The idea of shortening
the Jaguar cross-member to fit the MG chassis
rail was abandoned in favour of modifying the MG sub-frame to accept
the Jaguar wishbones and uprights. A new hub-hub track width of 54"
instead of the standard 52" was selected and filled the Sebring arches
nicely with my 245/45/18 tires on XJR supercharged rims.
The disks and calipers shown are standard and have now been replaced
with Brembo 320mm items and alloy calipers.
At around the same time, those nice people at Race Tech magazine (Credit to Mike McDermott) were giving away a free wishbone suspension design program, written in Qbasic. One Email later, I downloaded the program into my eagerly awaiting computer. The first realisation was that I needed to know a lot more about suspension operation /design before I would be able to use it effectively.
These dimensions are from 2006 and have
made so many changes since, you will need to come up with your own
dimensions
Download Wishbone Suspension Design Program (214 kb)
Run go.bat, then enter filename mgb1 when asked to get started.
My local engineer at Rustler Racing gave me a crash course in suspension design in exchange for a computer running the program, which was obviously going to be a benefit to us both. Many happy hours of keyboard tapping and brain storming later a design was calculated which retained the rack and anti-roll bar in their original positions, and was based on the Jaguar set-up, leaning towards the MG configuration as below.
The tried and tested method from several Cobra kit car companies of Avo coil-over shock absorbers was adopted. Cobra’s are about the same weight and distribution as the MG, so I have taken their recommendation for my initial setting of 380lbs springs at a 2 to 1 ratio.
The engineering undertaken by Rustler Racing took over two weeks, and included fabrication of lower inner pivot mounts, upper inner pivot/upper shock mount combination, lower shock /anti-roll mount combination, heavy modification to the cross-member including reinforced steering rack mounts and track-rod end extensions using Peugeot 309 items, to allow for the extra track width. His engineering is "second to none" with endless attention to detail, combined with practical solutions. My only regret being that maybe I should have used a rubber-bumper cross-member, to allow the engine to sit lower and attach the bottom pivot spindle mounts directly to the member instead being mounted slightly below it.
The rebuild includes a polyurethane bush kit, lashings of powder coating, new bearings and the new type sealed for life ball joints. Since these pictures above the car has been raised with longer Gaz units to cope with ever increasing number of traffic calming bumps around.
Updated
: Brembo calipers and
320mm vented disks fitted during winter rebuild
I have come across a number of problems with this suspension. The new castor of 3.9 deg was causing excessive camber change during turning, so reduced it back to the Jaguar standard 2.25 deg. To eliminate it completely ended up with 1.3 deg of castor. Steering was too twitchy and have settled back in the region on 2.25 deg. KPI is standard Jaguar 1.5 deg, which involved resetting the camber to zero to achieve.The spring rate of 380lb seem about right, right. Still have some issues with bump steer having changed racks, so will have to shorten rack center and modify steering arms again to eliminate that.
Its not easy at all if you have never done it before. The slightest change has dramatic effects to the geometry, but it is fun!