We took a similar bike tour several years ago but, with a different operator and with a much better overall experience.
While Bike Maui's equipment was in good condition (bikes & brakes and helmets), the actual guided tour experience was just average. The van driver spent more time talking about himself and telling stories about bike accidents and car accidents on the road we would be traveling than he did about the volcano, area details, etc. He raised the level of nervousness of several of the inexperienced bike riders with his diatribe. The actual downhill bike ride seemed to be focused on getting to the end quickly moreso than stopping to enjoy the scenery, taking pictures, talking about the local history, etc.
One benefit of the guided tour was having the van travel behind the group that tended to block the traffic for a safer rider. If I returned again I would do the self-guided tour so I could travel at my own pace.