Requiem for a Jaw

For a few days now, I’ve had this nagging feeling that my headset was getting loose. Every time I hit the brakes, I could feel a slight wobble in the bearing. My bike isn't exactly a showroom model—it’s 17 years old—but I’ve kept it in "good" shape. All the vital components have been regularly serviced, lubed, and pampered. Everything, that is, except for the fork.
So, yesterday, I’m cruising down Grushko Street. The fork felt even looser than it did the day before. I’m riding past the botanical gardens, and as I pass under the overpass, I take a massive jolt, like I just slammed my rim straight into a curb. After that, the bike was handling like a drunkard. Once I realized what was happening, I pedaled home like my life depended on it... barely made it. As soon as I got it into the garage, I lifted the bike up and the wheel and part of the fork just... fell right off. If that had happened on Grushko near Chase Bank, they would've been scraping me off the pavement with a shovel.
So, tell me, how much do you actually trust the critical parts of the machines you rely on to keep your head attached to your shoulders?

Which specific fork are we talking about here?

To be honest, I’m not even entirely sure how all the individual components fit together—which is why whenever you buy a bike, they hit you with those intense warnings right out of the gate. It's always "ride it like this," "don't do that," "watch out for this," or "make sure you maintain it exactly this way..." 😬

Dennis Collins38 said:So, how much do you actually trust the critical parts of your ride—the stuff that keeps you from ending up in a ditch?

Pretty much.
I gotta be careful since I love tearing it up on the highway...

Right now, I’m not totally happy with just the tires (they've done their time and are begging for replacements) and the worn-out pads, especially the fronts (those definitely need swapping).
Everything else is still sitting at a solid 5.

John Thompson872 said:Which fork are we even talking about here?

I honestly don't know enough about the specific parts to say... which is why when you buy a bike, they hit you with all those heavy-duty warnings. Ride like this, don't ride like that, watch out for this, make sure you maintain it this way or that way... it's endless...😬

Just a standard rigid fork, whatever stock part they slapped on the frame at the factory.

silentpanther15 said:Quite a bit.
I have to be careful since I tend to drive like a maniac...

Right now, I'm not just unhappy with the tires (they've seen better days and are begging for replacements), but also the worn-out brake pads, especially the front ones (which definitely need replacing soon).
Everything else is still at a 5.

Are you sure about that? My cousin's three-year-old mountain bike had a seat post snap right under them. Talk about an unwelcome surprise.

I’m behind the wheel, and if this thing falls apart 🤷! I’d give him 🙂 if it actually breaks down, but maybe he's too scared of that to let it fail completely—or at least not all at once.
There’s zero security here; you're basically just driving on pure faith.

I’d argue that high-end bikes are thoroughly stress-tested against every predicted load, pushed right to their breaking points—at least the prototypes are. Of course, factory defects can still pop up on individual units here and there. Most issues actually stem from things being under-torqued or over-tightened (which is why torque wrenches exist) or just poor assembly. Then there's material fatigue, which is exactly why manufacturers provide time-based warranties.
@Dennis Collins38/">@@Dennis Collins38, sorry, but after 17 years, you can't really be surprised if the bike was a daily driver. If it’s an iron fork, there might even be internal rust by now... anyway, you clearly know way more about metallurgy than I ever will...
For what it's worth, my own build is pretty sketchy because I’ve put it through stunts that aren't even in the manual. Sometimes a crank arm snaps when it definitely shouldn't, and then you have to wonder what happens to me 😬 ...
The safest bet would be to let a professional downhill racer handle it, but that's a job better suited for Conan Simerijanac 🙂

17 years on this steel. Aluminum ages way faster and just snaps. Carbon fiber? That stuff fails without any warning, no plastic deformation or signs beforehand to let you know it's coming. The welds on the fork are especially sensitive. Honestly, maybe they should start using old-school railroad methods—just tapping the frame every now and then and listening closely. A section with a crack should sound dull... X-rays and ultrasound aren't exactly accessible for the average person.

Seventeen years, steel. Aluminum ages way faster and just snaps. Carbon fails without any warning, too—no plastic deformation, no signs, nothing. Those fork welds are particularly sensitive. Maybe they should start using old railroad methods and just tap the frame occasionally to listen. A section with a crack should sound dull. Of course, X-ray and ultrasound inspections aren't exactly something you can do on your own.

... have you checked for corrosion yet? From what I can tell, it’s the tube running through the frame that snapped... maybe you could try to wedge something in there to fix it, or just—get a new fork...

