Ti Frame / Ally Shim / Carbon Post – 10 years on …

[WD Pro]

Dads bike – Ti frame with a factory fitted ally insert. The post has been in there for around 10 years (ish) and hadn’t been moved (road bike) … :?

Stuck tight, very tight … :?

We had been dosing it with plusgas and GT85 for about two months before attempting removal, and riding with a loose seat clamp.

An old seat went on the post (to save his nice USE seat) and that just snapped the top of the post off … :



So it got drilled and levered out – two man job of about 40 mins of twisting and cursing How the post didn’t snap is beyond me, I was expecting to be cutting this baby out … :?

I know he should have periodically removed it, but he didn’t, everything else on the bike is spot on (condition wise) and the bike is always kept clean / dry weather only.

The shim in the frame can’t be removed but giving it a good finger suggests that it now has a rough bore ?

I have come up with two possible reasons, what do you think :

1 : Ti frame and ally shim combination had started to corrode the shim, corrosion expands the shim clamping the hole assembly mega tightly ?

2 : The resin on the post has reacted / bonded itself into the frame ? Check the difference in finish between exposed and non exposed sections of post :





Any ideas ?

WD

PS : Anyone got a 27.2 reamer they would lend out if I cover costs and beer tokens … ?

 

[steelhardtailer]

Could you try something like this http://www.toolstation.com/shop/p91986? ... tAodFTsA1A
If you cant get them in the exact size then by removing sections it thins out to the correct diameter, they are also available in longer shaft lengths, I`ve used these in the past at work for polishing welds prior to NDT`ing.

 

[syncrosfan]

Carbon and Aluminum don't like each other at all, you could get a galvanic reaction going (over time) especially if moisture is involved. If that post hasn't been moved for years and no carbon friction paste has been used, I could see how the post can get stuck. In theory the resin on the post should be enough, but you never know... when bonding carbon tubing to aluminum inserts it's quite crucial to allow for an even bond-line gap (ca. 0.001") to make sure that the galvanic reaction never happens (e.g. they shouldn't be touching at all!). Just ream out the seat tube again, and use an aluminum seat-post.

 

[WD Pro]

Interesting - thank you

He has got another post to go in - he's dug out his old / retro campag record Ti ...

It will be covered in Ti prep though and I know for sure he will remove it on a frequent basis now ;-)

WD

 

[legrandefromage]

Plusgas & that would have reacted with the carbon and possibly expanded it making matters worse.

Sounds like the lacquer reacted with lubes and any grease. It doesn't take a lot.

 

[Rampage]

You should be able to get a cheap adjustable reamer from the Model Engineer places if you want to remove the shim.
I think from memory caustic soda etches titanium so might be best to avoid that method.

 

[WD Pro]

1 : Ti frame and ally shim combination had started to corrode the shim, corrosion expands the shim clamping the hole assembly mega tightly ?

It was the above :-(

Dad spoke to the supplying shop - they were very good and offered to ream it out. Dad got the impression that they knew of the problem / had seen it before on this bike type (the shim is a factory fit job).

They did the job today and confirmed shim reaction / corrosion. It only took two mins but it was FOC - very good service for a thirteen year old purchase !

WD