Leaf Springs

by Paul Ireland

Leaf springs are a simple and strong solution to mounting axles on vehicles and have been in use since medieval times. The benefits are that they both provide springing and locate the axle without the need for complex linkages. Unfortunately, they suffer from two problems.

Firstly, trying to locate an axle with a spring is not the ideal solution. It allows the axle to move. The semi-elliptic leaf springs fitted to MGs are poor under torsion i.e. when the car is braking or accelerating. The springs adopt an S shape allowing the axle to twist. This is made worse in the older T Types where the centre of the wheel is offset from the mounting point on the spring increasing the leverage. This generates an increased torsional force, causing the spring to flex to a greater degree. Coupled with the offset of the centre of the wheel, causes significant forwards and backwards movement of the wheel. Not ideal.

Secondly, although more rigid under sideways force, leaf springs also allow some movement, made worse on those cars fitted with rubber mounted shackles. The result is that the axles can also move sideways relative to the body when cornering. If you are considering servicing your leaf springs, and you have a TB or TC, why not replace the rubber bushes with polyurethane ones? These better locate the axle and will not perish. They are available from NTG or the Octagon Car Club.

In practice, this movement is only of academic interest as the solid axles keep the tyres firmly planted on the road. The only “negative” effect of this movement of the axles relative to the chassis is that slightly disconnected feeling from the road you have when driving a T type compared to a modern car. This is what adds to its character.

A more serious problem and really the reason for this article; as the axle moves up and down, the different leaves of the spring slide over each other. Unless they are lubricated, they rust, wear and squeak, becoming stiffer and less springy. The problem is that greasing them attracts road dirt, which increases wear. In addition, water can wash out the grease which means the springs should be regularly cleaned and re-greased. A maintenance headache.

The “posher” of the early 1900’s cars had leather jackets fitted to their springs, or they were carefully bound with rope. When I rebuilt my TC 12 years ago, I used a cheaper and simpler solution, Denso tape and self-adhesive insulating tape. After some 20,000 miles, some of it in very wet conditions, I decided I needed to re-grease and re-bind my springs. So how had they faired?

The picture shows the rear spring after the leaves

had been split. Other than slight rusting on the ends of the longer leaves, you can still see the original lithium grease on the leaves. Not bad after 12 years and no maintenance. How is it done? Firstly, unbolt the axles from the springs then clean and re-grease them. This time I used Penrite Graphite grease. Either prise the leaves apart and work the grease in between the leaves. I used my compressor blow gun to help.

Alternatively, split the springs as shown above with my rear springs. Remember if you split the springs to reassemble them in the correct orientation and be careful to locate the dimple on the middle of the spring when you put them back together. When you refit the axles make sure they go back in their original position by measuring from a fixed point on the chassis.

Bind the front and rear part of the spring separately with Denso tape (or as some suppliers call it Spring Binding Tape tape), starting at the back and working towards the front with a ½ width overlap of each wrap. Do not wrap the springs too tightly. Finally work back over the bound spring, squeezing the tape with your hand to ensure all the bindings are stuck together.

1. Front spring greased

2. Denso tape on front spring

3. Self-adhesive insulating tape on front spring

Denso tape is a greasy, semi sticky waterproof tape that seals in the grease and still allows the leaves of the springs to move. My TC needed two rolls of Denso tape. The most efficient way is to use one roll per side as the front and rear springs are different lengths.

Unfortunately, the Denso tape on its own is rather unsightly and not sufficiently robust to survive the rigours of road use. Next comes the self-adhesive insulating tape, again binding the springs in two halves and working from the back to the front with a ¼ width overlap. If you have never come across self-adhesive tape before, do not worry that it is not in the slightest bit sticky. It does stick to itself. Slightly stretch the tape to encourage it to form a closed, rubber like binding. Only remove the backing from one wrap after the tape has been positioned and as with the Denso tape, work back over the bound spring, squeezing the tape.  With both tapes ensure you get as close to the ends of the spring as possible. Three rolls of self-adhesive insulating tape were sufficient for my car.

The final result, an acceptable looking, waterproof, cover on your springs and no more maintenance worries for many years to come. What are the downsides? Once completed, none that I have experienced, the only problems are while you are doing the work. The black graphite grease gets everywhere and is difficult to wipe off, you are likely to get as much grease on you and your tools as on the springs. The Denso tape is soft and covers your hands with a sticky “goo”. I suggest you ensure you have an adequate supply of rubber or similar gloves, at least two pairs per spring, and plenty of wipes. I also keep a bottle of white spirit handy to soak the wipes as this helps to remove the grease and stickiness.

Ed’s note:

The Wilcot (Parent) Company was bought by Wefco Gaiters www.wefco-gaiters.com who operate from Yatton, 15 miles south west of Bristol.

I spoke to a most helpful lady who told me that the proprietors of The Wilcot (Parent) Co. Ltd were quite elderly and were wanting to retire. She and her husband bought the business from them. The website has a measurement form which is downloadable. She was obviously very enthusiastic about her work and confirmed that she has supplied leather gaiters to Vintage M.G.s. in the past. I find it heartening to learn that with so many sources of spares and services drying up, this particular service lives on.

Oops!

Paul Ireland sent me this picture of his broken leaf spring – it reminded me that I had one go in exactly the same place. NTG to the rescue as they had them in stock.

If Paul had bought his TC springs from Bill Thomson in 1964……

“Front spring, complete with all needed bushes and rubber parts”                              
Part number 99546
£2.12/- (two pounds, twelve shillings) £2.60, or $3.50, or €3. or AU$4.70.

Rear spring, complete with all rubber bushes for rear end of spring”            
Part number 99561  £4 (four pounds) or $5.40 or €4.70, or AU$7.30.

Amounts have been rounded up or down, as appropriate.

These descriptions were in a typed list sent to Bill by Björn-Eric Lindh from Sweden for Bill to insert prices, prior to a “raiding party” from Sweden coming over to England to collect.

Those were the days..!

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