Long, low and slack, the Polygon Siskiu T7E is e-enduro ready, providing it doesn't fall apart!

Product Overview

Overall rating:

Score 9

Polygon Siskiu T7E


  • * Great handling and geometry
  • * Shimano EP801 motor + 630Wh battery
  • * Fully adjustable suspension
  • * Shimano SLX gears + wide-range cassette
  • * Flip-chip for MX wheel option


  • * The battery fell out, three times
  • * Hard compound tyres limit grip
  • * Suntour rear shock blew after two rides
  • * Geometry slacker than claimed (actually that’s a positive!)


Testing the Polygon Siskiu T7E was a rollercoaster ride, with a terrifying battery ejection, but fixing the issue made it my budget e-bike test winner


Price as reviewed:


Polygon builds on the success of the popular Siskiu T series analogue trail/enduro bikes, by going all in on a sleek new e-bike version with the same progressive geometry and ride-hard attitude. There are currently only two models in the range and we are testing the top-end Siskiu T7E. But can £4k really get you an enduro worthy e-bike? And is it worthy of a spot on our list of best budget e-bikes? Time to find out.

Polygon Siskiu T7E

The Polygon Siskiu T7E was lower and slacker than claimed, not that we’re complaining.

Polygon Siskiu T7E Need to know

  • Enduro ready e-bike with a Shimano EP801 motor
  • Shimano 630Wh removable battery
  • 29in wheels as standard
  • Geometry flip-chip for MX wheel conversion
  • Fully adjustable SR Suntour suspension
  • 150mm travel fork, 144mm travel frame
  • Four-piston Shimano SLX brakes
  • Shimano SLX 12-speed drivetrain
  • Weight 24.62kg (54.28lb) size L

Frame and geometry

The burly aluminium Siskiu T7E frame is designed around Shimano’s excellent EP801 motor and 630Wh removable battery. It comes stock with 29in wheels, but the frame also sports a flip-chip to correct the geometry for an MX setup with a smaller 27.5in rear wheel.

Polygon Siskiu T7E

The high shock position corrects the geometry for a 27.5in rear wheel.

Now, given that Polygon offers the Siskiu T7E in four frame sizes, S to XL, and that the flip chip is such a great feature, we’d like to see Polygon deliver the size small and medium bikes with the 27.5in rear wheel as standard, as this would offer shorter rider more room to get off the back of the bike on steeper descents without buzzing the rear tyre.

Polygon Siskiu T7E

No expense spared. Shimano’s EP801 motor powers the Siskiu T7E

With a short 435mm seat tube, our size L test bike had plenty of standover clearance. It also had considerably slacker and lower geometry than claimed – 2º slacker at the head tube and 12mm lower in BB height! It was also the only bike in test with a relatively short 445mm chainstay length. Taken together, the Polygon instantly felt like a modern enduro e-bike. No bad thing, right? And that wasn’t the only anomaly. We couldn’t find the claimed frame travel for the Siskiu T7E anywhere on Polygon’s website, but seeing as we measure all of our test bikes, we know for sure that the Siskiu T7E pumps out 144mm of vertical rear wheel travel.

Polygon Siskiu T7E

The Polygon needs a longer chainstay protector to reduce chain slap and paint chips.

Overall, the details on the alloy frame are neat. The bridgeless seatstays offer stacks of mud clearance, but we’d like to see the chainstay protector extend all of the way along the chainstay, like on the Decathlon Rockrider in this group test, because even after a couple of rides the paint was chipped next to the chainring where the chain had been hitting the frame. Not only would this protect the frame finish, it would also ensure an overall quieter ride.


Most entry-level e-bikes don’t come with all of the top-end suspension bells and whistles. That’s clearly not the case with the Polygon, the SR Suntour suspension offering both adjustable rebound and compression damping and then some. The piggyback Suntour TriAir2 3CR rear shock features rebound adjustment and a three-position compression lever to firm things up for climbing.

Polygon Siskiu T7E

There’s a second air valve on the shock piggyback for adjusting the  IFP pressure. The what?

And if you want to get really techy, you can change volume spacers in the air can and adjust the pressure and overall damping curve, by playing with the air-spring backed IFP. If you don’t know what the IFP (internal floating piston) does, don’t fret, as you don’t need to adjust it, but be aware that it has to be kept within an operating pressure range of 170-200psi for the shock to function correctly. Now, given that most high-end shocks don’t allow riders to mess around with the IFP pressure – because riders are prone to messing it up – it’s probably not a good idea to have it on an affordable e-bike.

