Bigger and Better

By Vernon Felton

WHAT: 2005 GT ID5 1.0
WHERE: www.gtbicycles.com
HOW MUCH: $2,799

I-Drive Through the Ages
I remember walking down the corridors of GT headquarters and stumbling upon something I wasn’t supposed to see. An engineer was walking some kind of dual suspension bike through the office and, apparently, wasn’t aware that a magazine hack was on the premises.

I immediately realized that the bike was some kind of top secret, prototype because the PR guy who was giving me a tour of the facility began flapping his arms and making loud primate noises in an attempt to distract me. The monkey-birdman gambit proved effective—while I struggled not to poop myself, the engineer whisked the prototype through a door, but not before I’d glimpsed a bike that appeared to have some sort of car alternator strapped to its bottom bracket.

The prototype out to be I-Drive and it proved a very important design for GT. Like many other companies in the bike industry, GT was in a tough position. Specialized Bicycles had just purchased Horst Leitner’s four-bar “Horst Link” patent and they weren’t interested in sharing the design with other major bicycle brands. Thus, GT needed to create a new full-suspension frame design that ate bumps adequately without robbing a rider of pedaling efficiency on climbs. I-Drive was their answer.

At the heart of the I-Drive design was a massive eccentric mechanism which housed the bottom bracket. The I-Drive eccentric allows the rear triangle to rotate freely around the bottom bracket—in essence separating the suspension from the drivetrain. GT’s engineers claimed that this design was immune to both pedal feedback and pedal-induced bobbing.

Old school I-Drive. Check out that massive eccentric.

Pedal feedback is a term that describes the following series of events: your suspension compresses, your rear wheel moves away from your cranks and your chain is pulled backwards, causing your pedals to also rotate backwards…in sum, this results in an inefficient, “lumpy” sensation in your pedal stroke.

Pedal-induced bobbing is a bit more straightforward. Basically, the force of your downward pedal stroke causes the rear suspension to compress, resulting in lots of unwanted bobbing that sucks your energy on climbs.

I-Drive Gets Simplified
The GT guys claimed that I-Drive conquered these twin suspension ills. In truth, the design was more effective at killing pedal feedback than at reducing pedal-induced bobbing. The bikes were super smooth on descents and didn’t feel loopy and psychedelic when you were climbing and hit something big, but I-Drive still required a very smooth pedal stroke on the climbs.

More distressing still was the massive, eccentric which housed the bottom bracket. While the eccentric proved surprisingly durable (given how exposed it was to trail slop), it was still a bit of a mechanic’s nightmare—requiring a fairly extensive list of tools.

Now, here’s where I start conjecturing a bit. No one at GT ever told me that they were on a mission to simplify I-Drive and ease consumers’ fears about that shiny eccentric, but I’m guessing that such concerns were at the heart of the facelift they gave I-Drive back in 2004.

New school I-Drive. The eccentric is gone, but the swingarm still rotates free of the bottom bracket.

The only tools you'll need to service the new I-Drive design are a splined bottom bracket tool and an allen wrench. Good beer just makes everything easier.

Beginning with the 2004 IDXC line, GT greatly simplified the design—the bottom bracket still floats between the front and rear triangles, but does so without the complicated eccentric mechanism. It’s a much simpler design. So simple, in fact, that you can tear the whole thing apart with a single allen wrench and a splined Shimano bottom bracket tool. The new I-Drive system rolled on readily-available headset bearings. The bikes also climbed with greater efficiency.

GT is still transitioning this lighter, simpler, friendlier I-Drive design within their bike line—at first it only appeared on the four-inch travel, ID XC bikes, in 2005 a five-inch version was added (ID5), and in 2006, you can expect to see the design completely replace the older eccentric design which is (as of this writing) still spec’d on the freeride Flowta models.

Theory Meets Reality
2005 was the year of All Mountain bikes…Every bike supplier worth their marketing salt has at least one, efficient-pedaling, not-too-damn-heavy five or six-inch travel model for sale (think Cannondale Prophet, Giant Reign, Specialized Enduro, etc.). And so it was that GT released the ID5 line this year: three bikes ranging in price from $1,499 to $2,799. What you see here is the pimp-daddy, top of the line model.

The ID5 1.0 boasts an impressive mix of components including a RockShox Pike Team fork (for more on that fork, click the following ROCKSHOX PIKE REVIEW), Fox RP3 rear shock, DT Swiss Onyx disc wheelset with 20-millimeter front thru-axle, Syntace bar and stem, SDG I-Beam seatpost and saddle, and Shimano XT shifters, derailleurs, and external bearing bottom crankset. This very worthy collection of parts is bolted to a 6061 aluminum frame that features swank, hydro- formed top and down tubes and the usual headtube/downtube gusseting.

