Archive: RocketMAX Gen4

The Cotic RocketMAX Gen4

Discontinued. This page is kept as an archive record for owners and for anyone researching an older Cotic RocketMAX.

Years of production: 2022-2026

See the RocketMAX archive for the earlier generations.

The RocketMAX Gen4 was Cotic's 29er steel enduro bike for the fastest, gnarliest, steepest trails: 160mm rear travel, a 170mm fork and Longshot geometry.

Its Reynolds 853 front end gave a tactile, ground-hugging feel that tracked the terrain and held a line, calm at speed and quick to respond when needed. It was built to make sketchy lines feel natural and chaotic trails feel calm, carrying speed through roots and rough ground with control to spare.

RocketMAX Gen4 frames were made in small batches in the UK and built to order, with Cotic's A La Carte custom paint available on every frame.

In Cy's words

It's all about speed and confidence. Where I ride most of the time the trails are fast and rough, so I want the travel the RocketMAX offers to look after me. The speed across the ground on this bike is breath-taking. I also love it when it gets dirty, steep and technical. The Golfie is one of my favourite places to ride, and the RocketMAX is just amazing in steep terrain: so much poise, confidence and precision. I remember riding down Ghetto at Revolution Bike Park on an early prototype and laughing out loud because it felt like I couldn't go over the bars. The RocketMAX makes me a better rider than I think I am.

Cy Turner, Owner and Bike Designer

What was new for Gen4

C-Sizing. Gen4 introduced Cotic C-Sizing: five sizes instead of four, with reach steps of around 19mm. C2, C3 and C4 got shorter seat tubes and more standover than the old Medium and Large that covered a similar height range. C1 is broadly the same as the previous Small, and C5 stretches reach to 520mm, slightly more than the old XL, to account for the steeper seat angle. Cy tested an adjustable prototype out to 530mm reach and a 63° head angle, and settled on 520mm at 63.5° as the sweet spot for C5.

Geometry. The dynamic BB is a little lower than Gen3, while still keeping pedal strikes to a minimum. C3, C4 and C5 get a steeper seat angle so every rider sits at around 76° at the saddle. The head angle stays at 63.5° with a 170mm fork, and the geometry was revised around the latest 38mm stanchion enduro forks of up to 170mm travel. As always with Longshot, 35mm stems keep the bike responsive.

Frame. A new, stronger and stiffer Cotic-exclusive Reynolds 853 down tube. Cotic chose steel for the flex characteristics it can tune along the length of the bike to enhance grip, and because it is durable, repairable, recyclable and has the lowest environmental impact of any frame material.

Suspension. Gen4 kept 160mm of rear travel, but with a reduced leverage ratio and a revised droplink kinematic that made it compatible with both air and coil shocks. A new droplink design, exclusive to the RocketMAX Gen4, keys the links to the axles to eliminate twist and flex through the linkage. The shock stroke sets the travel: 65mm for 160mm, 62.5mm for 155mm, 60mm for 150mm. With a shorter stroke shock and a 160mm fork, the RocketMAX also makes a tough trail bike. The mullet option carried over from Gen3, using an angleset to correct the geometry for the smaller rear wheel.

Builds. New fork options were the RockShox Zeb Ultimate and Fox 38 Factory 170mm, with the Cane Creek Kitsuma Coil added as the coil shock option.

Reviews

Singletrack (long term test, Ben): rated it fearless on steep terrain up and down, very grippy, and a remarkable climber, and summed it up as an amazingly capable bike with a unique level of calm, control and comfort. The reviewer also praised the practical external routing.

Blister: described it as quietly confident and unflappable, singled out its comfort at speed on rough trails, and credited Cotic's tuning of the tubeset and frame flex, paired with well-sorted kinematics, for its excellent ride quality.

MBR, 9/10 (Gold XT 150): praised its composure and balance in rough terrain and precise line holding in long turns and off-cambers, credited to the steel front triangle and alloy chainstays, and rated it the best pedalling bike in the test.

Pinkbike (Gold AXS, Kitsuma Coil): found the 63.5° head angle and coil shock let the rider get away with a lot in corners and on descents, with straightforward, quirk-free ride dynamics.

BikeRadar, First Ride (Gold XT/Fox): very smooth, massively capable on gnarly terrain, with addictive cornering and a calm, composed, bottomless-feeling rear end. Called it a true enduro racer's bike.

