Some time ago (i.e. years) I acquired a really nice Alpinestars Al-Mega mountain bike. The frame is (I believe) 7005 aluminum, with oversized tubes.
Over the weekend I noticed a fairly huge crack in the head tube, running from the upper headset race downward, around 2/3rds of the way down to the bottom. Needless to say, I didn't ride it.
I absolutely love this bike, so I'm seriously considering having the frame repaired. I've heard that they have a history of cracking in this area, so I wouldn't mind getting the area reinforced. I'm also thinking about having a rear disc brake mount added.
Since I've never had to have a frame repaired before, I'm sort of starting from scratch. Does anyone have a good shop they can recommend for aluminum frame repair? I don't mind paying for quality work.
That's not really fixable- a crack like that calls for a tube replacement. A bunch of work, but no big deal....if the frame was steel. Even if you could find someone who could/would do the work in alu (and do the post-weld heat treat) it would end up costing almost as much as a new custom frame and WAY more than a brand X off the shelf job.
The unfortunate truth is aluminum bikes have a finite life span and none are shorter than performance mtb's. RIP Alpinestars.
ya, that is the stock 1-5/8 OD, .155 wall Easton head tube. That would mean your frame was made from "varalite" tube set. They produced two different specs for each tube. Do you know what your frame weighs? 7005 suffers from "fatigue corrosion" and while the modules of elasticity is better than 6061, the fatigue life is pretty short.
I don't know exactly what it weighs, but it's not terribly light. I remembered it being 7005, which was verified by someone's scan of the brochure. It says "7005 front triangle" which suggests that the rest of the bike isn't 7005?
A few guys on Retrobike have had head tube failures like this, but for some reason the rest of the bike seems to hold up. I'm guessing they just went too thin on the head tube wall thickness or something.
Looking at it, and admitting that I know nothing about this sort of thing, it seems like the thing to do would be to pull the headset out (it's actually a 1-1/4 to 1-1/8 adapter), weld the crack, grind the bead down, then slip a slightly larger diameter piece of tubing over the top of the head tube and weld that extra piece in place to reinforce the whole thing. Maybe it's not that simple, I dunno.
I'm an old guy, and I don't do anything fancy. I just like going fast on single track and keeping the rubber on the ground, so it doesn't have to be bomb-proof. I would however, prefer not to be impaled by a frame that suddenly lets go underneath me. I wonder if there's a way to check the frame to see if it's otherwise sound.
well the first problem is the head tube is an extrusion and has sort of a "grain" running the direction of the tube. The second issue is,as you mentioned, is too thin, next is it could have been reamed a bit tight. Specially when you mentioned "adaptor". Head cups are designed to shrink a bit when being pressed in the head tube. Adaptors don't. Aluminum isn't happy about stretching real far. The whole frame is 7005 (5087) only the front is Easton and if it's not freaky light it's the burlier set.
There is no way welding the crack will work no matter what anyone says.
Here are a list of your options, all will work, starting with the cheapest
remove adaptor, have steel ring machined to fit snug on the outside, install outer ring then press in adaptor (should be no more than .005" bigger than inside of headtube)