Stripped Stem Threads Problem
 

So I have this Takara Kabuto Single Speed Road Bike that I got a long time ago. Lots of changes and stuff, but the stem fork combo is still there. It's a fork that's headset is connected to the stem with a weld. There's a plate that goes over the handlebars and connects to the stem, fastened by two bolts above and below the stem. The bottom bolt isn't stripped but the hole it goes into is. Is there any good fix's for this? I could go out and get a tap kit and re-thread the hole, but I don't know what that'll do to it. I could also get a wing nut to put inside the stem to hold a bolt in place. But before I try any of those things, I'd like to know your thoughts. The type of stem is called a quill stem I believe.

Photo? Never saw a fork where the headset was welded to the stem:rolleyes:

Really now- the stem's pinch bolt hole might be drilled and tapped one size larger (and the plate hole also oversized as needed) but how much stem material exists around the bolt hole is a concern. The existing bolt could possibly be LocTited in place. The hole could be repaired with a threaded insert (Helicoil). A through bolt and nut might also be used depending on the stem's design.

But none of these methods can be suggested over another via blind long distance. So back to the beginning. Photo? Andy.

You should post up a picture, but my advice will probably be the same. Your teeth are way more expensive than a new stem.

http://bikeforums.net/attachment.php...hmentid=482007http://bikeforums.net/attachment.php...hmentid=482008 It's the bottom one that's stripped. Also I already have to replace my teeth with dentures from a student who hit me with their car.

Drill oversized hole and retap.
Or, best is.... pull that stem out and buy a new one.

Good job, thanks. Yes it's a quill stem. Depending on the area offerings you might find it easier to just replace the stem. A through bolt won't likely be an option as the hole doesn't go all the way through, it is "blind". Oversizing the hole and tapping to a larger bolt size will be tricky because of the lack of much extra material around the hole. Same with using a threaded insert. Both are possible but breaking through to the stem's outside surface would ruin it. Also cracking gets far more likely as the stem's "wall" gets less.

I do wonder about using a thread locker compound. If the hole's threads are not completely augered out, if the bolt does grab thread remains maybe deep in the hole, I would try thread locker compound first. It's reversible and you can go to the next and more destructive step if this doesn't work. Use as long a bolt as you can fit. Follow the thread locker compound instructions. Place the bars in the stem and secure them from moving around while the lower bolt is installed and the compound cures. Only then would I install the upper bolt and only using this bolt tighten the stem cap in place, with the bars where you want them. Do some stress tests (twist, yank, pry) on the bars to confirm all it good and tight.

Good luck. Andy.

So a wing nut won't work when put on the other side? The hole goes all the way in so wouldn't putting a bolt in with a wing nut on the other end work?

Stems are relatively inexpensive. Dental work isn't. Less fun too.

Like I mentioned before, already have to get dentures.

toss it.. now the common practice is... a quill to threadless adapter, then put a threadless type stem on .

they have become the most common.. as New Bikes use threadless type forks.






Facial reconstruction surgery is not done as a cosmetic. that is more than a few face plant teeth lost

Everyone here just seems to assume I have money lying around.

Got Jobs ?

That changes nothing.


Custom titanium frames are cheap, right?

Basic stems are pretty cheap. Used off Ebay, or maybe a bike shop has some used, or older cheap stems in the parts box behind the workbench.

If you tried retapping it, I wonder if there's an "English" (non metric) thread that's a bit bigger, but not as big as the next metric size, so less material get's removed. . If the pitch is about the same, maybe it would be good enough.

Regular machine nuts are generally of better quality than wing nuts and would be preferable if it fits. But a new (or used) stem would be my choice. Extra points for a stem with a 4-bolt plate; no single point of failure. Having your bars come off is only funny in the cartoons.

Do you have money for a dentist and/or facial reconstruction surgery?

Seriously, you're going to have to spend some money to make your bike safe to ride. A helicoil might fix the stripped socket, but a new stem wouldn't cost much more.

The idea of drilling an old stem and retapping it scares the **** out of me. I've seen the consequences of an unplanned front end failure on a bike. Cost me years and my profession (and 5 days out in a coma). Compared to that, a brand new Nitto Pearle stem at $80 is cheap. (One of the nicest stems ever made.)

Sounds like you got good use out of that stem. Also sounds like the stem is saying "replace me". I know a lot of you will consider this just dumb superstition, but I feel that there are good bikes that look after us, but we have to play our part and listen. (My first 10 speed never left me stranded in its first 19,000 miles. Chainstay broke. I rode home on it, then had a friend weld it. Two years later I collapsed the fork on a car door. The bike did better than I did. Maybe that first break was a hint I did not hear. A year ago, I rode up the the highest point around and struggled to get my chain tension right after changing the fix gear cog from the 23 to the 13. Nursed the bike slowly down the 2000' of descending (and rode very gently around a corner I love to fly into, slam the brakes and take very fast). Got down to flat ground and felt the front end of the bike start to shudder violently every time I touched the front brake. When I got home I saw that I had 1/4 of the diameter of the fork blade left at the crown on one side and 3/4s on the other side. Good bike! It told me to slow down and I listened, thank G**. (The fork failure was due to the summation of 3 separate decisions, one by me, one by the builder and one by the contractor who nickleplated the fork. (I choose a minimalist fork crown with no scallops. The builder found some light Columbus SL blade tubing and the plater chose not to heat treat the plated fork. Two years later, hydrogen embrittlement had started the cracks in both blades. Now I have heavier painted 531 blades on a heavily scalloped fork.)

You can call my experience just plain luck and that it doesn't apply to you. It's your choice. But the crash you might be looking at might involve more than just teeth. (Front wheel and fork also often buy it in stem failure crashes because the front wheel often gets turned and the bike loads it and the fork sideways. Probably will help you a little by absorbing energy, but on the money front, that wheel and fork will cost more than a stem.

For saving money - old school quill stems are a fairly safe bet to buy used. (Cinelli, TT, Nitto) They rarely break. Don't use an old one forever, especially the Cinellis or TTTs because they could be very old and have a lot of miles and experiences under their belt unless you really know its history, but a couple of years on one would be a far better bet than trying to salvage what you've got. (And by that time, you might be able to justify a new quill like that treat of the Pearle.)

Ben

Where did you get that..?

07-30-15, 02:12 am:

Buy a new stem, that one is ugly. If you can't afford a stem you should be out looking for work instead of wasting time on the internet. :thumb:

Huh...

It means that on July 30, OP wanted to buy a titanium bike, but now can't afford $20+ for a stem.

Public pud pulling might be a simpler explanation. When the respondents advise to avoid a face plant and the OP argues, one has to question motive.

"..So I'm going to be doing my first expensive bike build later next year, ..."

The wing nut will brace against a slanted surface. If exposed to serious pull the screw will bend. Maybe less poor, but still not good.
If I had to choose, I'd either rethread one size up, or use a length of threaded rod, bond it in place and then use a nut and some washers to tighten the faceplate down.