Photos - Building the steering & suspension

Standard MX5 upright fitted to original MX5 wheel. The round fitting in the centre of the upright is the ABS sensor. Wheel is 7x17 and upright is deeply offset into wheel which provides improved handling over the ancient Cortina set up commonly used in Locost construction.

Ford Transit Van tie rod ends were used for the upper mounts on the MX5 upright. These are the same as recomended for Locost builds with Cortina uprights and while they were a close fit the MX5 upright needed a bit of machining.

The Transit Van tie rod end had the same taper angle as the MX5 upright but the opening had to be enlarged (using a custom made tapered reamer) to allow the tie rod end to sit deeper into the MX5 upright and enable the retaining nut to be installed. In the original condition it's sitting too high and there is not enough thread sticking through to put the nyloc nut on correctly.

A straight 18mm reamer was purchased as the basis for a tapered reamer to bore out the MX5 upper ball joint mount to take the Ford Transit Van tie rod end.

This is the reamer after it was modified to provide the correct taper to match the Transit Van tie rod end. The angle may be a bit difficult to pick up in the photo but it was achieved by having a tool maker "sharpen" it at this angle. It was a straight forward and inexpensive operation once I located the right tradesman.

While the uprights were in the milling machine having the taper corrected they also had 6mm machined off the top surface to allow the tie rod end to protrude far enough for the nyloc nut.

And here we have the result of the machining. A Ford Transit Van tie rod end perfectly fitted to a Mazda MX5 upright. You can also see the adapter sleeve that was machined for the upper wishbone.

After a great deal of research, measuring and head scratching I finally settled on Mazda B2200 utility lower ball joints for the lower wishbone ball joint. They had to be mounted upside down to suit the original position on the MX5 upright. They did not fit straight in and the uprights required machining, but they were the most suitable that I could find. These were my solution but I am sure other Locost builders will come up with other alternatives.

Here you can see the problem with the Mazda B2200 lower ball joint. The length is correct but it does not fit into the hole and the taper is the wrong angle. The bottom of the MX5 upright has a tapered sleeve pressed into it and this was pressed out and a lathe used to enlarge the hole and change the angle of the taper. It was then pressed back into place and it looked like that was the way the factory made it.

My jig for the construction of the lower wishbones. I based my front end on the Haynes Roadster but because I am using Mazda MX5 NC uprights I had to modify the design to suit my components. The arms are longer than the Locost specs and will provide a wide track equal to the MX5 rear.

Here is the mock up of the first wishbone. Because the arms are long I used 25mm x 2.5mm seamless tubing for added strength. My life will depend on these items holding up under extreme conditions and the last thing I want is to be worried about them every time I hit a bump or fly around a corner.

The ends of the lower wishbone tubes were cut in half to allow the Mazda B2200 lower ball joints to be recessed into the tubes.

The reinforcing panel has been fitted and the wishbone is ready to be tacked together.

I was very pleased with the quality of the TIG welding in this very important safety area. Peace of mind was well worth the cost of the professional welding service.

The completed lower wishbone. I didn't feel confident with my own MIG welding abilities for such vital safety items, so I tacked all the wishbones together and had them TIG welded by a professional.

View from the top of the reinforcing plate where the ball joint mounts. The shock absorber lower mount was added later when the suspension design was finalised.

Viewed from underneath you can see the mounting holes for the ball joint. The top two holes have crush tubes welded inside the tubing.

View from the top with detail of the ball joint position.

The assembled lower wishbone ready for installation.

Wishbone and ball joint viewed from underneath.

Side view of the wishbone construction and ball joint mounting design. The ball joint was recessed into the tube to provide clearance with the upright.

My jig for the construction of the two upper wishbones. I allowed for a 20mm off-set for the Transit Van tie rod end and both wishbones were built using the one jig. This offset equates to around 5 degrees castor, which can be adjusted using the rod ends.

To provide a good range of adjustment for the steering geometry rod ends were installed for the top wishbone inner mounts. My engineer was OK with this as long as I used quality rod ends of the recomended size and they were correctly and safely fitted. Rod ends can produce more suspension noise and harshness but they overcome the lack of adjustment in the Locost suspension which is a design fault with Locosts.

Quality, heavy duty rod ends are not cheap, but the range of adjustment they provide is beneficial. The custom made threaded sleeve was inserted into the end of the wishbone and welded in place.

To accept the rod ends a threaded insert was TIG welded around the end of the wishbone tube and also plug welded in the side for extra strength and safety.

The right hand top wishbone in the jig.

Custom made threaded sleeve for the upper ball joint (Ford Transit Van tie rod end) welded in place.

Both top wishbones compared. The off-set (20mm to the rear) to provide 5 degrees of castor is easily seen here.

Assembled top wishbone ready for installation.

A pair of simple jigs were fabricated to correctly position the lower wishbone chasis mounts. A jig was bolted to each mount, which determined the height on the vertical tube, and the rear bracket on each side was measured and positioned at the same distance from the firewall. Once the rear bracket was positioned the front bracket located itself, simple and effective.

Another simple jig was fabricated to locate the top wishbone chassis mounts. One jig was used for all four mounts. It was bolted to the lower wisbone pivot bolts and held the upper front bracket in place so it could be tacked. The upper wishbone was then bolted to the mounting brackets and the process repeated to locate and tack the rear bracket.

Right hand front suspension mounted and ready for the next step.

My low tech answer to checking for bump steer. The system actually worked quite well and enabled me to judge the best position for the steering rack to minimise potential bump steer.

Holden Gemini steering rack. Due to the wide chassis the rack did not need shortening, which is needed with most Locost builds. In hindsight the Gemini rack was not a good choice as it has too many turns lock to lock. An Escort Mk2 quick rack would be better.

The steering rack mount. It's removable and adjustable by adding spacers under the bracket and intentionally made lower than the desired height to provide a full range of adjustment to remove bump steer. If the ride height of the car is altered then the rack can be repositioned accordingly.

Top coilover mount also doubled as the mounting point for the headlamp.

Lower coilover mount was positioned as far out on the lower wishbone as possible to reduce stress on the wishbone and act close to the load area of the lower ball joint.

The MX5 upright pivot centre is positioned well inside the centre of the wheel, which reduces steering kick back and makes the vehicle more stable over rough roads. A big improvement over outdated Cortina uprights.

MX5 steering column is height adjustable to aid comfort and assist entry and exit of vehicle. The steering column is offset to one side and the collapsible steering shaft is angled with two universals to prevent the shaft spearing the driver in an accident.

Steering shaft components ready for fabrication to desired length using thick walled tubing and a universal joint and splined section from a Holden Gemini. Luckily the Gemini and MX5 splines are the same.

The tube and shafts were drilled, pinned and welded and then for good measure plug welded and end welded by a professional TIG welder. A bit of overkill perhaps but no short cuts should be taken on safety items such as this.

Completed shaft ready for installation.

Gemini universal and MX5 steering column splines were the same and matched up perfectly.

Rack and steering components modified and mounted.

Front steering and suspension nearing completion.

Finally sitting on its wheels and at the correct ride height.

In this view of the right hand suspension you can clearly see that the design of the top wishbone allows for the top ball joint to be offset approx 20mm to the rear, which results in about 5 degrees of positive caster.

Steering shaft offset to the right side of the vehicle provides plenty of clearance and safety.

Left front suspension and steering etc following painting and final assembly.

Right front suspension and steering etc following painting and final assembly.

Locost Clubman build

Meeting the challenges of the steering & front suspension

Wrong choice for steering rack

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