Chimaera / Griffith 'B&Q' Guttering Splitter How-to

I successfully made a splitter from plastic guttering, and after 3000 miles of abuse it is still in one piece and hasn't destroyed any bodywork, so I thought I would share this with you.

Basically cheap square plastic gutter is used, but to ensure that in the case of impacts the guttering (oops – splitter) breaks sacrificial holes and cuts are made in the section. To finish the splitter duct tape is used, which in the event of aforementioned impacts, will ensure the splitter stays in one piece and does not propel fragments into engine, pedestrians etc. This also allows a modicum of taste above and beyond the appearance of cheap plastic gutter under the car.

I must add that from a technical point of view that I did not perceive any benefit to cooling from the addition, but I thought that high speed stability was improved along with reduction in bonnet lift.

As usual, your mileage may vary, feel free to experiment...


Cut required length of “Squareline guttering” to fit width of car, I use 1m length. The guttering costs about £5 for 2m at most DIY stores. This is enough to make 4 splitters.

Cut the guttering in half length ways. The flat part where you cut will be the surface which attaches to the underside of the car.

Draw a central line along the length of the middle section. Mark off along the length at 50mm intervals, then draw lines from the original finished edge to the central line. On the central line mark 12.5mm from each intersection.

Drill 5mm holes at each line intersection.

Cut out from each hole 12.5mm in both directions along the central line.

Cut from the original finished edge to the hole.

You now have something that looks like a cheesy grin, if you so wish you may leave it like this, each to his own...

Cover the section in Duct Tape, whichever colour you prefer, I just happened to use silver. This will keep the 'teeth' together if one happens to get broken.


Offer the splitter up to the underside of the car and mark 3 places where hole can be drilled through the bodywork. Ensure that you can get bolts through, and hold them with a spanner.

I used 3 10mm bolts 30mm long, with large washers and rubber washers for a little flexibility, These are hidden just under the radiator.

Once you have made one of these it is only a couple of minutes with a power drill & hacksaw to make another, keeping one as a template means you can knock one up very quickly.