Fell into a big hole, steerer tube went up by 1 mm. Bad???
 

I was puttering along a flooded street during a strong rain. The water was muddy so I can't see what's underneath and fell into a big hole right in the middle of the road lane. Fortunately, I was going real slow like 6 mph so I didn't fall, didn't crash, unhurt and uninjured and avoided pinch flat.

As soon as I got home, I noticed the headset developed some play so I loosened the stem bolts, removed the top cap and noticed the steerer tube have gone up by 1mm, almost to the top of the stem. What might have happened? I have sealed cartridge bearing headset on my bike. For sure, something on the headset, especially the bottom components moved or deformed by 1mm due to the impact. I already checked both the aluminum frame and aluminum fork and there's no damage, no crack, whatsoever.

I manage to re-tighten the headset and eliminated any play without problems. I checked for any binding, rough spots, loose spots, etc, there were none. In fact, steering was perfectly smooth like it was new. Apparently, the problem seems to have been fixed but should I be worried about the fact, the steerer tube went up by 1mm??? I didn't bothered to take apart the headset to see what really happened piece by piece as I needed to use the bike pretty soon.

There may be an easy answer. I'm trying to logic this out though....

The forces that hitting a hole would incur would seem to compress the bearing/spacer stack. Many explanations for your experience would seem to imply the opposite - a stretching force.

is it possible that your lower bearing was not fully seated on the fork bottom, and the force of impact fully seated the bearing?

Or that the lower cup wasn't seated fully? The OP didn't say what the age or make of bike is or the headset type so this is all a guess. It seems to me that an impact insufficient to even cause a pinch flat or distorted the headtube shouldn't have shortened it either.

Ah, I think that this is what I'd meant - Hillrider has pointed out the corrrect terminology (thanks Hillrider)

Also, I think that if the frame's not bent or cracked, you should be good to ride on it. In fact, the bump may have improved the OP's frame alignment!

My first thought also. All my HS experience has been the old cup and cone variety. Either the cone on the fork crown or the cup on the bottom of the headtube could have settled fully. If this is the case, all's good. (Look to make sure and turn the handlebars to see if there's binding.) I"m guessing that the issue would be very similar with cartridge headsets and the lower cartridge.

I do have one bike with a cartridge headset; my 14 yo custom with a Chris King threadless. It's been so trouble free I've never taken it apart so I still don't know the details at the fork crown and bottom of headtube!

ummm, how do you know it moved 1mm?

I've done over 5000 miles road on it on many bad roads. Regularly took on washboard roads and even big potholes at 20 mph. Hopped it over kerbs and over tree roots. Not a single problem. The headset never got loose, never had play. Always stayed solid, quiet, no play, and silky smooth until I fell into a big hole hidden by muddy water with sharp rocks at the bottom. Actually, the front rim also sustained very light damage. It was knocked out of true also by 1mm by the impact. But the damage is unnoticeable until you turn the wheel and notice the rim is slightly out of true. I have disc brake so the rim damage is of no consequence. I can't even tell it's out of true even on smooth roads, downhill at 30 mph so I won't even bother to get it fixed.

The headset is still silky smooth after I preloaded it again and tightened everything.

Not very surprisingly, the tires did not sustain any damage. It's a puncture resistant commuter / touring tire (Panaracer Ribmo) that has bead-to-bead puncture resistant layer and was indeed advertised to resist pinch flats and that it did so well. Great tire if you wish to survive WW3 but won't win you any races

The bike is a cheap Walmart type gravel bike that originally had cup and cone bearing headset. bought last 2020 and upgraded the headset to sealed cartridge type the same year. The headset product was ZTTO that only cost $7 commonly available from aliexpress.

I recently swapped out the stem for a shorter one just two weeks ago. I can still remember where the steerer tube used to be in the stem and the smell of fresh paint and I think Leonardo Di Caprio was there too.

If the steerer tube is pressed into the fork crown it may have been moved slightly. Check under the crown for signs of movement.

