Gravity vs Mongoose vs Diamondback: Best Budget MTB? (2026)

Gravity, Mongoose and Diamondback all show up when you search for a cheap mountain bike, and all three sell 29er hardtails for well under $800. They get there in very different ways. Gravity is sold only online by BikesDirect, Mongoose is a Pacific Cycle brand you will find on mongoose.com and in big-box stores, and Diamondback is a long-running bike shop brand that also sells direct on diamondback.com.

One thing to clear up first: Gravity in this guide is the brand, not the riding style. If you are shopping for long-travel gravity-style downhill and enduro bikes, that is a different (and much more expensive) category.

Below we compare the 2026 budget lineups of all three brands on frames and sizing, gearing, brakes, forks and tires, price and the buying experience, then pick the best model for each type of rider. Prices and specs were checked on bikesdirect.com, mongoose.com and diamondback.com in November 2026.

At a Glance

Gravity vs Mongoose vs Diamondback Compared

Prices and specs from bikesdirect.com, mongoose.com and diamondback.com (November 2026). Gravity shows high “compare at” list prices next to its sale prices, so judge it by the price you actually pay. All three brands change prices often, so check before you buy.

Brands

Who Makes Them and Where You Buy Them

Gravity is the in-house mountain bike brand of BikesDirect. You can only buy it on bikesdirect.com, and it ships to your door in a box. That direct model is why the prices look so low, and BikesDirect says most bikes arrive up to 90% assembled, with free shipping to the lower 48 states and a 30-day money-back guarantee.

Mongoose belongs to Pacific Cycle, the same company that owns Schwinn. Its mountain bikes run from the $199.99 Inertia to the $1,299.99 Salvo 1, and you can buy them on mongoose.com or at big retailers. If you are also looking at Schwinn, our Mongoose vs Schwinn comparison covers that matchup in detail.

Also looking at department-store bikes? Our Schwinn vs Huffy comparison covers the two brands you see most at Walmart and Target.

Diamondback sells through bike shops and on diamondback.com. Its current budget mountain bikes are the Hatch 2 ($675) and Hatch 3 ($775); above those it jumps to Release and Yowie trail bikes from $2,850. When we checked in November 2026, every mountain bike on diamondback.com was marked sold out, so you may need a dealer or a used bike to get one.

Frame and Fit

Frames, Sizing and Fit

All three brands use aluminum frames on these bikes. Gravity’s HD Trail 29 has a 6061 hydroformed frame with a replaceable derailleur hanger and comes in six sizes, from 13 to 23 inches. Its geometry is old-school cross-country: a steep 71-degree head angle and 440mm chainstays. That feels quick on smooth trails but less stable on steep, rough descents.

Diamondback has the most thoughtful sizing. The Hatch uses “Progressive Wheel Sizing”: XS and S frames get 27.5-inch wheels, while M, L and XL get 29-inch wheels. Shorter riders get a bike that fits instead of a 29er that feels too tall. The Hatch also has rack, fender and bottle mounts, so it doubles as a commuter.

Mongoose is the weak spot here. The $399.99 Grafton 29 comes in a single 18-inch frame, and the Switchback Expert was listed in L and XL only on mongoose.com when we checked. If you are under about 5 ft 6 in, check the size chart carefully before you order a Mongoose.

Drivetrain

Drivetrain and Gearing

At around $400, both the Gravity HD Trail 29 and the Mongoose Grafton 29 use 21-speed (3×7) Shimano Tourney-level gearing. It works, but three chainrings and a 7-speed cluster mean more shifting and more adjustments than a modern single-ring setup.

Spend a bit more and Gravity pulls ahead. The $599 HD29 1by uses Shimano CUES 1×9 with an 11-46 cassette and a narrow chain, the newest drivetrain in this group. Mongoose’s $699.99 Switchback Expert uses Microshift Acolyte 1×8, which is simple and reliable but has one gear fewer.

Diamondback stays with 3×7 on both Hatch models. The Hatch 2 uses a 14-28 freewheel, while the Hatch 3 upgrades to a 12-32 cassette and a Shimano Tourney TX800 rear derailleur. Both have plenty of low gears for climbing, but they feel dated next to a 1x setup at the same price.

Brakes

Brakes: Where the Money Goes

Brakes are the biggest difference between these brands. Gravity puts Tektro M285 hydraulic disc brakes with 160mm rotors on the $399 HD Trail 29. That is rare at this price: Mongoose’s $399.99 Grafton 29 uses mechanical disc brakes, and Mongoose only gets to hydraulic discs at $699.99 with the Switchback Expert’s JAK Y2 brakes.

