over the 2 pre-drilled holes and fit the U bolt. The U bolt supplied is far too large and a new one will need to be purchased. 2 1/4" cts. If you intend using wedges go to section XIII first.

Drill the 2 x 12mm holes at the other end and secure with 2 washers & nylock nuts to each assembly. Using a jack, lift up the two sets of wishbones until they are parallel to the road. Set the wheel hubs as close as possible to dead ahead. Fit the 2 tapped rods one to each of the steering rack ends c/w locknuts. Screw fully home leaving about 1/2" of thread for future adjustments. (M14 x 2 ) Now measure the gap between the end of the rod and the wheel tie rod ends. This should be the same both sides at approx. 70mm +/- 5mm. (A) Now ascertain the length of the female threads in the rod and tie rod ends.(B) (C) The kit contains a length of 14mm threaded rod. This needs to be cut into 2 lengths = A+B+C less about 6mm for adjustments. Careful mark the centre of the screwed rod, so in future you will know how much thread is down each side. Fit 2 x 14mm nuts, smear the threads with copper grease and fit. The Steering Rack ends will rotate which makes life a lot easier. Set the gap back to (A) and nip up the 3 lock nuts. Fit a stage label as this will need a final setting later in the build. It is vitally important that sufficient thread remains in each tapped hole, at LEAST 15mm. Once the set up is established it may be a good idea to make new 14mm screwed rods so as to allow full thread engagement.

The SVA requires some form of cover for the outer portions of the Steering Rack. My own opinion is that in the interests of safety inspection, loose nuts, damaged etc, this part of the steering should be visible. However to comply with the SVA I have fitted a cover consisting of a length of 25mm bore convoluted hose with a slit along the full length. This covers the ends of the steering rack right up to the ball joints and is held in place by 3 plastic tywraps. The cover can be removed at regular intervals for inspection or to carry out any tracking adjustments that may be required from time to time. See photograph and notes in the Front Wishbone section. Tifosi can supply some nice moulded track rod end covers.

All that now remains is to fit the 2 Coil overs. Fit the top pivot bolts as per the wishbone instructions but with a 6mm spacer bush each side, so that the Coil over sits in the centre of the box. Drill the lower trunnion as per the AutoCAD Drg and fit together with a couple of 2mm spacer washers to eliminate any side float. Since these form a highly visible part of the Front Suspension they will be replaced with a more elegant item in polished steel. Due to various production tolerances, giving an exact location for the mounting holes in the lower wishbone is not possible, for a start the 2 mtg. holes in the trunnion are not drilled anyway ! I have shown some figures on the drg. but treat these as a guide only. Clearances are most important. The dummy MacPherson ball joint mtgs. have yet to be painted in all the photographs.

Proceed as follows :- With the Front Hub & Wishbones fully assembled push the Assy hard to its lowest position possible (one of the arms will foul on the box section and act as a lower bump stop) The Coil over lower trunnion will now find its own position on the lower wishbone infill panel. Mark off the position of the 2 High Tensile bolts & drill 8mm. The inner could be increased to 10mm dia when the final position is firmly established. Note that 8mm is the largest bolt head that will fit UNDER the Coil over rubber bush. Secure the assy with a Nylock nut. It is important to ensure that the Shock absorber spring does not foul the upper wishbone arms in the lower (worst case) position. SVA will check this point. Position it centrally, it should be 2/3mm away from each arm. If there is a problem alter the top spacer bias i.e.: from 6/6 to 9/3 etc. to move the unit sideways. (On my car a full 12mm spacer was required at the rear of the rubber bush on the offside but 6mm each side on the nearside.) The lower nuts on my RH coil overs failed the SVA, and the lower end of the spring came in for critisism, see Section XXV The SVA Test.

As the arms move up to the normal position, i.e. parallel to the road, the spring clearance in the angled arm increases, but the straight one remains constant, so this one is best made slightly wider initially. It is also essential that when the wishbones fall to this lower position no stress is placed on the Coil over piston/trunnion. DO NOT USE THESE AS A BUMP STOP. To this end it may be prudent to drill the two 8mm holes slightly inboard to the marked off positions. Say 1/4" (6mm)

We can now put the dummy road wheels on and we have a Rolling Chassis. Use the old wheels off the donor vehicle to avoid possible damage to your new Alloy's. Brake pipes and the steering column etc. will be fitted much later on, once the Engine is in the chassis and we can see more clearly where all the bits go and what room we have. Some bits are set in stone ! Others can be moved (with trouble) Make sure the chassis cannot roll out of the garage !! It has no steering or brakes. One learns the this the hard way !! Chock the wheels.

