thundercleese

Last summer my daily commuter developed play in the headset, despite repeated adjustment. Looking at the fork I noticed some scoring on the steerer and pulled the cups. Well, I found the culprit: I'd overlooked removal tool damage to the cups (last pic) when I transferred them over from a different frame. The deformed edge scratched the back side of my steerer tube as shown. I'd gladly ignore this if it was just missing ED coating (the black stuff) but it looks like it's scored the steel a slight bit as well.

So is this fork safe to ride, or shot? This is a steel touring / MTB frameset (which I occasionally ride front-loaded). I could source a new replacement fork for ~$125 or just put it back together and not worry about it. What do you think?

Additionally, a friend suggested I take sandpaper and lightly take the edge off the score mark so it's less likely to turn into a crack. Is that a legit technique for addressing this, or bunk?

base2 

It is a legit technique to prevent a stress concentration that later invites fatigue, cracking, & shorter service life/early failure. You must get all the way to the bottom of any deformity so that it is completely undetectable. For the stress to pass through undiminished.

Items under compression don't crack. High stress parts tend to be peened to compress the part surface to some Engineer's predetermined depth. It is an easy process given the right tools & resources.

If your steerer is peened & you are not with the tools & training to re-peen the damaged area, don't do it. The fork is done for.

Edit: I can see the the surface texture. Your steer tube is peened. Your damage is too deep.

thundercleese

Bummer. Well, thanks for taking a look. This is what I get for trying to save a few bucks re-using a headset. Feel like an idiot

shelbyfv

Good to know! Always more to learn. I'd have figured "it's steel, I'll give it a buff and ride it." Ooops....

Andrew R Stewart 

At least one here has a different opinion, me. I've seen far worse being ridden every day. Not saying that the scoring is a non issue, just not the death trap suggested.

I have to admit that peening isn't something I've seen much of in the bike frame world. I understand the reasons why a company might peen their products but a high volume/low profit item like a consumer MtB makes me doubt the peening claim. BTW there are plenty of shots of unfinished frames with the same "textured" surfaces and no claims of peening. Were I to make a frame using such a higher level of surface conditioning I'd sure want the world to know. I think peening is not what's going on here.

As to what to do, I'll leave that to the OP as his confidence in what he rides is the bottom line. Andy

thundercleese

Thanks, honestly I am not sure what the other poster was talking about re: "peening". I'm familiar with shot-peened finishes and that's clearly not what I have here; it's a Surly with the standard powder coated finish over an ED coating (the black finish on the steerer). Nothing too fancy. Did they mean it was "peened" by the headset cups banging against the steerer? Maybe? No idea really.

I'm really just concerned about catastrophic failure sometime down the road. It's a rigid touring / bikepacking bike, I'm not going to be taking it off drops of more than an inch or two. But given that a replacement fork is available I guess I'm just trying not to waste money on an unnecessary replacement that won't fail in a hundred years. Maybe I'll just buy that extra fork and re-inspect the scored one each time I do my yearly teardown...

dsaul

I've built a few forks with steel steerer tubes and they are all very thick in that lower section, with most being 2.3mm wall thickness and tapering to 1.6mm wall thickness at the top.. That little scratch would not give me any cause for concern. I'd sand that with some 120grit emery cloth, touch up the paint and keep riding it.

HillRider

Tha scratch is pretty deep and, if it were mine, I'd replace the fork just for peace of mind. Surly makes strong stuff but a steerer failure is no joke. Since you can get an exact replacement, I'd spend the money and do it.

70sSanO

Nothing to add, except I wonder how much damage a quill stem does to the inside of a steerer tube but no one sees it. Especially one that is stuck and someone is beating on the bolt to get the wedge to move.

What I don’t know can’t hurt me.

John

Crankycrank

To my eyes it looks like a very, very shallow groove that wouldn't be a problem but having said that I wouldn't bet any money that what I think I see in a photo is correct. I recommend the OP take it to several shops where it can be seen in the flesh and get their opinion. OP could also insert a short pressed in or bonded sleeve at the gouge for peace of mind rather than buy a whole new fork.

Andrew R Stewart 

The big problem for me is that this wear mark is in an otherwise unviewable location. So the often-given advice for a steel bike, of monitoring the spot, won't be easy and likely won't done.

I will also question the term "scratch". This type of mark is done by forming, not by material removal. The surface layers are displaced, IME usually to either side of the mark with extreme cases (and this example is far from that) causing some loss of steerer straightness. I doubt this mark has a sharp root or other serious stress riser. Forming steel generally results in a work hardening too. Could someone make an argument othat this mark is now stronger?

As I said before this is a risk/value/peace of mind type judgement and we will have different tolerances of this or that. Given what I have experienced and how this case looks (all 2D and long distance) my peace of mind is ok with continuing to ride this fork. I respect that others feel differently. Andy (who enjoys the discussion process)

base2 

Even if the rest of your bike is a steel touring bike, your fork looks aluminum to me. I feel a crown race remover would have a pretty tough time damaging steel in the way seen here.

Peening is a surface treatment that compresses the surface into the part some depth. It is done for structural integrity of the part. Most people don't know what it is, what it means, or how it would make the part "better." So any mention of it in marketing literature would be meaningless.

