1" Steerer forks are not 1"

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This topic has 8 replies, 5 voices, and was last updated 13 years ago by aP.

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1" Steerer forks are not 1"
simonlovell999
Free Member

I have a old gt outpost 1992 which i am building up at the mo. Wanted to change the stem to a girvin flexstem which is 25mm, but the fork is 22/23mm. Are all 1" forks like this

Posted 13 years ago

coastkid
Free Member

sure they arnt 1" 1/4 diameter? looks like it
some old cannondales i have had were that,if so will need to source an 1" 1/4 stem,

Posted 13 years ago

uplink
Free Member

1 1/4" is 31.75mm

Posted 13 years ago

tron
Free Member

I point you to Sheldon Brown:
http://www.sheldonbrown.com/gloss_st-z.html#stem

It sounds like your flexstem is designed for 1 1/8" forks.

Posted 13 years ago

simonlovell999
Free Member

the girvin flexstem is a quill stem and is a 1" and the forks are gt, but measured the diameter of the fork and is 23mm. So its under-sized?

Looked on sheldon browns and the internet, including retrobike.

Posted 13 years ago

uplink
Free Member

Are you measuring the O/D of the steerer?

Posted 13 years ago

tron
Free Member

Inside diameter of a standard threaded 1" fork is around 22-23mm. Outside should be around 25mm – ie, an inch.

The inside diameter of a 1 1/8" inch fork should be around 25mm. Outside diameter is about 28mm.

The above info is on the link I gave you…

Posted 13 years ago

simonlovell999
Free Member

measured both inside diameter of steerer which is 23mm and outside is 25.4. So i have to just accept that the stem is a 1" (25.4) and thats why it wont fit. So i stick to original stem

Posted 13 years ago

aP
Free Member

No, the stem is 1 1/8th and the forks are 1". The steerer is measured on the outside and it must have a thickness, which is why the inside is less than 1". The stem must be less than 1" to fit inside the steerer.

Posted 13 years ago