Polygon Siskiu T7E

With a 35mm chassis, the 150mm travel Suntour Aion fork is plenty stiff enough.

Up front, the Suntour Aion 35 RC fork has 150mm travel, and again it is air sprung, and comes with rebound and compression adjustment. Out of the box the fork feels really smooth and composed. Maybe not as buttery smooth as the RockShox Lyrik on the Yamaha Moro 07, but definitely more composed than the basic RockShox 35 on the Giant Stance E+1 when you get into faster, choppy terrain, where the fork has to recover quickly from each successive impact.

Polygon Siskiu T7E

The 15mm Q-Loc axle is fast and easy to use, once you know the correct technique.

As the name suggests, the Aion 35 fork has 35mm upper tubes and it also gets a 15mm Q-Loc axle to improve chassis stiffness and steering precision. Just be aware that there’s a specific technique for the Q-Loc axle, so read the instructions, as it’s really fast and easy to use once you know how it works. It’s also worth removing the axle and greasing it regularly, just so it doesn’t seize into the hub or dropouts.


When an e-bike weighs the best part of 25kg, and has geometry akin to an enduro rig, you need really good brakes. Thankfully, the 4-piston Shimano SLX units on the Polygon deliver. They didn’t exhibit the variable bite point that Shimano’s XT and XTR units are prone to, instead we were treated to ample braking power and good modulation with just one finger covering the lever.

Polygon Siskiu T7E

Shimano’s 4-piston SLX brakes are a great set of anchors.

And this is important, as it leaves three fingers and a thumb to form a tight grip with each hand on the handlebar for improved control. Best of all, any bike shop will be happy to service or bleed Shimano brakes, while the same is not always true of the Tektro brakes on the Rockrider and Giant in this group test.

Polygon Siskiu T7E

Schwalbe’s Super Trail casing is great, but the Polygon needs softer compound tyres.

In fact, the speed modulation limiter on the Polygon is ultimately the harder compound 2.6in wide Schwalbe Hans Dampf Evo tyres. If you’re into mile-munching, then the hard compound will extend the life of the 630Wh battery, but given the attitude of the Siskiu T7E, it really needs softer compound tyres as standard to unlock the bike’s full potential.

Polygon Siskiu T7E

In a blind test, Shimano SLX feels just like XT, minus the double-downshift feature

We’re not convinced that e-bikes really need 12-speed drivetrains, but it is really useful to have the wide-range 10-51t cassette on the Polygon, especially when you’re in Eco mode trying to eke out the miles. That big 51t cog is also really handy for conquering crazy steep climbs in Boost mode. All of the Shimano SLX kit worked flawlessly, but we suspect that the KMC chain will cause problems when it starts getting muddy.

Polygon Siskiu T7E

The short stem puts the rider in complete control.

The cockpit on the Polygon is totally dialled. The stubby 35mm stem, 780mm bar and 170mm dropper post are all on point. Even the imitation DMR Deathgrips are excellent. And while the cool kids and park rats like to have the nose of their saddle pointed up, be sure to run the saddle on the Polygon flat, as this makes seated climbing that much more comfortable.


Some test bikes you simply gel with straight away. The Siskiu T7E was one such bike. With progressive geometry, composed suspension, a great specification, and a Shimano EP801 motor, the Polygon Siskiu T7E looked set to be the runaway success in our Affordable E-bike test.


With the Shimano EP801 motor delivering 85Nm of smooth, controlled torque, the Polygon does not shy away from the steepest climbs. It has limitations, though. Namely, the harder compound Schwalbe Hans Dampf rear tyre struggles to maintain traction in both wet and dry conditions. Also the distinct lack of overrun with the Shimano EP801 motor makes it more difficult to navigate really technical climbs.

Polygon Siskiu T7E

Getting the power down is easy, maintaining traction, less so.

Basically, when you stop pedalling the Shimano motor cuts out, rather than powering you forward a little longer, like on the Brose and Yamaha motors in this test. So, if you momentarily stop pedalling to hop up over a rocky step or fallen tree, you don’t get that extra push from the motor, which can be really helpful to get you up and over any awkward sections. Especially on a heavy e-bike. Also, because the frame geometry of the Polygon is considerably slacker and lower than claimed, you’ll probably want to run the flip-chip in the high setting, even with the 29in rear wheel, if you live anywhere with rocky, techy climbs, as you’ll be forever clipping pedals in the low geometry setting.


