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Would a 645 M be suitable for an avid mountain biker?

Former Member
Former Member

Hey all, 

I'm about to order my first wearable from Garmin and was hoping to get some advice as I'm leaning towards the 645 M for a few reasons. The watch seems like a great mid-level wearable that has had mostly positive reviews over the years, but I wanted less review-y style opinions on this before I jump the gun. I'm really active and would use the watch daily to help track my daily mountain bike rides that are around eight miles each as well as the time I spend in the gym. I also hike quite a bit and snowboard in the winter. I'm much less of a runner although I do run a mile or so just to warm up in the gym. I do have some features that I would consider a priority:

  1. Seamless integration with Strava
  2. Accurate tracking for my daily rides
  3. Decent metrics so I can see improvements over time
  4. As an engineer, I'm big into data so I like to be able to see these things when I sit down and look for areas that need improvement

I also want a watch I can wear to work and I really like the design of the 645 and I would invest in some nicer bands for the office. I feel like the Fenix series may be better suited for me, but is it worth the extra investment? 

Thanks for any and all responses! 

Top Replies

  • Former Member
    Former Member over 6 years ago in reply to Luca +1
    rather inconvenient to look at the road and the data fields on my wrist,

    I wear a chest strap (WHR pretty much worthless while cycling), a handlebar mount for my watch and the data fields set…

All Replies

  • Absolutely YES. I mostly use my fr645 for mtbikng and except not calculating VO2 Max on bike rides you can have all the data you want. You can also load Strava or Connect segments and see in real time your position. 

    I sometimes for use it for navigating routes as well and it works almost flawlessly.

  • I practice bodybulding, running and road bikes, with the 645 track everything but by bike it is rather inconvenient to look at the road and the data fields on my wrist, in the end I bought an edge 130, cheap but does everything you need, on the 645 you only have 4 data fields per screen, on edge 8 and navigation is much clearer, on the data page you will see popup changes of direction

  • I own a FR645 no music and use it for mountain biking from time to time. GPS and altimeter data is good enough for me. But to get reliable heart rate data I wear a heart rate chest strap. It is known that optical HR sensors of watches become inaccurate when heart rate goes quickly up and down, which might be the case with mountain biking. You will also get Training effect and Training load data, but no VO2 max (needs a power meter pedal). Until you run outside at least once a week you will not get Training status data.

  • Former Member
    0 Former Member over 6 years ago in reply to Luca
    rather inconvenient to look at the road and the data fields on my wrist,

    I wear a chest strap (WHR pretty much worthless while cycling), a handlebar mount for my watch and the data fields set to auto scroll. No problems and much safer than trying to look at a watch on the wrist. 

  • I mount the watch and pair an HRM-RUN and Garmin's speed and cadence sensors. The speed sensor may be more accurate than GPS if you don't have a clear view of the sky, like under tree cover or a roof. I ride just to cross train, so I only have one screen with heart rate zone and cadence, but I like the scrolling idea. Garmin has an official mount, and Amazon has cheaper alternatives.

    The downside to the 645 for cycling is it can't be paired with a power meter, if that matters to you. For that you need a 945, Fenix, or Edge.

  • I use my 645 for road cycling and pair it with HRM-Run for HR. I am not one of these cyclists who feels the need to use power meters or follow routes whilst riding so a watch works fine for me. I actually find the altimeter to be more reliable for cycling than running for some reason. Maybe because it's less likely to get covered in sweat when I'm riding my bike?