When it comes to bicycles there are an endless number of component incompatibilities. And anyone attempting to mount a new road-style flat mount disc brake caliper onto an older or less-road-focussed frame (or fork) with post mount tabs will have likely experienced such an issue. In most cases, the simplest answer is to mix mountain bike brake calipers with road levers, but there may be a better option.
Today, bicycle component manufacturer Wolf Tooth has announced an adapter, the sole purpose of which is to let you mount a flat mount brake caliper onto a post mount fork or frame. And it’s a welcomed product given that the latest road and gravel groupsets from Shimano, SRAM, and Campagnolo are only available with flat mount style calipers. This black anodised machined aluminium adapter is intended to be as simple as it sounds, but there are a few stipulations.
Firstly, the limited clearance available through mixing these two standards means the adapter requires you to add 20 mm to your rotor size. If the post mounts on your frame or fork are native to a 140 mm rotor, then using this adapter will require a 160 mm rotor. If your frame/fork was intended to be a direct fit for a 160 mm rotor, then you’ll need a 180 mm rotor with this adapter. And so on.
The other stipulation is that you need at least 13 mm of clearance beneath the height of the post mount tabs. Some frame and fork designs will clear this with ease, while others will see the adapter rendered unusable by bottoming out on the frame.
On paper, Wolf Tooth’s design doesn’t appear to add anything substantially new to the pre-existing and relatively unknown flat mount adapters from Canadian-based A.S.Solutions. And while Wolf Tooth just simply offers one adapter, the original creator builds on the idea with several more specific solutions that aim to keep your rotor size unchanged (frame clearance providing).
However, what Wolf Tooth does bring to the table is a more established distribution network that will hopefully mean this compatibility issue will stump fewer people. Wolf Tooth’s appropriately named “Post to Flat Mount Brake Adapter” retails for US$30, while A.S.Solutions have the original concept at CA$40.