Glen Tromie is a beautiful glen that I thoroughly enjoyed cycling through during my Cairngorms bikepacking trip. The lower part of Glen Tromie is on a hard-packed gravel road that's easy to ride with most bikes. A gravel bike is the ideal choice there, but keep in mind that the paths higher up in the glen deteriorate quickly, and a mountain bike might be a better choice. The singletrack near the pass isn't always rideable, and you'll also have to cycle or hike through rivers several times. Nevertheless, the scenery here is beautiful, and the views over the various lochs make this glen well worth a visit.