Aluminum front derailleur braze-on adaptor band clamp (Shimano) on bare titanium frame

  1. can the interface be dry or should it be lightly greased to isolate against galvanic corrosion? 2) seat tube is 34.9? OD, about 4-5NM band clamp bolt torque?

    TIA

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Not an endorsement per se but I’ve always greased the band clamps before torquing up to spec (mostly to protect paint) never had an issue with slippage even on painted seat tubes.

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The clamp is probably anodized which should protect against corrosion, I doubt any grease is needed.

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I would use anti seize or grease. I have anodized Campagnolo clamps on both my Ti bikes and have gotten corrosion on clamp (and a bit on seat tube) when assembled dry. Of course, I live deep in the Perspiration Belt (in central Texas) and sweat that drips/runs down the seat tube can seep in and accelerate galvanic process.

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Dry, no issues at all but prefer a carbon clamp.

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I defer to those with actual experience with ti vs al, and just to add an alternate solution - I have a fd clamp on one of my bikes that was slightly loose for the cro-mo seat tube and (actually to protect the paint), cut a ‘c shaped’ shim from a white plastic film canister that I shaped to the outline of the clamp, and roughened both surfaces with sandpaper. No slippage, not the most elegant solution, but almost invisible and it worked. If you try this, you might need a thinner shim as you have a clamp of the correct diameter (maybe some good 3M tape)…

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I have considered using a strip of that clear protective plastic frame protector material under the clamp but if it’s too thick, I’m not sure it will fit.

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Just a word of warning - I used a Shimano FD clamp on my custom titanium frame. I tightened it to 5NM a couple of times, but both times it slipped down / sideways. I then went to 6NM, and while it seemed like it worked OK, unbeknownst to me at the time, it must have cracked the frame. It seemed fine for a while, but then I started chasing a ticking sound every time I got out of the saddle. After exhausting all other possibilities, I took off the clamp only to find a pretty bad crack there, which I think took a while to get to the point where it was causing a ticking sound. I had that frame for about 15 years. The finish looked perfectly fine even though I never used any kind of frame protection. I REALLY miss that frame, so whatever you do, don’t go beyond 5NM. If it slips, I’d see if you can find something to put inside of clamp that will add some friction. That frame went through some pretty awful crashes, but none of the crashes ever dinged up the front derailleur, so don’t think it was those impacts at fault.

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I have a clamp-on front derailleur on my old Ti bike; I simply put a strip of clear polyester tape underneath it. I’ve probably replaced the tape a couple of times in the twelve years I’ve had that bike (though I only use it on the indoor trainer these days).

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that surprises me, actually. I figure if you’re needing to go past 4-5nm on one these front derailleur seat tube clamps, something is wack, off. what do you think the problem was, can it be narrowed down to anything apart from simple poor tolerances?
is it possible that initially going to 5nm that was enough to put the tube out of round (throw off the tolerances) and cause slippage?

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The fact that the crack happened on the drive side and I never broke a front derailleur in any of car-vs-bike the crashes makes me believe that it was the tightening of the clamp that did it in. That frame was SO well made, meaning the tolerances everywhere else (bottom bracket, dropouts, frame alignment, etc) were as close to perfect as you could get, so I don’t believe it was a frame defect. I had at LEAST 100,000 miles on that frame over the course of about 15 years. I had to replace the clamp at least twice because of corrosion, and I’ve had several groupsets, so I wouldn’t be surprised if I tightened the clamps 100 times fighting with front derailleurs. That frame was crazy light though. According to my scale it was 1120 grams completely stripped, although that was not a calibrated scale - just one I use to measure food items. Anyway, the moral of the story is to be careful - start at 4NM, maybe with a bit of blue threadlocker in there, and only go higher if you absolutely need to.

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blue threadlocker is good idea. too bad I just installed it with phil wood grease an hour ago, didn’t tighten it though.

At least when I had a fder on my ti mtb, always installed dry. I never saw any corrosion. Never even considered it, was never an issue.

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I’ve over 20 years on a Ti frame with the FD clamped directly to it.

I’ve never moved the clamp so I can’t comment on any adhesion between the two but once set correctly, there’s little need to ever move an FD.

it’s not the ‘adhesion’ problems of corrosion I’m worried about with this interface so much as expensive gear getting eaten alive by it.

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I don’t think this will be an issue. Titanium has a pretty good layer of oxidation on it, and even silver aluminum clamps are almost always clear-anodized.

To add another data point, lots of titanium frames use aluminum rivnuts for bottle bosses and whatnot, and it’s not like those are turning to dust left and right.

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I’ve been using aluminum band clamps on a series of titanium frames for over 25 years and always install them dry (no lubrication, anti seize compound, or loctite) after cleaning the inside of the clamp and the outside of seat tube with alcohol. I’ve never had a problem with corrosion at the interface, whether or not the clamp is anodized. I live in a damp climate, but don’t often ride in the rain and always store my bikes in a dry place. I tighten the clamp only enough to keep it from slipping. When using a torque wrench for the band, I first tighten to 4 nm, then readjust the wrench tighten toward 5nm, stopping if the band starts to flex (some cheap bands do). I never go beyond 5nm. I’ve crimped an inexpensive steel frame with a cheap generic band by simply setting the torque wrench at the specified maximum torque of 7 nm and tightening the bolt all at once. I wouldn’t install tape because that increases the outside diameter of the tube, but not the inside radius of the clamp. That would increase risk of damage to the tube or clamp.

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I appreciate your detailed post. looks like I’m going to go with a little bit of grease inside clamp (which matches the OD of the seat tube perfectly) and torque to an initial 4nm and see how that settles down.