Ti to alloy,no grease, risk of corrosion ?


Gold Trader
MacRetro Rider
I dont think its going to be an issue, but thought I'd ask.

Right. Ive bought a Hope type D stepdown lower headset cup, and while its for 1.5" and the cup is also 1.5mm there is actually about 0.7mm of a difference so the cup is loose, so I need to fill that gap.

I could give it a few turns of self adhesive alloy tape, which is very good at filing gaps on a slightly ovalized headtube, though thats not the prob here but it should make the fit better.
It's not a high end bike, more something to go shopping on, so its just really to get the headset fitted so i can complete the build.

Ive got some Ti sheeting, though thats 1mm and too thick, but I can get 0.5mm which would probably be better as its over sized by 0.3mm(or less) which will make for a tight fit.
I'd have to cut a thin strip, wrap it round the insertable part of the cup and press it in. Obviously no grease as I want it a tight fit. But how is Ti going to affect the alloy.
If it starts corroding, thats going to eventually cause damage to the bottom of the headtube and I'd think thats not a god thing. But if it corrodes a bit, say 'bonds' the two together, which is what im hoping something like that might do that is going to be better than a few wraps of tape

Thoughts ? Opinions ? other solutions ?
You can/will get galvanic corrosion with Au alloy and titanium. I'd use a quality anti-seize between the Ti, the cup and the head tube even if it's just a bike to hack around on.
Is that 0.7mm difference all the way round (both sides) or total difference? Either way, a 1mm or 0.5mm thick shim is too much interference and I don't think you'll be able to press that in without breaking something. You certainly won't be able to easily cut or roll a 1mm thick Ti shim into a 1.5" ring and 0.5mm will also put up a fight.

I'd have a look on eBay for some 0.35mm steel shim stock or whatever the difference is when you measure it up properly. Coke can can be useful as a bodge shim, which is usually around 0.15mm, but it can be difficult to get it in.

Do use grease.

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