Chassis Restoration

If you are considering a full chassis restoration, then this section will give you an insight into probably the most important component of your M Series TVR. The photos are of slightly lesser quality than other pages in the M-Fix library due to them being scanned from my old SLR camera (rather than digital pics elsewhere). The chassis was restored in 1999

Strip down the chassis, marking each item with a tag so you know where it goes - chassis restoration takes a while and over time it's easy to forget where everything came from.
This photo shows the extent of the corrosion on the rear end of the chassis, especially on the top and front bars. These get the most road dirt and water thrown at them, and the coating tends to come off here first. Also, the top of this section is where the original factory padding was fitted (between the chassis bars and the bodyshell to reduce vibration and provide a solid fit) which was a type of hessian matting. This tends to absorb water and doesn't dry out for a long time - speeding up the corrosion process.

Front of chassis was rusty on surface and in need of shotblasting, but due to less road dirt accumulation, and oil spillage/leaks from the engine & gearbox it doesn't tend to suffer from the problems at the sills and further back. As I was to shotblast the whole thing and change all the chassis bushes/bolts etc I decided to go all the way!

Another view of the rear chassis area. The outriggers (square tubes joining the chassis spine to the sills) were patched in places, and were very weak. These are normally used as a jacking point beneath the vertical central supports for the top crossmember and top wishbone tubes, and so have to be 100% solid.

The sill members of the chassis were thoroughly rotted, and the nearside tube had a bend in it from a side impact suffered sometime in the past. Again, road dirt is thrown up from the front wheels and without attention will cause major rot.

Be prepared for a few days working in uncomfortable conditions to strip down your chassis. Rust, dirt, oil sludge & grease, bolts to be sawn off, bushes to be drilled out. All the problems of lack of maintenance and old age take their toll even on a "space age" frame of the 70's.

More rust photos - just for info. (if you need to see certain areas before working on the car).

Before you remove any tube, you have to make sure you jig (or support) the surrounding tubes so they don't move while you are cutting off the old one, or when welding on the new one. I have marked two such jig bars above with pointers. These were angle iron lengths which I welded to various points on the chassis to stop movement when cutting away sections as necessary. Use enough weld to make sure they are rigid, but try to make them easy to grind off later.
This chassis had a total of 29 new tubes and floor mounting plates (gussets) welded onto it (excluding end plates and bush tubes). The welding itself took me 5 working days, and was a bit tricky when the welding torch was forced to take a different angle than usual when other tubes got in the way. It was necessary on most of the horizontal tubes to tilt or totally invert the chassis - this made the process more time consuming as the weld is best left to cool before turning. In hindsight a revolving chassis holder would have been a good idea.
I used a MIG welder (130amp), which was well up to the job, and I used 0.8mm wire to make sure the weld was thick enough (0.6mm wire gave a welding bead that was too thin). Note also that welding will cause tubes to change shape as they heat and cool, and you have to ensure jigging of each tube is done prior to final welding of the original joints. Failure to do this can cause visibly warped tubes. The sill tube will warp visible however even after jigging, but the original sill bar that wasn't damaged had a similar curve. The most important areas are at the front and rear where suspension geometry could be affected.

These two photos show some of the new tubes fitted. The above pic also shows at the bottom right a bolt which is fitted through the chassis (at the rear body to chassis fixing hole) which I attached some castors to. This made wheeling the chassis about much easier. The bush itself was a metal tube welded into place in the crossmember, as per original. It looks like a bit of a pointless task to spend this amount of time and trouble to repair your chassis when you can buy one off the shelf, but if you have the space, time, and motivation it will save you a great deal of money. The total cost of the steel tubing I used for this work cost me £45.00 GBP (in 1999 - and I'm sure it wouldn't be much more than £60.00 GBP in 2003!). Estimate at using approx. 2 rolls of the 1Kg small welding wire for MIG welders, but I suggest you get a contract with a gas supplier to save you wasting your time with disposable bottles - they are pretty unreliable and cost way too much. Argoshield gas (a mix of CO2 and Argon) is available in different mixtures and gives much better weld penetration than just CO2.

End caps have to be fitted to all tubes. Prior to this apply some waxoyl to inside of each tube. Keep it away from welding area as this will burn & stop weld

The finished chassis prior to shotblasting. Use a suitable grinding disc to remove any pointed welds which both look unsightly and prevent the coatings from protecting the metal correctly.

