I have been using a helmet mirror every time that I have ridden a bicycle since 2002. I have long been of the opinion that the best place for the mirror is on the off side of the helmet just inside the visor. This places the reflective plane of the mirror as close as 40mm from the eye. This has the following advantages.
This mirror is mounted too far in front
Many riders make the mistake of wearing the mirror too far from the eye. A 57mm mirror 90mm from the eye gives a 35° field of view. At 100mm the field is 32°. If you bring the mirror in to 40mm you only need a 40mm wide mirror to view 53°
After recently purchasing a new helmet I decided that it was time to retire the old helmet mirror and came up with the idea of permanently fixing a mirror inside the visor without the need for a long adjustable stalk. In my might-come-in-handy box I had a sheet of plastic mirror intended for the repair of a cracked motor car rear view mirror. This had been purchased from the local motor car spares shop. The packet reads Lion (Aust) Consolidated Pty.Ltd Easy Mirror. It is only 1mm thick and can be cut with a pair of strong scissors. After much messing around to determine a suitable profile to fit between the helmet and visor I fixed the mirror temporarily in position with masking tape until I had it in the correct position for the vertical image and 3° outward from the fore and aft datum. The mirror has a protective film on the front face which I removed too early and by the time I had the position and angle just right I found that my fingerprints where I had handled the back of the mirror were showing through at the front so I simply cut out a fresh mirror and glued it in position handling it very carefully by the edges.
The glue that I used was SOUDAL Fix All a synthetic polymer that dries overnight to a rubbery consistency. After the first dry and a rear view check I added a second coat for reinforcement and to cover the back of the mirror for weather protection. Fix All is very messy and a cream colour which does not look very nice on a helmet so I finished by painting over it with black Ormanoid gutter paint. When the paint was dry the next day I finally removed the protective film from the face of the mirror.
The old mirror inside the old visor
The new mirror inside the new visor
The D.I.Y. mirror kit
The new mirror in use.
A very old mirror with the helmet peak removed.
The new mirror works really well. The field of view is very wide. More than half of the mirror works in an area that would be obscured by the helmet peak anyway. I see from this fragment of a picture on the ride to Horrocks in September 2004 that at that time I was wearing the mirror on a stalk but I had removed the peak or visor completely. I concede that in such a case there is marginally more clearance from the side of the head for the rear view with the mirror slightly further from the eye but the mirror must be a greater diameter and it would be necessary to wear the peak higher or remove it at least partially. The alternative is to wear the mirror further to the right with the unpleasant strain of rolling the eyeballs to their extreme limit.
The rear view field is excellent.
The field of view already covers the full width of the road behind and a slight turn of the head to the right shows a vehicle close behind. A stalk is an unnessary inconvenience.