Wil reviews the Polygon Siskiu T9

A brand new bike for 2024, the Polygon Siskiu T9 joins the lineup as a higher-spec version of the popular Siskiu T8 that we reviewed back in 2021. The Siskiu T9 kicks things up a few notches with a suite of hard-hitting upgrades that includes a Fox 36 GRIP2 fork, a Float X piggyback shock and TRP DH-R EVO brakes. That makes it a whole lot of bike given its sub-$5K price tag, but what exactly does the more aggro spec bring to the party? And is it worth the extra cash over the T8?

An overview of the 2024 Polygon Siskiu T9

Straddling the gap between the Siskiu D and the Collosus, the Polygon Siskiu T9 is a contemporary mid-travel trail bike that’s designed for all-round riding.

It’s available with 29in wheels and 140/135mm of travel, or with 27.5in wheels and 150/140mm of travel. That puts it into competition with other mid-travel trail bikes including the Merida One-Forty, Norco Fluid FS, Giant Trance X and Marin Rift Zone.

The Siskiu T9 is built around the same chunky 6000-series alloy frame as its cheaper siblings. It features a single-pivot suspension platform with a one piece rocker link that serves to brace the swingarm and control the shock rate. You’ll find sealed cartridge bearings at most pivot points, while IGUS bushings are employed at the seatstay pivot. That’s a smart cost-saving decision given the small amount of rotation at this point.

There’s clearance for big 2.6in wide tyres, and room underneath the shock to fit a water bottle. Along with the threaded BB, simple cable routing and thick chainstay protector, the Siskiu T9 frame is a low-frills but practical affair. Perhaps the only disappointment is the lack of a UDH-compatible dropout, meaning owners won’t have the ability to upgrade to a SRAM T-Type Transmission.

Geometry

There are four sizes available with the new Polygon Siskiu T9. The 27.5in platform is offered in Small and Medium, while the 29er bike is produced in Medium, Large and Extra Large sizes.

It’s worth noting that there are no geometry flip chips to be found on the Siskiu T9. However, the frame is rated for use with a 150mm travel fork. You could achieve this by simply fitting a 150mm air spring to the Fox 36, which would kick the angles back a touch and lift the BB slightly.

The stock geometry is otherwise unchanged on the Siskiu T9 compared to the rest of the Siskiu T range;

2024 Polygon Siskiu T9 price & specs

For 2024 there are now four models in the Polygon Siskiu T range. Prices kick off at $2,299 AUD for the Siskiu T6.

The Siskiu T9 we have here is the top-of-the-range model, and the current retail price is $4,299 AUD.

Because Polygon bikes are sold direct to consumer in Australia through Bikes Online, you will have to add on the necessary shipping fee to have the Siskiu T9 delivered to your door. It arrives inside a cardboard box, with some basic assembly required to get it into riding shape. More on that in a bit.

2024 Polygon Siskiu T9

• Frame | ALX 6061 Alloy, Single-Pivot Suspension Design, 135mm Travel
• Fork | Fox 36 Performance Elite, GRIP2 Damper, 44mm Offset, 140mm Travel
• Shock | Fox Float X, Performance Series, 210x55mm
• Wheels | Shimano MT410 Hubs & Entity XL2 Alloy Rims, 35mm Inner Width, Tubeless Compatible
• Tyres | Maxxis Assegai EXO Dual Compound, 2.6in Wide
• Drivetrain | Shimano Deore XT 1×12 w/ 32T Crankset & 10-51T Deore Cassette
• Brakes | TRP DH-R EVO 4-Piston w/180mm Rotors
• Bar | Entity Xpert Alloy, 35mm Diameter, 780mm Wide
• Stem | Entity Xpert Alloy, 35mm Length
• Grips | Polygon Lock-On
• Seatpost | Tranz-X Dropper, 30.9mm Diameter, Travel: 150mm (S-M), 170mm (L-XL)
• Saddle | WTB Volt
• RRP | $4,299 AUD

Polygon Siskiu T9 sizing & fit

At 175cm tall I’ve been riding a Medium size in the Polygon Siskiu T9.

The 460mm reach and relatively steep 76.5° seat angle are on-point, though it’s worth noting that the 607mm stack height is on the lower side. For perspective, compare it to the Giant Trance X (621mm), Specialized Stumpjumper (622mm) and Norco Fluid FS (626mm). Thankfully Polygon gives you a good amount of headset spacers for adjusting the bar height. I found lifting the stem up almost to the top was necessary to get things comfortable.

