Jamis Dakar 650b Comp - First ride £2000

130mm trail bike with 27.5in wheels

BikeRadar score 4.5/5

Jamis Bicycles have been around for over 30 years. They were one of the first big brands to take a serious look at the advantages of 650b wheels and now offer several models, both hardtail and full suspension, alongside the usual array of 26ers and 29ers. There’s a superbly equipped Dakar 650b Pro at £3,500, but the Comp is a more down to earth (£2,000) offering that’s ready to take on big mountain rides as well hard-hitting singletrack and trail centre rollercoasters.

Ride and handling: Suspension shines more than wheel size

The sturdy chassis and fork of the Dakar, and consequent 14kg (31lb) heft, mean it’s never going to be an especially easy bike to haul up the hills – though £2,000 130mm travel full sussers never are. Happily, the rear suspension is stable and efficient enough to prevent all but a tiny amount of wallow when you’re stamping on the pedals, thanks mainly to the low leverage ratio of the rocker and shock setup.

Combined with the shock’s big air volume, which can be run at a relatively low pressure with minimum rebound damping, it makes for superb small bump response with a progressive compression on bigger hits that only very rarely results in full travel. That’s even the case with the sag set at around 25 percent of travel.

The fork performance matches the rear perfectly, with the sat-slightly-forward ride position (in relation to overall bike length) encouraging full use of the front end on rough descents rather than constant hanging off.

So what about the wheel size? Well, just as you’d expect, 650b wheels roll more smoothly than 26ers on rough terrain, but with 130mm of plush suspension it’s simply impossible to quantify how much more smoothly. What is noticeable is that acceleration kicks out of the corners are slightly better than on a 29er, and not obviously any slower than on a 26er. To be honest though, the differences are so minor as to be almost insignificant in the overall scheme of things.

Frame and equipment: Intelligent choice of geometry and parts 

650b (27.5in) wheels sit roughly halfway between standard 26in wheels and the 29in size. We say roughly because all three sizes are nominal: the imperial sizings refer to the tyre edge to tyre edge width and that varies between tyre sizes and brands.

The advantage of not going all the way up to 29in is that frame designers have more room to play with in terms of fitting in all the suspension gubbins, and that will usually mean fewer clearance compromises at the back end and a shorter fork. The smoother roll of bigger wheels means that less suspension travel is needed, so a 650b bike like this, with 130mm of travel front and rear, is always going to give a slightly smoother ride than a 26er with the same amount of travel.

Jamis use most techniques of modern tube-forming to create a swoopy and reinforced main triangle with a beefy tapered head tube, lots of standover room and enough easy-access cable routing channels to allow for a dropper seatpost. The suspension configuration is effectively a single-pivot swingarm (seatstay pivot), with loads of mud drop-through room, and the rocker-activated, high volume RockShox Monarch air shock offers a very effective rebound damping adjustment dial.

The fine detail is sweetly done: pivot bearings are quality units, there’s a single set of bottle bosses, a thru-axle rear wheel helps keep the back end stiff and the rear brake is mounted on an extension to the dropout assembly.

There’s a bottom bracket mount for a single set of bottle bosses, a thru-axle rear wheel helps keep the back end stiff and the rear brake is mounted on an extension to the dropout assembly. There’s a bottom bracket mount for a chain retention device, too.

It’s easy to argue that 650b would have been the ideal size to have plumped for way back at the beginning of mountain bike history (650b rims were widely available in Europe then). But today you’re sorely limited in tyre, rim and fork choices – just as riders were in the early days of 29ers.

Yet the fact Jamis have sourced decent tyres, rims and a fork, and that other companies are taking more than a passing interest in 650b, means it isn’t the issue it was a couple of years ago. Most of the major fork manufacturers recently released 650b options, with rim and tyre choices growing monthly.

The Jamis comes with an excellent 130mm travel X-Fusion Velvet air-sprung thru-axle fork – it lives up to its name for compression feel. It has a 1.5/1.125in tapered steerer for strength, a lockout dial on top of the right-hand leg and rebound damping adjustment tucked underneath.

WTB’s Laser Disc Trail 650b wheels are well suited to this bike’s character. Catalogue spec says WTB Wolverine tyres, but our test bike came with Kenda’s popular all-rounder Nevegals – 2.35in up front, 2.1in rear. Wheel size pedants should note that a high profile tyre like this up front actually creates a 28in wheel…

Braking is performed superbly by Avid Elixir 3s, with a 180mm rotor up front, while the drivetrain uses a Shimano SLX 3x10 setup.

This is simply a very well put-together bike that’s increasingly at ease as the terrain gets increasingly challenging. At the same time, it’s a massive amount of fun to ride on fast, winding local singletrack. It loves being thrown around and exhibits absolutely no nasty habits. It’s a class act.

This article was originally published in What Mountain Bike magazine, available on Apple Newsstand and Zinio.

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