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Colnago Star fork...what the heck is this thing?(26 posts)

Colnago Star fork...what the heck is this thing?Bonked
Nov 13, 2002 9:07 PM
Just received my C40. I didn't seem to get what Campy calls a "expandable adjusting nut," but did get the thing in the picture. Does this take the place of the expandable adjusting nut? If so, how does it work and how do you get it out (i.e. if you wanted to cut the steerer shorter)?

It's an adjustable expanding nut.Winona Rider
Nov 14, 2002 3:47 AM
It works like a quill stem. Losen the nut, tap it down, and the wedges part, losening the grip. Reverse to re-fit.
re: Colnago Star fork...what the heck is this thing?altidude
Nov 14, 2002 3:56 AM
will most threadless headsets such as a Chris King threadless come with an expanding nut or is that something which usually comes with the fork?
Gee, that sure looks like..........Alexx
Nov 14, 2002 4:48 AM
an expandable adjusting nut to me..........
you need an allen socket to install it-do you know what that looks like???
Gee, that sure looks like..........bobobo
Nov 14, 2002 5:08 AM
Perhaps he's new to the sport and doesn't know. Were you an expert on all components from day one retard?
Bite Me! (nm)Alexx
Nov 14, 2002 1:51 PM
Your Dad already has that job description. :-)bobobo
Nov 16, 2002 11:06 AM
that is a pretty wierd looking adjusting nutweiwentg
Nov 14, 2002 6:01 AM
but it is an adjusting nut. if you've never used a carbon steerer fork, consider having the LBS do it.
that is a pretty wierd looking adjusting nutaltidude
Nov 14, 2002 6:06 AM
Does an adjusting nut take the place of a star fangled nut in a threadless setup and if so, what's the difference between the two. What about a top cap.
YesWinona Rider
Nov 14, 2002 6:46 AM
the difference is that this spreads the strain over a larger area, and gives the steerer more strength. Particularly good if you are into spacers of course. And it's easier to use/adjust, although heavier.

Many manufactureres are now using these on all-carbon forks for that reason.

You need a top cap in the normal way.
Updated question.Bonked
Nov 14, 2002 7:28 AM
I guess maybe I didn't explain the question well enough. Also, to explain things better, I have been riding a Trek for the last 15 years; this is my first threadless fork.

In my original post, I was trying to ask three questions:

1. Is the pictured item an adjusting nut?
2. How does this item work?
3. How do you get it out of the fork?

I was pretty much just looking for confirmation on #1 and #2. However, I am still confused about #3.

Looking at the exploded view below, piece "A" threads onto "C" and, in the process, expands "B." "D" threads into a blind hole in the top of "C." I figure that you thread "D" into "C" and, when "D" bottoms out in the hole in "C," it will start pulling "A" up onto the lower threads on "C" and expand "B" in the fork. I tried this last night and everything seemed to work fine.

However, when you unscrew "D," it just unscrews itself, leaving "C" and "A" screwed together (and, hence, "B" expanded in the fork). I needed two pliers to get "C" and "A" appart this morning and can't figure out how you could do that when the whole thing is stuck down in the fork.

Thanks again!
Does either A or C not have an allen key hole in the top?Winona Rider
Nov 14, 2002 7:53 AM
If not - just get a long "D" and make sure you put the whole expanding bolt down to the headtube area.

There ought to be some way of tightening the bolt up independent of "D", or you would be pulling it up towards the top trying to tighten it/straining the steerer trying to collapse its top to tighten the expanding bolt.
No allen (or other) holes in A or C...Bonked
Nov 14, 2002 8:30 AM
hence my confusion. You can tighten the expanding bolt somewhat independently by using D to tighten it, removing D and then installing the headset cap, but, again, I can't figure out how you would get the expanding bolt out once it is in.
Fit and ForgetWinona Rider
Nov 14, 2002 9:15 AM
Design then. Just put it low enough down to give you some slack to shorten the tube if you want to (you should be able to guess the lenght you need close enough for that?)

I would suggest in a position that straddles the top bearing in the steerer tube. others may have a different opinion.
Nov 14, 2002 9:38 AM
I've installed several. This is basically an expanding mandrel. There is a 5mm internal hex in the top of part C the allows you to screw it into part A, expanding part B, so that it supports the inside of the steering tube.

