Handlebar size
Flat stems, aero and non-round bars: which mounts list them
Quad Lock's separate Flat Bar Adaptor, SP Connect's included flat adapter, Wahoo's round-bar out-front mount, and why 'most tubes' is not a fit promise.
Also listed as aero bar, flat stem, non-round bar
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Short answer
A diameter only describes a round tube, so for a flat stem or aero bar look for a mount whose maker names that shape. Quad Lock sells a Flat Bar Adaptor separately for flat stems, and SP Connect includes a flat adapter with its Universal Bike Mount. Wahoo's BOLT 3 / ROAM 3 out-front mount is for round 31.8 mm bars. See how to measure your handlebar.
Key facts
- How to check yours
- A diameter applies only to a round tube. On a flat stem or aero bar, check that the mount's maker names that shape, such as Quad Lock's Flat Bar Adaptor for flat stems, rather than going by a millimeter range.[1]
- Mounts whose maker range includes it
- Quad Lock sells a Flat Bar Adaptor separately for mounting its Handlebar/Stem Mount on flat stems. SP Connect includes one flat and one round adapter with its Universal Bike Mount.[1][2]
- Mounts that do not list it
- Wahoo's BOLT 3 / ROAM 3 out-front mount is for 31.8 mm round bars.[3]
- Shims, straps and adapters
- Quad Lock says the zip ties supplied with its Handlebar/Stem Mount can fit most tubes outside its 25-40 mm range.[1]'Most tubes' is Quad Lock's wording, not a guarantee for any bar shape.
- Devices and lights
- Quad Lock says its Handlebar/Stem Mount works with all Quad Lock cases and Universal Adaptors. Peak Design's Out Front Bike Mount V2 holds the phone with its SlimLink magnetic and mechanical system.[1][4]
- Not confirmed
- No source we read gives aero-bar shapes or dimensions for any mount, and Peak Design's bar range for the Out Front Bike Mount V2 is not stated on its page.[4]
Watch out for
- Quad Lock's Flat Bar Adaptor is sold separately, not in the Handlebar/Stem Mount box.
- Quad Lock's 'most tubes' zip-tie wording is not a guarantee for a flat or aero shape.
- Wahoo's out-front mount is made for round 31.8 mm bars only.
- We give no drilling or improvised-mount advice; use a mount whose maker names your shape.
What fits
Product details below are the seller's own description unless a source is shown. Pick the variant named for each item.
Phone mount with flat adapter
SP Connect Universal Bike Mount (phone, 20‑44 mm bars and stems)Choose the Universal Bike Mount (SKU 53342).
SP Connect includes one flat and one round adapter and lists bars or stems of about 20-44 mm.
Next: bike phone mounts and their fit and Garmin vs Wahoo computer mounts.
Questions
Will a Quad Lock mount fit a flat stem?
Quad Lock sells a Flat Bar Adaptor separately for mounting its Handlebar/Stem Mount on flat stems.[1]
Will Quad Lock's zip ties hold the mount on my aero bar?
Quad Lock says its zip ties can fit most tubes outside 25-40 mm. That is not a promise for any specific shape, so check with Quad Lock for yours.[1]