2026 Grand Design RV Lineage Series M 25TK Review
Grand Design RV has gone from not having a single motorized RV to being in the top five in sales. And there’s a big reason. They’ve stepped up with offerings like the 2026 Lineage Series M 25TK which showcase exceptional quality, innovation, and design at a price that’s very competitive.
The build materials and components in the Lineage Series M 25TK are generally best-in-class and impress. However, that does not mean that this model is for everyone. In particular, the bathroom layout might be polarizing for some buyers. But make not mistake: There’s a lot to like here.
So, let’s take a closer look at the 2026 Lineage Series M 25TK, and you can determine if it is the right model for you.
At a Glance: Lineage Series M 25TK
I rated the 2026 Lineage Series M 25TK a 8.3 out of 10. As mentioned, the build quality and materials on this RV are absolutely top-notch. But the realities of the design also create compromises that will be big pluses for some buyers and detractors for others. For example, the innovation employed in the bathroom is truly impressive, but it involves a unique integration with the kitchen. While some shoppers will delight in this new layout, for other buyers, a more traditional approach may be preferred.
2026 GRAND DESIGN LINEAGE SERIES M 25TK
- Exceptional build quality that rivals any Class C in the industry
- Excellent driving and safety features with the MB Sprinter 4500-Series chassis
- Solar package with lithium batteries, a 1,800-watt inverter, three 180-watt solar panels
- Untraditional bathroom layout may not be for some buyers
- Limited headroom in bedroom may be less than desired
- Big price tag that comes with all the superior build-quality features
- Couples who want a Class C to live comfortably and drive/park easily
- Road-tripping friends who want some ability to configure sleep space
Check the Specs
- Sleeping capacity: 4
- UVW: 10,915 pounds
- CCC: 1,210 pounds
- Exterior length: 25 feet 8 inches
- Exterior height: 11 feet 5 inches
- Exterior width: 7 feet 11 inches
- Fresh/Gray/Black: 36/30/35 gallons
- Propane: 88 pounds (20.3 gallons)
- Awning: 16 feet
- MSRP: $228,776
Features We Love
- Mercedes-Benz Sprinter 4500-series chassis (with greater cargo carrying capacity, better-than-stock shocks, and ride control)
- Built-in safety technologies, including anti-lock brakes, predictive braking, adaptive cruise control
- Fiberless rear cap
- Whole-house energy management system
- Solar package: 310 amp hours of lithium battery packs, 800-watt inverter, three 180-watt Merlin solar panels
- True Level tank sensors
- High-end plumbing fittings with 25 year warranty
- Dual-pane windows that open 90 degrees
- Superior build components
- Innovative bathroom design
- Versatile sleeping spaces and configurations
- Latches for passengers in theater seats
- Hidden safes in captains chair headrests
Benefits
- Top-notch build quality. The way the structure of the coach body itself is built from both a materials standpoint and also in terms of underlying structure this is an exceptionally well-constructed RV — there’s no caulk, seam tape, or trim pieces allowed in the plant. All these are commonly used for filling where pieces aren’t put together properly. The underlying structure is a stout steel cage. The exterior of these is fully painted rather than loaded with stickers. The roof on this is a fully laminated and vacuum-bonded structure. (I could go on.)
- Superior driving and safety features. By opting for the Mercedes-Benz Sprinter 4500-series chassis, Grand Design RV got more than a greater cargo carrying capacity. This model also comes with better-than-stock shocks, ride control, antilock brakes, predictive braking, adaptive cruise control, and a luxurious cockpit.
- Power possibilities. The power and energy management system can enable charging by solar, the on-board generator, the alternator, or shore power. This makes it possible to have power under virtually all circumstances.
- Plumbing you can actually count on. The plumbing in this RV features RDC fitting which are, essentially, Shark Bite fittings. They are of such high quality that they carry a 25 year warranty.
Challenges
- Limited headroom in bedroom. If you like a little more head space, the bedroom may leave something to be desired, even though it is not problematic.
- Untraditional bathroom layout. As we’ll talk about further, the bathroom layout integrates with kitchen. This could certainly be polarizing for some buyers who are looking for a more traditional bathroom setup.
- Big price tag. With an MSRP over $228K, this Class C motorhome may be out of the price range for some buyers.
Best For
- RV couples who want both living room and parking room. The most obvious use for this RV would be couples who want something that’s small enough to be nimble but large enough to travel extended periods of time.
- Road-tripping friend groups. This rig might also be well suited to friends who travel together with the twin bed design.
