Garbaruk hails from Kyiv, in the Ukraine, where the company's founders, Valeriy and Yuriy Garbaruk, machine a comprehensive range of drivetrain products, including: oval and round narrow-wide chainrings to fit almost every popular crankset; one-piece-machined wide-range cassettes (ala SRAM); extender cogs; wide-range derailleur cage plates; and the three-cog Shimano cassette extender which we review here. The Garbaruk Shimano Xtender has an aluminum spider with steel cogs, and is a direct replacement for the three-cog segment of Shimano's 11-speed M8000 XT cassettes. MSRP is $119 USD, and $139 with the recommended derailleur-cage extension kit.
The Xtender, alongside Garbaruk's chain-take-up-plate upgrade kit for Shimano XT M8000.
• Material: 7075-T651 aluminum spider, 1066/1566 nickel-plated steel cogs .
• Compatible with: Shimano XT CS-M8000 11-40 and 11-42 cassettes.
• Options: 32-38–45T, 34-40-48T, or 34-40-50T
• Gear ratios:
Using an XT 11-40T cassette: 11-13-15-17-19-21-24-27-34-40-48(50)
Using an XT 11-42T cassette: 11-13-15-17-19-21-24-28-34-40-48(50)
• Cassette range comparison:
Shimano 11-40T cassette = 363.6%;
Shimano 11-42T cassette - 381.8%;
With Garbaruk 34-48T Xtender - 436.4% (454.5% with 34-50T Xtender)
• Note: Garbaruk recommends purchasing the Garbaruk 48 or 50T Xtenders with their modified rear derailleur cage for Shimano XT M8000 or XTR M9000 derailleurs to improve shifting.
• Weight: 246g (34-48T with spacer), 258g (34-50T with spacer)
• MSRP: $119 USD Xtender, $139 with derailleur cage extension.
• Contact: Garbaruk
Garbaruk's Xtender replaces Shimano's 42-tooth segment (top-left).
Why Use an Xtender?
For those who might need an explanation, Shimano's smallest cassette cog is an eleven tooth, while SRAM offers a ten tooth - which is the key to XX1's wider, more useful, 11-speed gearing range. Shimano one-by owners who need a lower gear for climbing can opt for a smaller chainring, but then that eleven tooth kills their top speed. The addition of a 48-tooth or 50-tooth extender-cog, like Garbaruk offers, allows the use of a larger chainring (34 or 36-tooth) to maintain or to increase top speed in the highest gear option, while also providing a slightly lower climbing gear. Garbaruk's three-cog Xtenders don't alter spacing of the first eight Shimano cassette cogs, so it also suits riders who want to enjoy the close-ratio gearing options of the standard Shimano cassette, but with the addition of a couple of stump-puller climbing gears. I chose the second option, pairing a 32-tooth chainring with Garbaruk's largest Xtender option - the 34, 40, 50-tooth combination.
Garbaruk's Xtender is a one-piece assembly constructed from a CNC-machined 7075-T651 aluminum alloy spider that is riveted to three nickel-plated steel cogs. The cogs are machined with shifting ramps and angled tooth profiles to assist the rear derailleur, and the overall construction and finish is top notch. The Xtender replaces the existing three-cog segment of the XT cassette and maintains the same alignment and spacing. Shimano's spider assembly has an aluminum 42-tooth, but the weight difference was minimal: Garbaruk's 50-tooth Xtender at 258 grams and Shimano's assembly at 235 grams. Shimano's 11 x 40 and 11 x 42 cassettes differ by one tooth on the eighth cog position, (27 or 28T), so keep that in mind, as that difference can be felt when shifting to the Xtender's 34-tooth cog. I converted an 11 x 42 and the shift felt proportional.
Assembling the Xtender is simple: Remove the cassette, line up the Xtender with the wider indexing-spline on the Shimano cassette, slide it on, add the included aluminum spacer, reinstall the remaining eight cassette cogs, and then re-torque the retainer ring. The larger cog necessitates adding some chain links, up to four in the case of a 50-tooth, so take care of that before you get excited and spin test your new transmission.
At this point, you can choose to run a standard Shimano XT M8000 ot XTR M9000 rear derailleur and screw in the B-tension adjustment until it shifts up to the larger cassette cogs, or remove the derailleur and install Garbaruk's longer chain-take-up arms. I installed the arms, which required a small amount of fiddling, but the task should be an easy one for an above-average home mechanic. Give yourself 30 minutes and have a spare derailleur cable laying around in case the existing one can't be reused.
Garbaruk's aftermarket chain-take-up plates increase the offset of the upper pulley, which allows the derailleur to follow the cassette cogs more closely.
Riding the Garbaruk Xtender
Remarkably, after resetting the derailleur cable tension, the modified cassette shifted perfectly without the need to turn an adjustment screw. Shifting was crisp and quiet until the 50-tooth, which made a buuurp sound as the changer hefted the chain upwards. The 50-tooth was slightly noisier than the stock Shimano cog, but not enough to worry a fastidious ex road racer. If Shimano's shifting was a ten out of ten, then I'd rate the Garbaruk Xtender cogs' performance an eight, with SRAM XX1 rated at nine. I'd call that good and not complain.
Not having used the standard Shimano derailleur chain-take-up cage, I have no information to offer there, but the Garbaruk cage, with its longer arm and additional offset offered a consistent distance between the upper pulley and the cassette cogs and required no B-tension screw adjustment. I'd call that a win too. The hybrid rear derailleur shifted effortlessly under load and never waivered when I asked for a shift at an inopportune moment.
Problems arose when I back-pedaled the drivetrain while it was shifted in the big, 50-tooth cog - a situation which often caused the chain to jump from the 50 and land somewhere in the middle of the cassette. One revolution in the correct direction would set it all straight, but that single turn of the crankset was occasionally, the crux move I needed to top a nasty boulder. In defense of the Xtender, as the steel sprocket teeth started to wear in, I found that I could back-pedal more frequently without risking a jump. Using a non-Boost chainring would move the drive sprocket inwards three millimeters and could solve the issue entirely. Pinkbike's Take:
|Garbaruk's 50-tooth Xtender spans the gap that Shimano's existing one-by drivetrains have yet to fill by sufficiently widening the standard gearing range without requiring a different cassette. I found the spacing of the 50-tooth option to be intuitive enough that, beyond climbing at a walking pace, the only signal to remind me that I was using an alternative transmission was the "bruuup" sound of the final shift. In retrospect, I would also like to try the 48-tooth version as well, to experience if the closer final ratio would be a benefit. If you can forgive the occasional meshing issue when back-pedaling - also a problem with many 11-speed one-by transmissions - then you should consider Garbaruk's beautifully constructed Xtender when the time comes to expand the gearing spread of your Shimano XT transmission. - RC|