The expanding mandrel can be moved up and down or removed simply by loosening the (internal) hex in part C. The top of the expanding mandrel should be set 2-3mm below the top of the steering tube. Once it's set, you never have to mess with it, unless you want to shorten the steering tube.

Bolt D goes through the top cap on the stem. It is used to apply pressure to the top cap on the and adjust the headset bearings to zero clearance.
He said there is no hex thereWinona Rider
Nov 14, 2002 9:53 AM
Which is odd - in my experience there always is.
but there is... (nm)C-40
Nov 14, 2002 2:10 PM
C40 is correctjhr
Nov 14, 2002 9:59 AM
You must remove the bolt (item D) from part C, once you do this you should see a hex socket insertion for expanding the mandrel. I have done this exact procedure 2 times on 2 different Star forks. I recall on one occasion grease on part C obscured the hex socket causing me some initial concern. Once I wiped the area it became obvious where the hex wrench inserted.

Fyi, I have moved the mandrel without any problems. Loosen part C and the whole thing loosens. It really is an excellently designed part. Other fork manufactures should copy it.

C40 and jhr thanks!Bonked
Nov 14, 2002 10:30 AM
I will try wiping off the grease when I get home. I must have just missed the socket head.

By the way, what kind of torque did you use to install this thing? I don't want to crack the steerer.

Again, thanks a lot!
C40 and jhr thanks!altidude
Nov 14, 2002 11:18 AM
I was gonna ask thge exact same question, how do you know when to stop tuning the part c screw which expands thre mandrel? Is this expanding mandrel a part you can buy separately and install on any threadless fork or does it only come with certain manufacturers forks? What does a Reynolds Ouzo Pro fork use?
Nov 14, 2002 1:30 PM
Unfortunately I have never used a torque wrench so I can't give you any exact torque value (I think torque wrenches are an old school new school thing, although I am old school I think the new school is one up on us as regards torque wrenches. I have been buying one for ages but just haven't pulled the trigger yet).

The mandrel serves two purposes (1) it serves as an anchor point for the top cap and allen bolt so you can adjust the headset and (2) it reinforces the carbon steerer tube where the stem clamps on to it(as C40 suggested you want to set it as near the top of the steerer tube as you can, while still allowing the mandrel to pull on the top cap [purpose 1]). I believe I used a Y shaped allen wrench (4-5-6mm) and snugged it up to the point where I knew it wouldn't slip upwards (my best estimate is 50% as tight as the stem bolts [both the bar clamp and steerer tube clamp]). Sorry I can't be more specific. Maybe somebody else here can provide specific torque wrench values.

Hope you enjoy your new ride. IMHO the STAR fork is far and away the best road fork made anytime, anywhere, ever! There I have started a flame war, someone will not be able to resist ragging nag's. Personally, I love it when they claim nag's are made in Mexico or Russia by under age, migrant, slave, prostitutes.

Torque- did the same...C-40
Nov 14, 2002 2:09 PM
I just used good judgement and a 4-5-6 Y wrench. You have to try real hard to overtorque something with a Y wrench.

The top cap bolt doesn't require much torque to adjust the headset, so extreme pressure on the expanding mandrel is not needed.

If you use a Campy record headset with the carbon fiber top cap, you will have to set the top of the mandrel a lot lower to accomodate the long unthreaded portion of the top cap bolt. The hole in the campy top cap is too large for a regular socket head cap screw, by the way. This setup has never caused me any problem, but don't get carried away when tightening the upper bolt on the stem's steering tube clamp. It doesn't require a lot of torque to keep a stem in place.
Thanks! Got home, cleaned off the grease and...Bonked
Nov 14, 2002 8:18 PM
there it was...I 5mm hex on the top of C. Thanks a million!
be careful...this is like a $600 fork you're messing withColnagoFE
Nov 14, 2002 2:25 PM
Don't mess with it unless you know what you're doing. A poster here once cut his too short.
That's why I'm asking <i>before</i> I do anything! ;) n/mBonked
Nov 14, 2002 3:27 PM
Closer to $750pmf1
Nov 18, 2002 1:51 PM
It was Doug Sloan who accidently did that. Bet it was painful to have to buy another.

And you kinda have to have it to make your C-40 look right. I never considered cutting mine myself. Not when a bike shop will do it and install the headset for $30.