Beginner who runs 2–3 times/week : Take 55, point. For what ? Autonomy which removes the mental load, suggestions of sessions, better security. The 45, only If found at very low reconditioned prices and you want the bare minimum.
Runner 10 km / semi : The 55 keeps the look and the load more consistent over 6–10 weeks. The track mode avoids the GPS traces Bancals (which flinch morale). To dig the screen/Race use subject, reread our comparison on Garmin race screens and profiles (anchor: Screen deviations and useful running profiles).
Runner + swimming pool : 55, without hesitation, for the "Pool Swim" profile with cardio wrist underwater. Please note: the swimming optics remain sensitive to tightening the bracelet and the technique (in short, tighten it with a notch).
Tight budget : if a 45 appears at broken prices, why not ... But the 55 is new around € 125–160 in France. It kills the debate.
| Criteria | Forerunner 45 | Forerunner 55 |
|---|---|---|
| Watch / GPS autonomy | ~ 7 days / ~ 1 p.m. | ~ 14 days / ~ 8 p.m. |
| Track / hit profile | No / no | Yes yes |
| Allure guidance (pacepto) | No | Yes (basic, efficient) |
| Swimming pool swimming | Basic (without useful cardio) | Yes + optical cardio underwater |
| Weight / Size | 36 g / 42 × 42 × 11.4 mm | 37 g / 42 × 42 × 11.6 mm |
| Screen | MIP 1.04 ″ (208 × 208) | MIP 1.04 ″ (208 × 208) |
Sources: Garmin technical and manual sheets, supplier recap.
Protocol : Route 10 km outputs (5'15–5'30/km), 6 × 400 m series (recycled 200 m), easy trail 12 km, and 2 1500 m pool sessions. Tests initially carried out in 2021–2022, re-tenified in October 2025 via reader loans (current software updates). Simple method: comparison with HRM belt, GPS gap on track tours, swimming distance validation.
Observation : continuously, the two sensors hold the road; In fractional, the 55 catches a bit faster the peaks. In the pool, the 55 gives an exploitable curve (not at the BPM nearest). If you play the precision card, HR Ant+ belt recommended. (That is obvious.) For the Party Race VS Supper Models, we refer to Forerunner 9XX families for advanced use - see key differences between Forerunner 945, 955 and 965 (anchor: anchor: anchor: anchor: anchor: anchor: Compared advanced training tools).
Note: DC Rainmaker already pointed out at the exit of the 55 an optical sensor "OK" in endurance, less good in short (classic) sprints. Nothing dramatic, just the reality of optics.
The 45 : old model, officially listed as "discontinuous" according to the region. It is found at the end of the stock, sometimes reconditioned. To be checked: battery condition, after -sales service, version (45 vs 45s). This is a false good idea if the price difference is low.
The 55 : new in France between ~ € 125 and € 160 according to colors and promotions. For this ticket, autonomy + swimming + guided sessions ... it's unbeatable. Briefgo for a reliable offer (invoice, warranty). For more sophisticated racing uses (sorting, carto, dual-band), see higher-end-and compare with our analyzes type evolution of 9xx series endurance (anchor: anchor: anchor: anchor: anchor: anchor: anchor: anchor: anchor: anchor: anchor: anchor: anchor: anchor: anchor: anchor: anchor: anchor: anchor Evolution of 9XX series endurance side).
Experience : watches tested in real use (road race, track, light trail, swimming pool), first series in 2021/2022, rereading and updates in October 2025 On recent firmware.
Authority : Signed article, transparent protocol, cross -comparisons with recognized references from the sector.
Reliability : specifications verified via Garmin manuals (autonomy, waterproofing, profiles), detailing technical sheet "Underwater Wrist-Based Heart Rate", and price of France (Idealo). Refs: Forerunner 45/55 manuals (Autonomy, 5 ATM), FR55 sheet (dimensions, HR underwater), Dcrainmaker (accuracy trends), “discontinued” page FR45, Idealo (price FR).
Do you want a simple, enduring racing companion, who helps you structure your weeks? Take the 55. The 45 held the road… yesterday. Today, the gap in autonomy and functions is too large. And the price of the 55, honestly, kills the suspense.
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