Diamondback Bicycles El Oso Grande Fat Mountain Bike Review

Diamondback Bicycles El Oso Grande Fat Mountain Bike


Diamondback Bicycles El Oso Grande Fat Mountain Bike

The Diamondback El Oso range of ‘fat’ mountain bikes are aimed at all those looking for an affordable entry into the world of fat tire riding on a quality machine.

Fat biking has taken off over the past few years. It has evolved from a niche sporting pastime for off-road riding on snow and sand trails to something a lot more mainstream.

Nowadays you see fat bikes everywhere.

What’s the reason for this rise in popularity? In a word –  FUN!

Never far behind the trend, Diamondback has burst onto the fat bike scene with their El Oso range. I’m going to review here their mid-range bike, the Diamondback Bicycles El Oso Grande, which translates as “The Big Bear.”

The El Oso Grande certainly lives up to its name.

This bike is pretty much the go anywhere, ride with a grin on your face, kind of rig that many people are turning to as their all-year-round mountain bike of choice.

But they don’t stop there. You can also use this versatile machine for riding on the road, family bike trails and pretty much everywhere else.

It’s all down to those large tires and how much air you put in them. Creating a large contact area with the ground increases your traction, and with big tires, you get a lot of traction! Decrease the air pressure in the tire, and you can ride over sand, mud, snow or any other usually impassable surface. More on that later.

This big bear is built around a rigid frame of custom-butted aluminum with a formed top and down tube plus a 1.5-inch tapered head tube. This allows for a strong but lightweight frame.  Diamondback has shaved a few pounds of weight here by letting the fat tires provide the damping.  It will never be as good as the full suspension but works surprisingly well.  The frame is built to allow a large clearance at the back so that it can fit the 26 x 4.9-inch tire on a 197mm thru axle.

At the front, there is a custom rigid alloy fork with 1.5-inch taper and a 150mm x 15mm thru axle.  This complements the rigid frame providing plenty of strength and rigidity.  Rigid enough to climb over most things, with the fat 26 x 4.9-inch front tire providing the cushioning.

The SRAM X5 groupset provides the drivetrain on this model.  Not the best on the market it has to be said, but neither is it the worst.  For a bike aimed at introducing customers to the world of fat biking, these components are probably pitched at about the right level.  They will be fine if you are taking your bike off-road on a semi-regular basis and will see you through until you want to upgrade.

Gearing wise the El Oso Grande Fat has an FSA Comet Mega Exo 36/32T crank paired with a Shimano HG50 10spd cassette. 2 chainrings on the crankset and ten gears on the cassette gives you 20 possible speeds.

In practice, this is all really well suited to the bike allowing you to pick up speed on flat terrain quite quickly.  It also provides plenty of gearing to get up all but the steepest ascents.

The job of slowing you down is handled by a set of TRP Spyre 160mm discs with mechanical braking.  These offer plenty of stopping power but with great feedback allowing you to apply just the right amount of pressure, so no complaints there.

The medium sized model weighs in at 34lbs 13oz so it’s on the heavy side of average, but not overly so.  When you consider the advantages of riding a fatty over a normal mountain bike, it’s a pretty good trade-off.

The El Oso comes equipped with alloy pedals with molded traction pins and a Race M-series saddle complete with chrome rails.  Many will not have a problem with these, but they can easily be swapped out if you prefer something different.

And finally, we come to the all-important rolling stock.  Diamondback has chosen to equip the bike with standard 26-inch wheels that come with 95wide single wall rims with a 55mm cutout.  These roll on a set of alloy sealed cartridge bearings and come with two gigantic 26 x 4.9-inch tires. Some serious rubber there.

What is the Frame Material?

Taking a closer look at the heart of the El Oso Grande, as we know, the frame is made from custom butted aluminum with hydroformed tubes. Surprisingly for such a big beast this gives the bike an amazingly nimble ride.

Keeping things rigid means Diamondback have kept the weight down as much as possible.  A good idea as those big wheels and tires add quite a bit.

The frame is not as light of course as something like carbon fiber or titanium.  But that’s not everything.  The aluminum frame offers an exceptional strength-to-weight ratio. That’s important for this sort of bike.

Just to cap things off, the finish on the frame is beautifully crafted and looks stunning.  Get ready to soak up those admiring glances!

Which is the best size?

As with most things in life, many people will tend to go for the medium size frame whatever the size guide tells us!

But if you want to make an informed decision, let’s take a look at the actual dimensions.

The small size (S/16”) has a stand over height of 31 inches. The seat tube measures 15.7 inches and head tube length is 4.3 inches. The top tube is 22.8 inches long.

If you go for the medium (M/18”) you will find it has a stand over height of 31.7 inches and a seat tube length of 18 inches. The head tube on this model measures 4.7 inches, and it has a top tube length of 24 inches.

