Planet X’s Pro SL has been a leading top-value frame basis for bargain bike builds for several years now. The longer you can keep using the same mould, the cheaper each bike you produce costs too. That’s what keeps this energetic, effervescent lightweight evergreen a top option for tempo rather than torque riders.
Planet X have done an amazing job of getting an £1100 bike under the 17lb mark, and it’s a lively, smooth and comfortable cruiser. It does lack the stiffness to slice round corners and snap maximum power down though, so it’s more suited to light weight long distance spinners than powerful, punchy riders.
Ride & handling: Light, comfortable and smooth, but noticeable frame flex and twist under power
The minimal weight (7.6kg/16.67lb) is obvious as soon as you’re aboard the Planet X. Spin the pedals and it whips up to speed very quickly and, as long as you keep the gears low and the revs high, it ﬂoats up hills with an infectious effortlessness. The frame sucks up a lot of road shock too, smoothing out knobbly or cobbley sections and making it an obvious choice for those who’ll spend a long time in the saddle.
Despite the visual appearance of the super-compact frame layout, it still ﬁts like a full size bike. That means there’s ample room for big breaths if you’re surﬁng the anaerobic breakers up a long pull. Light weight makes it a breeze to ﬂick and drop into corners, and it dodges potholes with ease. The light weight and high levels of cruising comfort do come at a cost in terms of tracking and torquing stiffness, though.
Flex is obvious in the front end and the wheels as soon as you turn in hard, and as the rear end follows there’s a sensation of rotational twist as the sideloads increase. It doesn’t take long to learn to predict and ride round this more ambivalent rather than accurate handling feel, but we had some test ride slides from the Continental tyres.
Braking through the cam-assisted callipers is excellent, with a positive, powerful feel so we were never nervous committing to serious speed on the descents. There’s no frame wobble or oscillation from rippled braking surfaces either, although the frame ﬂex means trying to wrestle with deep section wheels in cross winds won’t be fun.
You can feel the ﬂex through the bars and front end, through the cranks, rear end and back wheel when you put the power down hard. It’s a squirm that does straighten out and spring you forward eventually, but it’s a bike that responds better to seated tempo riding than out-of-the-saddle torqueing.
Frame & equipment: Top-value groupset and light wheels give amazing performance for price
While Planet X have now introduced an all-new Nano road bike as their ﬂagship frame, the SL Pro is still a sweet chassis. The smoothly proﬁled head tube is reinforced with a web between top and down tube at the back. The gloss red frame ﬁnish also brings out the ribbed detailing on the front end of the maintubes much more obviously than the naked carbon versions.
It’s relatively skinny around the bottom bracket, but the mid-sized chainstays get more ribbed reinforcement, as do the hourglassed seatstays. The dropouts get a small cutout, while a very skinny wishbone completes the frame circuit. The Pro carbon road fork is an extra £110 if you’re planning on building the bike up yourself, but at under 370g, the full-carbon build helps create a bewitchingly light bike for the money.
Planet X have provided the lightest possible stop/go kit for the money by opting for SRAM’s Force groupset. The ‘double tap’ shifting takes getting used to, but it gives a small hand movement and fast shift here once you’ve acclimatised. Planet X have also ﬁtted their own brakes – the forged version of their cam-assisted superlight brakes, complete with high control cartridge brake pads.
The company also provide the impressively light wheelset complete with bladed spokes, which put a real zip into the acceleration of the SL Pro if you’re a spinner not a stomper. More useable Planet X gear makes up the cockpit, while seating is a mix of FSA post and a soft nosed, aero-tuck friendly Selle Italia saddle. The result not only works well, but drops bike weight to under 17lb, shaming bikes well over double the price.
Pro SL SRAM Force (11)
Top Tube (cm)
Standover Height (cm)
Seat Tube (cm)
planet X superlight team 100mm
fsa single bolt
selle italia X2
planet X model b
Rear Wheel Weight
Bottom Bracket Height (cm)
planet X strada anatomic 420mm
Front Wheel Weight
sl pro carbon
sl pro carbon
sram force 50/34t
sram force 11-25
planet X ultralight forged
SRAM GXP Road
M L XL L M S S S S S S M L XL XL S M L XL S M L XL