Weird Head Tube Diameter

[surveyorcam]

Hi Everyone.

New to the forum. I have an old Giant ATX900 dual suspension frame. I recently went to replace the headset and came up with a bit of an issue. The inside diameter of the head tube is 42mm, which puts it some where in between the 1 1/4" standard and the 1 1/2" standard.

Can anyone tell me what sort of headset was designed to fit into this diameter head tube?

The frame came with a 1 1/8 headset and a shim to make it work, but I was hoping to get away from this arrangement.

I know I should just buy a new bike, but there is something alluring about 90's color scheme that makes a bike look like a parrot.

 

[danson67]

Re:

Hi SVC,

Welcome to the forum Keep your hand on your wallet or before you know it you'll have a shed full of weird old stuff...

So, down to business: Useful Cane Creek spec document here:https://www.dropbox.com/s/1nar6oi4ezjqb ... 0Creek.pdf

If it's got a straight internal 42mm ID, the headtube the closest is a Cane Creek zero stack headset for a 1" steerer...official spec is 41.4mmØ. But that doesn't look right for a late 90s frame. :?

Otherwise, if there's a big tapered shoulder in there, it could just be a Campagnolo fit 1 1/8" integrated set, but that would be pretty weird on a Giant mountainbike.

So not much help, I'm afraid. Worth double checking the diameter against the Cane Creek specs above.

Depending on the headtube OD (50mm if possible), it might just be worth reaming it out that little bit to 44mm ID and running a normal ahead...

Parrot?...now this is a parrot :

All the best,

 

[coomber]

Re:

I briefly had a giant road bike that had a similar arrangement. Pain.

As far as I was aware it was 1 1/8on the atx range but obviously not.

Hopefully someone will know

 

[drystonepaul]

Re:

Sounds like it could also be a Microtech Integrated headset which is listed here: --> http://www.parktool.com/blog/repair-hel ... -standards

Also states that it's an obsolete standard, so it will be difficult to find a suitable replacement. I'm not sure exactly when they were available though.

 

[surveyorcam]

Re:

Thanks for the replies.

It does have a little shoulder inside the head tube, would this imply it is some sort of integrated affair. The exact measurement was around 42.8mm.

That park tool link is a great resource, thanks. It does look like it might be the obsolete Microtech Integrated standard. I'll post some pics if I ever get it back together.

Cheers

 

[surveyorcam]

Another Thought

As suggested above, How would a person go about reaming the head tube out to 44mm?? If I did this then I could buy a whole heap of different Zero Stack headsets that are readily available.

Actually that's probably not the right question, the right question is does anyone know how thin you could make the walls of a head tube before you compromise it's strength?

 

[drystonepaul]

Re:

Good question.

The Zero Stack or ZS44 headsets you refer to are still an interference fit, so they do still need pressing into the frame like the older conventional external cup types.
This means there will be some pressure exerted on the head-tube at the fitting stage.
The external diameter of the lip on the outer face of the cup is normally 50mm, which normally matches into the ~3.0mm tube wall thickness of the head-tube. Effectively giving the cups a flush finish with the head-tube.

I'd be looking at retaining at least 2.0mm of tube thickness around the head-tube after reaming. So if you are going from a 41.8mm to a 44mm internal bore diameter, then you are removing ~1.1mm from the wall thickess.
If the current wall thickness is just over 3.1mm then it could work.

Easiest way to check would be to simply measure the external head-tube diameter where the cups press in. If it's 50.0mm or more then I reckon the frame could take the modification. If it's less than 50.0mm then it could start to compromise the frames structural integrity.

The next tricky part would be to find a shop with a ZS44 headset reamer...