A debate over the tonneau cover

Updated: Mar 13, 2019

This weekend I decided to fit the tonneau cover, partly out of interest, but also because I thought it might be easier for the local Caterham specialist to store when assessing my build, well easier than the full weather gear.


As it happens a conversation on BlatChat over the fitment of additional poppers led to some interesting insights regarding the cover, and then ultimately I took the decision to stop the fitting process.


Before we get into the details please consider the information provided is relevant to the specification I selected and thus may not be accurate for your car.


I'll cover the debate first, and then the initial install steps should you be looking for those.


So it all started with the fitment of the 3 additional popper studs down either side of the car. These need to be added to the 7 chassis. I raised a query on BlatChat to get some hints and tips regarding drilling holes in the bodywork. I'm glad I did as the feedback yielded some interesting information.


Extra poppers, extract from Caterham's 2015 assembly guide.

First up, the 3 additional poppers per side should also be used to secure the half doors which are also available, and further the half doors are more sensitive to the accurate location of the poppers. I don't currently have the half doors to test. This point may or may not be important depending on whether I buy the doors.


I do however have the aeroscreen, and as a result, the front centre popper bases for the aeroscreen had already been added by Caterham. I didn't realize these bases were for the aeroscreen, and so used them for the tonneau. Luckily the aeroscreen fittings are doublesided, so I'd still approached the install correctly, more out of luck though. Personally, I think the half doors with the aeroscreen make a lot of sense.


Here comes the issue however, I have full doors or side screens and intend to run those most of the time with a full windscreen. The problem with my doors is that I specified them with armrests, I know, not in keeping with the ethos! The armrests clip inside the cab which prevents the tonneau from draping down the side of the car. They're just not compatible. I believe you can lay the doors inside your car before fitting the tonneau, but that's not great.


In conclusion, I can add the tonneau now but will need to take the doors off and store them in the car if I'm out and about. If I do install the tonneau now before I have half doors, I might not achieve an install which is fantastic for the half doors. I'm not really ready to make a decision over half doors.


I guess you could consider Caterham should have pointed out the incompatibility between the tonneau and armrests, however considering I'd also specified the aeroscreen it's logical to assume Caterham expected me to run the tonneau with the aeroscreen.


Many members on BlatChat suggested I ditch the tonneau, most seem to dislike them and instead use a half hood or bikini top. With the full doors fitted a half hood apparently provides 90% of the weather protection without the need for the additional poppers and is also far easier to install. I've taken a good look at various suppliers and I'm now tempted to go down the half hood route. Having some form of protection for the cockpit is essential on the Isle of Man, not just because of the obvious precipitation, but also due to the wildlife. Seagulls are notoriously inquisitive and would be inside the car in minutes potentially doing damage and that's without discussing the other type of mess they leave.


In terms of the install, how far did I get?


Basically I only added poppers to the tonneau cover, and only those that could be clipped onto the bases already installed by Caterham. This included the two forward-centre poppers, four across the back by the harness fixing points and one either side near the roll bar.


Installing the poppers into the tonneau is a doddle. It is critical to ensure you achieve the correct tension in the material otherwise you'll have water pooling on top. You also need to ensure the material is warmed through to prevent it sagging on a warm day.


The part of the popper which is installed through the tonneau comes in two pieces which are then compressed together using the 'Durable Dot Fastener' tool. For this to work, you need to accurately cut a small hole in the material for one of the two pieces to pass through. Accurately marking the location is essential. I applied masking tape to the tonneau cover and marked the base with a paint marker pen, when I was happy with the location the two were pressed together and the paint transferred to the masking tape, thus illustrating the location. Having marked the location on the tonneau cover I then cut the holes using a leather punch. I'd previously purchased a leather punch online and it struggled to cut paper, it was absolute rubbish. Before attempting this install I decided to replace the item and bought this from Screwfix.

https://www.screwfix.com/p/forge-steel-hole-punch-2-4-5mm/8840c


If you've not got a leather punch, this is brilliant. It cuts through the material cleanly and without any hardship, like a staple into paper. Bargin!


Once you've cut your hole, it's a case of passing the top half of the popper through the material and then adding the bottom half to the reverse.


Popper inserted through the material

Popper reverse fitted, ready to be secured.

Then place the top half in the Durable Dot Fastener tool base, locate on a sturdy surface, insert the driver into the otherside, and hit with a hammer.

Durable Dot Fastener tool located into popper ready for striking

Ensure you drive the tool square into the fastener and it will pinch the base against the material, securing everything together. Simple as that.


Popper secured (front)

Secured popper (reverse)

As mentioned I installed the poppers into the tonneau which married with bases already fitted by Caterham, and then decided to cease the install pending a wider decision over half doors and half hoods. Once I've taken a decision I'll update with a follow up, at present the half hood from Thunder Sport looks likely.

Part finished Caterham tonneau cover install

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