Focus overhauled their
Jam trail bike earlier this year, with 150mm travel suspension and geometry which put it into the aggressive trail or all-mountain category. Now they have a new version: the Jam Carbon. It uses the same swingarm as the alloy Jam, plus identical geometry and suspension kinematics, but with a carbon front triangle which not only saves a little weight (the alloy bike was a bit of a porker) but also adds a downtube storage compartment.
Yep, like
Trek and
Orbea, Focus have copied Specialized's SWAT homework and entered the storage wars.
Focus Jam Carbon details• Intended use: trail / all-mountain
• Wheel Size: 29"
• Travel: 150mm front and rear
• Aluminum swingarm, carbon mainframe
• Downtube storage
• Sizes S to XL
• 435mm chainstay
• 65-65.5-degree head angle
• Weight as tested: 15.6 kg / 34.4 lb (XL)
• £3,699 / €3,699 / £4,799 / €4,699
•
focus-bikes.com But when it comes to how it rides, it's not the smuggling capabilities or even the reduced weight that sets it apart from the alloy version, but the suspension products which make it more engaging and predictable.
Frame DetailsWhen Specialized first released the SWAT compartment for their carbon frames, they admitted the downtube door cancelled out much of the weight saving from going carbon. Even so, Focus claim their carbon frame weighs 760g less than the alloy version. I weighed my XL test bike at 15.6 kg - that's 600 grams less than the top-spec alloy bike (which has comparable but different parts) and slightly less than the claimed weight (15.8 kg). It's still far from the lightest trail bike, though.
Unlike most bikes with in-frame storage, Focus places the downtube door at the top of the tube, so you don't need to remove the bottle cage to access it and the supplied storage bag easily slides down (not up) the tube. It's easily big enough for a large pump or a medium-sized baguette.
Although we've seen it before on Focus's Jam and
Jam2 ebike, we have to briefly talk about the cable routing, which runs through the stem and the headset. There are no cable ports at the front of the frame or lugs for external cable routing, so cables have to be run through the headset. Focus still only offer their cable integration stem in this 50mm length. If you want to fit a different stem you'll need a
special headset top cap from Acros with holes for cables to enter, plus a lot of patience in the workshop to disconnect the hoses and cables and rebleed the brakes afterwards.
Suspension DesignThe Jam alloy and carbon use exactly the same linkage driven single pivot suspension layout, which Focus calls Focus Optimised Linkage Design (FOLD).
According to Focus, the leverage ratio is progressive throughout the stroke, with a generous 23% progression from 0 to 100% travel. Thanks to a relatively low main pivot position, there isn't all that much anti-squat to hold the suspension up under power - at sag in a 32:16 tooth gear, there's about 77% anti-squat, whereas most bikes these days are over 100% in that configuration. That means the bike bobs and slouches into its travel more than most when pedalling.
GeometryThe Jam C gets a flip chip to adjust the geometry. This changes the BB height by 6mm and the head and seat angles by 0.5-degrees. The effective seat angle (measured to the top of the seat post at a height of 750mm) is 76 degrees in the low setting and 76.5 degrees in high, while the head angle is 65 or 65.5 degrees. The chainstay length is slightly shorter than average, at 435mm, hinting at the Jam's playful intentions.
Models and PricingThere are two models to choose from: the top-spec 8.9 (which I rode) and the 8.8. They have broadly similar components to their alloy equivalents (the Jam 6.8 and 6.9) and cost about £1,000 more.
