Polygon's Siskiu has been around for a couple of years now, sold through outlets such as GO Outdoors in the UK. Designed to be a capable all-rounder with an impressive parts list, it offers attractive value for money.

The Fox suspension helps deliver a smooth, confidence-inspiring ride, taking the sting out of chunky terrain when the trail gets more hostile.

The competitive price opens up plenty of upgrade potential. However, those wanting a true all-round trail bike that excels going fast, may want to look elsewhere.

Polygon Siskiu T8 frame and suspension details

Polygon Siskiu T8 full suspension mountain bike — In common with other Siskiu bikes, the suspension is a single-pivot design with a linkage-driven shock. Mick Kirkman / Our Media

The Siskiu is not only attractively priced, it’s also well-made, modern and sleek.

The contemporary shape and geometry of the 6-series aluminium frame incorporates a low-slung seat tower using a Kona-esque welded gusset. It keeps the top tube well out of the way of your knees when chucking the bike about.

Chassis construction looks up to date too, with big pivots, a smooth one-piece forged alloy shock rocker link and chunky rubberised chainstay protector.

Polygon Siskiu T8 full suspension mountain bike — The kaleidoscopic logo under the down tube is likely to divide opinion. Mick Kirkman / Our Media

The multi-coloured Polygon logo under the down tube may prove too lairy for some, but most riders we encountered on the trails liked it.

The Siskiu's frame has 135mm of travel in this 29er guise. Smaller riders are offered shorter frames using 650b wheels and a touch more travel at 140mm, which presumably compensates for the less smooth rollover of the smaller wheel diameter.

Every Siskiu uses a relatively simple (and hassle-free) single-pivot suspension design with linkage-driven shock. That should enable designers to ramp up the progression or resistance through the travel so it doesn’t bottom out too easily under big hits.

Polygon Siskiu T8 geometry details

Polygon Siskiu T8 full suspension mountain bike — The geometry is modern, and the ride feel smooth and dependable. Mick Kirkman / Our Media

While the geometry is contemporary and the static bottom bracket height doesn’t measure too differently from the bike's rivals, when riding, there’s a sense Polygon’s longer 175mm cranks are a bit higher. This is likely due to the stack height and handlebar position being relatively lower.

That doesn't mean the Siskiu is skittish though, because even though it has a relatively short wheelbase, it feels very stable and the fairly slack 65-degree head angle keeps the handling calm and composed on the trails.

Polygon Siskiu T8 full suspension mountain bike — The impressive spec list includes a TranzX dropper post. Mick Kirkman / Our Media

The reach figure, which helps dictate how the bike will feel when stood up on the pedals, is relatively roomy across all sizes (495mm on the XL size).

	S	M	M	L	XL
Wheel size (in)	27.5	27.5	29	29	29
Seat angle (degrees)	76.5	76.5	76.5	76.5	76.5
Head angle (degrees)	65	65	65.5	65.5	65.5
Chainstay (mm)	425	425	430	430	430
Seat tube (mm)	385	400	400	415	430
Top tube (mm)	582.5	605.7	605.9	629.1	652.4
Head tube (mm)	105	120	90	105	120
Bottom bracket drop (mm)	20	20	39	39	39
Bottom bracket height (mm)	335	335	335	335	335
Wheelbase (mm)	1,172.8	1,199.1	1,193.5	1,219.7	1,245.9
Standover (mm)	666.6	672.5	676.6	686.2	695.9
Stack (mm)	593.5	607.1	607.6	621.2	634.9
Reach (mm)	440	460	460	480	500

Polygon Siskiu T8 specifications

Polygon Siskiu T8 full suspension mountain bike — There's a Fox Float DPS shock at the rear. Mick Kirkman / Our Media

There’s no question this Polygon has some great kit bolted to it.

A Shimano SLX drivetrain is a significant step up. It's more solid and precise under shifting and pedal loads than the latest Deore.

The KMC chain makes the drivetrain feel a bit rougher here than a full Shimano setup, though.

Polygon Siskiu T8 full suspension mountain bike — The 175mm Shimano cranks felt lengthy when getting up tricky tech climbs. Mick Kirkman / Our Media

It's the same story with the Siskiu’s suspension package; full Fox suspension brings kit that’s higher-performing than the RockShox equivalents on the Cannondale and Canyon I tested the bike alongside.

Tektro brakes might be lesser seen, but they work fine and use the same pads as many Shimano brakes, meaning they're easy to refresh.

This suspension advantage is especially noticeable on the Rhythm fork that’s much more supple and calm than the RockShox Rekon, and has sufficient support to charge reasonably hard down steeper trails without getting unbalanced.

Polygon Siskiu T8 full suspension mountain bike — The Tektro brakes performed well. Mick Kirkman / Our Media

It blows through its travel without some extra blue dial damping on G-outs and low-speed compression events, but is still about the best you can get at this price point.

One negative is the wheels and tyres are heavy, feeling slow to accelerate and roll.

The Spiky Vee tyres have decent bite into loose dirt and mulch, but the casing can twist under cornering loads (seen as casing flex marks unless you run pressures close to 30psi), despite feeling a little like overkill for a 29er trail bike.

