On test: Jamis Xenith SL, May 14, 2008

Jamis comes to play with its own sub-900g road rocket

The Xenith SL moves Jamis upscale

Jamis Bicycles' top-end Xenith SL road racer might not please the UCI officials but that shouldn't keep general consumers from partaking in the fun. Cyclingnews technical editor James Huang reports after a Rocky Mountain spring on this latest featherweight.

Jamis Bicycles is still a bit of an obscurity as compared to some of the bigger names out there but its Xenith SL monocoque carbon road platform provides a good indicator as to what direction these guys are headed in and how far things have progressed there in recent years. Whereas the sub-900g frame club was once rather exclusive territory, Jamis claims its newest carbon creation is a bona fide card carrying member.

Critical frame design elements include the rounded triangular-profile top tube and down tubes, full-length twin seat stays (as opposed to more common wishbone configurations) and asymmetrical chain stays, all of which are said to offer the holy grail of stiffness and comfort. Moreover, the top tube and down tube are also size-specific to maintain intended ride characteristics across the fairly generous 48-61cm size range. Rear dropouts are stiffer and more reliable forged one-piece aluminum units instead of the more commonly used two-piece bits.

Somewhat surprisingly, the Xenith SL really does weigh what Jamis claims it does: actual weight on our 54cm tester (yes, we took it apart) was just 890g and that even included the seat collar, rear derailleur hanger, bottom bracket cable guide, bottle bolts and barrel adjusters. The matching Jamis-designed Xenith monocoque carbon fork was similarly feathery at 290g (with factory-trimmed steerer).

The down tube and top tube utilize a 'tri oval' profile

In spite of the stiffness

The seat cluster is particularly clean.

Dual seat stays are supposedly lighter and stiffer

The bottom bracket doesn't appear all that monstrous

Asymmetrical chain stays are used

Forged one-piece dropouts are lighter and more reliable

Jamis' use of higher modulus fibers

Our top-end tester's stock build kit takes full advantage of its lightweight foundations. The nearly complete SRAM Red gruppo is punctuated only by FSA's superb K-Force Light crankset and an X10SL chain from KMC. Cockpit components include an Easton EA90 stem, EC90 Equipe SLX bar and EC90 post topped with a Selle San Marco Aspide saddle. As if there was any remaining doubt as to the Xenith SL's intended use, Jamis also includes a set of premium Zipp 404 carbon wheels and Vittoria Corsa Evo CX tubulars.

Total weight as equipped (but without pedals) is just 5.98kg (13.16lb). Yikes.

Ok, so it's light… so what?

We'll plead guilty to sometimes over-emphasizing the importance of minimal mass but there's little argument to just how a 6kg bike feels under foot particularly when there is so little sacrifice in terms of performance as seems to be the case here. Some of the credit undoubtedly belongs to the speedy Zipp hoops and their appropriate balance of low mass and sleek aerodynamics (if you've never tried a set of deep-section carbon tubulars, put off the kid's college education for a semester and treat yourself) but even swapping in our Mavic R-SYS reference wheels did little to alter the bike's get-up-and-go attitude.

In general, the Xenith SL may not quite be the stiffest bike we've tested but it isn't far off, either, and the overall experience belies one's expectations of how an ultralight machine should perform. There's no dullness or whippiness to speak of and unlike many other similar-feeling frames, Jamis doesn't resort to cartoonishly oversized tubing dimensions to get its point across.

Even the included fork offers up an astounding amount of handling precision easily comparable to forks a hundred grams heavier. The stout blades may not offer much in the way of aerodynamic performance but their reassuringly solidity is well worth the trade-off.

As a result, sprint performance is as you'd expect (which is to say, plenty fast) and handling reflexes are appropriately sharp in combination with the frame's relatively neutral 73/73 degree parallel angles and 271mm bottom bracket height. Naturally, a bike that is both stiff and light should also be a climber's dream and the Xenith SL is no exception… that is, until you run out of gears which doesn't take long given the stock setup's 52/38T chainrings and 11-23T cassette. Pure climbers likely won't have any issues here but something a little more befitting the rest of us would be very welcome here.

Just about the only place where we were mildly disappointed (and we mean mildly) was in the Xenith SL's ride quality. When fitted with the stock Zipp 404 tubulars, the Xenith SL delivers a buttery feel with excellent road feedback and a decent amount of liveliness. However, much of that buttery feel went away with some more conventional clinchers; small chatter was still absorbed well but anything bigger than typical pavement texture was felt loud and clear. The ride certainly wasn't harsh by any means in most situations but it's definitely on the firmer end of the spectrum, especially up front.

The rest of the finishing kit

The SRAM Red group continues to impress us with its superb ergonomics (man, we love the adjustable reach) and solid braking (augmented by Zipp carbon-specific pads). Shifting was very good overall and the KMC chain and OG-1090 cassette made for a surprisingly potent combination. Even so, it's still not quite on par with the kings of multiple-speed drivetrains in Sakai City.