BikeRadar Bike of the Year 2023, 4.5 stars (Silver Mullet): stable and confident through turns, with balanced suspension and an impressive ability to carry speed and fire out of corners.

Wideopen (Pete, GX Gold): found it stable at speed, a capable climber and playful in slow tech, fun on every type of trail, and said its UK manufacture made the price easy to justify.

Finishes and sizes

Standard finishes during the run: Golfie Green, Light Metal, Stealth Gritstone, Matte Copper Orange (added for 2024) and Gloss Ember
A La Carte custom colours: Amethyst, Army Green, Black, Copper Orange, Crimson, Ember, Forest, Golfie Green, Light Metal, Limestone, Metal, Moonstone, Navy Blue, Sage, Sunny Yellow, Teal, Topaz, White
Sizes: C1, C2, C3, C4, C5

Early photos show down tube branding. Later frames had top tube branding.

Origin: made in Britain

The RocketMAX Gen4 was designed, developed and tested by Cotic in the Peak District, with Cy Turner as lead designer, and lab tested beyond the ISO 4210 safety standard. Five Land Bikes in Scotland built the Reynolds 853 front triangles in small batches, and did the phosphate dip coating, automotive spec paint and hand finishing. Rear ends came from Cotic's suppliers in Taiwan, and Unite Components and Bear Frame Supplies made much of the remaining machined parts. Frames were assembled at Cotic HQ with Enduro MAX bearings and Datatag security as standard. Singletrack published a feature on how these UK made frames are built.

Frame details

Cotic Longshot geometry, designed for very short 35mm stems
Reynolds 853 front end with Ovalform top tube and Cotic exclusive HD down tube
44mm standard head tube with an external bottom cup for taper steerer compatibility and a zero stack top cup
Custom Cotic designed 35mm Reynolds 853 seat tube for super stiff support for the main suspension pivots
31.6mm dropper compatible seatpost size, with internal Stealth dropper remote routing
Integrated 3D printed Cotic chain guide and a regular threaded bottom bracket
Rear mech cable routed internally through the steel seatstay
Custom forged swingarm heads for stiffness and tyre clearance
6066-T6 aluminium swingarm with a Syntace X-12 Boost148 x 12 rear axle
15mm main and droplink pivots, with new keyed linkage axle and clamps for more torsional stiffness
Enduro MAX bearings
Datatag security fitted as standard
1 bottle mount
Clearance for 29 x 2.5" tyres
Designed around 38mm stanchion, 170mm forks
150mm, 155mm or 160mm of Cotic droplink suspension, depending on shock stroke

Geometry

Longshot geometry means the frames are low and long, with plenty of standover. We recommended the size for your height on the chart, with a short 35-45mm stem. C-Sizing's tighter gaps give more room to size up or down. Consider your leg length too: if you upsize, a long dropper may not fit, either because the collar hits the seat tube top or the post bottoms out on the droplink pivot. Cotic doesn't develop its bikes around a specific fork offset: it's down to rider preference.

Frame rear travel: 160mm with a 65mm stroke shock, 155mm with 62.5mm, 150mm with 60mm. Max rear tyre: 29 x 2.5" (29er), 27.5 x 2.8" (mullet). All dimensions in mm.

170mm fork, 29" wheels

Frame Size	C1	C2	C3	C4	C5
Seat Tube (centre-top)	390	417	444	471	496
Top Tube Length (effective)	599	621	639	660	679
Head Angle	63.5°	63.5°	63.5°	63.5°	63.5°
Effective Seat Angle (720 BB-saddle)	75.8°	75.8°	76.2°	76.2°	76.2°
Effective Seat Angle (815 BB-saddle)	75.5°	75.5°	75.9°	75.9°	75.9°
Chainstay Length	448	448	448	448	448
BB Drop	23	23	23	23	23
Head Tube Length	100	110	120	130	130
Reach	444	462	482	501	520
Stack	630	639	648	657	657
Wheelbase	1244	1268	1290	1314	1333
Usual Height Range	162-172cm	170-178cm	176-184cm	182-190cm	184-195cm
Stem Length	25-45	25-45	25-45	25-45	25-45
Maximum Seatpost Insertion (incl. actuator)	164	191	219	246	270

Static, based on a 170mm fork with 586mm static length.