If you spin up fire roads to access the best trails, you will not be complaining about the lower/slacker geometry of the Siskiu T7E, because it strikes a really good balance between stability when going flat out, yet it’s still agile enough for low-speed tech. Yes, you’ll also moan about the harder compound tyres within the first few turns, but even the distinct lack of traction wasn’t enough to prevent us from having a total blast on the Polygon. From the smooth, loamy trails of the Surrey Hills to the white knuckle runs at BikePark Wales, the Polygon impressed us with its composed handling and dialled geometry. At least until it all went pear shaped…

Polygon Siskiu T7E

Strap in. The Polygon Siskiu T7E offers a blisteringly fast ride.

Jumping into a rooty section of trail at BikePark Wales, our biggest e-bike fear became reality; the 630Wh battery pulled the ejection cord, dropping out of the down tube and hitting the front tyre before bouncing down the trail. Our first thought was ‘lucky it didn’t happen on a big jump’. Then we thought, maybe we hadn’t located the battery properly in the frame, so we slammed it back in and continued riding. Then it happened again in another jarring section… and again.

Polygon Siskiu T7E

Belt and braces. We ran a tool strap around the battery for extra security.

So we left the battery in the van and jumped back on the uplift. The bike felt completely different now, and we quickly realised that all of the damping in the Suntour TriAir2 shock had disappeared. So that was it for that day of testing. Pedalling back to the van we were reminded how the Shimano EP801 motor has very low pedalling resistance when you have no assistance from the motor, and it was probably the only time during the test that we were thankful of the faster rolling Schwalbe tyres.

Polygon Siskiu T7E

The Polygon Siskiu T7E does it all, and more of it too, thanks to the 630Wh battery.

Go Outdoors promptly sent us a replacement shock, and a Shimano tool to check that the battery latch had been fitted and adjusted correctly. It wasn’t, which explains why the battery was falling out on bigger impacts. Still, we used a Velcro tool strap around the down tube on subsequent test rides just to ensure that the battery wouldn’t part ways with the frame again. We also noticed on social media that some Polygon riders have adopted a similar approach. Better safe than sorry, right? Especially given that we could ride the Polygon way harder than any other bike in this test.

Polygon Siskiu T7E

With better tyres, the Polygon Siskiu T7E could have bagged a 10/10 rating


Without doubt, the Polygon Siskiu T7E is the best riding bike in our Affordable E-Bike group test. All that’s missing from the excellent specification is a grippy set of tyres. In fact, on the first few rides it felt like the only bike in this test, other than the Yamaha Moro 07, that wouldn’t fall apart when pushed really hard. So we pushed it really hard, then the wheels came off… figuratively, at least. With the battery falling out and the shock blowing, it’s hard for us to access the long term durability of the Polygon, even if it’s a really fun, capable e-bike. So it’s with a cautionary note that we are giving Polygon the test win. The frame geometry is sorted, the specification is also killer value for money, and you get the excellent Shimano EP801 motor and 630Wh battery. We fixed the battery ejection issue and Go Outdoors was quick to send us a replacement shock, but given how rapidly things started to go wrong, we are genuinely concerned that the Siskiu T7E could spend more time on the work stand than on the trails. So, if you decide to go down this route, you’ll want to be close to a Go Outdoors store just so you can pop in easily if anything does go wrong. Hopefully our test bike was the exception, not the rule.


Frame :ALX Enduro aluminium
Frame travel :144mm measured
Shock  :SR Suntour TriAir2 3CR (210x55mm)
Fork :Suntour Aion 35 RC
Fork travel :150mm
Motor :Shimano EP801 85Nm
Battery :Shimano 630Wh
Control unit  :Shimano EN600 + Assist Switch
Hubs :Shimano MT 400 110/148mm
Rims :Entity XL3
Front tyre :Schwalbe Hans Dampf 29x2.6in
Rear tyre :Schwalbe Hans Dampf 29x2.6in
Chainset :Shimano ERE80 34t, 165mm
Shifter :Shimano SLX 12-speed
Derailleur :Shimano SLX
Cassette :Shimano Deore 10-51t
Chain :KMC E12S
Brakes :Shimano SLX 4-piston
Rotor sizes :203/203mm
Handlebar :Entity Expert 780mm
Stem :Entity Expert 35mm
Seat post :Tranz X 170mm
Saddle :Entity Xtend
Weight :24.62kg (54.28lb)
Sizes :S, M, L, XL
Geometry :(low)
Size Ridden :L
Rider height :181cm
Head angle :63º
Seat angle  :71.3º
Effective SA :76.3º
BB height :325mm
Chainstay :445mm
Front centre :820mm
Wheelbase :1,265mm
Down tube :763mm
Seat tube :435mm
Top tube :615mm
Reach :465mm