Maybe I'm not understanding, but my first guess would be that the stem slipped on the steerer tube.

I'm not really understanding what happened and am too lazy to read any more carefully and think any more deeply than I have already (sorry!). The first thing I thought of is: did the star fangled nut or expansion plug that is used to load the headset bearings slip?

If the stem slipped down then it (a) wasn't all the way against the spacer or headset below it, or the fork or headset was not properly seated, and (b) the stem wasn't not sufficiently tightened - it certainly should not slip down even if there were room to move.

As cheap bikes go, the steel steerer tube and steel fork is welded together. Fortunately, no way it's going to move. It's pretty strong but also unbelievably heavy.

The stem only prevents the steerer tube from moving down but not up. If the steerer went up, you'll get a loose headset even if you tightened the stem bolts real good.

When I was trying to tighten it up, first the top cap, it won't preload the bearings anymore so I removed top cap and saw the steer is almost to the same level of the stem. Before I panicked (because I threw away all my spacers) so there's no way I could preload the bearings anymore, I found a good sized washer and used that as spacer to help preload the bearings.

It worked out. Took the bike for a ride in a really bumpy route, hitting washboard surfaces at 20 mph. Upon getting home, I checked the preload. NOW the headset is less preloaded. Meaning the steerer tube went up again but this time by an an incredibly small amount so the bearings are still preloaded just fine, no play, no unusual noises, working perfectly like new.

For now I decided to stop worrying about it. I'll guess I'll keep checking the preload level after each ride and see if it's diminishing. I really do hope I didn't break anything on the headset, for sure the sealed bearings are fine because it's perfectly smooth but I'm a little worried the lower cups may have cracked or something.

I think the star nut slipping is of little consequence. It's a much bigger deal if the steerer slipped against stem. In my case, it's the latter that happened. The star nut did not move.

Maybe this is an instance of further seating the crown race by riding into pothole?

good example of why not to ride thru unknown water. I have a spot I ride thru several times a year, but it's shallow & I know the bottom is firm. plus, in daylight I can see the bottom

does not appear so. but wondering what is is going on w/ the bike. got pics of the new stem?

I'm beginning to think and hoping that to be the case. It would be the best case scenario.

Not sure you'll see anything on the stem even if I take the top cap off. I was able to put the stem and top cap back, preload the headset bearings and eliminate play by-the-book.

For what it's worth, I did not install the sealed headset bearing upgrade myself. I bought the headset from a LBS and had them install it and they didn't actually use that special tool to seat the crown but simply used rubber mallet. I've seem them do it many times on other bikes and I might have done the same thing if I had to install the headset myself. I suppose there's a possibility it did not get seated all the way.

I was taking my chance on that day and I was following a motorcycle closely that's also moving slowly and carefully. I suppose I did not track their wheel perfectly, may have been off by 1 ft to the side and I fell in it (the motorcycle didn't).

I'm fairly convinced now my next bike will have at least 2" wide wheels if I have to ride in all weather conditions. Pavement, gravel, anything.

koala logs, I think at this point you really need to take the fork out and inspect everything for anything unusual or damaged. Otherwise, we're all just making guesses with no way to confirm anything.

There is no reason for this type of gorilla-fisting when installing a headset. If you have an option you should not get any more work done at this shop. I occasionally remove and install headsets on my family's fleet of bikes and I made my own crown race setting tool (and my own headset cup press), they aren't complicated tools. There is no excuse for using a rubber mallet to install a headset.

I bought one when I wanted to change a fork
https://cimg0.ibsrv.net/gimg/bikefor...6295c9769a.jpg
https://cimg4.ibsrv.net/gimg/bikefor...4444407f39.jpg
then the tube slides over this & you just thrust it down a cpl times
https://cimg7.ibsrv.net/gimg/bikefor...f9caf2fad3.jpg
until it's past the taper & can't go down anymore
https://cimg1.ibsrv.net/gimg/bikefor...84984a6f62.jpg

I'll have to do it eventually if I get more free time or the problem gets any worse.