Using a bell while riding crowded trails or busy multi-use paths is always a good idea. Alerting other users early in advance can minimize trail conflict, so MTB groups have taken to recommending the use of cowbells over commuter style bells, as it can be difficult to activate a bell when riding over technical terrain at speed. (ie, real mountain biking)

The Timber! Mountain Bike Bell.
Cowbells do a great job alerting other users and keeping the general vibe positive, the constant dinging can be annoying. We haven’t been alone in thinking, “if only there was a bell you can silence for climbs and when you didn’t need it.”
The folks at Timber felt the same way, and developed the Timber! Mountain Bike Bell as a solution. Small, durable and relatively inexpensive, the design of the Timber! MTB Bell was inspired by the classic cow bell, but includes an on/off lever so you can silence it when it isn’t needed. The lever offers a few levels of adjustment so you can set it to ding more or less for a customized sound.

The actuation lever has a good size pad and was easy to actuate, even on rough trail.
Like a cow bell, the motion of the bike activates the bell, and we found that in use, it was simple to flip it on at the top of descents, or even while riding when spotting another trail user up ahead.
Adding the Timber! bell to your bar is easily accomplished with the included o-rings, and it fits all handlebar diameters from 22mm to 35mm. It’s also easy to quickly change it between bikes, and we found it works just as well for commuting as it did on single track. Note: it is a movement actuated bell, so an action like a front wheel lift, is necessary if you want a bigger sound.
Replacement o-rings are also available for $1.00 (for a 2 pack) should you lose or break one.
Most of the animosity we’ve experienced on the trail is due to surprising or shocking other users on foot. Startled hikers can quickly turn to resentful hikers, so anything we can due to make sharing the trails a more pleasant experience is helpful for all of us. Our first experience riding with bells was in Santa Barbara; the local trails are so busy on the weekends that the local bike club set up bell boxes with caches of mini-cow bells. The program has received a lot of positive feedback from various user groups, as the bells can be heard on descending riders early in advance.
This bell is a big upgrade from those cow bells.
Timber also makes a really good point we hadn’t initially considered; having a bell can be beneficial when riding backcountry trails where bears or mountain lions reside… better safe than sorry.
The Timber weighs in at 69 grams, and will set you back $20.00; we recommend ordering a few for the crew to save on shipping. Timber! supports trail advocacy, and even offers bulk pricing for non-profit groups.
A bolt-on option is now available as well as the quick release model. Check out the Timber Mountain Bike Bell at MTBBell.com
Order one at Amazon.com