CrowSeph

Hello. I had a request to paint a carbon frame.
But there is a problem, the fork has a crack. Also the fork had already been cutted into the most low limit...
On amazon i found that there are some adapters that can extend the lenght of the steering tube.
I was thinking to cut the steering tube were the crack is localed and then use the most long adapter i can found.
Do you think this solution is safe enought?

Andrew R Stewart 

Without more/better info (like photos as a start, or maybe a link to one of those "adaptors") I can't say much that isn't opinion. However the steerer is the only frame tube that is attached at only one end...think about what the after failure inability to control your steering does to you day.

I'm no carbon expert but every steerer tube replacement or extension that I have heard about (and it's quite a few over the years) involved steel steerers and either a brazed in sleeve or a welded butt joint. I suppose that one could join an extension to an existing carbon steerer but that one has to ask suggests that someone else, more experienced, might best do the actual work. Andy

unterhausen

I just don't see why you would do that on any bike, especially for someone else. Those extenders are not intended for this application, and it really seems like a bad idea.
Before painting is the perfect time to get another fork so it can be painted to match.

CrowSeph

I know!!! i already told him to get another fork but he do not want to do.

here the adapter

Cynikal 

He must really like his dentist. I'd run away from that as fast as possible.

unterhausen

If it really lets loose, it's facial reconstruction surgery followed by a couple of years of visits to an oral surgeon. I'm not sure I would trust a regular dentist with that.

JohnDThompson 

Andrew R Stewart 

Thank you for at least photos of the extender you are considering. These extenders are designed to accommodate the stem's positioning higher up the steerer than the OEM length (or cut length) allows for. They are not intended to support the upper headset's bearing race. As I don't know yet where's the steerer crack or how it id shaped or how long it is I can't say if the amount you'd need to cut off will result in that upper bearing race now resting on this extender, or not. The only way I would consider using these extenders is if the OEM steerer is long enough (after being cut) to insert through this upper race.

BTW the majority of these extenders that I have worked with are not meant to be used off road, for racing or foe doing trick riding with. They just don't hold up as well as the OEM steerer would in those conditions. Andy

CrowSeph

The owner had a slam stem and the crack is localed on the bottom of the stem itself. So the adapter will not touch the bearing itself.
Will be a solution only for letting the stem to be installed by gaining more space.

CrowSeph

Probably you do not like the tread or the currently idea for a solution, but your message will not help either, is just a waste of time for both of us.

Canaboo

Can we see an actual pic of the crack? What caused it? A person who can do carbon work could likely repair and reinforce it.

Andrew R Stewart 

One aspect that concerns me is that crack. How long is it? Was it from poor previous cutting methods or a pressure plug that was tightened too much or maybe a missing plug and the steerer collapsed from the stem's binders?

The steerer extenders that we have sold and installed (for fitting needs, not for repair reasons) were not intended for a carbon steerer. The issue that I was told of is that the extender's expanding plug, that goes into the steerer, will be trying to crack open the steerer. Al and steel steerers don't have a grain or directionality and resist compressive and expansive forces far better than a carbon tube does. Carbon steerers are designed to have a stem on the outside of the steerer, where the pressure plug is inside. The two clamping forces will tend to cancel each other out (or get very close if torque settings are respected) and the trapped between steerer will see nearly no forces trying to pull it apart.

I strongly suggest that the OP does their homework very carefully WRT if those extenders are carbon steerer compatible (I tried a brief search for them w/ no luck finding any more info about them). If there's no mention about this consider that the lack of info might suggest something. Andy

base2 

The whole idea of this gives me the heebie-jeebies. I wouldn't extend a steerer at all, ever unless it was a braze job with a sleeved insert.

Think about it. How much expansion in a carbon steerer is effected by a compression plug? For super small weight-weenie plugs it's enough to noticeably swell a bulge the steerer enough that the stem can be difficult to install. That system only works because the stem also clamps the opposite direction squeezing the steerer in a plug/stem sandwich.

This? What is outside the steerer to counteract & balance the expansion force? Nothing. Then add some lever action at the top of the improperly stressed steer tube from the rider...No. This has "bad outcome" written all over it.

Buy another fork. Consider it the cost of admission.