Shift performance was very good up front as well but it's the silky smooth feel, absence of flex and low rotating mass of the FSA K-Force Light crankset that continue to win us over. As with the cassette, some riders may wish for compact gearing depend on their locale but thankfully, the K-Force Light is already endowed with a compact 110mm bolt circle pattern so a swap of rings is all that's required.

Simply put, the Easton EA90 stem was superb and lends ammunition to the argument that carbon fiber offers little advantage here. The accompanying carbon SLX Equipe bar, though, is still lighter, more comfortable and yet stiffer than any comparable aluminum bar but the unique bend might not be for everyone. The forward-leaning kink up top provides plenty of room for your wrists when you're in the drops but also puts undue pressure right on your ulnar nerve if you happen to rest your hands up there.

Unfortunately, the EC90 post was a bit of a letdown. While it never slipped during use, the molded-in carbon serrations eventually began to round off after a few adjustments and the generous 25mm of offset might be excessive for some riders' physiques. We had to slam the Selle San Marco Aspide saddle all the way forward on the rails for a proper knee-over-pedal spindle measurement but at least the perch was reasonably supportive and comfortable in spite of the relative lack of padding.

A racer's delight

All in all, the Jamis Xenith SL is a competitive rider's dream: it has a fantastically light yet rigid chassis that has just enough give to get you to the finish line reasonably fresh, competent handling manners, and a race-ready spec straight out of the box. Even the 1K woven top sheet finish and stealthy black, white and red color scheme on our test frame is flawless.

We won't call it inexpensive, but at US$6500, the Xenith SL is also a veritable bargain given the high zoot build kit (the wheels alone retail for over US$2000. Jamis also offers the same frameset with Dura-Ace and Mavic Ksyrium SL clinchers for US$1400 less.

The firm ride, flatlander gearing, aggressive positioning and race day-only wheels might give non-racers and more casual riders a bit of pause but all of those issues are easily rectified at your local shop if need be. Otherwise, most will find little to fault with the go-fast package.

Price: US$6500
Weight: 5.98kg (13.16lb), 54cm, without pedals
Pros: Fantastically light yet surprisingly rigid frame and fork, superb build kit, race-ready feel and positioning, excellent value
Cons: Ride quality could use a touch more refinement, flatlander gearing, love it-or-hate it bar bend
Cyclingnews rating:
More info: www.jamisbikes.com

Photography

For a thumbnail gallery of these images, click here

Images by James Huang/Cyclingnews.com

• The Xenith SL moves Jamis upscale and offers riders a top-shelf race-ready package at an attractive price.
• The advanced frame is said to be sub-900g and truly is; our 54cm tester was 890g including the seat collar, rear derailleur hanger, bottom bracket cable guide, barrel adjusters and water bottle bolts.
• Even with the light weight , frame stiffness approaches some of the best we've experienced.
• The down tube and top tube utilize a 'tri oval' profile that Jamis claims to optimize stiffness and weight.
• In spite of the stiffness , Jamis doesn't resort to ridiculously oversized tubes.
• The seat cluster is particularly clean.
• Dual seat stays are supposedly lighter and stiffer than monostay designs.
• The bottom bracket doesn't appear all that monstrous but the frame feels plenty stiff.
• Asymmetrical chain stays are used to better combat drivetrain forces.
• Forged one-piece dropouts are lighter and more reliable than two-piece designs (and they look better, too).
• Jamis' use of higher modulus fibers almost certainly has much to do with the solid frame feel.
• The rigidity of the matching fork belies its 300g weight.
• Carbon dropouts are reinforced with metal shields.
• The top-shelf spec includes a nearly complete SRAM Red group.
• The rear derailleur includes ceramic bearing pulleys as standard equipment.
• The titanium front derailleur cage helps save weight but is a bit flexy.
• The PowerDome cassette is one of the gems of the group…
• …with its unique hollow steel construction and ultralight weight.
• The new SRAM Red brake calipers deliver excellent stopping power and modulation, especially in concert with the included Zipp carbon-specific pads.
• Jamis trades in the SRAM Red crankset , however, for the significantly lighter FSA K-Force Light.
• The ceramic bearing theme continues to the FSA MegaExo Ceramic bottom bracket.
• Jamis shaves a few more grams by virtue of the surprisingly capable KMC X10SL chain.
• Zipp 404 carbon wheels and Vittoria Open Corsa CX tubulars make for an especially potent package.
• The front hub spins smoothly and includes carbon fiber shields (which are admittedly more for show than function).
• The premium Easton cockpit includes the EC90 Equipe SLX bar.
• The drops were plenty comfy but the upper bend was a love it-or-hate it affair.
• The light and solid Easton EA90 stem makes it even harder to justify carbon fiber models.
• The Selle San Marco Aspide saddle was comfortable enough but the matching Easton EC90 seatpost was a bit disappointing.