[url=https://flic.kr/p/ZarW53]30mm head tube[/url] by SIMON ASQUITH, on Flickr

I,ve decided to restore my 1980’s giant bike but its been easier to bang my head against a brick wall thatn trying to search and find out what size headset and fork steer size I need.
Am I right in thinking that I need a 1″ headset and a 1″ steer fork?
Cheers

Translate to Imperial to get 1 1/8″ headset, standard size for that age

no it’s not a 1 1/8th headset you’ll need …30mm is not 1 1/8th and anyhow headset required refers to the steerer tube OD .
I’d imagine it originally had a fork with a threaded 1 inch steerer tube and a 1 inch threaded headset . gets a little complicated as iirc there were two 1 inch threaded headset sizes ( tiny difference ) ISO and JIS .
which fitted 30 and 30.2 ID headtubes and different crown race sizes.
Have a look here for more info on sizes.
I’m happy to be corrected if anyone disagrees
HTH
Bill

1 1/8″ was not used on Giants in the 80s.

Kaiser is most probably correct.

It would have originally been fitted with something like this:

https://www.sjscycles.co.uk/headsets/tange-levin-cds-1-inch-chrome-steel-cup-threaded-headset/

bear in mind if the ID is 30mm as it looks ( rather than 30.2 ) the headset linked to above would not fit ..as it’s a 30.2 cup .DJ is just using it as an example of the type .

Thanks for input everyone. it was a thread headset/fork but ideally am wanting to replace everything with a none-thread headset and a new 1″ rigid forks.

Think this is the correct info I need

[url=https://flic.kr/p/Ct9u2y]Capture1[/url] by SIMON ASQUITH, on Flickr

Can you borrow a vernier caliper with tube I/D ‘tongs’ ?

Even then, it’s not going to be easy to distinguish between 30.0mm and 30.2mm, unless it’s a nicely machined head-tube.

Where can you buy new 1″ thread-less steerer MTB forks then ?

Here are some 1″ steerer forks:

http://www.carboncycles.cc/?s=0&t=0&rb=14&