I love how cool those aero bike helmets with built-in goggles or shields look. I also find that wearing regular sunglasses on a road or triathlon bike doesn’t really work that well, because when you are in the drops or on the tri bars with the head held low, the natural line of sight is right through the top rim of regular glasses (and its quite difficult to find large sunglasses without rim). As a budget athlete and tinkerer I didn’t quite see the point of dropping $200+ for a helmet with a built-in visor so I decided to convert my existing helmet on the cheap. Read on...

Step 1: Safety Disclaimer

You are about to modify a bike helmet, an essential piece of safety equipment for riding bikes. I am describing here how I modified my own helmet, and I have weighed the possible implications that I might have weakened the structural integrity of my own helmet. If you should decide to follow this instructable and modify your own helmet, you do so fully at your own risk.

For more information, see the Disclaimer section in Instructable's Terms of Service: http://usa.autodesk.com/adsk/servlet/item?siteID=...

Step 2: “Ingredients”

1 bike helmet of yours truly to convert
1 replacement goggle with magnetic clips
3 rare-earth magnets, 3/8" dia.
3 nailgun staples
1 syringe epoxy glue

You can find suitable replacement goggles from Chinese helmet manufacturers. They come in different colors, too, like clear, high-contrast yellow or grey for sunny days. Here are two sources for goggles...

Set of 2, clear + grey, currently just under $11, shipping free but 2-3 weeks. This is the model I used for this Instructable: https://www.aliexpress.com/item/CAIRBULL-2-Lens-AE...

Clear, yellow or grey, $16 each incl. shipping from the US, if you are in a hurry: https://www.amazon.com/Basecamp-Shield-Removable-M...

The three magnets will allow you to attach and remove the goggles from the helmet. The staples are used to place the magnets in the proper position and hold them temporarily in place while the epoxy cures.

Source: https://www.homedepot.com/p/MASTER-MAGNETICS-0-3-i...

Total cost: $20-30 for the whole operation.

Step 3: Position Goggles

Start with a "dry" fit: Put on the helmet and figure out where exactly you want the goggles to be placed. Do you wear regular glasses underneath? Make sure to leave enough room between goggles and face. Also pay attention that the goggles won't hit your nose. When you look at pictures of aero helmets with "built-in" goggles, you will notice that they attach to the outside of the helmet. However, I found that this would place them too high for my taste and with too much of a gap between goggles and my face. So I decided to attach them underneath the brim of my helmet, as is shown in this instructable.

While positioning the goggles, I needed to push the two sides of the goggles slightly together to make the goggles match the curvature of my helmet. In that case, use some Scotch tape to pull the two ends together and allow for a stress-free gluing process.

Step 4: Insert Staples

Next step is to carefully insert the staples in the right spot into the foam of your helmet to hold the magnets in the right place. Start with snapping one of the rare-earth magnets onto each magnet clip of the goggle. Then snap a staple onto each magnet. Now position the goggles in the desired position onto your helmet, and carefully and in a straight fashion push the staples into the helmet's foam. You may need to use a pair of pliers to help with that. Finally, use a few more strips of Scotch tape to prevent the goggles from shifting during the first gluing step.

Step 5: Glue Magnets in Place

Gluing is a two step process:

With the goggles in place, use a small amount of epoxy to connect magnet with their respective staple, and connect each staple to the helmet. Take care to NOT glue the goggles to the magnets (that's would be another instructable, goggled for dummies ;-) The goal is that once the expoxy has cured, you can pull off the goggles for better access while magnets and staples remain precisely positioned.

With the goggles removed, mix a bit larger batch of epoxy and strengthen the connection between magnet, staple and helmet. Keep the magnet surfaces facing the goggles free of epoxy, or it will weaken the strength of the magnet closures. Don't put on too much epoxy at once, or it will run off or form noses. Depending on the viscosity of the epoxy, you may want to do this last step 2-3 times with building up a thin layer each time.

Step 6: Hit the Road

Once the epoxy of the final layer has cured, attach the goggles of your choice and hit the road.

Step 7: UPDATE: Experience Report

I have used my new, cool "aero" helmet on two long bike rides now and LOVE how the goggles perform.

They provide unobstructed view almost 180deg in all directions. When I'm in the drops I can keep my head lower and as a result have a lot less neck pain afterwards, and can go a teeny tiny bit faster, too :-)
It is virtually windstill behind the goggles, which is very nice for anybody who wears contact lenses on the bike.
It's very easy to remove and reattach the goggles while riding, e.g. to scratch your nose or wipe away some sweat. While in place, the 3/8" magnets are sufficiently strong to keep the goggles in place (in contrast to what you hear in reviews about some of the commercially available helmets).

I noticed one minor caveat, though: While riding in aero position, my helmet slightly shifts forward. For that position I had installed the goggles just a bit too close to my face and as a result the goggles slightly touch my nose. I used a Dremel to carefully increase the size of the nose cut-out by a bit and reinstalled the nose piece. Problem solved!