Isaac Muon review

Time trial bike with 11-speed Shimano Dura-Ace

Our rating 
3.0 out of 5 star rating 3.0
GBP £4,880.00 RRP

Our review

Powerful and excellent-handling ride for skillful riders, but not as light or fast as others
Skip to view product specifications

Dutch firm Isaac have certainly delivered a distinctive looking and focused aero alternative to the established elite. Does it put the negative spin on your times that its name suggests, though?


Ride & handling: Excellent handling in a powerful package

DT’s DICUT wheels weren’t just a great aesthetic match to the Muon – they also provided a very good parallel for its overall character. The acceleration-aiding low weight and high-tension direct-pull spoking helped offset the heavy frame weight, and meant there was no loss of punchy power delivery pulsing down the big chainstays with every press of the pedals. 

The big stem and firm bars mean you’ll have no trouble recruiting your shoulders into any climbing or corner-exit stomp, either. In fact, you’ll have to feather your ferocity occasionally to keep the rear tyre connected. 

While the Muon responds to the spurs when needed, it’s still a mount that tends to sit at a given speed – particularly on slight upward gradients – rather than gradually creeping faster and nudging for the next gear up as you get into your stride. 

Interestingly, despite its obvious drivetrain stiffness, the Muon always seemed to ride better being spun at a high cadence rather than crowbarred along in a big gear, but we’ll admit that we’re unsure why. One possibility is the absolutely excellent handling, which has a surefooted stability and assured authority that refused to get flustered however fiercely we spun the pedals. 

Having experienced some gusting and tramlining with the DT Swiss wheels on our default test bike, we were impressed with how obedient and well behaved the Muon made them feel. We certainly didn’t have any worries about reaching for gels or taking an aero tuck down sweeping descents, even in blustery, slightly sleety conditions that would have us backing off on less confident bikes. 

The handling also helps to keep your mental fatigue in check over longer rides too, but that’s tempered by a decidedly firm ride quality that becomes more and more intrusive as the miles increase. 

Isaac muon:
Future Publishing

Frame & equipment: Firm and not aggressively aero 

The Muon frame isn’t brand new, but you wouldn’t realise that immediately by looking at it. The deep, triangular, tapered forks sync into a cutout in the down tube, and the whole frame uses geometric triangular and kite-shaped aero sections rather than smooth teardrops. 

The head tube is kept short, for a low position, while the big hunchback top tube has a rubber plug for the vertically inserted gear and rear brake cable routing. The top tube is aggressively triangulated and tapered to blend into the geometric seat tube with wheelhugger cutout. 

The similarly profiled seatpost comes in two versions, depending on use. The Type A triathlon version we tested gets a forward flare at the top, as well as a sliding rail for the saddle clamp to allow very aggressive forward seat positioning, while the Type B version reverses the top for conventional time trial positioning. The press-fit bottom bracket is asymmetrically shaped for maximum stiffness, with super-deep chainstays taking your torque to the rear wheel. 

The replaceable horizontal slotted dropouts also let you fine-tune tyre to frame clearance. The front brake is conventionally front-mounted on the fork, while the rear brake cable loops out from the down tube into a bolt-on mast ahead of the unmasked U-brake mounted under the chainset. It’s not the most aero method of attaching anchors but it’s a blessing in terms of braking control, maintenance and easy fat wheel fit. The powerfully built frame isn’t light, though.

Isaac supply the Muon in various complete bike formats, or you can go down the à la carte route, as we did with our sample. The new generation, conventionally cabled 11-speed Dura-Ace helped drop the overall bike weight to a competitive level, but we really missed the cow horn shift capability when swapping over from Di2 bikes. 

The Vision aero bars also caused distributors Jungle some setup issues, but they felt great once they were on, and for once the extension length wasn’t baboon specific if left uncut. 

Vision’s flexible arm rest plates are always a welcome sight on firmly focused rides like the Muon too. In contrast, the big broad Isaac box stem might not have helped comfort but it was a vital link in the precise and well-balanced handling character of the bike.

While most manufacturers list wider cassette compliant 11-speed compatibility, actual availability is still proving an issue. That meant the Isaac ended up rolling on the light, responsive and very precise feeling DT Swiss DICUT wheels


This article was originally published in Triathlon Plus magazine, available on Zinio.

Product Specifications


Name Muon custom build (13)
Brand Isaac

Available Colours Black & White
Front Wheel Weight 990
Weight (kg) 8.12
Stem Isaac
Shifters Dura-Ace TT
Seatpost Isaac
Saddle SLR Tri
Rear Wheel Weight 1310
Rear Tyre Size 700x23C
Rear Tyre Continental
Rear Derailleur Dura-Ace 9000
Headset Type Real Design
Handlebar Vision
Front Tyre Size 700x23C
Available Sizes 52 54 56 58
Front Tyre Continental
Front Derailleur Dura-Ace 9000
Frame Weight 1520
Frame Material Isaac HM Nano Aero Carbon
Fork Weight 465
Fork full carbon
Cranks Dura-Ace 9000 53/39T
Chain Dura-Ace 9000
Cassette Shimano Dura-Ace 9000 11-25T
Brakes Shimano Dura-Ace 9000 front, TRP/Isaac U brake rear, TRP levers
Bottom Bracket Dura-Ace 9000
Weight (lb) 17.9