Dynatech seatpost slipping ?!

[LittleSkink]

Ok got my old '95 Dynatech Diabolo frame (Half Ti half CrMo) all built up as single speeder and went for a proving run last night - all is well but seat post isnt staying put

It is a 27.0 Xlite post and afaik the frame is a 27.0 fit. Tightened the seatpost bolt as much as I dare and it is bending the bracket on the frame slightly - not sure what to try next . . . help please

 

[HullBorn]

Is there any grease on the post?

 

[LittleSkink]

tiny bit of grease yes - so the alloy post doesnt sieze in the steel frame

wondering if this is common / uncommon on these Dynatech frames or even XLite posts ? I know Thomson posts had a reputation for being slightly undersized

EDIT - okay removed grease with Meths from the inch or so at the top of the tube where clamp is, left some grease lower down. Cleaned grease from top of frame tube also. The clamp bolt was a little snug so (and ungreased) so cleaned and greased that to make it smoother

definitely still slipping, even when I tighten as tight as I dare

 

[mattr]

grip paste, the stuff they recommend for CF to CF joints.
Could try tooth paste as a try it and see first (very similar effect, but washes away in the rain!).

Unless the pin is actually undersized, or a previous owner has stretched the top of the seat tube

 

[mattr]

Might be worth measuring too. Just to double check

 

[ibbz]

Re:

27 or 27.2?
Mine is 27.2

 

[DA-EVO]

Ok got my old '95 Dynatech Diabolo frame (Half Ti half CrMo) all built up as single speeder and went for a proving run last night - all is well but seat post isnt staying put

It is a 27.0 Xlite post and afaik the frame is a 27.0 fit. Tightened the seatpost bolt as much as I dare and it is bending the bracket on the frame slightly - not sure what to try next . . . help please

Had the same with mine and I think the dynatech post is 26.8mm and the frame is 27.2 and there was supposed to be a shim in there. I put in a 27.2 and it was fine but I never did find the right shim. (Sold now).

 

[LittleSkink]

interesting, thanks folks

pulled out what I beleive is the original post from my box of bits (says 4130 up the side in big letters) and it is 27.0 also . . .

for the avoidance of doubt on model, there is apic of the bike here:
http://www.retrobike.co.uk/forum/viewto ... p;t=326268

 

[LittleSkink]

quick update, just had a play with a 27.2 off one of my kids bikes

needed to bend the clamp bolt open a little with screwdriver but 27.2 will go in, snug as you like but goes in about 3" ok

looks like I need a new post . . . bugger . . . anyone know where I can get a nice one cheap? Whats the going rate for a nice condition 27.0 Xlite?

 

[ljamesb]

quick update, just had a play with a 27.2 off one of my kids bikes

needed to bend the clamp bolt open a little with screwdriver but 27.2 will go in, snug as you like but goes in about 3" ok

looks like I need a new post . . . bugger . . . anyone know where I can get a nice one cheap? Whats the going rate for a nice condition 27.0 Xlite?

Was looking for 27.0 seatposts also and didn't fancy spending lots of £££'s on a metal tube . See my post here as I found a couple of nice, light seatposts cheaply on ebay (links in the thread). I think those sellers have different colour options too if you look at their other items.

Hope this helps!