Rear Suspension Struts

Following the rollbar install on Friday I was finally able to tackle the rear suspension struts, so that was going to be the tasks for this weekend. The struts were that last piece of the rear suspension puzzle to be fitted but were unfortunately delayed due to the roll bar. This task has been pending for ages, well since November 2017 anyway.


Let's quickly cover the delay, just in case fellow builders reading the blog aren't aware why such a delay might occur. Well if you recall from the roll bar install blog post, the rollbar boss is bolted from underneath, from the suspension turret. Immediately below the boss caphead bolt head is the mounting for the top part of the suspension strut. If you install the strut you can't access and install the boss caphead bolt. So you need to install the roll bar first, and then the struts, thus my delay as I'd been waiting for replacement roll bars.


Installing the struts, in theory, is straightforward, each strut is bolted top and bottom. The top bolt routes horizontally from inside the cabin area just behind each seat through to a bracket holding the strut top captive. Whilst the bottom fixing is a bolt straight into a fixing on the forward facing side of the DeDion bar. Of course, nothing is truly straightforward.


The first potential complexity is the threads in the receiving bolt holes. Each hole is located in a component which has been powder coated. The powder coat tends to ingress into the threads which can cause an obstruction, tightening of the threads and risk of cross threading. The best thing is to check the threads before attempting the install. The lower DeDion bolt holes in my kit were certainly clogged and took a little careful cleaning with some lubricant and a bolt. The top bolt also had a little friction but nowhere near as bad.


Another potential issue is the angle at which the DeDion tube mount and strut align, they're like ships passing in the night, tricky to align and with a risk of cross threading again if not correctly aligned, there seems to be only a few millimetres where that occurs.


During my installation I initially opted to install the top bolt first, basically to hang the strut from the top whilst I attempted to align the bottom with the DeDion tube mount. Unfortunately with all the will in the world I couldn't manually align the top bolt holes, the bracket was simply too tight around the bushing in the strut top mount. Oh while I remember, don't forget to place the insert in the bush as shown in the assembly guide, I nearly forgot. Having battled for around an hour I decided to try the bottom mount first. Given the restrictive nature of the top mount there was sufficient tension around the bush to hold the strut up without a bolt, I then lucked in and managed to align the bottom bolt with ease, within a short period of time the bottom fixings were secured, don't forget the washers here!


Having secured the bottom bolts I used a trolley jack placed under a brake disc to lift the hub, DeDion bar and subsequently lift the now attached strut into place. This technique was more successful than lifting the strut by hand, but not perfect, although I gained sufficient height I still struggled to achieve alignment between the strut, clamp and bolt. After lots of fiddling with screwdrivers trying to align things up, I eventually used a tapered punch to align everything. The tapered shape of the punch with an increasing diameter allowed for it to be placed as far as the insert and then using the taper pull everything into alignment with a small amount of circular rotation. The smooth tapered edge was perfect and avoided any damage to the fixings. Once aligned it was a case of inserting the bolt and securing. It seems common for Caterham to supply the required bolt for the top fixing screwed gently in place so check there before starting. As always I used copper slip to help prevent corrosion and ceased bolts.

Caterham Rear Suspension Installed

Fitting the top bolt behind the seats, can be tricky to gain access.

I hope this post gives you a few tips on how to approach the install, it's not difficult as such, but it was certainly more than just adding a few bolts, I hope my learnings will help speed up the process for you.

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Meet Mark
Loves cars, light weight specials, jDM, Lotus, Caterham, Rallying and Trackdays