canklecat

My 1993 Trek 5900 is disassembled for a long overdue overhaul. I've checked every online catalog and shop guide I can find but still have a few questions. A month or so ago a friend had offered to scan the frame for me at work, but with the coronavirus precautions he's off work for awhile and I'd rather go ahead with the overhaul while I have plenty of free time.

Head tube:
I can't tell whether the head tube is aluminum bonded to carbon fiber, or all-carbon fiber. No way to check with my phone's "metal detector" app which works only with ferrous metals.

I want to be certain because the old Trek shop guide cautions against using grease on seat posts or inside the seat tube, which Trek describes as carbon fiber coated with fiberglass to resist galvanic corrosion. I did need to use Park SAC-2 assembly paste last year to keep the seat post from slipping, but I may discontinue using it after this overhaul. I noticed the SAC-2 paste scored the soft aluminum shims I used on the headset last year to fit a larger stem/handlebar to the original 1" steerer tube. No harm done to anything important -- it was just a soft aluminum split sleeve shim. But I don't want to risk damaging the frame inside the seat tube. I wouldn't need assembly paste inside the head tube, but would like to know whether it's all carbon fiber or aluminum bonded to carbon fiber.

The inside of the head tube, steerer tube, Chris King headset, etc., were very grungy from years of neglect. The previous owner used it as a tri-bike and I suspect sweat and maybe electrolytes dribbled down into the headset and head tube. The crusty residue resembled rust and lime scale. I've seen hardened grease before but never in a bicycle. The grease used by German manufacturers in the 1940s-'60s on everything from cameras to airguns tended to harden into something resembling brittle green plastic.

The residue I found inside the head tube wasn't quite like that -- more rusty brown. I've carefully scraped it off using a stiff plastic card, pencil wood, and finally a brass rod and shotgun bristle brush for the most stubborn residue. And I used a bit of Lime Away, which worked well on the carbon fiber fork's steel steerer tube.

With a flashlight the inside of the head tube appears shiny, more like aluminum than carbon fiber, but I can't be sure. Tapping doesn't reveal anything -- the surrounding carbon fiber and thick paint deaden any sound.

Fork:
The fork label says it's carbon fiber but the steerer tube is definitely steel. However the place where the crown race is set appears to be a stepped aluminum sleeve swaged to the steerer. Is that correct? I notice a very slight difference in magnet pull using a powerful magnet.

The grunge from neglect left some pitting and discoloration, nothing dangerous. But while waiting for the Chris King headset to be rebuilt by King, I was thinking of temporarily using an Origin8 Pro headset. The Origin8 headset has a steel crown race and I'm a bit wary of damaging the part of the steerer tube that appears to be an aluminum sleeve swaged onto the steel steerer tube.

Any comments or experience with that? I'm wondering whether I should just put this project aside until the folks at Chris King overhaul my old headset for me. I think the original headset used some titanium bits, but it may be aluminum. Definitely not a steel crown race. It appears only the bearing cartridges used steel.

Bottom bracket:
I may leave the White bottom bracket alone. It spins smoothly, feels fine as-is. There are a few chips in the paint around the edges of the BB shell, which still has the original protective metal washer/shield doodad. But in case I do decide to overhaul the BB, I'm wondering whether the BB shell is also aluminum bonded to carbon fiber, or whether there are other precautions to watch for. The 1994 shop manual I found online doesn't specify any description of the bottom bracket shell.

Thanks.

davidad

I haven't had my 5200 for 15 years but the metal in the head tube is steel and the same for the steerer. I think the only problem that I knew of from friends was that the bottom bracket steel piece may come loose.

tFUnK

So, what were your questions exactly? What are you hoping to accomplish with this frame/overhaul? The head tube and BB shell will most likely be sleeved with some sort of metal where the cups interface.

canklecat

Thanks. I checked my frame with a magnet, no steel in the frame. I'm gonna assume it's aluminum in the head tube.

The 5900 was my first carbon fiber bike. Really rides more like a lightweight steel bike, not much different from my Ironman. A few months ago I got a mid-2000s Diamondback Podium frame from a friend -- frame was the wrong size for him, and he only wanted the components. I had enough stuff in parts boxes to build up the bike. Big differences in carbon fiber frames over that 20 year period. The Diamondback frame appears to be 100% carbon fiber, no indications of any metal sleeves or joints bonded to the carbon fiber. Ultra light.

But I still like the old Trek frame. Probably a nostalgia thing -- among the last frames handmade by Trek in Wisconsin. I'd like to keep it going as long as possible.

canklecat

Just fishing for anecdotes from folks who've overhauled these older OCLV frames. I couldn't find anything else Googling around, or in the handful of older Trek manuals online.

I'm mostly concerned about avoiding damage from scraping off the crusty old residue. It's hard to describe, but it's difficult to see inside the frame well enough to see the differences between crusty residue, corrosion, pitting, chipped paint, etc. I might get an endoscope to help inspect the frame tube interiors.

And which cleaning products are safe to use. Based on what little I can find in Trek's old service manuals, I won't use anything stronger than a rag barely moistened with mineral spirits or denatured alcohol to finish cleaning inside the head tube. They do recommend against using solvents to clean inside the seat tube, to avoid contaminating the bottom bracket. Presumably they mean don't flood the seat tube by pouring solvent down there.

tFUnK

Gotcha. I guess I don't see the point in deep cleaning the inside of tubes but sounds like you're on the right track in being gentle with it. Mild soapy water or diluted isopropyl alcohol should do it. Instead of a rag see if you can find a pipe cleaner/bottle brush that fits the tubes. Keep frame upside-down afterward to avoid pooling in the BB area.

Andrew R Stewart 

Craig Calfee has said that cured epoxy/carbon (as we use in frames) isn't bothered by just about any substance one can buy at their hardware store.

Head tube- IIRC there's a metal sleeve, AL on the higher end frames, just like steerers tended to go to Al as the cost went up. Carbon only HTs didn't become the norm for a decade more, give or take.

Fork- Again IIRC the crown is AL and bonded to the steerer. There would be no swaging. Look up Viscount death forks for why industry avoids press fits for mission critical systems Especially for dissimilar metals. Sure we see this in bearings frequently these days but if a bearing loosens within it's bore (the hub shell or BB shell as example) there's no liability consequence to speak of. can't say that with the most highly stressed joint on the bike that also has no secondary connection (as in a frame tube that's joined at each end. If one end would debond the other generally keeps things somewhat together. These days even the caliper mounting bolt might not be present in the steerer/crown joint).

BB- As with the HT there's a metal sleeve for the threads to be cut in. Any threaded shell will be metal. But there's enough examples of seized in the shell BBs to warrant removal, cleaning and reassembly with antiseize compound. It's called preventative maintenance. Andy

canklecat

Thanks! Good point about preventive maintenance. Maybe I should go ahead and do the bottom bracket, even though it spins well. If I wait it may become impossible to remove or replace the BB if it becomes seized to the shell.

m0142000

Hi there,
I have completed the restoration project of my Trek 5900 and I was finally able to obtain the Matrix Photon wheelset, the Dia Compe brakes and the Sella Italia Flite Evolution with blue and green decals, but during the process I detected that the BB of my bike was exchanged for a Shimano BB (which is technically ok), but to have a "perfect" bike I would love to get the original White Industries Titanium bb in 68x113, so if you decide to replace yours, could I buy yours? As I'm new to the forum I cannot write PM's yet, perhaps you can send one to me?
Thank you!
Gregor