Diamondback uses hydraulic discs on both Hatch bikes: Radius hydraulic brakes on the Hatch 2 and Tektro M275 hydraulic brakes on the Hatch 3. Hydraulic brakes need less hand force and keep working well on long descents, which matters most for lighter or newer riders.

The cheapest bikes, the Gravity Basecamp V7 ($249) and the Mongoose Flatrock 26 ($324.99), use V-brakes (rim brakes). They are fine for paths and easy dirt roads, but they lose power in the wet and wear out your rims over time.

Suspension and Tires

Forks, Full Suspension and Tires

Diamondback and Mongoose both list their forks clearly: the Hatch 2 and the Switchback Expert use an SR Suntour XCE-28 with 100mm of travel, and the Hatch 3 upgrades to an XCM-DS with 100mm. The Mongoose Grafton gets a basic 70mm fork. Gravity only describes the HD Trail fork as a preload-adjustable “advanced 29er suspension fork” without listing travel; the HD29 1by adds a lockout.

For full suspension, Gravity’s FSX V costs just $349, but it rolls on 26-inch wheels with V-brakes and 3×7 gearing. Mongoose’s Impasse 2.0 Dual is $699.99. Diamondback’s full-suspension Release bikes start at $2,850, well outside a budget. At these prices, a good hardtail usually rides better than a cheap full-suspension bike, which adds weight and has simpler shocks.

Tires are similar across the board: 2.25-inch knobbies on all the main models (CST Trail Fiend on the Gravity HD29 1by, WTB Trail Boss on the Switchback Expert and Vee Tire Rail Escape on the Hatch). Gravity lists a weight of about 30 pounds for its hardtails; Mongoose and Diamondback do not list weights for these models.

Price and Value

Price, Value and the Buying Experience

On paper, Gravity wins on value: hydraulic brakes at $399 and a 1×9 CUES drivetrain at $599 are hard to beat. Ignore the “compare at” prices on BikesDirect, though; the real comparison is the sale price against what Mongoose and Diamondback charge.

The trade-off is the buying experience. A Gravity bike arrives in a box, and you have to finish the assembly yourself or pay a shop to do it. Budget for a shop check if you are not confident adjusting brakes and gears, and learn how to tune and maintain a mountain bike once it is on the road. Mongoose bikes from big-box stores are often assembled in-store, and the quality of that assembly varies, so check the brakes, gears and bolts before your first ride.

Diamondback is the easiest to own if you can find one: dealer support, five sizes and hydraulic brakes. But at $675–$775 it costs more than Gravity for similar 3×7 parts, and stock was gone online when we checked. If you can stretch to around $1,000, a bike-shop hardtail like the Marlin or Rockhopper gives you a big jump in fork and drivetrain quality.

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The Verdict

Pros and Cons

Here’s how our top pick from each brand stacks up.

Gravity HD Trail 29

Mongoose Switchback Expert 29

Diamondback Hatch 2

Our Pick

Which Should You Buy?

All three brands make decent first mountain bikes, but each one suits a different buyer. Here is our pick by rider type.

Tight Budgets That Want Hydraulic Brakes

Get the Gravity HD Trail 29 ($399). No other bike here gives you hydraulic disc brakes and six frame sizes for this price. Be ready to finish the assembly yourself, or add the cost of a shop tune.

Beginner Trail Riders

Get the Mongoose Switchback Expert 29 ($699.99). Its 1×8 drivetrain, 100mm fork and hydraulic brakes make it the most trail-ready bike you can easily buy in stock today. If you want the newest gearing for less, the Gravity HD29 1by ($599) with Shimano CUES 1×9 is the alternative.

Shorter or Taller Riders

Get the Diamondback Hatch 2 ($675) if you can find one. The 27.5-inch wheels on XS and S frames and 29-inch wheels on M to XL give it the best fit range in this group. If it is still sold out, the Gravity HD Trail 29 is the next best option thanks to its six sizes.

Commuting, Bike Paths and Light Trails

Get the Diamondback Hatch or the Gravity HD Trail 29. The Hatch has rack and fender mounts, and both are comfortable on pavement and bike paths. Pump the tires a little firmer for road riding.

Snow and Sand

None of these hardtails is built for deep snow or sand. Mongoose sells fat bikes for that; see our Mongoose Dolomite vs Malus fat bike comparison.