Caterham Cars Carbon Bow Protectors

Before ordering my Caterham 420R and settling on the final specification I watched countless Youtube videos about the various models. One such video was from Youtuber JayEmm On Cars in which he covered daily use of a 420R. At the time I noted from the video that the bow tubes were particularly vulnerable to damage from the seat belt harness or doors. The video is below, and the relevant comments are about 6 minutes into the video.

As a result, I added Paint Protection Film (PPF) to the bow tubes on my 420R during the build. The PPF has done a good job, and after approximately 3000 miles and 18 months, there isn't a mark on the bow tubes.

Caterham Cars recently (2019) addressed the damage risk, releasing a carbon fibre protector similar to the carbon sill protector. Given my Caterham garage has now grown to include an additional 620R which didn't have any factory fit protection, I decided to fit the new bow protector to both the 420R and the 620R. My approach was to fit the carbon protector to the 420R and then to the 620R. Why? fitment required the removal of the rivets holding the interior side panel to the chassis. On the 420R it's a standard metal panel, on the 620R its a carbon panel. An expensive panel to replace if scratched or damaged during the install process. I guess you could consider the 420R my test mule, or learning device.

Over the last couple of weekends, I've gone through the process of carefully installing the protectors on both cars, and I have to say I'm over the moon with results. Sure you could argue PPF was working well on the 420R and the same approach could be used on the 620R. What can I say I'm a sucker for carbon, they just look great! If you have a black pack car, with existing carbon sills protectors or other parts then I highly recommend adding.

Installation isn't difficult, but if you're like me, starting the process was a little nerve-racking. I've only ever removed one rivet from the chassis when installing the oil catch can and I didn't enjoy doing that. The number of rivets involved with the bow protector interior panel is significantly higher and I was installing two sets! I didn't need to worry, patience and planning produced excellent results, and without any hiccups.

Before we get to the install let's take a quick look at the bow protectors. I ordered two sets from Caterham via the Caterham Parts website.

Caterham turned the order around really quickly, with a reasonable delivery charge. The order was shipped with suitable packaging to protect the consignment from damage. You can see from the photograph each protector is in an individually sealed pack. The part numbers appear to be the same.

Caterham Bow Protectors Consignment

I was sent a single pack of rivets with the kits. Caterham's website product image shows individual rivets, so it's unclear if I received a pack due to two sets of bow protectors being ordered, or if that's normal. Either way, even fitting two sets I've plenty of rivets left.

In my view, the product quality, including thickness, weight and finish such as the weave and polish is of a very high standard. I did find one imperfection in one bow protector which I still fitted as it was sufficiently minor for me to accept, plus I'd already stripped the car. I would recommend thoroughly inspecting the protectors before starting an install. It's probably worth commenting the bow protectors are labelled and I suspect manufactured by Tillet. They should be pretty good then.

Before starting the install I considered how I would go about removing the rivets. The rivets needed to be drilled out, so I invested in a new set of HSS-G drill bits in 0.5mm increments. I took the view that drill bits were cheap enough, and a new sharp bit would produce the best results. I also considered how I'd position the power tool (drill), again considering the best results. I'd either have to get in the car and drill away from myself, or I'd have to drill back towards myself while looking over the bow tube. The latter seemed better, but accurately handling a normal drill wasn't going to be ideal. I needed a 90-degree drill. Now I do have a 90-degree air drill, but it's all speed, no torque, tends to jam, and difficult to control. A new 90-degree drill was in order. I purchased a Dewalt DCD740C1 from Screwfix as it used the same LiIon batteries from my other Dewalt power tools. Without turning this into a power tool review, I'd offer the opinion the drill was spot on, good battery life, excellent power and easy to handle, most importantly when keeping the drill bit level. The integrated light was super helpful too.

With new drill bits, a power drill and plenty of masking tape I was ready.

As mentioned I started with the 420R. I masked the area around the rivets with masking tape and attached newspaper to the seats to catch falling metal.

Masking tape and newspaper to protect the car

As a first step, a 2.5mm drill bit was used to create a slightly larger centre hole in the middle of each rivet. Doing so helped guide larger bits used afterwards. The 2.5mm bit was also passed all the way through the rivet until it exited inside the chassis tube. A 3.5mm and 4mm bit if required was then used to remove the head of the rivet. Drilling the head of the rivet with the large bits would simply remove the head leaving the centre section, between the 4mm (5/32) outer the remains of the 2.5mm. This process was repeated on all accessible rivets but it soon became clear the top 3 rivets weren't accessible and the Tillet seats had to come out. Given this, the seats were removed at the start during the 620R install.

The 420R was jacked at the rear and put on axle standards, the seats were then carefully removed. Removing the seats is pretty straight forward, so doesn't really need much in the way of explanation. Just remove the 4 bolts underneath and carefully lift the seats out being mindful of the harness etc. Having recently removed and refitted four seats in two cars, I will say this. There is a technique to getting the seats in quickly and without fuss. Having been through this install I'm now pretty confident and happy to remove the seats if needed. Sadly it's a little difficult to describe, but it's all about leaning the seat while moving it forward and backwards.