Finally, the large (L/20”) size.  The stand over height measures up at 32.3 inches.  Seat tube length is 19.7 inches, and the head tube is 4.7 inches long.  The top tube on the large model measures 24.8 inches long.

Note these are the manufacturers quoted sizes and measurements.

What is the difference in the ride between the 5-inch tires and the 4-inch tires?

The Diamondback El Oso Grande comes with 4.9-inch tires, so we’ll call them 5-inch for the sake of argument. Those are some monstrous tires so you may be wondering what the difference is between these and something smaller, say a 4-inch version.

The answer really depends on who you ask!  Some people will claim there is little difference; others will say it makes a huge difference.

The reality probably lies somewhere in between but trending towards the big difference end depending on what surface you are riding on.

If we look at the sheer mechanics of the tires, obviously 5 inches is larger than 4.  We already know that these fat tire bikes are great to ride on all sorts of terrain because of the phenomenal grip they give you.

That traction is as a direct result of the amount of rubber meeting the road (or snow, mud, etc.) and with the 5-inch tires, there is going to be a bigger contact area than the 4 inch.  Let’s not forget the fact that you will be deflating these tires to an insane pressure.  We’re talking 2-4psi here when on those really tricky surfaces.  The amount of rubber you will be putting down then is even better.

The result – more traction and a better experience.  Many people who move up to the 5-inch tires never want to go back.

When using them back on the road for the ride to work then just put more air in them. The difference in rolling resistance between a 4 and a 5 inch will be hardly noticeable.

Does the 5-inch tire ride better on trails?

So, on mud, snow, sand, etc. the 5 inch will perform better.  On the road, there should be little difference if you get the tire pressure right.

But what about the middle ground, the regular bike trails you ride on during the summer months?

How well does a fat 5-inch tire perform on that type of terrain?

There’s no doubt you may find these harder work than skinnier tires as there is a bit more rolling resistance and of course some extra weight. But if you get that all important tire pressure right then you will find the extra grip balances out any noticeable difference.

Some riders find the fat tire bikes don’t handle as well through quick turns and corners.  Others have no problem, but it does seem to depend on the bike and how you handle it.

That’s pretty much the only issue you might come across when riding the 5-inch tire El Oso Grande on trails.

Why the Diamondback El Oso Grande Fat Mountain Bike?

So, we’ve taken a closer look at some of the specs and swooned over how good those fat 5-inch tires really are.  You might now be asking what else makes ‘The Big Bear’ the fat mountain bike you should go for?

Well for starters, it’s truly a well-built machine.  Although some components you could describe as entry level, they are still robust enough to see you through most things you can throw at it.

Those components are also how Diamondback have managed to push out a great bike at a decent price point.

I like the rigid frame and forks; they work well together, and the huge fat tires soak up all the bumps. You really only miss the suspension on the bumpiest and hardest terrain.

Yes, you could probably find other bikes with a few better components. But as an overall package, the Diamondback represents the best value combination of a trustworthy name with comparable specs at around the $1500 mark.


For $1500 (less if you can find it on offer) the El Oso Grande is a quality machine from a reliable brand and with a decent spec list.

The beautifully crafted frame is good looking and has an excellent weight to strength ratio.  It’s also surprisingly nimble.

And those gigantic tires, they mean you can go anywhere.  They just roll and float over anything and everything.


It’s great that the bike comes supplied with alloy pedals, but some riders have found them a bit heavy and have fitted their own.

The DB Race M-series saddle is also not to everyone’s taste although that comes down to personal preference. It’s easy enough to change it for one you like so no big deal.

Conclusion and where to buy it;

At under $1500 (on offer) the El Oso Grande is a great entry into the world of fat tire mountain biking.

You will be getting a solid machine with a decent kit list.  That’s what you should be looking for when you’re buying a bike as a complete package.

The SRAM X5 shifts very smoothly, and the drivetrain and gearing feel well matched to the bike.

Fat biking is really about having fun and enjoying being able to go virtually anywhere on your rig.

The Diamondback lives up to this ethos and then some.  That 5-inch (ok, ok ….4.9-inch!) tires can handle anything you throw at them, and this will quickly become the year-round bike you turn to for most of your riding pleasure.

Just remember, no matter how good the El Oso Grande Fat is, you still need to get out there and ride to appreciate it!

The El Oso is available from several retailers, but I always find that Amazon often has the best online price these days.  This nearly always beats anything you can get at a regular bike store.  Couple that with free shipping and excellent customer service and you will be hard pushed to get a better deal.

Click Here to see the great deal Amazon currently has on the Diamondback El Oso Grande Fat Mountain Bike.


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