Jam C 8.9 - £4,799 / €4,699
Fork: FOX 36 Performance, Grip, 150 mm travel
Shock: FOX Float X Performance, 210x55 mm
Drivetrain: Shimano XT 12-S W/ SLX cassette, 10-51T
Brakes: Shimano XT M8120, 4 piston, 200 / 200 mm
Wheels: DT Swiss M1900
Tires: Maxxis Minion DHF 2.5 3C Grip EXO / DHR II 2.4 3C EXO+
Claimed weight: 15.8 kg
Jam C 8.8 - £3,699 / €3,699
Fork: RockShox Revelation RC, 150 mm
Shock: Rock Shox Deluxe Select +, 210x55 mm
Drivetrain: SRAM SX/NX Eagle, 11-50T
Brakes: SRAM Guide T, 200 / 200 mm
Wheels: Novatec D041 / D462
Tires: Maxxis Minion DHF
Claimed weight: 15.3 kg
Ride ImpressionsI only had the Jam C for one day back in September, but I got to ride it on familiar trails in the Forest of Dean, some of which I had ridden the alloy Jam 6.0 a few months earlier. The Fox suspension on this bike was noticeably suppler and more linear than the RockShox SuperDeluxe shock on the alloy Jam. This made the bike work with less sag (just a little over 25%) while still doing a good job of soaking up the chatter. The reduced sag made the Jam Carbon a little more upright and spritely on the climbs. The suspension still bobs more than most under power, but with minimal sag and occasional use of the lockout lever it's not a bad climber at all, especially on mellower gradients where you're not punching on the pedals.
Meanwhile, the Fox 36 fork offers impressive suppleness and mid-stroke stability. The more basic Grip damper doesn't hold it back much (if at all) when compared to the top-end version. Most importantly, the Fox suspension is well-balanced front to rear, which helps to keep the chassis stable while providing plenty of grip and pop at the same time. Though it's hard to be sure given the time between riding them, the Fox-equipped bike felt a little more forgiving and predictable than the RockShox-equipped alloy bike I rode a few months earlier. That's not to say the Fox products are necessarily superior, but the shock tune seems to suit the bike and the fork better.
I'd still prefer a 40 mm stem, and I think the head angle could afford to be a shade slacker when riding steeper, more demanding features, but for the terrain it's designed for, the Jam C is engaging, poppy and easy to get along with.
Black & Decker: *whizzzz whizzz*
Bad ideas, but ideas.
And Now my cables are killing my aero coefficient?
"If only"... a simple "Potts mod" BMX stem would do it. Straight down the steerer tube and out at the crown. A couple zip ties and you're done.
But yea, just seems like this makes replacing my stem complex for NO F'n REASON... no way does this solve an issue that hasn't already been figured out another way...
www.youtube.com/watch?v=2eiiROwuwtk
Easily? Did you actually try that with a bag _full_ of stuff? That opening looks quite smaller then a SWAT opening, and I can tell you from experience that getting a full doesn't-want-to-bend storage bag in and out of a SWAT door is not the smoothest action. Now make the door smaller AND put the top tube right in the way? That thing is going to be a pain in the ass.
Also, with the hole at the top of the tube... I guess you have to use the bag? Because if you stuff various item in there without the bag... umm, you're not getting them back out. Maybe we'll have to start carrying a coat hanger strapped to the frame?
But most of the progression is in the first 2/3rds or so of the travel. Last 1/3rd only has like 5% progression (2.6 to 2.47), so it's not going to feel as bottomless as that 23% number implies.
BTW I was in touch with the service team of acros recently. That headset cover works with all acros zero stack cable routing headsets (and there is an is versions as well), so you can upgrade/downgrade most bikes with cable routing out there quite easily and cheaply.
Needs citation.
"That means the bike bobs and slouches into its travel more than most when pedalling."
That means the bike has great traction when rumbling over rough stuff under power. It does not mean it bobs more. In fact the opposite: more anti-squat means more extending force per pedal stroke, so unless those pedal strokes are perfect circles, that extending force is going to vary, thus lifting and dropping the rider with each stroke. With less anti-squat, each pedal stroke does not extend the suspension as forcefully, thus less bob as the pedal forces vary.
Yes, under 100% will squat ("slouch into it's travel"), but it doesn't automatically mean more bob.
Walmart has pulled out of Germany and their try here was a huge failure, so maybe Walmart should start to offer their products on Jupiter
I'm really impressed that you're the spokesperson for every mountainbikerider from Canada down to Argentina, muy impresionante!