Once the seats were out the remaining rivets were drilled, then the interior panel and rubber could be carefully separated providing visibility of what was remaining in the chassis tube. I carefully removed the remainder of any rivet inserts with a 3.5mm drill bit, or a flat cylindrical punch used to knock the remaining metal outer into the chassis. Each rivet came out nice and clean, without any panel damage or widening of the hole. I was quite surprised! Being a relatively inexperienced garage/amateur mechanic I found the process straightforward. If you are considering fitting the protectors, but concerned about this step, don't worry it's easier than you think.

Rivets removed passenger side, bow tube test fit

Next, I took the opportunity to treat the rubber edging strip with some Honda Shin-Etsu Silicon grease. Shin-Etsu is magic stuff, it sorts roof squeaks on convertibles, revives door seals, most automotive rubber products love it. Treating the edging strip should help maintain the life of the rubber for years come. The grease also gives the rubber a super slippery but dry feel which made it very easy to position, very helpful during the realignment of all the parts.

Honda Shin-Etsu Silicon grease = magic stuff
Add grease, smear into rubber

At this point, I was ready to fit the bow tube.

Now I've previously glossed over the fact each bow tube actually had a press stud base, one on the outside of the bow tube and one on the inside. These stud bases are screwed into the chassis so take seconds to remove with a screwdriver. You can see the outer hole in the above image, top left. When fitting the bow tube I refitted these stud bases first, why? It came down to how I approached the outer stud base. There's no marking or hole on the carbon bow tube to align with the hole underneath, so you need to find an accurate method of aligning the two while creating a hole. I spent a reasonable amount of time pondering my approach, should I use masking tape and measure then mark the carbon? In the end, I decided to go by eye, sounds a bit crazy? actually it was more controlled than you might imagine.

I applied quick detailer to the inside of the carbon bow tube and also to the painted part of the chassis which would be covered by the bow tube. This was done to reduce friction between the parts. Next, I placed the bow tube in its final position and placed low tack masking tape around the bottom edge. The tape would help prevent the tube from moving down and out of place. The bow tube was then lifted and lowered repeatedly from the top until it revealed the chassis hole. Each time the bow tube was lifted I aligned a 2.5mm drill with the revealed hole. The bit was aligned as close as possible without touching the carbon. When I was confident I had the bit in the right position and the tube in its final position I mark the carbon by hand with the bit. The bow tube was then removed, and the mark drilled through with a 3mm drill bit. I used this approach on both cars, so a total of four times, all lined up perfectly.

Carbon bow protector successfully drilled for outer popper base
Hole drilled and the screw test fit
Carbon Bow protector DOT fastener hole
DOT fastener base installed with the self tapping retaining screw

At this stage, the bow tube was held in place by the external fastener. Afterwards, I aligned the rubber trim piece and drilled into the carbon only which now obscured the internal fastener base hole. I believe with a 3.5mm or 4mm bit. Since the interior panel designates the location no measuring was required. Once drilled the self-tapping screw and base were fixed into place.

Internal fastener, not sure what happened with the colours

With both fasteners in place, I aligned the rubber trim and drilled out the carbon for 3 rivet holes using a 4mm bit. I equally spaced the holes and avoided the bottom two. Before adding the rivets I sprayed a fair amount of Waxyol into the bow tube cavity through the bottom two holes. This was done following recommendations made by fellow owners, it's designed to prevent the inner remains of the rivets from rattling in the chassis.

Completing the install is now a simple case of drilling all the holes (just the carbon) with a 4mm bit and adding the rivets while ensuring the rubber trim remains aligned. I installed the rivets on the 420R using a Stanley hand riveter. I wrongly assumed it would generate less kick during install. I was wrong, it was an awful tool to control. The Stanley hand tool eventually failed, getting stuck on a rivet during the 620R install. So unreliable too. I switched to my Draper air riveter which was much quicker and less violent. I'd highly recommend one!

Stanley riveter - Not reliable - Avoid
Draper Air Tools Riveter, much easier to control

Riveted Panel completesound

Before adding the seats back everything was given a thorough detail. All panels including the carbon seat backs were cleaned and detailed using quick detailer. The floor was swept, hoovered and protected with a thorough wipe down with XCP Rust Blocker. XCP is a cracking product, not only does it provide rust prevention, but it adds a deep water-resistant shine which isn't greasy. Perfect for metals including the floor. I also took the time to clean the seat runners of grit and other rubbish. Then added a good dose of XCP to ensure they maintained excellent operation in the years to come.

Once everything was back together on both cars I came to the conclusion the standard silver finish on the DOT fasteners looked out of place against the dark carbon. The fastener studs seemed to stand out more against the carbon than it did the paint. To improve this I've bought and installed a set of replacement studs from Trimming Shop ( It's finished the install off nicely.

Caterham 420R Bow Tube
Caterham 620R Bow Tube

I hope you've enjoyed this entry, and been inspired to fit the protectors to your Seven. If you've got an R spec or black pack car I would highly recommend them. They aren't cheap, but they do look fantastic. The only issue, I'm now talking to Chris at Redline Components to source replacement black bonnet catches, I'm on a slippery slope here!

Check my Instagram page above for plenty more photographs from the install.

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