I don’t love the stock handlebars, which feel a little too square and stiff. Chopping them down to my preferred width of 760mm helped to dial in the riding position, but if this were my bike I’d be looking to upgrade to a bar with more sweep and a taller rise. The stock grips and saddle are fine, and although the WTB Volt isn’t to my personal taste, it’s no doubt a popular perch with many bottoms out there.

It’s great to see a short seat tube that leaves plenty of room for the 150mm dropper post on our Medium test bike. This gives you greater flexibility to fit a longer stroke dropper in the future, should you feel the urge.

Polygon Siskiu T9 weight

Out of the box with inner tubes fitted, our Polygon Siskiu T9 test bike weighs in at 15.92kg.

That’s hefty for a trail bike, and indeed there are some notable components that contribute to the overall weight. The Entity wheelset came in at 2.41kg, and the big Maxxis Assegais weigh 1.15kg each. That results in some serious rotating mass, and it also sees a lot of weight hanging off the rear axle once you factor in the heavy Deore cassette.

With that in mind, a lighter wheelset would be well worth considering if you were going to pump any cash into upgrades.

Going tubeless, eventually

Speaking of upgrades, the most logical for any Polygon Siskiu T9 owner would be to go tubeless. Both the tyres and rims are compatible, and Polygon even installs tubeless tape from the factory. Unfortunately no valves or sealant are included in the box, so you’ll have to purchase these separately.

I had some spares in my workshop, and so I decided to see what the tubeless setup process would be like for the Siskiu T9 customer. It turns out the Maxxis tyres were quite loose on the Entity rims, making it nearly impossible to air them up with a floor pump. This differed to my experience with the Schwalbe tyres on the T8, which offer a much tighter fit.

The solution was to seat the tyre with an inner tube first, then depressurise the tyre, pop one bead off and remove the tube. I then fitted the tubeless valve, a generous amount of Champions Choice sealant, and with some vigorous pumping was able to inflate the tyre.

However, over the course of my first test ride I found the rear tyre was losing significant pressure. Upon returning home I submerged the wheel in a bucket of water, which revealed that the rim join was leaking air. This isn’t totally uncommon with cheap wheels, but it’s been a while since I’ve encountered such an issue. Removing the tyre and adding a wider strip of tubeless tape in this area did the trick to seal it up airtight.

While I was at it, I fitted a CushCore Trail insert in the rear wheel to help reduce the chance of punctures with the flexible EXO casing tyres. Because of their high volume, it’s possible to run quite low pressures. I typically ran 16-18psi up front and 18-20psi out back depending on the trail conditions.

Suspension setup

Bikes Online recommends setting up the rear shock on the Polygon Siskiu T9 with 25-30% sag. Initially, I tried 30% but found the rear end was too mushy. I was also bottoming out frequently. I had better luck with increasing air pressure to bring sag closer to 25%, but the back end still wasn’t offering the level of support I wanted.

Diving into the Float X shock, it turns out that Polygon specs a fairly small 0.2³ volume spacer inside the LV air can. After some experimentation, I settled on a much larger 0.6³ spacer, which proved to be a game-changer for the Siskiu T9. Not only did this eliminate the bottoming issue, it also added a tonne of valuable mid-stroke support that unlocked a much floatier and poppier ride quality. Instead of getting bogged down deeper in the travel where it felt firm and less responsive, the shock was able to ride higher in its stroke and remain in the sweet spot for longer. Grip and comfort were noticeably improved as a result.

Combined with 27% sag (150psi to support my 68kg riding weight) and the rebound set a click faster than halfway (8/14 clicks), the back end of the Siskiu T9 was humming.

Up front I actually needed to do the opposite with the Fox 36 GRIP2. This came set up with four volume spacers inside, which made it difficult to use all the travel and had the fork feeling overly firm. Removing one spacer was all I needed to have the 36 singing a similarly sweet tune as the back end. I otherwise ran the recommended air pressure and damper settings for my weight, albeit with the high-speed rebound and compression dials set a couple of clicks faster than suggested.

Given all the adjustments on offer, setting up the suspension on the Siskiu T9 is likely to be overwhelming for newer riders. If you’re in need of some tuning tips, check out our guide on setting up your Fox fork and Fox shock.

What do we dig about the Polygon Siskiu T9?

On the trail I’ve found the Polygon Siskiu T9 to share many of the same attributes that we loved about the cheaper T8.

