Mongoose Mountain Bike On The Market In Portage, In The included wheels function slender, 18mm rims which are even narrower than what you might discover on a gravel bike today. For that purpose, it doesn’t make sense to run anything  wider than the two.25? tires specced regardless of what appears to be loads of body clearance. I just like the WTB Trail Boss tires so my recommendation is to simply maintain ’em.