020" of the O-ring protruding from the bushing which will seal the entire system nicely when the carrier is installed. The bushing needs to have a slight counterbore turned into it on either side that is. This is something they can measure at the shop. 020" clearance when the carrier is compressed by tightening the pin and nut with moderate torque. Bring the pin and pin nut, and tools with you so they can get it just right. The machinist should be able to figure out the correct displacement. I found that 1.95" worked for me, but manufacturing differences may mean it's different in your case. Meaning, it can't be too wide or it will bind. Critical: the bushing width needs to take into account the deflection of the bottom bracket carrier when tightened. Ask them to fit the bearings into the swing arm by milling it out and creating the bushing. Bring the fully disassembled swing arm, the bearings, and the bottom bracket carrier with you. Any competent machine shop can do this for you. The next step is to fit the new bearings into the swing arm housing which requires a milling operation and the creation of a bushing. These can be bought on Amazon: Koyo B-1816 Needle Roller Bearing, Full Complement Drawn Cup, Open, Inch, 1-1/8" ID, 1-3/8" OD, 1" Width. We will start by replacing the floating roller bearing design with two encased needle bearings that fit perfectly, fully supporting the pivot pin. To repair the problem permanently requires a redesign. It carriers the brunt of the pedaling forces. Typically, the problem pivot (there are two) is the one closest to the bottom bracket. Of course, once the swing arm aluminum is worn it will never be right again. It's just too weak of a design to last under even normal use. A heavy or aggressive rider will wear it out very quickly allowing a slight movement during pedaling which translates into a pronounced creak or click that can be felt in the pedals. It works well until the steel of the bearing wears the aluminum on both sides. They use an off-the-shelf 1-1/8" roller bearing from a headset that is suspended between an aluminum split cone washer and the beveled interior shoulder of the swing arm housing. However, its fatal flaw is the eventual wear of the aluminum to steel connections in their floating bearing design. But as with anything we don’t know how to repair, it’s easier to learn in a video.The parallelogram design of GT's complex iDrive 4 rear suspension pivot is clever and effective at stopping pedal bob, especially while climbing in the saddle. In a nutshell, a simple truing job is the act of loosening the spokes on the side of the wheel the rim is bent towards and tightening those on the side it is bending away from. This particular I-Drive had a little tweak in its front wheel. It was made in a time before youtube, so it’s hard to imagine where it was going to get seen, which is maybe a good thing.Īfter watching that, maybe you’ve had enough history for the day, so we can talk a little about what we were actually fixing on this bike. But the I-Drive stood for well over a decade as proof that it’s ok to get weird once in a while, and there’s no better evidence than the launch video. Basically, it worked well enough for the concept to evolve into a couple other versions of the same general principle until GT finally abandoned it in 2018. And the axle path, relative to the rest of the bike, was more rearward than traditional bikes of the time. And in a timely twist, they offered some of the benefits of a high main pivot because … well … they had a high main pivot … technically.īecause the bottom bracket moved with the rear triangle, it didn’t purely isolate suspension movement from your body weight, but it came close. They were efficient, supportive pedalers that remained relatively active whether or not you were on the gas. But if you were to hop on a first-generation GT I-Drive today, apart from the outdated geometry, it might not feel that bad.ĭespite its convoluted appearance, I-Drive bikes worked pretty much as advertised. The unified rear triangles, softails and elastomer shocks seem nearly unrideable by today’s standards. Most of the unorthodox suspension designs of our sport’s awkward 90s stage have not aged well. Heading out the door? Read this article on the new Outside+ app available now on iOS devices for members!
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