Key Areas We Evaluate for RV Buyers
Sleeping Space: 8/10
The beds in the back of the Lineage Series M 25TK can be looked at as two individual twin beds because … well … they are. There’s also a platform and cushion that can be dropped between the beds to now make this a single king-sized bed. Each of the beds has a power lift mechanism to raise the head of the bed for watching TV or reading. (Nice!)
The bed on the camp side is 80 inches by 36 inches, and the one on the road side is 74 inches by 36 inches. But with the center cushion, now you’re 74 inches by 80 inches, which is a big ole bed. The ability to transform means this might be a great RV for couples on some adventures and friends on others. There are windows on each side of this space and a high-performance vent fan overhead. So, you could have great air flow in here even without the A/C being turned on. (Great for off-grid camping.)
Bedroom Storage and Additional Sleep Space
On the camp side, the bottom of the bed flips up to reveal a clothes hanging rack that can raise up using a strut. This provides hanging storage that is not immediately apparent. There are drawers under the road-side bed.
Because you’re standing on components under the floor, the headroom in the bedroom is a bit snug. But in reality, it’s nothing that really makes a big difference. You can just step down onto the main deck if it is a challenge.
On the opposite end of the RV there’s a berth above the cockpit that can also provide additional sleeping space. You’ll find a large window here with a power shade over it. (That window has several “Easter eggs” — little details in the glass that can be fun to seek out.) There are also household and USB power outlets here as well as ducts from the A/C . The latter really help, so that when you close the curtain, you’re not shut off from being cooled. (This feature is especially welcome with the large front windshield.)
Bathroom: 8/10
The bathroom is truly different in the Lineage Series M 25TK in that there are multiple doors on a track. One of those can be used to encircle the toilet while leaving the hallway space between the toilet and sink. Then there’s another door on a track that goes almost all the way to the refrigerator. It blocks the hallway, but makes the bathroom much larger. The floor is a teak series of panels, which is the shower floor now. This makes the whole bathroom pretty spacious for a Class C.
With the teak flooring, there is a hand-held shower as well as a “rain” shower head. It’s a really unusual arrangement. (And, if you’re wondering: Yes, it is possible to reach into the fridge from the shower and grab a frosty beverage while also washing off the day’s activities.) The whole bathroom system in the Lineage Series M 25TK is truly unique, and it’s likely to be either a challenge or a highlight depending on one’s perspective.
Living Area: 8/10
As I’ll mention a bit more in the next section, the living area and the kitchen in the Lineage Series M 25TK are pretty integrated with one another. Seating across the floor from the kitchen consists of theater seats with cupholder table inserts. So, it’s good that the two captain’s chairs in the cockpit swivel around to face the interior. That way, you have seating for four. The theater seats do have lap belts, which means that they can be used during travel. And —another win — the slide room in this is rated to be functional even when closed. (There is also the option of having a sofa or even a dinette instead of the recliners, if you prefer.)
The Lineage Series M 25TK uses a smart control system that can operate lights, slides, fans, the awning, and almost everything else. It can even raise and lower the heads of the beds in the back. All the features on here have the ability to be controlled by a smart phone. This method can also be used to automatically start the on-board generator if the temperature inside the RV gets too hot. (A good thing if you have to leave a pet behind in a parking lot and want to be sure that they’re comfortable.)
Kitchen: 7/10
The floorplan of the Lineage Series M 25TK is really unusual in a lot of ways, but as mentioned earlier, one of those ways is how the kitchen and bathroom interact. The floor is raised here in front of the refrigerator with a teak floor. (This is where the space goes from being open space in front of the fridge to the RV’s shower.)
There is a main kitchen cabinet that holds the sink and a two-burner propane stove top along with a convection air fryer microwave. In that cabinet are also a couple of drawers and some storage beneath the sink. Overhead, there’s a TV and a cabinet with some more storage. There’s also a pull-out pantry that’s large enough for cans or other items.
Grand Design RV put a counter extension here that flips up by the entry door of the rig, and this counter extension becomes flush with the rest of the counter when flipped up. (Not typical and certainly a nice touch.) There’s also a glass washer in the kitchen sink.
Four-Season Capabilities: 8/10
I would surmise that the Lineage Series M 25TK is more of a coach to be used in situations where temps don’t stay below freezing. The freshwater tank is actually inside the body of the coach, but the gray and black tanks are not and are not within heated enclosures. So, you won’t want to camp where it stays really cold for extended periods of time.