The own-brand bar and stem also felt odd, with an awkward sweep that was hard to make entirely comfortable at the wrist.

Polygon Siskiu T8 ride impressions

Polygon Siskiu T8 climbing performance

Polygon Siskiu T8 full suspension mountain bike — Turning up the pace on flat singletrack is more difficult than on other all-round trail bikes. Mick Kirkman / Our Media

Pointed uphill, the Siskiu’s 175mm cranks feel a little long, especially when trying to winch up rough, techy trails where clearance is an issue.

At 35mm wide, the Entity rims, coupled with the sticky Vee rubber, feel quite lethargic getting up to speed.

Combine this with a sense the rear shock lacks mid-stroke support, and it’s harder to inject pace on flatter sections of singletrack that require you to pump and push through the undulations.

It also makes the Siskiu harder to manual.

Polygon Siskiu T8 full suspension mountain bike — The Vee tyres felt somewhat sluggish and would be an area to consider upgrading. Mick Kirkman / Our Media

In an attempt to counter this feeling, I set the Fox shock fully open on the rebound side, which dials down the ground-hugging feel, but there’s still no real zip climbing or sprinting on mellower trails and a sense some of your efforts get absorbed by the suspension.

Polygon Siskiu T8 descending performance

Polygon Siskiu T8 full suspension mountain bike — It's a rattly ride when descending at speed. Mick Kirkman / Our Media

It’s clear, then, that the Siskiu T8 has a downhill bias, but it’s not all plain sailing.

The first sense that’s stimulated by the Siskiu when pointed downhill is your hearing – my test bike was seriously rattly.

Even with a chunky rubber chainstay protector, the chain slaps against the stays, and cables rattle and ding inside the frame over rough ground (going down or uphill), which quickly gets annoying.

All of this noise seems at odds with the Siskiu’s main personality trait as a composed and smooth operator. On trails of all surfaces, its impressive Fox suspension brings a really planted-on-the-floor sensation.

Polygon’s machine feels a chunk more solid and smooth than rival bikes, with a ride that numbs the feel when trail obstacles get chunky.

The muted sensation is likely aided by the fact there’s a different kind of chunk in this near-16kg machine. The extra weight makes the bike, and especially the wheels, harder to deflect, enabling you to pick a line and stick to it with decent levels of control.

That means that while the Siskiu smashes through rough ground and feels very planted, pedalling uphill, accelerating and enjoying longer rides is harder.

Polygon Siskiu T8 full suspension mountain bike — The Fox 34 Rhythm fork has a GRIP damper. Mick Kirkman / Our Media

With less pop or ‘bounce’ to skip over holes or fire out of steep berm faces than the Cannondale or Canyon, I found the Polygon less fun and sprightly.

The back end sits in the middle of the travel in a plush window and ploughs smoothly through the rough stuff, putting the Siskiu closer to an enduro bike than trail bike, with tons of straight-line, bump-swallowing capability.

The Siskiu’s fundamentals are so sorted and it’s so affordable, I’d consider upgrading to a set of the best mountain bike tyres and maybe even best mountain bike wheels. I suspect quite a different, more fiery ride character might emerge that would make it a better all-rounder.

Polygon Siskiu T8 bottom line

Polygon Siskiu T8 full suspension mountain bike — The Siskiu feels at times closer to an enduro bike. Mick Kirkman / Our Media

The Polygon has a mostly fantastic spec for the modest price and is a very capable bike for descending quite rough trails.

That makes it a top heavy-hitter, but, as it comes stock, it’s not the best all-round trail bike for getting about quickly.

How we tested | All-rounder trail bikes

The Siskiu was tested back-to-back with two other bikes, designed with the same intentions.

Because these are designed to be all-rounder trail bikes, we exposed them to just about every type of riding the modern mountain biker is likely to undertake.

That meant riding everything from fast-paced trail-centre laps to ripping around the local wood, along with everything in between.

A true all-rounder should offer balance and stability when the trail gets hectic, but provide a solid, efficient platform to ensure when you need to put the watts down, it’ll cover the ground quickly without too much wasted energy.

Also on test

Product

Brand	polygon
Price	2250.00 GBP,2199.00 USD
Weight	16.0700, KILOGRAM (L) - without pedals

Features

Fork	Fox 34 Rhythm Performance, 140mm travel
br_stem	Entity Expert, 35mm
br_chain	KMC X12
br_frame	‘ALX’ aluminium alloy, 135mm travel
Tyres	VEE Flow Snap Tackee 29x2.5in
br_brakes	Tektro M745, 180mm rotors
br_cranks	Shimano SLX
br_saddle	Enity XTENT
br_wheels	Entity, 35mm
br_headset	ZS tapered
br_shifter	Shimano SLX
br_cassette	Shimano, 11-51t
br_seatpost	TranzX dropper
br_gripsTape	Entity lock-on
br_handlebar	Entity Expert, 780mm
br_rearShock	Fox Float DPS
br_bottomBracket	Shimano BSA
br_availableSizes	M, L*, XL (29") and S, M (27.5")
br_rearDerailleur	Shimano SLX (1x12)