Now, while every bike company may agree that the All Mountain niche is worth exploiting to the hilt, no one seems to agree on what kind of geometry is actually suitable for light, do-anything bikes. Though geometry is a decidedly less-sexy topic than component and tubing talk, I’ll argue that it’s actually a hell of a lot more important since it plays a huge role in how the bike actually rides. The ID5 sports a 69.5 degree head tube (not too fast and twitchy, nor too slow) and a 71.5-degree seat tube angle. The bottom bracket on our test model measures 13.5 inches tall. The top tube measures out at just below 23 inches.

Finally, the Damn Review!
It’s amazing how minor adjustments can make a huge difference in how you feel about a bike. The ID5 1.0 is equipped with a 35-millimeter rise Syntace bar. I just never felt confident with that bar on the bike—on descents, I felt positioned too low and forward.

I eventually swapped the Syntace for an old Eason Monkey bar with much more rise and sweep and, ahhhh, the bike fit like a glove. With its low bottom bracket and mellow seat angle, the bike is supremely stable on fast descents—even though its medium-length, 43.5-inch wheelbase ain’t exactly what you’d call “sprawling”.

I’ve spent most of the year aboard bikes with much longer wheelbases, but decidedly steeper seat angles and higher bottom brackets—while those bikes clear logs better, I distinctly prefer the rider positioning on the GT. Where other bikes sometimes come across feeling a bit tippy and nervous, the GT ID5, has a mellow, assured feel. Of course, if I lived somewhere with a million downed logs to ride over, I might curse that lower bottom bracket from time to time, but I’d probably also install a bash guard and savor the bike’s stellar stability.

Downhill Ace/Surprisingly Able Climber
GT recommends running the ID5 with about a half inch of sag. I resisted that advice for a few months as the bike feels decidedly soft that way. These last few weeks, though, I’ve decided to actually follow the set-up guidelines for the RP3 and, man, what a difference. The bike’s five inches of rear suspension now feels much closer to six. The ID5 smooths out minor bumps and swallows big hits with stunning prowess. I find myself riding much faster and with far greater confidence on this bike than I do on any other bike I’ve ridden this year. The lack of frame flex also helps here. The bike feels bullet proof. Brake jack, by the way, isn’t an issue either.

The ID5 climbs pretty well—better than a lot of seat-stay pivot, rocker link type bikes, but not as efficient as some of the Virtual Link bikes out there. While GT has done an admirable job of reducing pedal-induced bobbing, this is nevertheless a bike with a fair amount of travel, and I think most riders will still find themselves reaching down and taking advantage of the ProPedal adjuster on the RP3 shock (which can be run with a lot of ProPedal compression damping, a little damping or wide open). On seated climbs the bike gained elevation with surprising ease. Out-of-the-saddle climbs were easily tamed by simply setting the RP3 at its firmest position and twisting the lockout knob on the RockShox Pike.

Notice the large, 180-mm rotor? The ID5 comes spec'd with a number of such features which add up to true "All Mountain" performance.

Component spec on the ID5 1.0 is stellar—aside from swapping the low-rise bars for something with more rise, there really aren’t any required upgrades. Everything is top notch, from the Crank Brothers Candy pedals to the Avid hydraulic disc brakes. While no reviewer ever seems to gush about Shimano XT drivetrain components, it’s only because we’ve come to expect flawless performance from them. Such was the case here.

If I could change one thing with the layout of the bike, it’d probably be the front derailleur cable routing—the bike sports a massive loop of exposed cable which juts out from behind the seat tube and occasionally snagged an errant branch. While the healthy loop of housing never seemed to actually impair front derailleur shifting, it’d still be nice to see a little cleaner routing.

Final Analysis
When it came to cross country riding, I was never as big a fan of the original I-Drive design as were many of my fellow magazine editors. The old I-Drive just never lived up to its claims on the climbs. GT, however, has made huge gains with this refined version of I-Drive. I never expected a bike that weighs close to 30 pounds to climb this well, but the bike gains altitude with ease and feels much lighter than the scales suggest.

Every rider has different tastes, so you can take this last bit with a grain of salt, but I believe many bike companies are producing long-travel “All Mountain” bikes with overly-aggressive geometry. GT, on the other hand, hit the nail on the head with the ID5’s geometry—the top tube isn’t too long, the seat-tube isn’t too steep and the bottom bracket isn’t too high. This is, after all, a bike with five inches of travel: it doesn’t need to steer just like a cross-country racer.

If I could improve one thing about the general frame design, it’d be the standover clearance. At 31.5 inches, the bike could use more clearance. Other than that, I have no real gripes. The ID5 1.0 is an impressive climber and a holy terror on the descents.