studbike1

I know that framebuilding may be the wrong sub for this but thought I could find legitimate expertise here.

The bike has been ridden this way for years. No visible problems. I didn't measure the length of the quill but the expansion wedge is definitely above the headset by 1-2 inches.

The solution that "follows the rules" would be to cut the threaded portion off the steerer and find a huge 1" threadless stem, but when I stand back and look at it, intuitively, that seems like it would be about the same strength. Doesn't that just move all the stress to a point about 2 inches lower, but now without the center bracing of the quill? Of course, cutting the steerer all the way down will require a freakishly large stem - didn't find anything on ebay.

guy153

I agree, I don't see anything actually wrong with it. Well apart from the fact that it's a bit ugly Either way you've got a long steerer and it's just whether you're attaching the stem with a couple of pinch bolts or an expander thing. Either is capable of holding the stem in place and at least the expander is closer to the bearing than the pinch bolts would be.

it looks like you really need a frame with a much longer head-tube.

Andrew R Stewart 

The big long term issue is the stem wedge bears on the threaded portion of the steerer. Which, BTW, is out of sight. The chance of a crack forming in one of the stress risers called threads is real. Every supplier and manufacturer that cares to list limits on their forks make clear that to do the above is wrong and voids warranties. That it requires some disassembly to monitor this possibility just adds the chance of chosen ignorance to the mix. Andy

guy153

Good point. It didn't occur to me it would be threaded all the way down but of course it is. They supply them with loads of threads because you're supposed to cut the top off.

unterhausen

It doesn't even have to be in the threaded portion. I have been collecting bikes to make bike racks out of and I have a fork with a steerer that burst because of an over-tightened wedge in the smooth section.

I would say there are no right ways to get the stem in that position on that frame. It's a flat bar, get a stem that's not 130mm long and mount it within a reasonable distance of the top tube. Do your arms have to be stretched out in front of the bike like that? I say no.

studbike1

I am 99% certain the wedge is below the threads. In my records it says quoted $80 to thread the steerer all the way down, and it's 20 bucks per inch.

This can be ran with no spacers - the clamp on the bottom holds the threadless headset in tension like a top cap would. If a stress riser where to form, do you think it would be noticeable if inspected from the outside of the steerer regularly?? Or are you thinking these things are invisible to the naked eye and fail catastrophically?

Andrew R Stewart 

If the steerer threads were exposed where the stem wedge is at then, yes, any issues due to the wedge's pressure should be in the open. Note I didn't say that a rider will see it (I am continually surprised how blind to easy to see or feel issues many riders can be). Steel has the wonderful quality of tending to tear once the crack has gone far enough to relax the stress. Tearing takes longer and sometimes gives a warning before complete separation. Andy

duanedr 

I think the best/better solution would be BMX handlebars. Lower the stem back down to normal height and install BMX bars to get the grips up high. This scares me for the reasons Andrew mentions. It might be fine for decades of normal use but that one time a car pulls out and you slam on the brakes and it shears will be the one time you'll regret it most.

studbike1

Thank you for your thoughtful reply.

I think we may have a misunderstanding here - the threads were *not* cut lower, the work was never performed. The bike has a threadless headset held in place by a generic 1" clamp. The lock nut up top is taking the role usually performed by the star-nut. Given that those are 10mm spacers and the original estimate was for a 4 inch extension in order to fit a *threaded* headset, I am interpolating that the threads only go about 2-2.5" from the top of the steerer. I can see from looking up the bottom that the stem is definitely *not* an exotic piece with an extra-long quill. I am quite certain that it is higher than the top cup of the headset by a couple of centimeters.

Of course, I need to take it apart and measure it. But if the *top* of the wedge expander is still *below* the threads, would you call this acceptably safe for casual riding? I know that's a loaded question, I take responsibility for the consequences regardless.

unterhausen

The only way I would run something like this is if I was dedicated to taking it apart on a regular schedule. That doesn't seem to be happening, so the answer is it's not safe. It does make me feel better if it's only threaded way up top.


