Day 8: Rear suspension & brakes

With the diff in place the next main step was to build out the rear suspension. The assembly guide is pretty much spot on in this area, which helps! Well, it’s spot on if you read it, but that’s a funny little story for later on in todays build progress.

First thing to do was squirt a little cavity wax into and coating (lightly) the inside of the DeDion tube. I used the same Dinitrol Cavity Wax 3125 as I used on day 1 for the grot traps.

And today Paul and Craig were supporting, as the A frame and other bits of the suspension are easier done with assistance. We are all enjoying tinkering, and the build continues to be a really sociable affair.

Brake Pipes on DeDion

The first real step was to work out how the brake pipes are positioned down the length of the DeDion. This was all simple once I realised that the final bends in the pipe at the calliper ends need to be manually done. It then all clicked into place and it was obvious how to attach to the tube. Rivets and little P clips made this simple. As you can see from the photo, the guide walks you through “dry fitting” the “ears” and callipers, so that you can easily work out how to make those final bends in the brake pipe.


in order of RHS then LHS these are how we set up the pipes. Beware here, although its easy to sort in situ. The RHS has a natural bend that keeps the pipe low to the tube before rising up to the calliper. The LHS doesn’t naturally do this. We had to tweak this when in place, as the brake pipe would have fouled on the spring and damper unit. The adapter you can see on the left edge of my workbench which the left and right brake pipes fits into is the three-way union. Basically the whole DeDion tube is moving when under suspension load, so this third brake pipe is actually a braided flexible one, identical to the ones used for the front brakes.

A Frame and DeDion tube fitting

I didn’t really take photos of the A Frame and Dedion going in. I was caught up in the moment and simply forgot. My advice would be to protect the lower chassis tubes with plumbers foam cladding, as it then is really easy to rest the Dedion in place.

The A frame is also simple. I mean neither of these jobs is anything like the challenge of fitting the heavy diff. You do have to space the A frame so that the DeDion is central. For me this was exactly as the guide said, an uneven number of spacers on each side. I ended up with 8.2 cm from the edge of the DeDion to the nearest chassis tube parallel to the Dedion, and 8.3 cm on the other side. I’d call that central!


The picture above also shows the rear ARB mounting, a lovely aluminium clamp, just like the steering rack clamp. The only challenge here is getting the rubbers over the ends of the ARB and more specifically around the 90 degree corner at each end. This looked like it should be tragically hard, but you need lots of rubber lubricant and a large flat bladed screw driver to “help” the rubber around the corner. Literally 2 mins for each end and rubber lubricant everywhere!

Springs and Dampers

The springs are mounted at the top via a bolt that is already in place in the chassis, just undo it from inside the cockpit and slip a spacer into the top mount before re-attaching the bolt. The lower mounts needed a little persuasion, but what I did was make life easy and rotate the adjustable platforms tighter (up) to allow me to more easily slip the bolts through.

Notice that in the second picture above, the brake pipe travels very close to the spring. When I had the callipers in place a little later I moved this pipe away. Its very soft so gentle finger pressure does the trick.

Radius Arms

Next step is to fit the radius arms. Key things to remember here are that you torque the bolt into the body horizontally and that you make sure the chamfers in the arms face outwards. This is so that the Callipers just miss these arms when fitted. A really simple job but the lower mount needed a rubber mallet attack to get it into place!IMG_1759

I did need to have a chat with a few folk about which hole to attach the radius arm to. There is an upper position, which I have used, and a lower position, you can see the lower hole above.

Allegedly the upper is the more compliant setting and the lower is the racier setting. The general conclusion I came to after listening to others was to leave it in the top hole. I also took this option because the inner skin has not been fully drilled out, which means it would have been slightly more effort to use the lower mounting holes. I’m happy with my choice, mainly because it was inconclusive and relatively inconsequential….probably!

Drive shafts

The drive shafts were then inserted, which is a simple job, and they are marked LHS and RHS and are different lengths. The splines engaged and they slot in with minimal effort. They need to go in now because the next step is to fit them through the DeDion ears as you fit them.


