Ever seen a fork crack like this (fixed gear bike)?

Been hearing the occasional sharp creaking sound from the front end on the commute recently – took a look today and it appears I’ve cracked both fork legs up top around the brake. It wasn’t completely obvious at first (looked like the outside of the first pic), but I scubbed it up and paint flaked off to show the cracks.

Not the best place to crack a bicycle. Is it just the braking force that’s responsible do you think? Bike is a fixed gear and has done 6000 flat, urban commuting miles (so a lot of stop start) – no rear brake and I never use my legs outright to brake, so all the braking force is through the fork (and I ain’t light).

The paint has bubbled as the fork is corroded, probably right at the point the fork flexes. Flexing corroded metal isn’t going to work for long, so now you have a sticker on each leg

you got lucky there. are they alloy?

Looks like the legs are bonded onto the crown and the cracks are where the join is. There is clearly quite a bit of corrosion under the paint there, which will be what has caused the problem. Once salty water gets under the paint on aluminium components it’s just a matter of time until they’re dead.

It is aluminium frame and fork, yes. Guess I might try the carbon version of the fork as a replacement.

That looks like an Alpina carbon legged fork to me and the crack is exactly where the carbon bonds to the alloy. The steerer and crown and first few cms of legs are alloy with carbon below that point.
That is the only fork Alpina make, they do not make a full carbon fork – even the carbon framed Seta has the same allot/carbon fork on it.

Cracks look to be exactly the opposite location to have been caused by breaking forces? Wouldn’t braking be putting that part of the fork jnder compression?

Landed any hucks to flat recently? 😉

http://www.boeing.com/commercial/aeromagazine/aero_07/corrosn.html

Galvanic corrosion
“For example, graphite fibers, which are used to reinforce some plastic structure, present a particularly challenging galvanic corrosion combination. The fibers are good electrical conductors and they produce a large galvanic potential with the aluminum alloys used in airplane structure.”

That looks like an Alpina carbon legged fork to me and the crack is exactly where the carbon bonds to the alloy. The steerer and crown and first few cms of legs are alloy with carbon below that point.

Pretty sure the fork is all Alu, it’s a few years old (I’m at work now, but will check tonight) – didn’t realise it was bonded in two parts though, thks for pointing that out (and NewretroTom too). It might not actually be cracked (seriously) in that case, just the join has loosened and cracked the paint. I thought for sure the line you can just about see in the third photo must be a crack, but it’s likely the joint.

Doesn’t seem too healthy either way.

One of the NW cross dads / bike club guys gave me a Ridley fork to have a look at in our materials lab. That was also a similar forged crown but bonded to aluminium legs (he thought they were carbon legs but the welded-on canti bosses sort of gave the game away).

Just be glad yours failed where it has – his were umpteenth hand and fatigue cracked in a hidden place through the 1″ steerer tube resulting in head injury and helicopter to hospital (luckily he is now OK).

Would be interesting to cut them open and see which bit has cracked (just the bond line or part way through the stubs on the crown).

Have two of those forks. Was it originally drilled for a front brake? Mine were not. Needless to say that a track fork does not have to be designed to take braking forces. When I drilled one of mine out, there was an aluminium insert where the bolt would be expected to go through. there is also a flat front plate which looks designed to take a front brake.

The fork crown is definitely aluminium – as I said, I took a drill to mine. Yours is “cracked” at the bonding of the carbon fork legs. I’m not convinced it’s a crack btw. Corrosion is a reasonable possiblity.

Contact Dolan, they’ll probably replace it ASAP. Don’t ride it.

I replaced the fork on my Seta with a very light Ritchey monocoque carbon fork – mainly to save 250g. The other drilled fork is on my Pre-cursa set up as a fixed TT bike.

Pretty sure the fork is all Alu, it’s a few years old

If it is I have never seen one and have had those Alpina forks for 10+ years. On the Matte finished option you can see the carbon weave (and where is starts a few cms down from the crown).

I always thought the drilled fork was same fork as non drilled just with a hole drilled in it and back is recessed as TiRed says so looks designed for a brake from the start. I have used that fork for years of off road riding and it held up to that but I don’t use a front brake so who knows if that helped or just down to corrosion only.

Corrosion fatigue, bubbles in the paint and cyclic loading. There’s probably a weld under there too…you’ll be fine.