What's my fork diameter? Giant Boulder Alu Lite
 

I recently acquired a mid- to late-90s Giant Boulder Alu Lite. I am thinking of replacing the threaded fork for a threadless fork, in order to have more access to oversized handlebars. (All the lower priced stuff appears to be oversized.) Several posts i read gave me impression that the quill to threadless adapters are not really that great, which is why I'm considering the threadless idea.

I am having the hardest time figuring out the exact diameter of the fork steerer. It appears to be between 1 and 1 1/8th. It depends on the measurement points used. Many people claim most MTBs made after 1995 have a 1 1/8th fork diameter.Is there another way to verify? I don't have any spare forks to usefor comparison.

I checked Giant's website for manuals -- no luck.

Thanks!

It's easy enough to confirm.

Forks are defined by the outer diameter of the steerer, which is typically either 1"or 1-1/8". The wall is almost always 1/16", so if you have a quill stem you can measure the diameter of the stem which is the same as the inner diameter of the fork. Add 1/8" for the two walls, and you'll have the fork size. ie. a 7/8" stem fits a 1" fork, and a 1" stem (actual, not nominal) fits a 1-1/8" fork.

Awesome, thanks. My stem is 25.4mm (1 inch), so that makes the fork 1 1/8.

Sure does, this opens you up to a big selection of theadless forks, headsets and stems.

I'm not a fan of the threadless quill adapters. They probably work, but are a kludge that adds unnecessary weight.

When you go threadless with a new stem, fork, and headset you will not be disappointed. Just add up the cost of the parts first to make sure a mid-90s Giant Boulder is worth the money.

Don't think it's worth investing in a new threadless fork. I realize the quill adapters add weight and aren't exactly pretty, but if those are the only drawbacks I'm comfortable throwing down $15 on an $80 bike. I believe the current fork I have is aluminum. $20 gets me a new steel fork, $50 for aluminum, and $80 for carbon.

I got a BBB stem raiser, being an internal quill , it also functions as an adapter, once wedge is tightened,
spacers are slipped over, and the shim from 1>1.125" , then the threadless stem grips the shim,

it worked... , my situation threadless , too short.. the clever bit is the steel wedge bolt, custom forged..
the 6mm allen hex socket is itself internally threaded, for the top cap bolt , that adjusts the headset preload.