Storage Space: 9/10
There is a large storage bay in the back of the Lineage Series M 25TK. That bay features a washable floor, but it also has click track that incorporates a movable set of standard rings which enable you to secure gear in the bay. Since this bay is big enough to even hold bicycles, these are particularly useful. Further, the bay also has heat ducts. So, you could put things back here that shouldn’t get too cold.
There are also several compartments in the basement of this RV that are molded plastic with drain plugs. That means, you could put wet things in here and have them drain — which is a plus.
Chassis/Suspension: 9/10
The vast majority of these Class C motorhomes based on the Mercedes-Benz Sprinter cutaway chassis are based on the 3500-series chassis. This one is based on the 4500-series chassis. What that means is that there is simply more cargo carrying capacity in the chassis, which translates into greater ability to carry your stuff. Many of these Sprinter-based Class C motorhomes are built so close to the gross vehicle weight rating that there’s little room for cargo. With the more capable 4500-series chassis this is less of an issue with about 1,200 pounds of cargo carrying capacity. Grand Design RV has upgraded the chassis with better-than-stock shocks and ride control.
Cockpit: 10/10
One of the most appealing things about the Mercedes-Benz platform is the driving environment. With the combination of safety technologies built into this rig including antilock brakes, predictive braking, adaptive cruise control, and all sorts of other safety technologies that are common in high-end passenger cars. Plus, the seats and driving position offer a good deal of adjustability and are very comfortable. This is a nice place to be on a long drive.
A surprise in the cockpit are little safes in the headrests of the front seats. This might be a great place to leave some important paperwork or even passports, and it’s likely that nobody will know that they’re there.
Off-Grid/Sustainability: 9/10
On board the Lineage Series M 25TK are 310 amp hours of lithium battery packs. This may be sufficient for many adventures, depending on those adventures. But there is also an 1,800-watt inverter which can run many household appliances that people commonly use.
The lithium batteries can be replenished with the three 180-watt Merlin solar panels, the alternator on the engine or a standard on-board generator as well as shore power.
Value: 8/10
Superior Build Quality Very Evident
There’s a lot of things that might seem hidden but will absolutely matter. For example, the company puts a diamond shield over much of the front of the rig to protect the paint. Mike Hums, the product manager for these motorized units, indicated that there is no caulk, seam tape trim pieces or allowed in the plant — all commonly used in the industry to fill where pieces aren’t put together properly.
The underlying structure is a steel “cage” like structure for strength. The exterior of these is fully painted (rather than loaded with stickers). The roof on this is a fully laminated and vacuum bonded structure. A detail that may seem small are the two door strikes on the entry door. This actually helps eliminate wind noise in the door as opposed to a single latch.
Lastly, all the plumbing fittings in this RV are from a company called RDC which owns Shark Bite. These are top-notch connectors for plumbing and the proof of that is that the plumbing in the RV carries a 25 year warranty. The solar panels, from Merlin, are considered the best in the business at the moment. In short this is one of the best built Class Cs on the market.
Quality Coupled with Cost
There are so many absolutely premium features on the Lineage Series M 25TK that the price seems quite fair. Over and over, I encountered components that were considered the highest quality available and the way these are built is truly unusual. As Hums said, there is no putty, trim pieces, caulk or other aspects of covering up mistakes on the production line. Instead, their goal is to just build these correctly. If that is what you are looking for, then the price is likely right, if it’s on the higher end of the market.
Closing Notes on the Lineage Series M 25TK
Often when I meet with RV decision makers, I wonder where their decisions are coming from. All too often it’s clearly not from time spent in campgrounds or on the road. Happily, that is not the case here. I am so impressed that Grand Design RV gave the team in charge of this the ability to make absolutely top-notch decisions about the product and the user’s experience.
The Lineage Series M 25TK is still an RV, and nothing’s perfect. But the focus and passion of the team — and the decisions they’ve made — make me think this is the best Class C I have come across in my years of looking at RVs. And that’s saying something. Alternatively, I understand that the unique way that the shower is configured isn’t going to float everybody’s boat. But I think that, should you be looking for a Class C motorhome, it would be a mistake not to consider these.
A Note on the RV Trader Review Process
RV Trader asked RV shoppers what was most important to them in their RV buying process. Potential buyers — like you — helped us to identify a list of six key areas that camping and travel enthusiasts always look at when they’re searching for the perfect RV: sleeping space, bathroom, living area, four-season capabilities, and storage space.
The RV Trader team then got to work providing you with honest and unbiased evaluations. If you’re wondering, that’s where I came in. As an RV expert and enthusiast, I provide an honest look at RVs from an RV industry insider perspective.
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