Fork with stripped thread
 

Hi there!

I'm having a situation with a fork thread.
It's stripped in the zone of the lower cup, so that cup cannot be tightened. The thing is that the adjustable cup zone is not stripped, so the headset can, eventually and totally, be tightened. I mean, it's smooth and adjusted.
So, my question is: will this damaged part of the thread bring me any problems while riding the bike? Can it damage the whole fork, and even the headset?

Thanks for the future advices!

(If it's difficult to understand, I can post pictures tomorrow!)

Cheers!

Take a look at the photo below so we can all be working from the same playbook.

http://bikeforums.net/attachment.php...hmentid=454268

I suspect that you mean that the fork is stripped where the top race (aka top cup) goes, and you're trying to hold it together using the locknut only. That can work, but there's no way to lock the adjustment.

You do have a few workarounds if there's no other option. One would be to use a Loctite product to keep the locknut from unscrewing. Or you might try putting a hose clamp around the stem, pushed down against the locknut so it can't spin back up and unscrew. Those are just ideas for salvaging a fork that otherwise would go to the scrap man, but the "right" option is to do just that.

Thread damage where the upper threaded cup engages is a result of riding with a poorly adjusted headset. This allows the upper cup to rock on the threads and eventually erode them away. The solution is either a replacement fork, a kludge such as FBinNY suggests, or melting brass into the damaged threads and cutting new threads in the brass. I have done this final method with good success.

Thank you both for the answers!

Yes, FBinNY, you got it absolutely right. Sorry for my lack of technical names.

I have an adapter, which is wider than the locknut... Is the same one I asked about a few weeks ago in the forum!

http://bikeforums.net/attachment.php...hmentid=454308

Really tightened, it will work as a lock, so the locknut won't be able to unscrew, right?

Will this be dangerous in any way? It's a temporary solution, as I will buy another fork in the next few months...

The stem adapter will work to hold it together if pushed down all the way. The beat way to do this is to slightly overtighten the headset and locknut, push the stem adaper down all the way & tighten, then back the locknut against the adapter to take out the slack and correct the headset adjustment. If you can't loosen the headset enough this way, loosen the adapter a bit, then use the locknut to jack it up a hair.

Done this way, it should all hold together fine until you find a new fork.

BTW- this won't in any way be dangerous, the worst thing that will happen is that the headset loosens, and it's a PIA to adjust it this way.

Thanks a lot FBinNY. I'll do it that way then!

Cheers!

plan B ( for Better, IMO) adding spacers and the star-nut makes it function like the thread-less type..

BBB BHP 20 IS A 22.2 Quill converter integrating the top cap bolt function with in itself.. gains easy adjustment..
BHP-20 - Headset parts - BBB

If this is a temporary "fix", and you have partial threads in the damaged area, you could try wrapping a little teflon tape around the damaged threads to tighten things up a bit. It may not help, but it can't hurt to try.

Hi Fietsbob,

Would that work? Using some spacers and the star-nut inserted in the fork tube?

the Quill stem raiser I linked to has center bolt that you tighten up the wedge at the bottom,

then the hex Head of that bolt is internally threaded, and the top cap bolt that compresses the loosened threadless stem,
and the spacers beneath that stem and pushes down on the top race of the headset setting it's preload, (standard threadless fork~headset practices)

no star nut needed.. it's the special design of that Bolt that does that.

then You tighten the threadless stem Bolts around what is Probably a Shim from 9/8" to 1" .. the BHP 20 as shown has its own stack of Shims

To go down to the 7/8" of the Quill that is the size inside of your Fork ..


I own the next larger one, the BHP21, I use it with my Threadless fork Bike that I got with too Short a Steerer tube cut.

Ive been using that bike for 6 years since..


there is another Kludge, Steel tube stem raiser, then stuff a star nut in the top of it.

One suspects this is the case with many of your posts... ;)

ah, hell... now is the perfect time to slap a carbon fork on that thing and go threadless...

I did have a Actual hands on Job at LBS to do yesterday. , likewise today..

Back when BMX bikes were still using threaded headsets, there were 'locking' headset locknuts with grub screws to keep the locknut from working loose. No idea if the 24tpi threading of those jibes with what you have, but that's also an option.

Something like this (others had the set screws threading directly into the steerer's threads):

http://i.imgur.com/LQtpHZ4l.jpg

Kor T2 Locking Headset Nut 1 1 8 Black Lock Nut New | eBay

have you tried loctite red?

Use locktite blue (medium strength). Red will be hard to remove when you do replace the fork.

A brazing job can add metal, then the fork steerer can be re threaded .

I too have a fork where the threads are severely stripped. The locknut begins to tighten then because the threads are stripped, the locknut eventually spins and will not tighten down.

I know there are several suggests on a fix already provided, I'll add one more to the conversation. I called my brother who is a 30+ year auto body expert, he owns his own auto body and frame shop. I told him about the damaged threads and sent him a few pictures...thought it can't hurt, given my only other option is to find a replacement fork as I didn't think the other options to fix were going to work for me.

His response..."No problem, should be a straight forward fix". My response was are you going to brazen some copper on the threads and then rethread the fork. Although he said he could do this, he said he had a different solution which will be stronger and safer.

Summary of his solution:
- cut the fork stem (half way between the threaded section and the actual fork)
- find an old fork with the same threading (he has a small inventory of bikes, he thought he could find a fork that would work. I sent him the locknut so he could match the threading)
- cut the threaded section from the old fork to the exact length as the section that was cut from the original fork
- use a 'sleeve' to insert into the inside of the fork stem to be repaired. The sleeve will ensure the fork is perfectly straight before repairing.
- tack weld the replacement fork thread to the original fork stem (being careful to measure the exact same length)
- complete final weld once fork straightness is verified

Just mailed him the fork yesterday. Have yet to see a repair (really of any kind) that he isn't able to fix. Will report back how the repair went, along with before and after pictures.

A few pics of fork before repair.


https://cimg3.ibsrv.net/gimg/bikefor...b3dde0964.jpeg

https://cimg5.ibsrv.net/gimg/bikefor...d0a9966c2.jpeg

https://cimg0.ibsrv.net/gimg/bikefor...4595c4c71.jpeg

I received the repaired fork back from my brother. Fork now almost better than new!

I’ve attached several pictures for reference.

He used a lathe to shave down a piece of tubing so that it would perfectly fit on the inside where the original fork stem was welded to the replacement threaded stem. The replacement fork stem was blue, but after grinding down the non-threaded section of the fork stem, you can hardly tell a repair was done.

For those that have bent and/or striped out fork, this may be a repair worth considering.


https://cimg2.ibsrv.net/gimg/bikefor...e77eba91a.jpeg
https://cimg7.ibsrv.net/gimg/bikefor...62a1ba983.jpeg

https://cimg3.ibsrv.net/gimg/bikefor...3f0903e1c.jpeg
https://cimg5.ibsrv.net/gimg/bikefor...edd056f65.jpeg
https://cimg9.ibsrv.net/gimg/bikefor...bcdaf0917.jpeg
https://cimg1.ibsrv.net/gimg/bikefor...df7cd8762.jpeg
https://cimg4.ibsrv.net/gimg/bikefor...3b7528a74.jpeg

Nice job. The only thing different that I would have suggested was to not file a flat on the new part's threads and instead filed the lock washer's (and/or the cable hanger's) ID to slip over the full threads. Andy