It’s got an enthusiastic and playful character that really encourages you to work the trail and search out any opportunities for getting airborne. The short chainstays play a big role in this, making it easy to pop up the front wheel for manuals and launching drops. Combined with the light steering and low BB, the Siskiu T9 loves to carve turns hard.

It’s worth noting that overall capability has stepped up quite a bit thanks to the 36 GRIP2 fork and Float X shock. Admittedly it took a few rides to dial in the suspension, but once set up properly it really has impressed. There’s excellent small-bump sensitivity front and rear, and with the bigger volume spacer fitted inside the shock there’s useful support for pushing into berms and off jumps. The active suspension allows the Siskiu T9 soak up big hits comfortably, and it also floats nicely through chunky sections of trail.

This is complemented by the high-volume tyres, which mould and conform to the terrain to help absorb sharp edges and general chatter. The Assegais deliver gobs of traction on all sorts of surfaces, bolstering your confidence when plopping the Siskiu T9 down into a bed of loose rocks and roots.

However, the way the plump rubber mutes feedback from the trail won’t suit everyone. Bigger and more aggressive riders will likely encounter some casing wobble when pushing the bike into high-speed banked corners, especially if you’re running lower pressures. Those folks will benefit from fitting a slightly narrower tyre with a sturdier casing.

I say this because the Siskiu T9 is remarkably capable given it ‘only’ has 135mm of rear travel. It feels a bit like a mini-Enduro bike that you can ride quite hard on some really challenging trails, providing you’re an active rider. The compact rear end means it’s no plough-machine, but I found I was able to get away with a lot thanks to the supple suspension, heavy wheels and aggressive tyres.

What does it struggle with?

The near-16kg weight of the Polygon Siskiu T9 is noticeable. It soaks up some of the bike’s eagerness on jumpy flow trails, and it requires you to invest more energy on longer trail rides.

On top of the overall weight, the dual Maxxis Assegai setup is a bold spec decision. Outside of bikes with a motor, it’s quite rare to see an Assegai fitted on the rear. I suspect it’s probably cheaper for Polygon to order two of the same tyre from Maxxis.

It does look badass, but the chunky rubber results in a lot of rolling resistance. Along with the heavy wheels, it takes considerable effort to twiddle your way uphill on the Siskiu T9. I routinely found myself wishing for a smaller 30T chainring.

Energy expenditure aside, the Siskiu T9 isn’t a bad technical climber at all. With monstrous amounts of grip on tap, it’s capable of tractoring its way up some pretty heinous trails. Push hard on the cranks and you can feel the suspension sharpen up to help propel you forward. Combined with the steep seat angle, which puts you in a great pedalling position, I was able to clean several technical features that I was dreading on the approach.

Admittedly the short chainstays don’t offer the same planted feel on the climbs compared to bikes with longer rear ends. I didn’t find it to be a problem, though it may be more of an issue for taller riders on the Large and Extra Large frames.

And it has to be said that it’s this long-front-short-rear setup that contributes greatly to the Siskiu T9’s fun-filled character. Along with its burly spec that favours grip and big-hit capability over weight and rolling efficiency, it’s well suited to hard riding on modern flow trails and bikepark-style terrain.

Component highs & lows

Given there are many frames on the market that cost more than this whole bike, there’s no denying that the Polygon Siskiu T9 is astonishing value for money on paper. However, my experience hasn’t been without blemishes.

Out of the box the front brake was rubbing quite badly, which seemed to be from a combination of calliper misalignment, sticky pistons and a slightly warped rotor. Even after giving it some TLC in the workshop I couldn’t get it to stop rubbing completely. The rear brake has been absolutely flawless though, so perhaps I was just unlucky with the front.

I do otherwise like the TRP brakes, which offer smooth modulation and oodles of power. The long levers feel great, but they’re not the easiest to set up alongside the other controls. The shifter ended up further inboard than I wanted, while the dropper post lever was a bit too far outboard, leaving some room for improvement when it comes to the cockpit ergonomics.

The Shimano drivetrain has worked well, though sneakily Polygon has spec’d a cheaper KMC chain that means shift performance isn’t as crisp as it should be. Also, the derailleur’s limit screws and B-tension did need some initial tweaking to get everything properly aligned. I normally wouldn’t mention this, but it’s relevant since this bike is sold direct-to-consumer. Without a bike shop mechanic checking it over and setting it up before you hit the trails, the build quality has to come under more scrutiny.

