Polygon Siskiu D24 and D6 Mountain Bike Review

Author: Kristen Bonkoski


The Polygon Siskiu is a budget-minded full suspension bike. Young riders who are ready to progress to bigger drops or tackle rowdier trails will appreciate the added cushion, and parents who aren’t ready to drop big dough on a bike that will soon be outgrown will appreciate the affordable price point.

The Siskiu comes in both a 24″ and small 27.5″ version. Our 11-year-old son (who currently fits most comfortably on a 26″ bike) tested both the Siskiu D24 24″ and the Siskiu D6 SE 27.5″ (size small). While a little big for the 24″ he was able to comfortably throw it around at the Boise Bike Park, and while a little small for the 27.5″ he found it fast-rolling on the trails of Arizona.

In addition to the two models we tested, there are several other build levels that we’ll discuss in this review as well.

For even more kids mountain bike options and reviews, check out our guide to the best kids mountain bikes.

Polygon And BikesOnline.com

Polygon is an Indonesian brand that has been in business since 1989. They manufacture several models and tend to provide a price point and build that is more accessible to the general public compared to the bigger names.

Polygon has sold bikes via BikesOnline.com since 2014 in the U.S. and is one of a small but growing list of builders to offer kids mountain bikes. Their direct-to-consumer model keeps prices low.

Polygon has chosen to provide bikes with component brands and models that don’t have sticker shock but still offer a bike equipped to function and be fun out on the trail. This is a great business model because it allows more people to get in on the fun.

siskiu unboxing

The bikes are shipped directly to your door, and are easy to assemble. Unlike other bikes we’ve had shipped to our door, the Polygon bikes arrive with the drivetrain and brakes adjusted and ready to go.

If you know absolutely nothing about bikes, you might be better off buying directly for a local bike shop, but otherwise the direct to consumer model works well.

Siskiu Frame And Suspension

When it comes to serious mountain biking, most people prefer a full suspension bike to alleviate the fatigue from rough trail chatter and rooted, rocky singletrack. The Polygon Siskiu, with its aluminum, boost-spaced frame, offers a full suspension platform that is trail-ready and capable of handling long days in the saddle. The frame has internal cable routing including routing for a dropper post.

internal cable routing

Although the two models we tested have fairly similar frames, there are some slight differences to the geometry. The Siskiu D24 has head tube and seat tube angles that are closer to the enduro end of the spectrum, while the slightly larger Siskiu D6 SE has more trail-oriented geometry. There’s only a one-degree difference in these measurements, but it can have an impact on the ride feel.

As I mentioned earlier, my son fits between these frames, and the handling for him was noticeably different. He could jump and maneuver both bikes well, but the D24 was easier for him to throw around.

All versions of the Siskiu, including the two we tested, have 120mm of travel front and rear. For a 24″ bike, this is fairly beefy and is on par with the Trailcraft Maxwell 24, for example. For a 27.5″ bike, this is on the lower end of travel, and certainly makes it more of a short travel trail bike.

The Siskiu D24 is equipped with a Suntour Raidon 32 fork and Suntour Raidon R rear shock. The Siskiu D6 SE is equipped with a Suntour XCM fork and Suntour Raidon Lo rear shock.

My son has been spoiled, and spends most of his time on bike park trails on his 140/160 travel Spawn Rokk. Although he still trail rides some, he has come to prefer the bigger travel challenges that parks can offer vs. general trail riding.

The reduction in travel didn’t stop him from sending both Polygons to his best ability. Both the Siskiu D24 and Siskiu D6 SE held up to the challenge and provided enough suspension travel to soften cased jumps and extend his rides longer into the day.

We don’t have a lot of experience with Suntour components and were worried they would perform like the Spinner fork that was previously stocked on the older version of the Prevelo Zulu. This was not the case at all! Polygon has kept costs low by providing suspension components that still perform and can be tuned to little riders. Suntour is certainly not on the same level with Rockshox or Fox, but neither is the pricetag.

Polygon Siskiu D24

polygon siskiu d24

There is a quote from Keith Bontrager: “Strong. Light. Cheap. Pick Two.” In the case of the Polygon D24, you get strong and cheap (or at least affordable). The bike is heavy, but is capable of some serious abuse.

Our kiddo put the bike to the test, throwing it around, and it came out unscathed. Talking to other parents who have the D24, this seems to be the overwhelming sentiment: it’s a tough bike meant for hard charging kids.

It’s also worth noting that while we tested the Siskiu D24, there’s another version of the bike: the D24X. It addresses most of the limitations we mention on the D24, and is well worth the extra cash. We explain in more detail below.


  • Direct to consumer model keeps costs low
  • Tubeless ready wheels
  • Thru-axles
  • Durable


  • Heavy
  • Mechanical rather than hydraulic disc brakes
  • No dropper

Price: $1,199

riding the boise bike park on the polygon siskiu d24

Durable Not Light

Have a kiddo who wants to huck? The D24 will survive big jumps and rock gardens. It’s best for kids who want to play around at the bike park as opposed to families who want to go do big trail rides.

