This is not going to be the usual post IVA mirrors story, where builders either remove the IVA mirror mounts and fit the mirrors to the side screens, or fit the well-known “Eccles” alternatives.

The IVA mirrors are fine, but they limit the side screen from being opened fully; they are easy to knock out of position, and are difficult to adjust while seated with the side screens fitted. This has resulted in many journeys over the running-in miles with the mirrors pointing anywhere but where I needed them.

The standard mirror fitted to the side screen does work as a solution, but does have one known downside: the mirror suffers from vibration which makes good rear vision difficult, especially when combined with the track day roll bar, where the rear view mirror is full of a big metal X.

I preferred the vision from the mirrors on my second Caterham, which was only fitted with an aero screen, and SPA Design mirrors, but my 420R is fitted with a windscreen and side screens. This is where “Eccles” mirror mounts come in. They where designed by a Lotus 7 Club member with the forum user name of “Eccles”, hence the name. They allow the SPA Design mirrors to mount to the side screens without drilling holes in the side screens. I have looked at them on other cars, and decided to purchase the SPA Design mirror mounts and get the mirror mounts 3D printed.

The advantages of the “Eccles” mirror mount are less vibration, no need to drill side screen and the side screen can be fully opened.

When the parts arrived I started with what I thought was going to be an easy swap over. Remove the grub screw from the IVA mirror mount, and remove the mirror, refit the original stanchion screw.

Press new hinge pins into the mirror mount, a little soak in warm water helped. With the pin in place I fitted the SPA Design mirror to the mirror mounts. One thing to note is the SPA Design adjuster locking grub screw is an imperial fitting.

With the mirror fitted to the mount I decided to adjust the mirror before fitting to the side screen. The mount replaces the lower side screen hinge so the final stage was to remove the hinge and fit the mirror mount.

But this is were things started to go wrong! The mirror mount as printed pushed into the side screen window when the mounting screws where tightened. I suspect this is partly due to a design change of the Caterham side screen hinge (sometime around 2016). The offset between the hinge pin and the side screen seems to have increased, which means the mount (at the mirror end) is angled towards the side screen.

I tried bending the mirror mount (as can be seen from the photo), to clear the screen. I tried applying a bend to the mount, 10mm bend over the length of the mount. I suspect the metal frame in my side screen may also be twisted exaggerating the problem.

I still didn’t like how close the mirror mount was to the Perspex screen. So I started looking for alternative solutions. Obviously, I could have fitted the standard mirrors to the side screens, but I had already invested in the SPA Design mirrors.

In the end I decided to use DPR Motorsports mirror mounts (https://www.dpr-motorsport.com). These have the advantage of being very stable and secured to the stanchion, and are 100% reversible – i.e. no modification is required – so it seemed like a ideal solution for the time being. The only downside is the side screen still can’t be opened fully.

Fitting is simple. The mount is screwed to the stanchion, but taking a leaf from Caterham’s book, I decided to fit a fibre washer to the mount to prevent damage to the stanchion. I used a self-adhesive fibre washer to make holding it in place during fitting eeasier.

The base is secured to the stanchion using a special screw (supplied) through the middle hold (as per the original IVA mirror mounts). I used the ruler to make sure the mirror base was level with the stanchion edge.

The base and locking nut secure the mirror to the stanchion. I used masking tape to prevent paint damage on the stanchion, and correctly sized spanners to prevent damage to the mirror base. I had to purchase a second stubby 19mm spanner to hold the base while tightening.

I am happy with the result, but obviously would have preferred a solution which would have permitted the side screen to fully open. Since I haven’t made any changes that aren’t reversible I will still investigate a modification to the Eccles mirror mount design based on the new side screen hinge profile.

Tools Used

Based on fitting the DPR Motorsport mirror mounts.

  • Flat screw driver hex adapter
  • 8mm ratchet ring spanner
  • 2.5mm Allen key
  • 3mm Allen key
  • 8mm open ended spanner
  • 2 x 19mm open ended spanners