Bikes Online explained that if a customer encountered any of the issues we experienced, these would be rectified by having the necessary replacement parts sent out either for the customer to fit themselves, or for them to take to their local bike shop to have installed professionally. In the latter case, Bikes Online would cover the cost of installation. That’s nice peace of mind, especially for less mechanically savvy riders.

Those issues aside, the rest of the component package has otherwise worked well. The TranzX dropper post isn’t sexy, but it does its job as intended. And the heavy wheels have been solid both on this test bike and the Siskiu T7E we reviewed separately.

Of course it’s the suspension that’s the big story on this bike. It’s rare to find high-end forks and shocks on alloy frames these days, let alone on a bike that costs under $5K. I know I’m harping on about this, but it’s worth reiterating that aside from the Kashima coating, this 36 GRIP2 fork is exactly the same as the $1,945 AUD Factory Series model we recently tested. That’s bonkers!

While the Fox fork and shock have performed really well, as mentioned earlier they did require some tuning to get to that point. Given I’m a fairly lightweight rider, I was surprised that I needed to add such a big volume spacer to get the most out of the Siskiu T9. This would suggest that heavier folks will definitely need to tweak the air volume, or risk having to over-inflate the shock just to stop it from bottoming out.

Unfortunately Polygon doesn’t include any volume spacers with the bike, so you’ll have to purchase those separately. I’d love to see some included in the box along with tubeless valves and sealant, which would be a really nice touch for the customer.

Should you buy the Polygon Siskiu T9 or T8?

With the arrival of the new Polygon Siskiu T9 we expect there’ll be a lot of folks weighing up whether it’s worth the premium over the Siskiui T8. In terms of the retail price, the Siskiu T8 is nearly a grand cheaper at $3,599 AUD.

Both bikes utilise exactly the same frame, and many of the parts are identical including the wheels, dropper post and cockpit. The key differences on the Siskiu T8 include the Fox 34 Rhythm fork, Float DPS shock and Shimano MT420 disc brakes. It also gets lighter and faster-rolling Schwalbe Hans Dampf tyres.

This means that despite being cheaper, the Siskiu T8 is almost a kilo lighter (15.08kg vs 15.92kg). I found this noticeable on the climbs and through twistier and flowier trails, where it was a little easier to pedal and manoeuvre. For riders who are after their first full suspension mountain bike for exploring green and blue-graded singletrack, the Siskiu T8 is a fantastic option that will likely do everything you need it to.

In comparison, the aggressive tyres and high-end suspension on the Siskiiu T9 provide a noticeably smoother and more controlled ride on rocky terrain. It offers more grip and big-hit support, allowing you to push the whole bike harder and faster on the descents. That makes it better suited to riders looking to tackle technical trails, push their limits and develop their riding skills. It’s a great option for ripping laps at the bikepark, and it’s sturdy enough to take on the odd enduro event.

It’s also worth noting that you can extend the Fox 36 on the Siskiu T9 to 150mm, which isn’t possible with the 34 Rhythm on the Siskiu T8. And really, if you’re a descending-focussed rider, the 36 GRIP2 will likely be worth the $900 price difference alone.

Flow’s Verdict

The new Polygon Siskiu T9 has impressed not just because of its incredible value for money, but also due to its ride quality on the trail. We’d already had a positive experience with the Siskiu T8, and the Siskiu T9 only reinforces that with its sturdy chassis and sorted geometry.

The addition of high-end Fox suspension has taken the descending performance to a whole new level, with added grip and support that means you can get away with a lot on rowdy trails. Add in the powerful TRP brakes and sticky Maxxis tyres, and you’ve got a highly capable package.

At almost 16kg it is heavy, and the slow-rolling Assegais make it hard work up the climbs and on longer trail rides. Those who are after a lighter and speedier bike for bigger backcountry missions may want to look at something like the Canyon Neuron or Specialized Stumpjumper instead.

The Siskiu T9 is considerably more aggressive, putting it closer to bikes like the Trek Fuel EX and Norco Fluid FS. It feels like a mini-Enduro bruiser, albeit one that’s a heckuva lot of fun to ride on jumpy flow trails thanks to its short rear end and poppy character. Factor in the solid, no-nonsense frame and you’ve got a great project bike that’s more than worthy of any upgrades you decide to make over time.

ABOUT THE REVIEWER - Wil Barrett

Hometown

Bendigo, Victoria

Height

175cm

Weight

65kg