Rollbar

I have fitted standard and track day rollbars of several Caterhams, including some for fellow owners’ cars. Rollbars seem to either be easy or a right pain to fit. I always assumed second hand rollbars were easy and new ones were the pains, and this install sort of backed up that theory.

With my 360R build, I followed the old build manual (2015c) which doesn’t recommend fitting the bottom bolt on standard roll bars. This has changed with the new manual (v1.2 and v2.0) and regardless of the rollbar you are fitting, I would fit all the bolts provided for safety reasons. This means, the rollbar must be fitted before the rear shock absorbers, or you can’t get access to the mounting bolts.

Remove rear shock absorber mounting bolt

I started by removing the upper rear shock absorber bolts. These are fitted to the chassis (much like the front upper shock absorber bolts), but due to their location, mine had some nice orange over spray on them. For reference, I haven’t refitted the boot cover and boot board after the differential fit, but I don’t think either would have caused a problem if they had been fitted.

Next to be removed was the hood sticks, which are also installed by the factory these days, before the kit is delivered. Remove the hood stick straps first on the back panel top tube, then remove the small bolt near the rollbar mounting point. It’s best to have a helper here to hold the hood sticks in place while the other side bolt is removed, to protect the paintwork.

Next I did a quick check of the threads for the small bolt next to the front rollbar mounting point. As I expected, the paint in the thread needed removing. A M8 tap quickly sorted the problem.

I missed a trick here, because the seatbelt mounting bolt holes also need to be cleaned of paint: now I have a track-day rollbar in the way. So, as a build tip: clean the threads of the seatbelt mounting bolt holes now.

Placing the rollbar onto the chassis, is easier with two people to prevent paint damage.

You may have read about a special cut-down nut being above the shock absorber, and a cut-down socket being needed. This is no longer the case with a metric chassis, a standard cap head bolt is used now.

This is where I ran into my first (and not unexpected) problem. The alignment on one side, I my case the right-hand-side, was problematic. The left-hand-side had no alignment issues, so I put the left-hand-side bottom bolt in first. This is a mistake, because putting in the bolt (however loose) on the side without alignment issues makes it impossible to put the bolt in the other side. So, start with the side with the alignment issues, and then go to the other side.

Once the bottom bolts where installed, I fitted the top bolts, and then it was time to move to the back bolts.

Again, don’t work on the easiest side first. I had to work through all my pin punches, to be able to finally pull the holes into alignment. This took a fair bit of effort; I even broke a smaller punch, because I tried to apply too much force. Thankfully I was lucky and this caused no damage to my Caterham.

Back bolt still needs to be worked into the hole

I had to screw the back bolts into the mounts to finally get them through the holes.

I torqued the bottom and back bolts to 47Nm as specified in the new manual (v1.2 and v2.0), but I didn’t torque the top bolts to 25Nm, because they are also the mounting points for the half-hood fixing straps. I have a half-hood from my 360R (never used) but haven’t ordered replacements for the half-hood fixing straps yet.

Tools Used

3/8” drive torque wrench
8mm 1/4” drive hex driver
1/4” drive ratchet
17mm 3/8” drive socket
3/8” drive extensions
3/8” drive ratchet
1/4” to 3/8” drive adapter
M8 tap
Tap handle
10mm combination spanner
17mm combination spanner
Philips screwdriver
Many pin punches

Build sequence

On my 420r SV, I had gone for full carpets and the usual r-spec 4 point harnesses. I changed the build sequence a bit here, as follows:
1. Remove the upper rear shock absorber bolts and hood sticks as per Chris’s instructions.
2. Remove the boot cover.
3. If you’ve gone for full carpets, install the rear firewall carpet (the big one behind the seats) at this point, using spray adhesive. Before doing so it’s worth cutting holes in the leatherette flap that goes over the boot edge for the roll bar bolt holes. I also cut holes in the carpet for the upper rear shock absorber bolts (the carpet covers them otherwise). I used a hole saw for this which gave nice clean holes. Clamp the carpet either side close to each hole before cutting.
4. Now replace the boot cover with the 4 self tapping screws on top of the carpet leatherette flap, screwing through the carpet flap as well.
5. Install the seat belt harness upper straps, following Chris’s ‘Seat belts (Upper) and Boot Cover’ post. These bolt through both the boot cover and carpet flap.
6. Finally install the roll bar and torque the bolts.

On my build the seatbelt bolts were fairly long and would have been a real struggle to install if the roll bar was already installed – perhaps impossible. The above sequence effectively goes bottom up – carpet, then boot cover, then seatbelts, then roll bar, which seemed to make everything much simpler to access.

The alignment of my roll bar to the chassis mounts was way out, and I couldn’t get enough pressure on my punches to bring the rear bolt holes into alignment (using Chris’s technique) with the front bolts already loosely fitted. Instead I put the rear bolts in loosely first, and then forced the roll bar into the front cylinder-shaped mount recesses just bending by hand. Needed a lot of welly but finally just popped in.

Now you can install the shock absorbers. Except mine were wider than the upper chassis fitting… more tweaking to do…

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One thought on “Rollbar”

David Stocker says:

April 14, 2021 at 9:56 pm

Build sequence

On my 420r SV, I had gone for full carpets and the usual r-spec 4 point harnesses. I changed the build sequence a bit here, as follows:
1. Remove the upper rear shock absorber bolts and hood sticks as per Chris’s instructions.
2. Remove the boot cover.
3. If you’ve gone for full carpets, install the rear firewall carpet (the big one behind the seats) at this point, using spray adhesive. Before doing so it’s worth cutting holes in the leatherette flap that goes over the boot edge for the roll bar bolt holes. I also cut holes in the carpet for the upper rear shock absorber bolts (the carpet covers them otherwise). I used a hole saw for this which gave nice clean holes. Clamp the carpet either side close to each hole before cutting.
4. Now replace the boot cover with the 4 self tapping screws on top of the carpet leatherette flap, screwing through the carpet flap as well.
5. Install the seat belt harness upper straps, following Chris’s ‘Seat belts (Upper) and Boot Cover’ post. These bolt through both the boot cover and carpet flap.
6. Finally install the roll bar and torque the bolts.

On my build the seatbelt bolts were fairly long and would have been a real struggle to install if the roll bar was already installed – perhaps impossible. The above sequence effectively goes bottom up – carpet, then boot cover, then seatbelts, then roll bar, which seemed to make everything much simpler to access.

The alignment of my roll bar to the chassis mounts was way out, and I couldn’t get enough pressure on my punches to bring the rear bolt holes into alignment (using Chris’s technique) with the front bolts already loosely fitted. Instead I put the rear bolts in loosely first, and then forced the roll bar into the front cylinder-shaped mount recesses just bending by hand. Needed a lot of welly but finally just popped in.

Now you can install the shock absorbers. Except mine were wider than the upper chassis fitting… more tweaking to do…

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