I'm all for meeting people's physical needs. Is there a reason why your arms can't be lower? Can you show us a picture of the entire bike?

mack_turtle

I burst out laughing when I saw that photo. some people should not be allowed to work on bikes!

threaded steerer tubes can be cut and tapped to a reasonable length.

studbike1

Here is the entire bike. The story behind it is that it was 2 sizes too small so lemonade was made from lemons and it was converted to a "road bike" by reducing the fork length and increasing the offset, decreasing the bar width and increasing the reach. It is a lot of fun to ride, everyone who hops on it loves it. It has the darty steering of a road bike but is still reasonably upright and comfortable. It has 57mm of trail according to the calculator at yojimg dot net

I recently dropped big bucks on these tires, and only then did I realize... should I even be riding this thing? lol

Pro tip: 11 speed sram gripshift plus 11 speed shimano road derailleur = 7/8 speed cassette spacing.

guy153

Why is it worse than a regular quill stem though? If there aren't threads there.

​​​​The only difference I can see is that the part of the steerer with the wedge in it is more free to bend around. But that should mean it's harder for the wedge to chowder out the inside of the steerer because it will bend rather than allow relative motion.

Having such a long unsupported steerer (however the stem is attached) is unusual but they're often 1.3mm or so seamless cromoly which is stronger than the average seatpost. We have those sticking out by miles these days while we bounce around on them with all our weight. OP will also have less weight on the bar as he's quite likely set it so high in order to take weight off his hands.
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unterhausen

It's unexplored territory. I'm not sure we can really say one way or the other. Like I said in a previous post, I have in my possession a couple of forks with broken steerers, so it's not unheard of for them to break. Those broke inside the head tube. Breaking above the headtube is far worse. Steerers see a lot more deflection that most people recognize. Weirdly, I have an 820 that's about to become part of the bike rack in my garage.

To the OP: If you were local to me, I have a frame and fork that I would give you that would fit much better than that.

Andrew R Stewart 

Yes you are right. I thought that you had a threaded headset and thus the stem. That the steerer is "now" unthreaded my big concern is not as critical as I felt before. But I do agree with the bike's size as being likely not the best. Andy

unterhausen

The part of that bike that's going to break first is the top tube/seat tube weld. Nobody that builds frames expects to have the rider's weight cantilevered over the frame like that. Trek had trouble with some bikes breaking there anyway, although that was on aluminum frames.

guy153

There's a big cantilever on the other side though (the fork). And it's the same welding down there. The DT is usually 1/8 in larger diameter but that's all.

Interesting that you had some frames fail at the TT/HT though. DT/HT is also a common failure point I think (that's where my Trek steel frame failed).

unterhausen

I happened to see broken MTB treks at the LBS, there were no mtbs when I worked at Trek other than some converted cruisers that were being ridden on dirt roads. Broken MTB frames at the seat tube/top tube is not uncommon, because they have long seat post exposure. Which is why you see extra tubes back there on a lot of bikes.

I like the way you think about the loads at the head tube. OTOH, the TT and DT are there to take up the moment. Certainly there are a lot of failures there, particularly on small frames with short head tubes. The problem at the seat cluster is that the seat tube will bend, and there is essentially a pivot set up by the stays and the top tube.

Nessism

Disaster waiting to happen. Or at least, an inappropriate solution for a frame that's WAY too small. I'd get a new frame ASAP. If the steerer doesn't break the seat tube might.

studbike1

Do you think an extra-long seatpost could help mitigate the possibility of a frame failure near the top of the seat tube? Seems intuitive to me that distributing the force over a larger area inside the tube could be helpful. Regardless the post definitely needs to go. It's over an inch above the min insertion line. hadn't even thought to look until i saw this

studbike1

are you seriously giving away frames? :-)

guy153

You've still got a big lever pulling back on the TT/ST junction giving it a fatigue cycle with lots of tension. Yes it certainly has to be inserted past the line and not doing that does also increase the chance of a frame failure. But it looks like you just need a bigger frame. Can keep the wheels and tyres and everything.

unterhausen

Someone gave me this frame, so yeah. If I don't see using a frame in the future, I try to get rid of it. Can't turn this one into part of my bike rack because it's aluminum.