Creaking seatpost advice - options

[Nambra]

Tried a different saddle to eliminate it as the cause?

 

[mas2]

Can’t be arsed reading back...positive it isn’t seat rails? 9/10 times it is for me.

Yep I get the same too, often its the rails.
Also, I had one I thought was bottom bracket but found it was derailleur hanger that creaked because it was slightly loose and would pivot a little.

 

[Binaural]

I can tell you the answer, but you dont want to hear it.

Well, you're not wrong, but I'm cheap and it's a custom frame that fits my weird dimensions like a glove. So I am willing to tolerate these infuriating little dramas and the time necessary to hunt down and eliminate. Seatpost is a 3T Stylus 25 LTD Stealth Carbon, 31.6mm.

@several: I've tried the bike with a different seat to no effect previously.

So I have re-inspected the seatpost area looking for micro cracks, and still cannot find any sign of anything. Given I've had to get 2 previous frames repaired, I feel like I'd know one when I saw one (open and shut case, Johnson! </chappelle>). However, this did lead me to discover something interesting - the cutout for the seatpost look like it has to compress much more than it should - see photos. I can get a folded post-it note in there really easily. Does this indicate that I might need to apply a small shim?

 

[pink poodle]

Bigger seat post perhaps?

 

[Oddjob]

Well, you're not wrong, but I'm cheap and it's a custom frame that fits my weird dimensions like a glove. So I am willing to tolerate these infuriating little dramas and the time necessary to hunt down and eliminate. Seatpost is a 3T Stylus 25 LTD Stealth Carbon, 31.6mm.

@several: I've tried the bike with a different seat to no effect previously.

So I have re-inspected the seatpost area looking for micro cracks, and still cannot find any sign of anything. Given I've had to get 2 previous frames repaired, I feel like I'd know one when I saw one (open and shut case, Johnson! ). However, this did lead me to discover something interesting - the cutout for the seatpost look like it has to compress much more than it should - see photos. I can get a folded post-it note in there really easily. Does this indicate that I might need to apply a small shim?





View attachment 352276

I'd be checking the seatpost and the seat tube with vernier calipers. If its the seatpost thats out of spec then that is an easy fix, Thomsons have very good qc and are usually to spec. If its the frame then shimming might work but you would be better off looking for a slightly over spec seatpost. Maybe hit up bike bug or another big lbs with a stock of seatposts with your verniers. You could also use a 28.6 to 30.9 shim with a 30.9 seatpost which would give you 2.3mm of expansion rather than 1.7mm for a 30.9 to 31.6 shim.

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[creaky]

... rather than 1.7mm for a 30.9 to 31.6 shim.

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0.7mm.

Too much of a stretch from 0.7 to 2.3mm.

Seems like the post-it note is the perfect thickness and you should just wrap the inserted part of the post in post-it notes.

 

[Tim_the_Clyde]

I put a little bit of grease on the seat rails where they contact the seat post clamp.

That said the few times ive noticed a creak its actually been resolved with a couple drops of oil into the mould on the saddle where the rails attach. I just put a couple little drops of oil onto the rail near the ends and tip the bike so the oil runs into the ends.

Travis.

This is what’s solved my problems before



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[Binaural]

The plot thickens. At Oddjob's suggestion I borrowed a set of verniers from one of my mechanical engineers and checked the seatpost dimension (I vaguely recall doing this once to check seatpost diameter before buying). When I measure LHS to RHS, I get 31.7mm, which is within tolerance of normal. But when I measure front to back, I get.... 31.2mm. It looks as if the seatpost is slightly ovalised, which explains the small gap I observed earlier. Given the gap is around 0.4mm or a bit less, I am going to try jury-rigging an aluminium can shim (roughly 0.1mm) to take up the slack and see if that helps.

 

[Oddjob]

The plot thickens. At Oddjob's suggestion I borrowed a set of verniers from one of my mechanical engineers and checked the seatpost dimension (I vaguely recall doing this once to check seatpost diameter before buying). When I measure LHS to RHS, I get 31.7mm, which is within tolerance of normal. But when I measure front to back, I get.... 31.2mm. It looks as if the seatpost is slightly ovalised, which explains the small gap I observed earlier. Given the gap is around 0.4mm or a bit less, I am going to try jury-rigging an aluminium can shim (roughly 0.1mm) to take up the slack and see if that helps.

Jesus! Just get a Thomson! That sounds like a galvanic horror story waiting to happen. At least proper shims are anodised.

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[Oddjob]

0.7mm.

Too much of a stretch from 0.7 to 2.3mm.

Seems like the post-it note is the perfect thickness and you should just wrap the inserted part of the post in post-it notes.

I really can't count without a spreadsheet.

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[99_FGT]

You had your bb out before the creak started?
My ti roadie has a pf bb as well, i got the threaded bb at the outset.

 

[boyracer]

Grab some brass shimming sheet. Would be better than cokecan.