Exactly. That’s why aluminum frames usually come with a five-year warranty, while steel ones (the real deal, Reynolds tubing and such) often carry lifetime guarantees...
There's also a massive difference in aluminum alloys. For instance, the 7000 series starts out incredibly stiff, but it gets brittle and sensitive over time. Meanwhile, the 6000 series is softer, which makes it a bit more flexible and durable... I wonder what the 5000 series was like; they don't really use it much anymore...

By the way, someone mentioned that a good, proper weld (regardless of the method) can actually end up being stronger than the base metal itself. Is there still a place like Lincoln Electric out there somewhere where you could get an ultrasonic test done?

I once had a frame split right under my seat—though that was because some previous owner had secretly welded it, so it actually cracked right at the weld site. Even on my new, high-end, triple-butted, hydro-formed, PM-coated masterpiece, I hear this vaguely unsettling creaking. I don't really notice it, though... but if I do, I'm terrified... 😬

^... uh, I realized I used the word steel in a few spots when I actually meant CrMo.... doesn't really matter though...

casualharbor9 said:... have you noticed any corrosion yet? From what I can tell, it looks like the tubing running through the frame has cracked... maybe you could just swap out a part or two... or honestly—just get a new fork...

Yeah, that’s exactly why aluminum frames usually come with a 5-year warranty, while steel ones (the real deal, using Reynolds tubing and stuff like that) often carry a lifetime guarantee...
There’s also a pretty big difference depending on the aluminum alloy used. For instance, the 7000 series starts out incredibly strong, but it tends to be stiffer and more prone to fatigue over time, whereas the 6000 series is a bit softer, giving it some flex and making it more durable... I actually wonder what the 5000 series was like—it isn't really used much anymore...

By the way, someone mentioned to me once that a really good, properly executed weld (regardless of the method) can actually end up being stronger than the base metal itself. I wonder if there's still an outfit like Lincoln Electric around there where you could get an ultrasonic test done?

The thing is, there's a type of corrosion you can't even see on the surface, and that's actually the most dangerous kind—it eats away deep inside the metal and compromises everything.
You could probably get an X-ray done at NASA, but I’m not sure if that would actually make financial sense for anyone. 😁
There are other, cheaper ways to check, like measuring electrical potential.

You can get X-rays done at Ruđer, but I honestly have no idea if anyone would find that cost-effective.

... getting scans from private clinics $133, if memory serves me right... doing this at Ruđer would likely be even more expensive...

There are other, cheaper methods available, like measuring electrical potential.

... yeah, you can probably tell how much corrosion has "contaminated" the material just by looking at the resistance...

casualharbor9 said:... Yeah, that’s why aluminum frames usually get a 5-year warranty, while steel—real steel, Reynolds tubing and stuff—gets a lifetime guarantee...
Someone mentioned once that a solid, properly executed weld can actually be stronger than the base metal itself. Is there still a place like Lincoln Electric out there where you can get an ultrasonic test or something done?

My bike has a lifetime warranty on the frame (a TREK), and it's aluminum! Or maybe it's some specific alloy, who knows.
If a weld is done right, it’ll always be stronger than the material it's attached to. But you actually have to know what you're doing to pull that off.

My bike has a lifetime warranty on the frame (TREK), and it's aluminum! Though, who knows, maybe it's some specialized alloy!

... which implies they have massive confidence in what they're putting out there. Yeah, I know that contradicts what I said earlier, but that's the word from people who actually know their stuff. From what I can tell, Trek frames usually utilize 7005 aluminum—and obviously, we aren't talking about pure aluminum like those soda cans you see lying around (seriously, people, recycle!)—they mix in other metals to dial in the performance. I’ve noticed their cranks and larger sprockets (since the smaller ones are steel) are frequently marked as 7025, while the rims are made from heat-treated 6061. Meanwhile, other big players like Marin or Giant tend to stick to the 6000 series for their aluminum frames...

Any weld, if executed properly, is actually stronger than the base material itself. But, you really have to know how to weld to pull that off.

