Carbon frame/headset sleeve issue… WTF do i even begin to do here.

[weeksy]

So today as some may have seen i bought new forks for one of the DH bikes.

2019 GT Fury. It's a carbon frame.

To fit the 29er setup you need to fit different cups, the reason being that the frame has a lower cup of about 22mm which raises the front end for 27.5 setup
2023-01-22_05-58-37 by Steve Weeks, on Flickr

So you knock out the headset cup and fit what's essentially a zero stack one.

However, this is where it all went wrong on this frame.

The inner sleeve also came out... Well i say also, the cup is and was completely seized in there. Lets just say, i've made a proper pigs ear of trying to remove them from eachother. So the hole in the bottom of frame is shaped slightly to match the flats on the sleeve and i presume it was bonded in some way into the frame. However, clearly it's no longer bonded. When trying to remove the sleeve from the cup, the sleeve is no longer round. It's not damaged apart from it's roundness... but lets say it's not perfect. I'm not even sure if it can be made perfect again.

2023-01-24_05-03-13 by Steve Weeks, on Flickr

Now, as to 'why' heck i have no idea.. It's not impossible it was seized, it's not impossible that the boy hitting the floor and snapping his forks completely spannered the frame at the time but only a tiny bit, enough though that when removing the cups, it's now borked.

So where do we go from here... if anywhere... Heck you tell me guys... because i'm right out of ideas.

[crust]

I'm guessing the cup is seized in by corrosion - have you had it out before?

I'll heat the lump and spray it with penetrating oil a few times, see if it can be persuaded to come out.

Some gentle persuasion will get it roundish again, then we can epxy it back in the frame.

Jobs a good'un.

[weeksy]

So finally with brute force and effort i got the sleeve and cup apart... there's a couple of tiny tiny marks on the sleeve, but with a bit of sandpaper and a gentle tiny file I got them smooth enough.

I then did a test fit, but it was slightly out of round... However, not a lot and was easy to get back again into the right shape. we're talking 0.1mm on the digital calipers.

Looking at the sleeve it's not bonded, there's no sign of any glue of any description on it. The surface on the frame is completely smooth and no discolouration to imply it's got any glue on it either. The sleeve slots in with a press, but it's a tight tight fit.. .tight enough to convince me that it's not going anywhere..

It fits flush and nice all the way around.

Whilst i can't say i'm 100% happy... i'm a lot happier than i was with it a few hours ago that's for sure.

2023-01-24_08-29-36 by Steve Weeks, on Flickr

2023-01-24_08-29-31 by Steve Weeks, on Flickr

2023-01-24_08-29-25 by Steve Weeks, on Flickr

I'm going to speak to a couple of carbon companies to get some thoughts tomorrow... but to be honest, i'd ride it lol.

[weeksy]

then we can epxy it back in the frame.

I wonder if we'll need it Epoxying... I don't mind persuading it back out again though if you think it's for the best. The flats are on the frame too, which i guess stops any rotational movement, it's got a lip on the inside, so it can't go 'up' there's only the possibility it could come 'out' but if you'd seen how tight a fit it was, i'm not convinced that's happening at all.

[Count Steer]

Dunno if it's a similar thing but the post Jody made about a rebuilt bike to be auctioned showed the bloke redoing similar bits in what I think is a carbon frame and they were interference fit, no epoxy used.

[Taff]

If I'm understanding this right, when a fork is fitted nothing can possibly move right?

[weeksy]

If I'm understanding this right, when a fork is fitted nothing can possibly move right?

That seems a reasonable assumption. The headset cups will be pressed in, then of course they're all held together.

[Taff]

If I'm understanding this right, when a fork is fitted nothing can possibly move right?

That seems a reasonable assumption. The headset cups will be pressed in, then of course they're all held together.

And then in the upper and lower cups there's bearings that take care of the rotational movement.

My main concern would be with the CF frame material, which you haven't mentioned, so it sounds like all is good.

[Mr. Dazzle]

Team GB Olympic bikes don't have that bit glued in, its just clamped in by the mating components. Glue would do buggery nothing here, hence the lack of it.

However...that part of the frame is also the weak point, smashing forks like thus is the top way to break a CFRP frame.

Have a good peak and poke around the inside of the frame, particularly "behind" the cup (from the viewpoint of someone sat on the bike).

[weeksy]

Need to try and check in light etc but can't see anything..

Don't forget, this is the frame he stacked and snapped the forks on though lol.

[Mr. Dazzle]

I'm on a PC now so I can type a bit easier...

With a carbon frame, the hardest strength test to pass IME is the "smashing the fuck out of the forks" test - i.e. exactly what you've just done! It's a standard test, normally you stand a bike vertically upright (with no wheels) and drop a big weight from a height onto the front axel.

This was the one test we really struggled to pass with our bikes, according to the bike manufacturer we were working with (Cervélo) it's always a toughy. Generally they break in one of 2 (well 3, if you count the forks snapping) ways. Either the bottom front bearing gets smashed "into" the frame, or the top bearing gets levered out "forwards" (up, in that diagram) and splits the front of the frame in half in the process.

FWIW, MTBs will be reinforced to fuck in this area for precisely the reasons you'd expect!

So if I were you Weeksy, I'd have a really good look and feel inside the frame 'behind' the front bottom bearing to see if it's been smashed backwards into the frame. Also have a really good look at the paint in teh sort of "chin" of the frame on the outside for evidence of cracks/tiny wrinkles etc.

Also have a look infront of the top bearing for the same sort of thing.

fig3.png (43.48 KiB) Viewed 505 times

[David]

Knowing sfa about CF except the little I have read on here...Dazzles advice is sound. Looking at the pictures of your frame there do appear to be a lot of marks around the repair site....as he said, close inspection required!
Good luck.

[weeksy]

So me and a mate have been looking... Happily we have a 2nd frame to pick any thoughts out of too, plus i needed to remove the headset cups on that one too.

What i've established is.... on the GOOD frame, there's paint beneath the spacer and potentially a bit of carbon too... on the purple frame that paint is missing. However, looking now, this is NOT new... this is old and has been removed from before when we've owned the bike. What it looks like has happened is that a previous owner has done this and removed the cups before, but when he's done it he's actually knocked out the non-removable (usually) spacer as well. You can see the chips/marks in the paint have been touched up (which you couldn't really see when everything was fitted without VERY close inspection).

So, removing the cup last night wasn't the cause of any issues, it's no worse than it was.... but admittedly it's no better. Whilst the paint is no longer present, there's nothing that indicates any extra additional damage to any of the carbon and it's truly massively over-engineered around that area.

Where does that leave us.. Well in truth, no better worse than we were before yesterday. Just with more knowledge that something has previously happened now. But i don't think the frame is any more 'broken' than he's been riding for the last 12 months lol.

[MingtheMerciless]

What Mr D said and also when it's back together keep an ear out for creaks (stealth edit....new or unusual creaks).