Castor, Camber, Steering Axis Inclination & Toe

There is little point in giving a long explanation of these four suspension parameters as they are a complete subject in themselves, they are already covered by many articles in specialist books and on the web. See the links page.

Camber

Castor and Steering Axis Inclination are set by the chassis design but Camber (the amount the wheels lean in or out) can be set up more or less correctly as follows. Set the chassis dead level and jack up the wishbones to the running position. (slightly down at the outer ends) Using the a Camber Gauge adjust the camber to give 3mm lean out measured over the wheel rims. This is best done by pulling out the dummy MacPherson strut and screwing the top ball joint either in or out as required. You cannot get this spot on as the smallest possible adjustment is one full turn of the ball joint. Re-tighten the Strut nut. This 3mm dimension may need re-setting as the car settles down during running in. Check after about 150 miles.

Wheel Toe

Wheel Toe does need to be set up very accurately as soon as possible during the running in period, as it affects tyre wear to a considerable degree. The Haynes manual gives a figure of 2mm Toe-In measured at the wheel rim. Bear in mind that this figure is for a Ford Sierra Saloon and has no relevance whatsover to a Robin Hood 2B, it is however a starting point. If you read the more detailed web articles you will discover that Wheel Toe gives control over understeer or oversteer, whilst zero Wheel Toe gives minimum tyre wear but a rather indefinite steering action. (car tends to wander)

You can get Wheel Toe set up by Laser at your local Tyre depot but it will cost between £35 - £70. To do it yourself you will need a couple of Bungee cords and two DEAD STRAIGHT 25mm square tubes. To check they are straight lay them side by side on all 4 faces. Gaps will show up any distortion. With the wheels dead ahead, strap these to the outer tyre faces at the wheel center and support the ends with a couple of car jacks, set both tubes dead level. By making the tubes long eneough you can magnify the toe-in x 3 or 4 times ie. measure over 3 or 4 wheel rim diameters. (6 or 8mm Toe-In) The photo' below shows the set up. By altering the length of the tie rods the correct Toe-In can be set. (2mm Toe-In) Take care to keep the amount of threads more or less equal on each side and an equal amount of thread in each screwed ball joint and spacer. Lock up secure. At the same time you will need to ensure that the steering wheel spokes are set at 3, 6 & 9 oclock in the dead ahead driving position. I fitted a couple of Tifosi ball joint covers at this stage. Strictly speaking you should measure over the wheel rims, not the tyres and also support the wheels on a couple of friction free bearings. I put a bit of grease on a pad of steel, and wiped it off after.Waggle the wheels a tad after each setting. Take the car for a run, center up the steering wheel and re-check your settings. Re-check after about 150 miles and keep an eye on the Tyre Treads.

Wishbone Setting (Ride Height)

Now that some 1,000 miles have been covered the front of the car has 'settled' to some degree and the wishbones have assumed a slightly negative angle. (sloping up to the wheels) Although there are no specific settings given in the RHSC's video (RHSC's please note) it would seem that the wishbones must be set at a positive angle to the road and as a rough guess 6- 8 degs seems about right. As a guide, the wishbones must never 'go negative' under normal hard driving and cornering with two passengers. Tightening up the coil-overs is not the answer as this only increases the stiffness. The solution is to move the lower trunnion mountings inwards and the new dimensions have been annotated on the AutoCad drg. In retrospect a row of holes drilled in the lower trunnion (pitched to suit the trunnions) would make this job a lot easier, trying to drill a new set of holes with the wishbones fitted to the car is not easy. Once this has been done the wheel Camber & Toe must be re-set as described above. Make sure all the nuts etc. are tight and the steering wheel is centered when driving straight ahead.

Go to Section XI

Back to Home Page

© Colin Usher 2006