... which is exactly why I prefer when robots handle the job. A robot doesn't care if it's Monday or Friday, or if it's working on its first weld or its millionth. It doesn't deal with mid-day slumps, distractions, or headaches, and it certainly doesn't have hands shaking because it was drinking too much last night. 😁

The 60xx series Al alloys are basically corrosion-resistant—they have moderate mechanical properties, but they hold up great against rust. On the other hand, you've got the 70xx series, which are zinc-alloyed. They’re incredibly strong, but they're also super sensitive to impurities, so you can't just go machining them with tools used for something else. Welding always weakens the material structure, except when you're dealing with CrMo steel, which is exactly why it's the go-to for high-end bikes and aircraft.
I just put a new fork on my cruiser, hoping it'll last me another 17 years. It's a little prone to rust, but whatever. Functionality comes first. My old one snapped at the fork leg about an inch from the weld (where the vertical tube meets the two holding the wheel), right through the hole they drill for mounting the fender. I could tell a total havarija was coming a couple of days before it happened, but I just didn't catch the warning signs. So, listen up everyone: if you feel like your ride is acting weird—creaking, pulling, rattling, shaking, etc.—you need to do a thorough inspection immediately. No excuses.

... but that’s what I’m asking you 😁 ...

When it comes to building frames and forks, magnesium is an option. It’s about 25 times more elastic than any aluminum alloy out there, but there's a catch: it’s incredibly sensitive. You have to deal with complicated, expensive anti-corrosion treatments, precise heat treating, and specialized welding just to make it work...

Here’s how the materials stack up against each other—same volume, different weight (based on a 2005 Giant catalog):

Steel - 100
CrMo - 90
Titanium - 58
Aluminum - 35
Magnesium - 23

... if you really want my opinion, I’d go with titanium. They say you could drive a semi-truck over a titanium frame and it would pop right back into shape exactly like it was before...

casualharbor9 said:... that's what I'm asking you 😁 ...

Magnesium is used for frames and forks because it’s about 25 times more elastic than any aluminum alloy. But there's a catch. It's incredibly sensitive. You need complex, expensive anti-corrosion coatings, precise heat treatment, and specialized welding just to make it work.

Here is how the materials stack up by weight for the same volume (based on an old 2005 Trek catalog):

Steel - 100
Chromoly - 90
Titanium - 58
Aluminum - 35
Magnesium - 23

... If you ask me, I'd go with titanium. They say you could drive a semi-truck over a titanium frame and it wouldn't change a thing. ..

... only the design changes. 😉

My fork felt weird today—I'd even say panic-level soft. I don't know when it ever had this much travel or felt this mushy. Like some sort of tedious requiem. Maybe the heat is getting to it. 🤷

Patrick King7 said:... the only thing being changed here is the design😉

My jaw felt—I’d go as far as saying—absolutely panicky soft today! I have no idea when it ever had this much play or such an incredible softness. I suspect it might be some sort of grueling requiem, or maybe the high heat is to blame!🤷

... or maybe you just finally broke it in properly! 😉
Which fork are we talking about? (I don't really see it in your posts.) By the way, I've heard that elastomers behave significantly differently in the summer versus the winter, though I'm not sure about the spring or the oil... I just hope it doesn't warp too much... I'm actually headed to check mine now; it's sitting in the attic where it's probably hitting 120°F...

casualharbor9 said:... you basically just optimized it perfectly! 😉
But what’s the spring rate? (I don't see it in your footage.) I heard elastomers behave totally differently between summer and winter, but I'm not sure about the spring or the oil... just hope it doesn't get too soft. I'm actually going to check mine—it's sitting in an attic where it hits 120F...

Spin Master
Factory install, which means it's seen 13947 miles plenty of abuse!
It's on the spring, obviously.
Let me know how that spring holds up coming from the attic. I'm curious.

Spinner Grind 1
Stock build, which basically means it's survived 13947 miles absolutely everything you can throw at it!
The spring took the brunt of it, obviously.

... man, you really put this thing through the ringer 😍 !
Well... the specs say it’s a spring/elastomer combo, so it’s hardly surprising it went soft after sitting out in the heat... plus, it hits the bottom out pretty easily (70mm travel). It feels solid, but it's a bit of a tank at 2257g... might actually be worth swapping in some fresh springs and a stiffer elastomer if you're planning on keeping it for a while...

Let me know how the fork holds up once it's back from the shop—I'm dying to know!

From what I can tell: same old story. It's feeling mushy, almost like my Manitou Relic (maybe I'm just carrying too much weight for it)... as long as there aren't any leaks, I guess it's fine... though now I'm more worried about my tires. I pumped them up to the max a few days ago when it wasn't even that hot... (honestly, they've already blown out 😬 twice just sitting in the sun)