There’s nothing light about this bike. The claimed weight on BikesOnline is 30 pounds. On our scale, it came in at 31 pounds 5 ounces. (That included pedals). Even if we go with the 30 pound weight, that’s still heavier than any of the full-suspension bikes on our best 24 inch mountain bike list.

How much does that matter? It really depends on the kind of riding your kiddo will be doing. If you have a tow rope or are driving a shuttle, it won’t matter much at all. If you’re doing 10 mile trail rides, your child will be much happier with a lighter bike.

If you do want to lighten things up, a good place to start would be the tires.

trail riding on the d24

Tubeless Ready Wheels (But Not Tires)

The wheels are tubeless-ready (tape already installed), but the tires are not. You could drop a couple pounds of weight by installing a lighter tire and losing the tubes.

While not tubeless, we are fans of the Vee Tire Co Flow Snap 2.4″ tires. These are nice high volume tires with sticky tread, and like the rest of the bike, are appropriate for aggressive riding.

Both front and rear wheels have thru-axles which we appreciate. The front Suntour axle on the front wheel is a little unique. It has a spring lock and quick release rather than threading, which makes it fast and easy to remove the wheel. (Ideal if you have a rack that requires front wheel removal).

Microshift Drivetrain

While Microshift doesn’t have the same brand name recognition as Shimano or SRAM, their budget-friendly offerings hit it out of the ball park. The Acelyte groupset is reliable and simple. The trigger shifter is easy for kids to operate, and the clutch derailleur reduces chatter and keeps the chain on.

While it performs well, the drawback here will be that it’s a 1×8 system. There’s an okay-ish range of gears (12-42T) BUT it’s still a limitation.

Again, this might not be a big deal if your kiddo is just hanging out at the skills park, but for longer trail rides, a larger range is helpful.

The bike has appropriately sized 140mm cranks. While you would think all 24″ bikes would have scaled down cranks, that’s not always the case unfortunately, so we appreciate that the D24 does.

Tektro Mechanical Disc Brakes

One of my biggest complaints with the D24 is the fact that it has mechanical rather than hydraulic disc brakes. Not that many years ago, mechanical disc brakes seemed like an okay trade-off for cost savings, but today the price has come down and nearly all of our favorite kids mountain bikes have hydraulic disc brakes. Not only do they have better stopping power, they also cause less hand fatigue for young riders.

That said, the mechanical disc brakes did okay on shorter trips to the skills park. For bigger lift serve days or long rides, they will be a drawback.

The Tektro brake levers, on the other hand, are adjustable and fit well for young hands. These are stock on a lot of the bikes we test and we have no complaints.

Routing For A Dropper But It’s Not Included

Considering that this is a bike designed for hard charging young rippers, they are going to want/need a dropper post. The D24 has internal routing for a dropper, but it does not come with the bike.

Until you can pony up the cash for that upgrade, the bike does have a quick release seatpost collar for manual saddle height adjustments.

Worth upgrading to the D24X?

Polygon also offers another version of the bike, the D24X. For an extra $300, you get some significant upgrades including hydraulic disc brakes,  1×10 drivetrain, a dropper post, tubeless-ready tires, and X-Fusion suspension. This is kind of a no-brainer as far as I’m concerned.

Polygon Siskiu D24 vs The Competition

Usually when I’m comparing a bike to it’s competition, there’s a bike at a similiar pricepoint with a very comparable build. In this case, there’s not much else out there to compare the D24 to. I’m not aware of any other full suspension 24″ bikes under $1,500.

Compared to hardtail bikes at a similar pricepoint and with a 120mm fork (the Prevelo Zulu for example), it’s significantly heavier and has cheaper components. But, it has that rear shock that your kiddo might be begging for.

For some extra dough, the next full suspension bike you might be looking at is the Transition Ripcord 24. It also has 120mm of travel both front and rear, but gets you higher end suspension (RockShox) and a slightly lighter build.

Polygon Siskiu D6 SE

polygon d6

The Polygon Siskiu D6 SE is a good option for pre-teens who have outgrown “kids bikes.” The size small frame fits folks as short as 5’1″–and arguably shorter since my 4’10” was able to clear the top tube just fine.

As mentioned previously, the geometry and 120mm on the Siskiu D6SE is more cross-country oriented than the 24″ model. This is a bike for kids who are ready to start tackling longer rides on rocky trails, but whose parents don’t want to spend a fortune on a bike that will be soon outgrown.

