My Modern Classic - 1997 Giant ATX990

[DuncanDesigns]

I raced this bike back in 1997 when I was a teenager and have used it very little since then. I decided last year to use it as a pass time build and it has snowballed into a bigger project than I had intended. Before I started I had thought about restoring it as it was back in 97 but after a while I decided against this and instead decided to go modern. I stripped it right back to the frame and started with the geometry.

When I rode this as a teenager I was about 3" smaller in height and had a shorter reach so I felt back then it fitted me great. Today however the geometry feels dated and the frame a little small. I felt there was something i could do to overcome some of these issues by modifying the linkage plates.

In 97 Goldtec made alternative plates for this frame to increase the travel from 3.5" to 5" but it altered the head angle, raised the BB and made the rear end very unsteady. Even with the original plates this bike handles like a wet noodle but it was exagerated greatly with the long travel plates. My plan here is manufacture new plates which will alter the geometry


*pic found online


Original plates


My new plates


Old plates v new

The new plates will do a combination of 3 things. They will 1) increase the travel to approximately 110mm, 2) lower the bb height & 3) slacken the head angle by approx 1 degree.



When installed on the frame

 

[DuncanDesigns]

As well as manufacturing these linkage plates, I replaced the stem, handlebars, seat post and seat collar with Thompson components. I have used these parts on builds I have done in the past and I am a fan.

Another thing i wanted to alter on this build was the forks. I had an old set of Marzocchi Dirt forks which i wanted to replace - but this led to problems. The headset in this frame is 34mm and just large enough to house 1 1/8th straight steerer forks, which seemed to all but die away about 6 - 8 years ago. I had thought, incorrectly, that I could use the external headsets and squeeze a tapered set on there but that wasnt to be. Before I realised this I bought a set of Rock Shox Reba forks, with a tapered steerer. Unfortunetly they were useless. I was stuck with 1 1/8th options, which limited my market. I bought and sold several forks after this until I settled with Rock Shox Revelations, 150mm.

I have since discovered a company that can replace the crown and steerer on more modern forks to straight 1 1/8th steerers and I am considering this as an option, further down the line.


Rock Shox Reba forks which were of no use


I settled on these... for now. Rock Shox Revelation

 

[jinjrich]

Nice skills!

Are you modifying for a rear disc or leaving it rim brake?

 

[DuncanDesigns]

The groupset i had on the bike was a mish mash of various components I had in the garage which were replaced most weekends when I was racing. I had an Ultegra rear derailleur (short cage), AC DH cranks, XT Shifters and XT V Brakes. I decided all this had to be replaced - which led me to my next problem.

I bought a XT 3x crankset some years ago and had it kept in a box. I didnt want to let it go to waste so I decided it could be used now. I didnt want to run 3x though, I wanted this bike to be 1x. So the rings were removed and the outer was replaced with a Hope Narrow Wide 32T Chainring. The rear would be a 10 speed as I hoped to use wheels I currently had, and the max they could house was a 10x cassette. For now i will use a Shimano Zee rear mech which i have. Later this will be upgraded to XT.



The brakes however led me to some issues. 20+ years ago the go-to brake was the V Brakes - and they worked very well compared to the cantis which had gone before. Today however, disc brakes are the norm and I wanted this bike to run disc brakes front and rear. The problem with this frame was that it had no brake mounts on the rear stays. I looked at solutions that existed and didnt like any of them. I bought them, tried them, and decided I needed to do something a bit different.


The A2Z solution was never gonna cut it for me so I experimented with alternatives for quite some time until I found a solution I was happy with.


What i did here in the first iteration was remove the linking bolt from the rear stays and the chain stays, replacing it with a custom made part which would be bolted from inside, in the same way the original bolt was. The lower end of the bracket would be held in place much the same way the A2Z adapter was installed - by using the clamping force of the rear skewer.

To ensure the bracket did not move, I added lugs to the inside of the rear drop outs, which ensured it was held securely in place, no matter what abuse it was given.


3D prints were created to ensure the fit and placement were 100% before I got the part CNC'd

I was 90% convinced that I had a solution until I took the part to the CNC machine and I realised quickly the part was not impossible to machine, but rather difficult to cut on 3 sides, and would have taken quite some time to perfect. A revision was done and i decided on this -


A much more simple solution and means I can increase the disc sizes at a later date, as I would be using the existing interchangeable adapters already on the market. In this case I am running a 160mm XT disc, which I think will be sufficient for what my intentions are with the bike.

CAD images of both sides

 

[Kevhl]

Nice work, following this one!

 

[Baulz]

Great work on the link and brake adaptor!

 

[DuncanDesigns]

Thanks for the feedback so far guys. I have updated the previous posts with points i missed. This is an ongoing project and no doubt i will be adding and changing bits and pieces as time goes on!

Below is a picture of the XT levers, Thompson bars and Ritchey WCS grips.

 

[DuncanDesigns]

I picked up a new Fox shock to replace the knackered RST coil shock that has been on the bike since 1997. The original shock measures 180 i2i and the new one measures 184 i2i. This means that my new plates don’t fit- so i will have to remake them with a few alterations to allow for the difference.

Some time ago i had made carbon plates to experiment with travel and leverage, but they allowed me to place the shock and test for fit so i installed them to show the space needed and the measurements if need to take for the new plates. Just another job on my to-do list!

 

[lukewheels]

This is really interesting to me as I recently took a job as an engineering teacher; I'll need to machine some bushings having picked up a Kona stinky frame yesterday. I have an ATX DH which came out just after yours, same colours!

 

[jimo746]

Looks great, loving the cnc work on the bespoke parts.
For the rear disc brake adapter though, as you're using Post mount brakes, why not make it a Post mount adapter instead of IS and bolt the caliper straight to it!?