There are various ways to do it. If you know what shot-peening is, then you are already familiar with what a treated part should look like.

The process is not cosmetic.
The process is extraordinarily common.
So common it's not worth mentioning. Even El-cheapo Origin8 stems have a respectfully peened surface.

It also allows for much less material to be used to meet acceptable safety margins. IOW: It allows your steerer to be stronger and lighter using much less material.

What we don't know is the depth of the treatment for your steerer. In most of my experience the engineer usually calls out disturbing the molecular structure to a depth of 12-14 thousandths of an inch for high load, heavy structure, & somewhere between 4 & 7 thousandths the for standard/light load/secondary structure. A steerer, being critical to safe operation where failure would prove catastrophic would very likely be peened to a great depth.

Think of the tension load on the lower side of an airplane wing...Carry that tension all the way to aircraft wing root where the wing connects to the fuselage. That tension load caused by holding up the plane by the wing tips is going to want to tear the metal apart like paper. In the factory I worked in, every surface on that 1/2 inch thick lower panel would be compressed (molecularly squeezed smaller) by a peening process at least 12-14 thousandths of an inch to fool the part into believing that it was not being pulled on. There is no place on the part surface for stress to gather. So the aircraft lives a very long, safe service life. The top & bottom 2.5% of compressed part thickness literally prevents the part tearing like paper from some random knick on a sharp edge of a bolt hole or elsewhere.

The peening process was discovered by accident when engine makers would literally unload crankshafts from the delivery train & throw them into a pile outside to get rained on & rust before a factory worker would get to using them. They would then sand blast the rusty ones in preparation to build an engine. Crankshaft failure was extraordinarily common back then. It didn't take long before somebody realize the blasted ones didn't shatter as frequently & a new manufacturing process informed by materials science was born.

The load on the steerer is not simply torsion to point the front wheel somewhere. There is a lot of tension/compression going on as it counters the flex levered off the lower headset bearing. Every bump you hit flexes the fork blade in some direction. That much is visible, all you've got to do is look down. The counter to that where you can't see is going on inside the head tube. Imagine every bump the front wheel hits trying to bend the steer tube to the shape of a banana & then it springing back based on it's own rigidity. How deep & how long would you cut a leaf spring before it fails?

That the treatment in your case is scored through to virgin material is what has my concern. $125 is cheap insurance against $3000 of dental work.

Iride01 

Do you pull hard on the handlebars a lot for most of your riding? Probably not. It's a steel tube, I wouldn't worry about it.

But if you are doing a lot of off road trail riding and going down ravines and across a lot of bumpy paths it wouldn't hurt to be a little extra cautious and change it out. You really have to assess your own risk level.

Unless you are getting a deal you can't refuse on another fork, I wouldn't buy one for a spare. If you get it then put it on and keep the other for a spare.

Moe Zhoost

If this steerer is indeed steel, I wouldn't have any concern about riding it. Your slight damage is nothing compared to the scoring I've seen on quill stem bikes due to a mis-installed keyed washer that plows a groove when the headset is adjusted. Also, steel will not fail catastrophically like aluminum so you should have plenty of warning before a failure.

easyupbug 

I was a design engineer my first 6 years out of school and I suspect a typical stem design needing high reliability and ideally light weight would have a safety design factor of 1.5 times the max loading. Shot peening is used in cycling components, auto engine blocks and turbine blades, etc, to inexpensively reach the design/manufacturing engineers margin of safety for the load bearing capacity of the component. We often get away with scratches or other damage in an area that have the same overall safety margin of the component but is not in a highly stressed area. In this case replacing the original cup which restrains the tube to the same damaged spot might not be a good idea.

thundercleese

Thanks for the info about peening, that's interesting stuff.

The steerer is steel (and to my knowledge Surly has never made a fork with anything else). The crown race didn't factor into the damage. What seems to have happened is that my headset removal tool (an actual proper split-tube steel bike tool-- not a flat screwdriver!)gouged the top of the aluminum lower cup and left a pointy edge on the inside surface (this happened when I removed it from another frame before installing here). Tolerances at that spot are apparently close enough that it made constant contact with the steerer for a while, for at least a couple thousand miles.

During this time I intermittently noticed play in the headset, and it was difficult to adjust out. I think this was because my steerer was dealing with the interference from that edge. Unfortunately my attempted remedies (re-seat crown race, make sure cups were completely pressed in) didn't catch the cup-edge problem.

thundercleese

Thanks! Yeah, I saw a few of those keyed-washer-damage posts while researching my situation. In my youth I thought nothing of riding rusty, abused hulks all over the place... I recall one threaded steerer where half the threads broke off while doing a routine adjustment. Took some spacers out and kept riding it

I also think of the countless people I've seen riding along happily on obviously-crashed and bent forks. How are they all not dead? And how do I justify having a few beers and jumping curbs on the way home, on a 22 year old rigid 1x1? Maybe I'm being paranoid.

Andrew R Stewart 

One more data point has been revealed... the cup is Al. Now I'm no pro machinist or metal guru but I find it hard to think an Al burr removed any material from a steel shaft. Another data pint still missing is what amount of gauging has happened. I suspect far less than what most here think. Andy