# Fork upgrade. How do I measure my steerer tube?



## c0ld (Jun 29, 2010)

Well im planing to move on to an air fork when I find a good deal, and I have no idea on the fork steerer tube lenght or diameter or how to measure or if it will fit my bike? Im pretty clueless, how do I measure it or how do I know which lenght of a steerer tube will fit my bike. I have a 2010 GT Avalanche 1.0.


----------



## qreeek (Sep 22, 2010)

Most reliable way is to unmount your stem and pull the fork off your bike, then measure the tube on it.
Then you only need to estimate the crown ring thickness.


----------



## c0ld (Jun 29, 2010)

Hmmm so I have to take out the bolts of the stem and then I can pull my fork out? Whats the crown ring?


----------



## metaljim (Apr 22, 2009)

"Crown ring" is actually the fork crown race. It's what the lower bearing sits on when your fork is in place. It is right where your steerer tube meets your fork crown.

To remove your fork, remove your top cap bolt, loosen the stem bolts, lift stem off, pull fork out. You may need to hit the top with a mallet to get it to pop free, as your headset may have a retaining ring that is holding it in. Don't lose any headset parts, and keep track of where they all go. Your bike will have a 1 1/8" steerer tube diameter.

Do the reverse to put it all back together, making sure you properly pre-load the headset bearings. See here for directions: http://www.parktool.com/blog/repair-help/threadless-headset-service#adjust


----------



## Ken in KC (Jan 12, 2004)

*There's an easier way...*

The measurement doesn't need to be so exact that you're taking off your fork. Jest measure from the headset cap to the bottom cup of your headset. Add a couple of mm for tolerance and you'll have an accurate enough measurement to purchase a fork with.


----------



## c0ld (Jun 29, 2010)

Do I need any special tools for removing the fork? Seems complicated now.

So I measure from the headsetcap to where the crown starts? Dont know whats the bottom cup of the headset.


----------



## Ken in KC (Jan 12, 2004)

*Sure...*



c0ld said:


> Do I need any special tools for removing the fork? Seems complicated now.
> 
> So I measure from the headsetcap to where the crown starts? Dont know whats the bottom cup of the headset.


Close enough. There is a top and bottom cup to every headset. Your stem sets on top of the top cup. The fork crown (the crown race, actually) sits underneath the bottom cup.


----------



## Clones123 (Apr 29, 2010)

Ken in KC said:


> Your stem sets on top of the top cup. The fork crown (the crown race, actually) sits underneath the bottom cup.


Wait...so the top is under the bottom...but then if the bike is upside down...


----------



## c0ld (Jun 29, 2010)

So in this pic the bottom cup is the black ring where the cooper tube starts?


----------



## mullen119 (Aug 30, 2009)

Clones123 said:


> Wait...so the top is under the bottom...but then if the bike is upside down...


Awesome pic:thumbsup:


----------



## AndrwSwitch (Nov 8, 2007)

c0ld said:


> So in this pic the bottom cup is the black ring where the cooper tube starts?


Yes.


----------



## Zoke2 (Nov 16, 2007)

this might help


----------



## c0ld (Jun 29, 2010)

That makes it much clearer now, imma go measure it know. So when looking for a fork search for one thats longer than what I measure on my bike right?


----------



## AndrwSwitch (Nov 8, 2007)

Not necessarily. If you have a few spacers, just matching is fine - they'll give you some wiggle room if the new fork turns out to have less steer tube.


----------