DeDion Ears, Uprights and Callipers

The assembly guide is weak in this area. There is a really good exploded diagram of the whole of the suspension/upright assembly, one of the best diagrams in the guide, if a little small. But it is completely let down by its legend. There are number bubbles all over the diagram, and different length bolts need to be used, but the legend calls out each of these bolts as simply “bolt”. Its tragic and pretty much impossible to achieve without third party guidance.

And the saviour for this assembly is Andrew Bissell, whose build diary provides very good annotated colour photos of which bolt goes where. I have reproduced them below, and what I did was print them out and reference them throughout. Where Andrew mentions “Ford Bag” for some bolts, I found mine were pre attached to the Callipers in the Calliper boxes.

These diagrams should be added to the assembly guide in my opinion!

My big embarrassing mistake!

In my defence it was late in the evening and I was very tired from a fairly big build day. I had completely made up the LHS uprights perfectly according to the assembly guide and the above bolt photos.

I then moved to the RHS to repeat what I had just done. I guess I was slightly less engaged because I had just completed the first side, and I didn’t take the assembly guide with me from one side of the car to the other.

I just went for it and when trying to insert the hub carrier, I simply couldn’t get it to fit. No matter what I tried, I couldn’t get it to move far enough inboard with the drive shaft attached to be able to bolt it to the ear.

I asked Simon Calvert, also building the same car what he thought it could be, and I was convinced that my RHS drive shaft was too long. I even measured it and asked him to provide his measurement.

They were identical in size and this threw me completely. Simon asked me to send a photo and I sent him both sides to show that I had completed one OK, but the other didn’t fit.

This is the photo. Spot the problem?


Within about 15 seconds he came back and told me that i had fitted my hub carrier the wrong way around. In effect I had tried to insert the fat end into the hole.

What a numpty. I did it right on the first one, but brain fade caught me out on the other one. Fairly embarrassing, I am likely to continue to be reminded of this in years to come!

Brake Discs

Brake discs went on fine, but its really important to carefully read the assembly guide, because there are two little spacers for each side which space the floating callipers so that the brake discs are nicely aligned in the centre of the callipers.



You can see the handbrake cable fitted above. On both sides of the car the cable exits the prop shaft tunnel and is routed over and around the back of the drive shafts before looping back up and entering the front of the callipers as you can see here. The trick is to start with the handbrake lever fully vertical, and then slacken off the big white knurled wheels for adjustment until you have so much cable left at each side that its a simple job to hook the ends over the claw you attach them to. Leave the handbrake lever adjusted like this to make it possible to fit the tunnel top. The handbrake can be properly adjusted right at the end of the build. Or thats what I’m going to do.

Drop Links for ARB and Speedo sensor

The next job should have been a 2 minute one, but it took a lot of effort simply trying to work out what the assembly guide meant. The way the job is described I am missing an extension bar to be able to fit the drop links, but this is a load of rubbish (after checking with others)!


The objective if you follow the guide is to get them looking like the above photo. But the gap is too large between the bracket and the ARB bar, hence me thinking I do need this extension bar. But actually, what you do is rotate one end through 180 degrees. For example, in the photo above, rotate the RHS so that the screw thread points downwards.

This was they fit. But use washers and the Nyloc nuts and bin the extra brass nuts as they aren’t required.

On the RHS there is a hole to insert the speedo sensor, a hall effect sensor. The trick is to line it up with the drive shaft toothed ring and to then get it to within 1mm of this ring, and the theory is it should register speed correctly. We will wait and see, but it looks simple to adjust if I need to.

End of day…

And so that was it for Day 8. I’m a little bit behind writing up this build blog, so I’ve also already completed Day 9 in my garage. So for the next instalment, I will be writing up testing the electrics and sorting out the interior and boot of the car. I’m now formally into the fiddly small stuff that seems to take an age!


One thought on “Day 8: Rear suspension & brakes

  1. Really enjoying this build blog. I am considering building a Caterham and am researching now. Your documentation is very helpful Thank you for taking the time to do so.


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