Forks and adjusting headsets

[maxcr]

There was a conversation on the Roadini thread about adjusting the headset after fork removal.  This is something I've wondered for a while - some say you need to wrenches others one, my experience is if I tighten and back a bit I can move the nut with my hand.

Does anyone have a solid explanation of how it's done? When installing one of my forks on a new bike I had found this video from Rivendell where you can see the process but I'm still unsure of how tight I should go? Should I use a wrench or is it enough to hand tighten?

Also, how many spacers should one use when setting up a fork?

Thanks
Max

[Wesley]

This advice all applies only to threaded forks (all Rivs except Gus and tandem):

1. Use as many spacers as necessary so that the lock nut (top nut) is fully engaged with the threads but doesn't bottom out.

2. Most (or all) threaded forks have a key groove in the steer tube, cutting vertically through the threads (it is barely visible at 4:23 in the video you linked). A lock washer goes on the stack above the bottom nut (which is the top bearing's inner race), with a tab or "key" that fits in this groove. As a result, the lock washer cannot spin relative to the steer tube. Thus, friction from the spinning of the locknut and spacers above this lock washer cannot cause the bottom nut to spin. So that bottom nut will stay where you left it, even though you may crank down the top (aka lock) nut with just one wrench.

3. There is an ideal tightness to which you will set the bearing. But the lock nut works by stretching the steel of the steer tube (just a tiny bit!) until the threads don't engage the bottom nut (this is why the bottom nut doesn't work loose over rough terrain). Stretching the steer tube elongates it, so the bearings get looser. Therefore, you must adjust the bearing to be too tight before the locknut goes on, so that the stretching brings the bearing to ideal tightness. Accomplishing this requires a feel that develops over time. Or you could just get a sealed-bearing headset, which allow much more leeway in bearing adjustment without feeling loose or tight (because a sealed bearing headset squeezes the bearing races, not the balls.)

Hope this helps!

-Wes

[Wesley]

Oh, and to be more practical: If you can turn the top (lock) nut by hand, it is not doing anything. I am not sure why the video recommends backing off the lock nut, but I don't think you should. The "lock" function comes from tightening that nut until it stretches the steerer. Taken to the extreme, this will cause the threaded section to be in tension between the lower and upper nuts until turning either nut in either direction would feel like "tightening" it. Hence, the nuts are locked. This is how the lock nuts on loose-bearing hubs work, for instance. You don't need to go to that extreme on the headset, since the upper bearing doesn't really do anything other than keep the steerer centered (the bottom bearing carries all the weight). So just go ahead and turn the lock nut until it is snug (guesstimating: 15 ft-lbs) and go ride.

-W

[George Schick]

Adding to Wesley's excellent advice, I've found that applying a thin layer of LocTite "blue" to the threads of the top locknut will help keep it from loosening up over time.

[Piaw Na]

Are the FSA Duron headsets that come with Rivs sealed bearings? The FSA website claims angular contact bearings but lists the seals separately?

On Tuesday, July 25, 2023 at 10:00:56 AM UTC-7 Wesley wrote:

[George Schick]

There's another aspect to adjusting threaded headsets: holding the fork stationary while using the two wrenches (one on the bottom of the upper stack and the other on the locknut).  Stein Tools sells this device to accomplish that: https://steintool.com/portfolio-items/fork-stabilizer-tool/.  But instead of paying $60 for a specialized tools that gets used only occasionally, I just put the front wheel into the fork blades and hold it steady with my knees while tightening those headset nuts.  I have what used to be called an "Ultimate Rack," now just called a Feedback Sports Rakk bike stand https://feedbacksports.com/products/rakk-bike-stand-black?variant=44392877752618 to stabilize the bike so it doesn't tip over. It's close to the same cost as the Stein tool, but it can be used much more frequently to hold the bike upright while inflating tires, etc.

[maxcr]

Thanks Wes, George and Piaw - It seems like I need to go back and readjust my headset!

Max

[maxcr]

For those that missed it, the Riv crew posted a little how-to on their news blog:

https://www.rivbike.com/blogs/news/how-to-adjust-a-threaded-headset

Max