Giant ATX-D 990: 650b conversion

[Osella]

Okay, so it's a 1997 frame, but considering the way this build's gone, it better off 'hiding' here I think..

Spotted this on eBay a couple of months ago, and with no bidders at a starting price of £40, felt is was worth a punt..
Only went & won the bloody thing..

It would be in 'need' of a touch-up to the paintwork if it's to look original again, but given what it looks to have been through I'm not worrying about a restoration - this is going to be used & dragged through mud, hedges, (possibly backwards) so hey, the lived-in look is fine!
It had the front-end repainted with a 'fetching' shade of Grey daub, and from the Hope sticker I saw in some of the ebay pics, I suspect was raced at some point.

*pics from auction*

It's a bit of an oddity - the auction forewarned about a possibly damaged swingarm brace, but it's just bubbled paint fortunately.
The frame itself is a '97, but I think the chainstay has been replaced with a Tomac or '98 purple version (possibly a warranty replacement owing to crackage..) either way, no matter!

The bike's got the long-travel plates fitted too, which for me makes the original coil shock too spongy for its 'intended' XC/trail/uphill & down use. Really I'm an air shock fan, and that's kinda where the whole project moved sideways & started changing the endgame..

 

[mk one]

Re: Giant ATX-D 990

Good find :xmas-cool:
Could maybe try a stiffer spring, it looks as if the preload is wound on a bit so probably too soft for previous rider.
What forks are you thinking of using?

 

[Osella]

Re:

I should say that I was out of work when I started this, hence taking a punt on a cheapo frame I could do up slowly & with parts-bin pieces first of all, just to stave off boredom on days where it was too wet/dark to ride properly.

And so, it arrived...

Step 1 was to knock out the IMO hideous white headset cups & replace with the FSA Orbit Extreme I'd ordered in preparation from CRC.

Then fit the (pricey) but very nice replacement mech hanger, another CRC-saviour moment, as one of the few places with plenty of hangers in stock for all kinds of old junk like this

Next step was to clean out all the dried gunk & crud from inside the frame.. I think it slept in the barn and was possibly ridden through a dairy farm regularly let's put it that way..

So next was to search for a suitable Fox 180mm Air shock (still on the wait list that one!) and in the meantime I test-fitted the 165mm air shock off my decommissioned FSR, just to check actuation, responsiveness etc of the air vs coil on this frame. I had wondered whether I could use a 165 shock on this anyway, given it's relative 'old-school' geometry, so it's on the cards - having checked a few other possibilities out too, to follow later.

 

[Osella]

Re:

Having decided a shorter shock wouldn't be a terrible idea; I then mapped out the knock-on effects on the geometry and the 15mm shorter shock makes little overall difference to the headtube angle - partially compensated for by the longer-travel plates - and can be assisted by a nice short a2c fork keeping the front end low. The only danger/problem being the lower BB height this would bring.

Cue consideration #2; much wheel space. Originally I was going to build this up with some LX wheels on X222 rims, Magura HS33s and SIDs, but that changed on reviewing the wheel spacing & cost/weight of parts I had ready to go..
In order to raise the BB, one option that came to mind was trying to fit in some big wheels.
A quick check online check showed Dukes are compatible with 650b wheels, and a quick A2Z adapter to the rear from the spares box & I've got a 650b Giant ATX!

The wheels are some custom-built Hope ProEvo2 on Chrome Spank Oozy rims; weigh next to nothing and should roll really nicely on this bike! Trusty Schwalbe RR/NN combo.

A couple of considerations though; it's not just a case of whether things fit, but do they work? The Dukes do fit a 650b, but also the tyre:crown clearance is such that even under full compression the tyre won't contact the crown underside.
Likewise the rear wheel has 48mm of clearance between the tyre and seatpost; when running the 165x38 stroke shock, the tyre cannot contact the seatpost as the travel path for the rear axle doesn't allow the wheel to come into contact with the SP.
There's an increased leverage on the shock (through the long-travel plates+shorter stroke) and I can find very little info about the difference in the travel on the longer plates, however.. the air shock advantage is that I can tune the shock to account for the leverage, it gives me more progressive ramping (which I'm a fan of) and small vol shocks are great in this respect.

650b wheels wouldn't work on this bike with a shock having a longer stroke, and a longer e2e shock would elevate the BB to stupid heights and muck up the handling badly. Right now, it's got a high BB (tho not so much by today's standards) but a nice medium HT angle, steering is still quick with a short stem and there's no 'chopper' effect from the slacker angle, thanks to the shorter forks. Wheelbase is a touch on the long side - but that's a drawback of many big-wheel bikes.

 

[Osella]

Re:

Okay, many words of 'this is what & why'; so in the interests of brevity: Pics!

Lucky that the Dukes had enough steerer to get through the frame & provide enough area for both stem clamps to bolt to!
The bike's not finished yet.. Need to decide what to do with the paintwork around the front. I was originally going to go with Blue, but might just re-cover in a silver/grey. The rest needs T-Cutting eventually, which I'll do when i get a new shock & can ride the thing properly..
It's not going to be restored or put in a museum tho. If you've ever seen early episodes of the show 'Roadkill', they use the same way of going about builds as I do with older bikes, so paintwork not a priority on this one.

One thing I forgot is how much you need 32/34T cassettes with bigger wheels, given the increased gearing up of the wheel size. I'm still not sure how much travel the thing has, roughly 90mm front and 80mm rear by my estimation; which is nice for a woodland/trail/singletrack type bike I think!
I've got a 130/120 modern FS for heftier use. Total weight in current spec is an honest 12.6kg so should be nice as an all-day/explorer-type bike. Probably get plenty of use in the mud tho, I suspect..

 

[BobCatMax]

Re: Giant ATX-D 990 650b

I think that's turned out superbly. Aside from the visual clearance of the tyres, it just looks like a smaller frame.

Colour matching is nice with the yellow highlights on the nukeproof saddle and like the yellow bars up front. might have gone for some red QRs myself but otherwise, me likely.

 

[Osella]

Re:

Funny you resurrect this thread just as I've had time to tweak and fettle a few bits on it last weekend!

The blue QR's were just placeholders - the bike as pictured was really just a mock-up to fit & size parts. It's now (nearly) finished..
Cranks & BB have been replaced; I upgraded my Ghost's cranks so this has now inherited an ES51 Octalink + Alivio cranks. Managed to pick up a triple chainring set of Middleburn hardcoat rings for £25 on eBay, so those are also on. Also fitted black Clarks floating rotors I had spare, which goes better with the black spokes. Skewers have been swapped out for black, and the plan this weekend is to mask up & spray the front end black, to replace the grey and to T-Cut the frame, particularly the yellow & red areas. This is why no photos of it at the current stage of development..
Weight has upticked a bit to 13kg-still under 29Lb for a full-sus 650b for under a grand

It felt very nice on a short 15-min test ride on Sunday eve, so in the next weekend or two I hope to get out on a 'proper' ride with it!

 

[fatfixie]

Re:

For,future reference the rear hanger is the same as used n all atx/xtc models.

Yo can buy em on eBay from China for,a couple of quid,posted

Andy

 

[Osella]

Re:

Thanks for the tip about the hanger - might pick one up as a spare - just in case!

 

[Osella]

Re:

And a Saturday night ride!

No flash

Flash! (well, phone's best effort)

Lights on low-beam

High-beam:

And back home...