MK2 Nomad Seat post Diameter

[spoof]

Just wondering if anyone has done away with the 27.2mm shim reducer in their MK2 Nomad seat tube when fitting a new seat post? If so, what diameter seat post would be needed? My digital calipers give an internal diameter of approx 29.95mm but they could be out for all I know. I don't have any calibration objects to hand unfortunately.
Any advice much appreciated. Reason I ask is just for price / availability. Happy to run with or without shim.
Thanks K

[PH]

I don't understand why anyone would. 
27.2 is probably the most common size available, my favorite seatposts are only made in that size. 
Plus (Though I have no knowledge if this is the case with Thorn) if a shim was intended the reaming of the seat tube, post production, wouldn't need to be as precise as the shim will absorb slight irregularities.  Double plus, the advantage of a shim is that it'll probably eliminate any chance of a seatpost becoming seized in the frame - that's something which shouldn't happen if re-greasing the post is a part of your regular servicing and the shim should not stop you continuing to do this, as it has other benefits.

[spoof]

The benefits of the shim do put it in favour to use so thanks PH, I'll stick with it and buy the suitable 27.2mm post I have found in correct length. If the grease between seat tube inner and the outside of the shim is sufficient to prevent water ingress and hence steel rust and galvanic corrosion, is the general rule to also apply grease the seatpost itself in addition?

[PH]

I grease both sides, it probably doesn't need it and I don't know what the official advice is.  I can't see it does any harm and I already have the seatpost out and the grease open.

[jul]

Hi,

Please, do you know the seat post length for a Nomad MK2 ?

Thanks in advance

[JohnR]

Hi,

Please, do you know the seat post length for a Nomad MK2 ?

Thanks in advance

Long enough to keep the minimum recommended length (10cm?) in the seat tube. Getting something longer just adds weight.

[jul]

My Nomad is not close to me and I plan to buy a Thomson seat post.

I don't know if I have to choose between 250, 330 or 410mm

[mickeg]

My Nomad is not close to me and I plan to buy a Thomson seat post.

I don't know if I have to choose between 250, 330 or 410mm

If you have a photo of the bike, you might be able to estimate how much seatpost is exposed.

If yours has a Thorn post and you want to upgrade, maybe those came in only one length?  If so, that might be on their website.  I would be surprised if they had more than one length since they had custom printing added to the post.

If it is of any help, I have 230mm between the top of frame and the saddle rails on mine, I just measured it.

My frame is a 590M size.  My frame is slightly undersized because Thorn did not make S sized frames and I wanted drop bars, so I bought a slightly smaller frame to get a shorter top tube length.  Thus, my seatpost might be higher than average.

[jul]

Thank you but I didn't find this information on their website.

I think simply this seat post is not available.

Of memories i've around 20cm from the clamp to the saddle rails, probably 330mm for my next seat post should be fine.

[PH]

This is the one that came with my Thorn bikes, though I don't have a Nomad MkII
https://www.sjscycles.co.uk/seat-posts/thorn-353-alloy-seat-post-with-micro-adjust-black-350-x-272-mm/

I don't know if I have to choose between 250, 330 or 410mm

Get the 410, I can't imaging there'd be any issue with it being a bit long, but if there is you can chop a bit off.

[mickeg]

Both of my Thorn seatposts are in storage, not on bikes, so it was easy to pull them out of the box to measure.

Silver seatpost that was on my Sherpa (size 610S) frame that I bought used in 2010.  Measured 250mm from rails to limit marks on the seatpost, 350mm long.

Black seatpost that was on my Nomad Mk II (size 590M) bought frame new in 2013.  Measured 290mm to the limit marks on the seatpost.  400mm long.

So, in both cases, THorn wants at least about 100 to 110mm of seatpost to remain in the frame.

The silver one has soft paint that scraped easily, I replaced it with a seatpost that looked better.  The Nomad now has a suspension post, the original black Thorn post is not currently used.  But if I go on a tour, the black Thorn seatpost will likely be re-installed.

[mickeg]

Based on what they sell now:
https://www.sjscycles.co.uk/seat-posts-rigid/?brand=thorn


My 400mm black post is no longer sold by them, both of mine are 27.2mm diameter.

[PH]

Getting something longer just adds weight.

The weight is too small to bother me, though if it's a frame with a shim anything below that might as well not be there as it isn't in contact with the seat tube.

[mickeg]

I bought a used seat post on Ebay, a Cane Creek Thudbuster.  The bottom had been cut off with a hacksaw, and not even a very good cut.  But it was long enough for my needs.

If you want to worry about a few grams, that is an option.

But, if the longer post costs more to buy, I can see trying to buy the right one.

[jul]

Ok, so 410mm is preferable for me and for taller than me..

Thanks again !