Seatpost sizes!

[cellleader]

Imagine this - you buy a new 26.8mm seatpost for your frame which takes a 26.8 seatpost but it only goes in about 3 inches and no more despite grease of the slippery and elbow kinds. What is going on - I've measured it with a micrometer and everything checks out - I'm stumped - help :?

 

[Corduroyboy]

Corrosion in the frame further down? Seat tube not properly reamed? Major misalignment in the seat tube?

Any marks on the 'post from your attempts at insertion?

 

[cellleader]

The only marks are on the back of the post - I prevented any more from appearing by opening out the slot in the frame. I think maybe your corrosion idea is the most possible corduroyboy - any idea what to do?

 

[Corduroyboy]

Get an old, much narrower seatpost or any other appropriately siazed tube, wrap some not-too-fine sandpaper around it (sand side out!) and work it round the inside of the seat tube - if there is any corrosion (or build up of crap) then the sandpaper should remove it. Hope this helps!

 

[cellleader]

Sounds good - thanks

 

[utahdog2003]

26.6?

 

[scant]

what seatpost & frame is it? I had 1 of the last US made yeti arcs around 05 & the RF XY post just wouldnt fit. measuring the post with verniers the paint massively changed in thickness. sanded the post & all was well (sold the arc a year later, lovely frame, just dented too easily)

 

[cellleader]

It's an old peugeot black mamba - steel (531) - for winter commuting. Trying to squeeze in a tioga t-bone 26.8. Verniered the inside of the seat tube giving 26.8! Maybe a 26.6 is the way to go?

 

[utahdog2003]

It's an old peugeot black mamba - steel (531) - for winter commuting. Trying to squeeze in a tioga t-bone 26.8. Verniered the inside of the seat tube giving 26.8! Maybe a 26.6 is the way to go?

I'd try it before I forced the 26.8 or tried to somehow make the 26.8 fit. The 26.6 will only slip around a bit if it's wrong, no harm done, then you can make the 26.8 work if you need to step back up to it.

 

[stew-b]

you cannot measure a bore with a vernier caliper! you need to use a bore gauge,a completely different instrument.the top of a seattube will be squashed in,the only bit you can try and measure with a vernier.where the seattube meets the top tube is the true size,this is why you need a bore gauge to reach further in.