How deep in the frame should seat post go??

Unknown

I am building up another frame tcr carbon compact,
and wondered if I can use my old seat post in it, but it is only 250mm long so will be just past the joining from top tube to seat tube in depth as its a carbon frame just wondered if this is ok not too much stress on it

p.s its a tomson elite do I need to grease ??

sorry bit of a numpty Q probably [:I]

Grifcp

I would'nt use grease myself. As far as depth, you should be looking for at least an inch below the lower part of the top tube/seat tube join.

Unknown

At least an inch below the bottom the join of the top tube used to be the advice for all frames. Not really sure this applies to Carbons. i've got plenty more than that on my TCR. not sure that help you much. sorry

Don't need grease between carbon and ally.

Mleh Mleh Mleh

Unknown

thanks for your quick replys

CPcp

I disagree with Steve and would advise anti seize grease between a carbon seat pillar and an alloy frame. Thin smear on the pillar. Took me quite a bit of effort and penetrating oil to free mine off after fitting it dry. The alloy oxidises and gets engrained into the carbon. LBS confirmed my views and even suggested regreasing every month!

Garybee

You will get 'galvanic action' between aluminium and carbon so it is worth putting a barrier between them if possible. Aluminium is further away than steel is from carbon on the galvanic scale so will actually react faster. Therefore if it is worth it with steel it is even more worth it with aluminium.

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Hypocrisy is only a bad thing in other people.

Unknown

oops Never meant to start this off. [:0]

here you go guys, use some of this and we can all be happy

Mleh Mleh Mleh

monty_dogcp

Firstly, your seatpost is anodised, so it forms an effective barrier to galvanic corrosion whereas the inside of an alloy frame isn't - it's bare metal and so prone to corrosion. Many petroleum-based greases can react with carbon so aren't recommended but their are other effective non-petroleum based assembly compounds available. Engineering principles for an effective tube fit are at least 3x diameter e.g. seat post shims are only 75mm long, but as a general rule, the post needs to extend past the top-tube junction.