160mm fork, 29" wheels

Frame Size	C1	C2	C3	C4	C5
Seat Tube (centre-top)	390	417	444	471	496
Top Tube Length (effective)	597	623	641	662	681
Head Angle	64.1°	64.1°	64.1°	64.1°	64.1°
Effective Seat Angle (720 BB-saddle)	76.4°	76.4°	76.8°	76.8°	76.8°
Effective Seat Angle (815 BB-saddle)	76.1°	76.1°	76.5°	76.5°	76.5°
Chainstay Length	448	448	448	448	448
BB Drop	28	28	28	28	28
Head Tube Length	100	110	120	130	130
Reach	451	470	489	508	527
Stack	625	634	643	652	652
Wheelbase	1237	1261	1283	1307	1326
Usual Height Range	162-172cm	170-178cm	176-184cm	182-190cm	184-195cm
Stem Length	25-45	25-45	25-45	25-45	25-45
Maximum Seatpost Insertion (incl. actuator)	164	191	219	246	270

Static, based on a 160mm fork with 571mm static length.

170mm fork, mullet (29" front, 27.5" rear)

Frame Size	C1	C2	C3	C4	C5
Seat Tube (centre-top)	390	417	444	471	496
Top Tube Length (effective)	599	621	639	660	679
Head Angle	63.5°	63.5°	63.5°	63.5°	63.5°
Effective Seat Angle (720 BB-saddle)	74.8°	74.8°	75.2°	75.2°	75.2°
Effective Seat Angle (815 BB-saddle)	74.5°	74.5°	74.9°	74.9°	74.9°
Chainstay Length	448	448	448	448	448
BB Drop	32	32	32	32	32
Head Tube Length	100	110	120	130	130
Reach	435	451	473	492	511
Stack	638	647	656	665	665
Wheelbase	1233	1257	1279	1303	1322
Usual Height Range	162-172cm	170-178cm	176-184cm	182-190cm	184-195cm
Stem Length	25-45	25-45	25-45	25-45	25-45
Maximum Seatpost Insertion (incl. actuator)	164	191	219	246	270

Static, based on a 170mm fork (586mm static length) with a 1° angleset fitted to steepen the head angle.

160mm fork, mullet (29" front, 27.5" rear)

Frame Size	C1	C2	C3	C4	C5
Seat Tube (centre-top)	390	417	444	471	496
Top Tube Length (effective)	597	623	641	662	681
Head Angle	64.1°	64.1°	64.1°	64.1°	64.1°
Effective Seat Angle (720 BB-saddle)	75.4°	75.4°	75.8°	75.8°	75.8°
Effective Seat Angle (815 BB-saddle)	75.1°	75.1°	75.5°	75.5°	75.5°
Chainstay Length	448	448	448	448	448
BB Drop	37	37	37	37	37
Head Tube Length	100	110	120	130	130
Reach	440	459	478	497	516
Stack	635	644	653	662	662
Wheelbase	1226	1250	1271	1296	1315
Usual Height Range	162-172cm	170-178cm	176-184cm	182-190cm	184-195cm
Stem Length	25-45	25-45	25-45	25-45	25-45
Maximum Seatpost Insertion (incl. actuator)	164	191	219	246	270

Static, based on a 160mm fork (571mm static length) with a 1° angleset fitted to steepen the head angle.

Maximum seatpost insertion leaves 25mm clear below the actuator for a hose or cable to route through the frame. Your post may need more or less, and an externally routed dropper won't need this margin. Not sure about sizing for a used frame? Email size@cotic.co.uk.

Component sizes

Seatpost diameter: 31.6mm (380mm long minimum)
Front mech: not applicable, 1x drivetrains only
Fork: maximum 170mm travel, 586mm axle-crown (unsagged)
Bottom bracket width: 73mm
Bottom bracket thread: conventional English/BSA
Chainline: 52mm Shimano / 53mm Boost for up to 32t round or 30t oval; 55mm Shimano for up to 36t round or 34t oval
Chain guide mounting: ISCG05 bottom two tabs, plus the integrated Cotic Top Guide (supplied with the frame or bike)
Headset: 44mm for taper steerer forks: Hope 2H, Cane Creek ZS44 top/EC44 bottom, Chris King Inset I7
Rear hub: Boost148 x 12 bolt through
Rear axle: Syntace X-12
Rear mech hanger: Syntace X-12 Type 1 (conventional or Shimano Direct Mount)
Shock: 230 x 65 (160mm travel), 230 x 62.5 (155mm) or 230 x 60 (150mm), air or coil
Shock fittings: 20.0 x M8 down tube end, 24.0 x M8 seatstay end
Dropper post routing: Stealth via the down tube
Rear brake mounting: I.S., compatible with rotors up to 203mm

Owner's manual: download the Cotic droplink Longshot user manual 2021 (PDF).