Shotblasting done, the chassis is a matt grey finish. A few things to note here are that copper oxide is the best and safest blast media to use (sand dust can cause cancer and is very irritant). It's best to mask up an area if in a garage with some transparent plastic sheeting (masking plastic from car paint suppliers is ideal for this) so that you're not restricting the light available. My workshop above had striplights in the walls, an extractor fan, and I wore a paint spraying suit (disposable paper type) but with thick gloves and full breathing/face apparatus. It's also a good idea to tape up your boots over the laces, tape around your ankles and wrists! The blast media gets everywhere, and can hurt if it hits any bare skin - therefore cover up well.
These days it's becoming more common to get someone to visit with mobile shotblaster and blast the chassis in your garden. I would recommend this to save buying the apparatus (unless you already have a large compressor and all the airlines/masks etc). A shotblaster suitable for this type of work costs around £100.00 GBP.

After blasting, it's really important to cover the bare metal with etch (or acid) primer as soon as possible. Even if left for a day you'll start to see surface rust forming. Use an airline (with suitable safety clothing) to blow off any dust & grit that remains & remember any fragments can cause injury to eyes/ears/skin/breathing.
Use a proprietary etch primer to coat all areas of the chassis. This ensures a good bond to the metal preventing flaking. The chassis will need turning over to ensure all areas are coated, so make sure you have an assistant available.

To allow the chassis to be protected against corrosion while storing, and for future rust prevention, I suggest using a zinc based primer for the next two coats. Available through car paint suppliers or your local car accessory store, this may need to be mixed with thinners to allow application with a spray gun. Again, wear protective clothing & respiration apparatus as all automotive paint is harmful, and remember the chassis will need turning over.

The final coat can be any colour, but I chose to do it the same as was chosen for the body colour. I chose a two pack type paint - due to it's excellent shine straight from the spraygun (which reduces the need for polishing), and also because it seems to be more durable to stonechips than cellulose or enamel type paints. This type of paint is however extremely poisonous and correct breathing/skin protection apparatus should always be used.
Some people choose to hot dip their chassis, for example in a galvanising bath - this is good for anti corrosion and I would recommend it if you have a facility willing to do this near you. Another coating option is to have the chassis powder coated. This is a process where the chassis is given an electrical charge and paint powder (with an opposing charge) is sprayed onto it. The paint powder is attracted to the chassis due to this charge and then a hot oven bakes the paint on - a bit like glazing on pottery. Some reckon this is more durable than two pack paint, others don't. All I will say is that from my experience (I used to work for a company who powder coated their products) is that this durability depends on the quality of the chassis prior to coating, and the quality of the powder coater's processes. Just realise that where paint will chip around a swing arm bolt hole, powder coating will too.
The tin of rubbing compound in front of the chassis was to polish up the visible tubes in the engine bay - just to make it look even better!

Skipping forward to the rebuild of the chassis, these two photos show different angles of the rebuilt differential and rear suspension areas. Note new bolts/nuts/washers were used throughout the rebuild - the cost was approx £110.00 GBP in 1999! This isn't too bad when you realise the old nuts & bolts will fill a small bucket, and weigh about 10Kg!

Another view of the diff carrier

Steering rack in after finishing the rear suspension.

Front suspension assembled. All items if not new were shotblasted and sprayed (another section will cover these items).

Finished rear suspension. All components renewed or refurbished.

Plenty of sheeting and paper for the components to be assembled on is essential to prevent dust contamination. Note grease is essential on re-assembly to prevent premature failure or sized components.

The finished rolling chassis - this weighs quite a lot now and is more difficult to manoeuvre! Special castored wheel trays are available to make pushing your chassis around easier in small workshops.
As a final treatment I applied clear Waxoyl to all chassis tubes on top of the paint. After 4 years of driving the chassis is still remarkably in great condition - the two pack paint seems to be pretty tough against stone chips. Even where it has chipped off the zinc primer coat is untouched.

Apart from the metal tubing (available from local metal stockholders), you will need the following tools to carry out the actual cutting and welding of the tubes:

• 12" Hacksaw + plenty of spare blades

• 4½" Angle grinder + 2 grinding discs, 10 cutting discs

• 130Amp MIG welder, approx. 2 rolls of 0.8mm wire, 1 large bottle of Argoshield Gas

• Suitable clamps for this size tubing

• Spare angle or box section steel to make jig bars

• 4 castors to enable easy movement of stripped down chassis

• Bench vise

• Mitre square

• You could hire an industrial metal saw to save your arms!

One further word about the tubing - make sure you get the same thickness as original. There are two types and the thicker type is unsuitable due to its weight.