Price: $1,399


  • Affordable
  • Includes dropper post
  • Thru-axles
  • 1x drivetrain
  • Hydraulic disc brakes
  • Tubeless ready rims


  • Heavy for petite riders
riding mesa bike park on the siskiu d6

1x Shimano Drivetrain And Hydraulic Disc Brakes

The Siskiu D6 has a 1×10 Shimano Deore drivetrain. This is a durable, reliable component spec though it will certainly give you less range than the SRAM Eagle for instance. This could be an issue if you live somewhere with steep terrain.

Similarly, the Shimano MT-201 hydraulic disc brakes are significant step up from mechanical disc brakes. They are a solid choice with excellent stopping power. Combined with a 180mm rotor up front, these are plenty for younger, lighter riders.

Wheels & Tires

Like the D24, the Siskiu D6 comes with taped, tubeless ready wheels. Unfortunately, also like the D24, the tires are not tubeless ready. Plan to ditch the tubes and upgrade the tires to lose a pound or two of weight (and avoid flats).

spiderbait tires

If you do choose to keep the tires, they are Entity Spiderbait 2.25″ tires. Interestingly, this is narrower than the tires on the smaller D24.

Both the front and rear hubs have thru axles for extra stability and safety. The rear is boost-spaced while the front is not.

Dropper Post Included

In my opinion, every single mountain bike should come with a dropper post installed, so it’s fantastic that the Polygon Siskiu D6 does! It’s not the norm at this price point.

The spec list for this bike on BikesOnline has the Rage-I Dropper listed for the build. I don’t know what you’ll get, but our bike actually ended up coming with the TranzX dropper with remote lever. This is a budget-friendly dropper that I’ve tested on a couple of bikes now and it seems to work well enough. It’s not adjustable like more expensive droppers, but for this price of bike, so what.

Appropriately Sized Handlebar

So many mountain bikes are being offered with 800mm handlebars, regardless of frame size. That’s way too wide for the average pre-teen! The 760mm on the D6 is much more realistic, and what we’ve cut some of his other handlebars down to.

mountain biking on the siskiu

Weight Will Be The Biggest Limiter For Kids

On our scale, the D6 weighed in at 34 pounds (without pedals). In and of itself this isn’t bad. There are plenty of full suspension trail bikes at double or triple the price that come in near this. For my husband, a bike at this weight is totally acceptable.

d6 on scale

The issue is going to be for kids. They weigh so much less. For a scrawny, 90 pound kid, they will struggle, especially on longer rides.

We took the D6 to Arizona for spring break with us. Riding around the campground and hitting some laps at the skills park, our kiddo had a great time on the bike. When we took him on a longer trail ride, however, it was obvious he was going slower and getting tired faster on the D6 than on his Prevelo Zulu, for example.

If your kiddo is fairly petite, you’ll probably be better off getting them a lighter weight hardtail mountain bike at a similar price.

Worth upgrading to the Siskiu D7?

The size small Siskiu frame also comes in an upgraded component build, the D7. This gets you a RockShox fork and shock which is a definite step up. It also give you a 1×11 drivetrain for a bit more range. At $500 more, there isn’t a cut and clear answer, but I’d spend the money every time to get higher quality suspension.

Have more wiggle room? The Siskiu D8 and D9 builds continue to get upgraded component builds at each pricepoint.

Polygon Siskiu vs The Competition

There aren’t a ton of sub-$2,000 full suspension mountain bikes, and even fewer that will fit a kid. The closest competitor might be the Giant Stance ($1,400). The extra-small frame will fit similarly to the Siskiu small, and it also comes with 27.5″ wheels and 120mm of travel.

One thing that’s nice about the Stance is that is has wider (2.6″), tubeless ready tires. On the other hand, it has a quick release skewer on the back wheel rather than a thru-axle. Beyond that, the components are very similar.

If you can bring your budget up, a kid-friendly full suspension bike like the Spawn Rokk 26/27.5 (my son’s usual full squish bike) or the Trailcraft Maxwell 27.5 are worth a look.

Bottom Line

The Polygon Siskiu series offers an impressive entry point into the world of full suspension mountain bikes for young riders without breaking the bank. With both 24″ and 27.5″ options, it is a solid option for kids, pre-teen, and small teen riders who are ready to take on more challenging trails.

While the bikes are on the heavier side, their robust build, reliable components, and budget-friendly price make them a solid choice for families who want a capable bike that won’t be quickly outgrown.

For those looking for a bit more performance and are willing to invest a bit more, the upgraded versions (D24X and D7) provide even more to like.

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About Us

The Rascals are a family of three. Kristen (mom), Blair (dad), and Parker (kiddo). We started Rascal Rides when Parker was born and we didn’t want to give up our passion for biking. As we learned, we shared. Over the years, we’ve tested hundreds of kids bikes, helmets, bike trailers, and more.

Kristen is a USA Cycling certified coach and loves to share her passion for biking with other families. Blair is a bike geek, mechanic, and mountain bike junkie. Parker is our resident tester and inspiration.

If you see us out on the trail, make sure to say hi!

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