Setup guide

There is also a Cotic sag setup video on YouTube.

Shock options. 65mm stroke for 160mm travel (Fox Float X2, Cane Creek Kitsuma Coil or Air, RockShox Super Deluxe on Gold and Platinum builds); 62.5mm for 155mm (RockShox Deluxe Select Plus on Silver builds); 60mm for 150mm (not offered from the factory, but usable with your own shock).

Sag. droplink suspension works best with 28-30% of the travel as sag, with 28% as the preferred starting point. Aim for 18-19mm at the shock (start at 18mm), 34-40mm on a 170mm fork (start at 38mm), or 32-38mm on a 160mm fork (start at 36mm).

Setting air shock sag. Start with 170psi in the shock and any lockout or climb switch off. Ride in full kit, with your pack and water if you carry them, saddle at full pedalling height. Bounce on the saddle to work the shock, stop, slide the o-ring against the seal, then sit on the bike with your feet off the pedals and get off gently without compressing the shock. Measure from o-ring to shock body and adjust pressure until you hit your target.

Coil shocks. Always ask Cotic for the spring rate. We need your weight in full riding kit, which can be up to 7kg more than your bathroom scales weight. Cotic frames are progressive and need stiffer springs than online calculators suggest: too soft a spring can damage the frame, and using a spring without Cotic's advice voids the warranty. To measure coil sag, have someone measure the shock's eye-to-eye length with you on board and subtract it from the unloaded length. For example, 230 - 209 = 21mm, so add preload to reach 19mm. Never use more than 2 full turns (2mm) of preload from the point where the spring just stops rattling, or less if your shock manufacturer says so. More than that voids the warranty, and if you need more you need a stiffer spring.

Setting fork sag. Then check the fork, aiming for 20-25% sag. Ride slowly with the saddle dropped, slide the o-ring to the seal while rolling, stand into an attack position, then sit back and roll to a stop without braking hard. Measure, adjust, and recheck the rear. Repeat until both ends are right. Because weight distribution varies with saddle position, stem length and bar width, always set up by sag measurement, not a generic pressure.

Volume spacers. Forks and shocks come with spacers set for a rider of about 75kg. For forks, add one spacer per 10kg lighter, or remove one per 10kg heavier (or move the HELM adjuster one click). Shocks are less sensitive to rider weight: add a spacer if you want more support, remove one if you're heavier and not using full travel.

Base tunes (all relative to fully open):

Cane Creek Kitsuma Air: 1 large volume spacer, HSC 0.5 turns, LSC 3 clicks, HSR 0.25 turns, LSR 1 click
Cane Creek Kitsuma Coil: no more than 2 turns preload, HSC 1.0 turn, LSC 5 clicks, HSR 0.5 turns, LSR 2 clicks
Fox Float X2: 1 x 0.6" volume spacer, HSC 1 click, LSC 4 clicks, HSR 2 clicks, LSR 5 clicks
RockShox Deluxe Select Plus: 2 volume spacers, MM tune, rebound 3 clicks

Other shocks. Start with rebound 3 clicks from fully open, and add damping only if the bike kicks you out of the saddle or springs back too hard off drops. Run compression or pedal platform off or at minimum: droplink is designed to pedal well without it.

Fork damping. Start rebound mid-range, then go faster until it feels sketchy and back off one click. Run high speed compression fully open or close to it, and add a volume reducer rather than damping if you use the travel too easily. Start low speed compression mid-range: reduce 3 clicks if it feels chattery, add 3 clicks if it dives under braking or on steeps.

A bit of advice. Don't set rebound with the bounce-in-the-street test, it leads to rebound that's too slow for grip on the trail. If you catch pedals or want quicker steering, add air and reduce sag by 1-2mm. Lap a trail you know, change one thing at a time, and keep a written base setup to go back to. Our base settings run on the lively, fast rebound side, so give them a couple of rides before changing them.