Isaac Muon review£4,880.00

Time trial bike with 11-speed Shimano Dura-Ace

BikeRadar score3/5

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:
Isaac muon:

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.

Guy Kesteven

Freelance Writer, UK
Guy started filling his brain with cycle stats and steaming up bike shop windows back in 1980. He worked the other side of those windows from '89 while getting a degree in “describing broken things covered in mud" (archaeology). Dug historical holes in the ground through the early '90s, then became a pro bike tester in '97. Guy has ridden thousands of bikes and even more components the world over since then and can remember them all in vivid, haunting detail. Can't remember where the car keys are, though.
  • Age: 45
  • Height: 180cm / 5' 11"
  • Weight: 68kg / 150lb
  • Waist: 76cm / 30in
  • Chest: 91cm / 36in
  • Discipline: Strict sadomasochist
  • Preferred Terrain: Technical off-piste singletrack and twisted back roads. Up, down, along — so long as it's faster than the last time he did it he's happy.
  • Current Bikes: An ever changing herd of test machines from Tri bikes to fat bikes and everything in between.
  • Dream Bike: His Nicolai Helius AM custom tandem
  • Beer of Choice: Theakston's Old Peculier (not Peculiar)
  • Location: Yorkshire, UK

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