Staffordshire's Independent TVR Specialist
Tel: 01782 333008
Mobile: 07976 560006
E-mail: ian@sportmotive.com
Evolution Chassis for Griffith and Chimaera

The Chassis has Evolved!

Our new Evolution chassis is here and the first cars to receive it are currently in build. Building on the success of our improved standard chassis and further wanting to improve the materials, design and ultimately the handling capabilities of the cars we embarked on a virtually complete redesign of the existing chassis. Using suspension modelling software, we entered the current geometry data of the Griffith and that of the Tuscan and Sagaris so that we could assess what each car was actually doing under certain conditions and analyse the improvements and developments TVR had made. The software allowed us to model the geometry further to produce an even better set up but in order to achieve this we knew we had to rid the car of the Sierra front hub carrier; designed to be used with a Macpherson strut it is completely wrong in a wishbone suspension set up and gives far too much steering axis inclination.

Initially we were going to use the Tuscan alloy hub carrier, we modelled this in the software and found that TVR had significantly reduced the inclination of the steering axis down to a figure of 6 degrees; we calculated the geometry around this but found that we got better results with a slightly higher figure of 7 degrees, this gave us the best results in keeping the tyre where we wanted it; in constant contact with the road.

From this analysis we developed our own new billet alloy hub carriers for the front and rear, these carry the Tuscan 5 stud hub/bearing unit and the geometry is modelled around 18” wheels with the TVR Spider wheel in mind although any wheel and tyre combination with the correct overall size and offset can be used.

Chassis Development
Chassis Development Click to see more images

The hub carriers are designed to carry a range of brake callipers including AP, Brembo and Hi-spec, to the customer’s choice and we will be initially offering the chassis with a 320mm front disc and 4 pot AP calliper with a 298mm rear disc and standard rear calliper.

Another area to address was the poor torsional stiffness of the standard chassis, with careful measuring of body clearances we found that the main backbone structure of the chassis could be widened significantly with only minor modifications to the body shell. The intermediate tubes between the top tubes and bottom rails have been increased by three per side and an improved arrangement of opposing tubes has been achieved, rather than tubes that follow the same direction, as in the front section of the original chassis. More bracing tubes have been added particularly around the engine bay and transmission tunnel area which is one of the main areas of flex in the chassis and the diameter of the main cross brace tubes underneath the front of the engine and those around the diff have been increased from 25mm to 38mm. Wherever possible tubes have been formed and bent into shape, the top tubes are formed in only 2 sections rather than the original 5 cut sections butt welded together.

Alloy Hubs
Alloy Hubs Click to see more images

Materials have been dramatically improved, no more seamed pipe, all tubes are CDS Aerocom 33 grade seamless and can even be specified as T45 grade tube if required, chassis’ are MIG welded as standard but TIG can be specified if required at additional cost.

Main tube and box sizes are as original, 38mm tube and 60x40 box, however, the main box section wall thickness has been increased from 2mm to 2.5mm and a round corner section box selected as this resists twist much better than the sharp square section original. We have also added steel seat frames into the chassis to carry the seats rather than just fixed through the fibreglass. All this and with the addition of our existing CDS roll hoop gives a dramatic improvement to the torsional stiffness and impact protection of the chassis.

You may think all this extra steel adds weight, it does, but we believe the trade off is worth it, plus whilst we are adding “sprung” weight to the main chassis, by replacing the heavy front and rear uprights with billet alloy items we have reduced the un-sprung weight, which is what really affects handling and grip.

Having now placed our main tubes and beams at wider points gives other benefits. Wishbones can be shorter and with more compact hub carriers set further into the wheels, there is more space to mount the shock absorbers in a much better, more upright position, wider top tubes giving us a wider and higher pick up point allowing a longer less inclined shock absorber giving improved damping and spring rate control and a much improved wheel travel to shock absorber movement ratio.

Body Test Fit
Body Test Fit Click to see more images

Our wishbones are all tubular items again in CDS tube and incorporate an “in situ” camber adjustment system which allows accurate incremental adjustment rather than undoing some bolts and sliding a ball joint in between two plates to guess at a camber setting!

Anti roll bars have been redesigned and the front bar has increased in diameter from 22mm to 25mm and our rear bar is very similar in design to the Tuscan item spanning the full width of the suspension and picks up on the widest point of the lower wishbone giving the bar a much greater effect than the more inboard mounted original.

The chassis has been designed to take standard Tuscan length shock absorbers with our own spring rates and can be supplied in a variety of makes to the customer’s choice. Steering is taken care of by a Subaru power rack which gives a quicker ratio than the original rack and is much more readily available than the original TVR rack and at a fraction of the cost.

LS3 Installation
LS3 Installation Click to see more images

We have explored various options for coatings and have settled on a standard process of; full sand blast followed by a hot zinc spray coat, epoxy primer powder coat followed by a final epoxy powder gloss coat in any standard RAL colour.

The chassis was developed alongside our GM LS3 Engine and Tremec 6 speed gearbox installation, a wider engine bay was therefore a must to allow us to develop the correct size exhaust manifolds which could be routed down the side of the engine rather than the traditional forward system which puts all the exhaust heat into the engine bay and causes major problems packaging ancillaries onto the engine.

From our experience of fitting these engines and gearboxes into standard chassis’ we knew where we needed more space for the exhausts and gearbox, tubes that were in the way that needed to be re-routed and also how we could incorporate the install and make it work more as part of the chassis, for instance our new engine mounts are much more substantial and are designed to hold the engine rather than just have it sit in the engine bay, our new gearbox mount is a bolt in cross member which ties the bottom chassis rails together rather than two separate independent mounts that the gearbox just sits on.

Finished Chassis
Finished Chsssis Click to see more images

In conclusion, a dramatically improved chassis, with greater structural and torsional rigidity, better impact protection, greatly improved suspension geometry for more predictable handling, controlled steering and constant grip is achieved. The improved geometry allows the use of larger wheels and better tyre profiles and in turn larger brakes. High quality materials and surface coatings for greater longevity and a chassis that is designed to carry and handle the substantially increased power of the Rover V8's successor, the GM LS3.

If your car needs a new chassis or you need more power, why now would you opt for a replacement standard chassis?

Please call us for more details and prices and availability.

Demonstrators will be available soon!