2026 Forest River XLR Boost366BX

The XLR Boost 366BX leaves Forest River's factory at 13,074 lbs dry with 5,300 lbs of cargo capacity. Forest River publishes no GVWR for this line, so the loaded rating is not quoted on this page and is not computed from the other two figures. What the cargo number covers is defined by the factory: fresh water, gear, food, batteries and every dealer-installed accessory come out of it. Fresh water is 8.3 lb per gallon, so filling the 150-gallon fresh tank spends 1,245 lbs of the 5,300 lbs before anything else goes in.

Dry pin weight is 3,220 lbs, which is 25% of the dry weight. That figure lands on the truck's rear axle and comes straight off its payload rating - not its towing rating, which is the number most often quoted and the wrong one for this decision. Pin weight rises as the trailer is loaded, and a fifth wheel loaded toward its cargo capacity will put substantially more than 3,220 lbs over the bed. Read the payload figure on your own door sticker rather than a brochure maximum for the model.

Tank capacities are 150 gallons fresh, 114 grey and 40 black, 154 gallons of waste capacity against 150 gallons of supply. The ratio is what governs how long the trailer can sit off hookups: waste capacity exceeds fresh, so the fresh tank is the binding constraint and refilling extends the stay. Forest River publishes these three figures per floorplan, and they are the factory's numbers rather than a segment average.

Against the rest of the XLR Boost roster this is the 11th of 11 floorplans by dry weight, in a line that runs from 6,473 lbs to 13,074 lbs. It is the heaviest plan in the line, so the tow vehicle should be settled before the floorplan is. Comparing floorplans inside one line is more reliable than comparing across brands, because every figure here comes from the same factory channel on the same day.

A useful way to read these figures is to stop planning against the dry weight. Nobody tows a trailer at 13,074 lbs: that is the weight before water, batteries, propane, bedding, food, tools and anything the dealer bolted on. Load half the published cargo capacity and this plan is already near 15,724 lbs on the road. Because Forest River publishes no loaded rating for this line, the ceiling has to come from the trailer's own weight label rather than from this page, and the comparison you make against the tow vehicle should use the loaded figure.

Every number above was captured twice from Forest River and checked against itself before it was published. The line roster block and the individual floorplan page are two separate factory renderings of the same trailer, and this plan's 4 shared figures agree exactly on both. There is no published GVWR on this line, so the usual arithmetic check - dry plus cargo equals the rating - has nothing to test against here. Where a figure is missing from this page it is because Forest River does not publish it in this channel, not because it was hard to find - and the row says so rather than being quietly dropped.

Forest River publishes no floorplan description for this plan in the channel this page is built from - only the numeric specification block. Rather than describe a layout from the floorplan code, which would be a guess dressed as a fact, this page carries what the factory publishes and says where it stops. 366BX is a XLR Boost designation and this site does not decode it into a layout claim.

XLR Boost is the hardest of Forest River's toy-hauler rosters to read from the outside, for two reasons. It mixes classes: three published floorplans are XLR Boost travel trailers at 6,758 to 8,393 lb dry with 1,175 to 1,500 lb on the tongue, and three are XLR Boost or XLR Boost X fifth wheels at 9,094 to 13,074 lb dry with 2,090 to 3,220 lb on the pin. And Forest River publishes no GVWR for any of the eleven plans, so the loaded figure that determines whether a given truck can legally tow a given plan is not available from the factory in this channel. Cargo capacity is published, 2,507 to 5,300 lb, and dry weight is published, so what the roster tells you is what the trailer weighs empty and how much it will carry - not what it may weigh when full.

This floorplan carries its water comfortably. A full 150-gallon fresh tank is roughly 24% of the 5,300-pound cargo capacity, leaving the 366BX with a usable gear budget even when you tow full.

The published dry pin weight of 3,220 pounds is 25% of this floorplan’s 13,074-pound dry weight. Fifth-wheel pin weight rides in the bed of the truck, so it comes off payload rather than off tow rating — and it rises with the trailer as you load it, not in proportion to what you put over the axles.

Tank balance is generous here: 150 gallons of fresh against 114 grey and 40 black, so waste capacity keeps pace with supply and the fresh tank is the constraint that ends a dry stay.

Of the 6 XLR Boost floorplans profiled here, the 366BX carries the highest dry weight at 13,074 pounds. It is the top of the line by weight, which makes tow-vehicle capability the first thing to settle rather than the last.

Either side of it in the same line: XLR Boost 363BX is 1,010 pounds lighter at 12,064 lb dry.

Against the 366BX: the Bighorn 31RL is 14 lb lighter and 8 ft shorter; the Momentum 320G is 26 lb heavier and 7 ft shorter; the Sandstorm 3217GX is 50 lb heavier and 5 ft shorter. Those are differences in the published numbers only — what they cost, how they are built and how they live are separate questions each of those pages answers on its own terms.

Those are the nearest fifth wheels from other lines by weight — one per line, picked by proximity on that figure and nothing else. They are listed so the same tow vehicle can be checked against real alternatives, not because they are equivalent inside; layout, build and price diverge sharply across that group.

For scale, the XLR Boost floorplans profiled here run 6,758 to 13,074 pounds dry and 28 to 44 feet of exterior length across 6 plans. Where a floorplan falls in that spread usually says more about which vehicle can tow it, and which site it fits, than the layout name does.

Every profiled floorplan in this line, with the full weight table, is on the XLR Boost line hub.

This catalog tracks 18 specification fields per floorplan. Named sources publish 10 of them for the 366BX. The rest are not shown, because the alternative is reading a figure across from a sibling floorplan or from what the segment usually does — and a number nobody published is worth less than an admitted gap.

Not published for this floorplan: GVWR, interior height, sleeps, slide count, axle count, tire specification, refrigerator, air conditioning. If you find one of these in a manufacturer document for this plan, it belongs on this page.

The completeness figure at the foot of this page (83%) measures the same thing on the full field set: it is a measurement of how much this floorplan’s manufacturer publishes, not of how much research went into the page.

How every figure here was sourced and checked is set out on the methodology page.