Downtube Gravel Bike Shield

Albert Wavering December 3, 2020

The gravel bike shield is a frame-mounted, laser-cut shield to protect your gravel bike downtube and bottom bracket from dirt and rocks kicked up by your front wheel.

March 2023 Update: I've re-built the gravel shield with laser-cut plywood for a more precise fit and greater durability. Read on below!

2023 Version 2.0

I redesigned my prototype for better protection and durability. Laser-cut at BLDG61 out of 1/8" plywood, it features 2.5" more downtube coverage. A slight taper towards the top of the guard keeps it narrow and reduces the chance of catching it with your foot.

Detail view of the bosses and bottom bracket.

After cutting, I sanded the guard with medium sandpaper and covered it in mineral oil for a simple weatherproofing barrier. Varnish or primer/spraypaint/topcoat should also work well but would require a bit more work.

If you'd like to build a guard for your own bike, grab my Illustrator file below!

Get the file on Thingiverse.

Compatible Bikes

The gravel shield is compatible with any bike that has mounts on the bottom of the downtube. This definitely includes the Cannondale Topstone, and probably includes the following bikes:

Cannondale Synapse
Specialized Crux/Diverge
Canyon Grizl
Most Surlies
Niner RLT/MCR
Salsa Cutthroat/Journeyman/Marrakesh/Stormchaser/Vaya/Warbird/Warroad
Ibis Hakka
Ritchey Outback/Break-away/Ascent

You may need to change the mounting hole spacing or shield width to work with your bike; let me know if you've added a gravel shield to your bike!

2022 Prototype

I built a custom purple direct-mount downtube gravel shield to protect my Cannondale Topstone downtube from errant gravel bits kicked up by my front tire. The shield is made out of a cardboard core which I spray-painted purple and then covered with packing tape; it mounts to the Cannondale's downtube direct-mount bosses. The shield measures about 2.5" x 9" and provides good protection for my bottom bracket and lower downtube without getting in the way of pedaling or maneuvering.

Prototype Build Photos

Cut out a rough shape based on my tube width and the vertical coverage I wanted.

I got pretty even coverage but there were still some irregularities.

Laminated the shield for protection and longevity.

Mounted on the down-tube bosses of my Cannondale Topstone.

Prototype Performance Update

After a few years on my bike (~2,000 miles of mixed pavement, trail, and gravel riding), the prototype is pretty beat up but has done a great job of protecting my downtube and bottom bracket.

There is one scratch on the downtube above the range of the guard.