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The transformation


Captain Fastbastard Mayhem
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Hey guys,

 

So as some of you might know, I recently bought a GT DHI from Pittstop, in an attempt to get closer to my goal of becoming a DH daemon.

 

It needs a bit of TLC, as well as a few more parts before she is rideable. Most of all though, she needs a new coat of paint and made to feel shiny and brand new again.

 

I've decided to give her a fresh lick of paint, in the form of Rustoleum's metallic "Black Midnight" which is really just gun metal grey. This is thread is going to mark the progress of her transformation, and will show you guys the end result of my hard work at getting her ship-shape again.

 

So - here goes. She is now all disassembled, and ready for the strippers (as am I, but don't tell my wife that!) to take hold of her and get her down to all her glory...

 

I will carry on updating as I progress... Timeline to completion of paint etc = 1 week. Timeline to total completion = inconclusive at this point in time. Relies heavily on sale of road bike, seen here.... BUY ME!

 

Here she is though, ready for the 2nd step towards a brand new life! I thought a bed shot was better than a couch shot, for obvious reasons ;-)

 

post-3056-0-70303100-1313875080.jpg

post-3056-0-70375500-1313875152.jpg

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Oh - btw - that green bag on the RHS of the first pic holds the iDrive assembly, chainring, rear derailleur, linkages, bolts nuts and screws necessary to keep her together. Only thing missing is brakes, tyres, shifter & chain.

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For me at least, not the ideal bike to race hardcore downhills with, but not a bad start at all. URT (Unified Rear Triangle) bikes (again, my opinion) aren't ideal for heavy bumpy applications. Your cranks, and with it feet, are in the same structure as the wheel that will be hitting the bumps. The some bumps will come through to your feet, albeit very little.

 

http://en.wikipedia.org/wiki/Bicycle_suspension#Unified_rear_triangle

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Let it be knows though... Many years ago (and I do mean mid 90's), I won a Giant Warp DS1 mountain bike at the Giant Knysna Oyster Festival at the lucky draw the night after the XC. The next day I won the Junior category downhill on it (Gavin Ragsdale Memorial). It was a URT design with 2.5-3" travel on the back and 3" on the front. So yes my friend, it can be done. Rock on.

 

http://www.thaimtb.com/webboard/109/54899-1.jpg

Edited by Azonic
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For me at least, not the ideal bike to race hardcore downhills with, but not a bad start at all. URT (Unified Rear Triangle) bikes (again, my opinion) aren't ideal for heavy bumpy applications. Your cranks, and with it feet, are in the same structure as the wheel that will be hitting the bumps. The some bumps will come through to your feet, albeit very little.

 

http://en.wikipedia.org/wiki/Bicycle_suspension#Unified_rear_triangle

 

It's not a URT, it's GTs original I-drive system.

What you see today is a more refined/lighter version

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Yeah, but the BB is still in the swingarm regardless?

 

Yes, but moves independantly of the swing arm, it is also connected to the main triangle.

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Not to mention that it has 7" travel front and rear...

 

All GT's FS bikes use the iDrive system, so not technically true that the system isn't designed to take big hits and carry on riding...

 

Have a look for figs on the GT DHI, and you'll see that they've been VERY highly though of in DH circles...

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Azonic - from your link to Wiki. Totally different design to a URT. Totally independent BB, independent of both front and rear triangle.

 

 

Unified rear triangle

 

The "Unified rear triangle" or "URT" for short, keeps the bottom bracket and rear axle directly connected at all times. The pivot is placed between the rear triangle and the front triangle so that the rear axle and bottom bracket move as one piece, and the saddle and handlebars move as another piece. This simple design uses only one pivot, which keeps down the number of moving parts. It can be easily modified into a single-speed, and has the benefit of zero chain growth and consistent front shifting. On the other hand, when the URT rider shifts any weight from the seat to the pedals, he or she is essentially standing on one end of the swingarm, resulting in an increase in unsprung weight which varies according to the length of the swing-arm and distance between the bottom bracket and the pivot, and as a result the suspensions effectiveness is reduced to some extent. During braking, riders naturally brace themselves on the pedals,[citation needed] and combined with brake dive leads to more severe pitching, sometimes called "stinkbugging".[citation needed] Because of lockout and pitching, along with persistent suspension bob in low-pivot URTs, and a constantly changing saddle-to-pedal distance, the URT design has fallen out of favor in recent years.[7]

 

Examples of bike with this kind of suspension include the Castellano Zorro, Catamount MFS, Ibis Szazbo, Klein Mantra, Schwinn S-10, Trek Y, and Voodoo Canzo.

Independent Drivetrain

 

The Independent Drivetrain (AKA IDrive) Pat # 6,099,010 / 6,073,950, was the 4th commercialized suspension design developed by pioneering MTB suspension designer Jim Busby Jr. The independent drivetrain system was a direct result of the limitations encountered with the GT LTS (links tuned suspension) 4 bar linkage design used by GT Bicycles from 1993 to 1998. The defining feature of Independent Drivetrain is the isolation of the bottom bracket (crank) from the front or rear triangle. This isolation allows the BB to move in such a manner as to neutralize the unwanted characteristics of chain growth at the pedal. Some may call this a "modified URT" but in reality it is a highly reconfigured 4 bar if examined theoretically. By using this isolated BB construction, pedal forces do not induce undesired suspension compression or extension nor does suspension activity produce pedal actuation through chain growth.

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Okay, so the paint stripping has commenced. Fork is almost completely bare, just a few random spots.

 

Rear triangle is a work in progress, but shouldn't take that much longer.

 

As for the main triangle - oh. my. word.

 

Decals are all over the place. ALL the colour on it, apart from the blue, are made up from decals. What does that mean? Paint stripper fail. Especially seeing as the paint stripper I got isn't the best, but I couldn't find the Genkem that Martin Hattingh was talking about earlier. Guess I'll just have to sit it through and carry on slaving away.

 

Anywho.

 

Tomorrow, I'm off to get me the rest of the bits & bobs that will make this puppy rideable.

 

Can't wait to start the paint, and then get on her and ride!

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