Exped seems to have fixed the older problem with baffles separating. We have newer expeds for 2 years now, overall 3 months of camping without problem. Many years back we gave up on exped because of baffle separation, but their newer products have apparently fixed this problem. I gave up on Klymit because 3 had delamination near the valve. I can fix a puncture on tour, but not delamination.

The exped have an internal foam pump, but I use a small rechargeable pump (flextailgear) that works very well. For 2 of us this pump greatly simplifies inflation each night. 10 inflations per charge.

This bike has been in storage, & now going to be a bit more proactive in selling as I need the space & never use it ,Comes with quite a few extras, Please contact kevskeys1@gmail.com for pics & questions ,Any sensible offers  considered, I paid £3600 .  Comes with a new brooks saddle,& the original Crank/arms plus the ones I had fitted all original Thorn .Thanks

Where are you located?  I am used to USA brands that might not be sold in UK or EU.  Do you prefer the self inflating pads that have internal foam, or the air mattress pads that are more compact to pack but thicker in use?

I preferred a REI branded one (only sold in USA) air mattress, but I had two of the REI ones fail, no more REI ones for me.  It had internal baffles that quit being baffles, which I am guessing is what happened to yours because I remember hearing the pop.  See photo.  I do not know if I over-inflated mine to cause the fail or not.  But I now intentionally put less air in them so they are less likely to be over-pressurized.  That said, I had less air in the second one when it failed.  Perhaps it had some material that failed due to age, as some plastics appear to do.

I have a Neo Air XLite air mattress that I have used on some trips, I only bought it for trips where I wanted the lightest amount of weight and I got it at a very good discount.  It was very noisy at first.  I think there was an internal thermal barrier that was very noisy when it was flexed, but after several weeks it seemed to get quieter.  So, if you get one and do not like the noise, it gets better fairly quickly.

After having two REI air mattresses fail, I decided to buy a spare of another brand when I saw a really great price on a one on sale.  I have not yet slept on it, this one has no internal insulation so it could be cold on cold ground, price even at full price is not bad, this is my spare:
https://klymit.com/products/static-v-camping-sleeping-pad

I used to use the self inflating pads. I like them too, but they consume much more space when packed, even when I always bought the shorty versions.  So, for bike touring where my pannier volume is a key factor, I use air mattresses.  I think the self inflating pads with some internal foam are much better on cold ground.  And if it leaks, it still gives you a tiny bit more cushion than a deflated air mattress.  And when backpacking, I can strap the self inflating ones on the outside of my pack.  Second photo.

Quote from: PH on June 12, 2021, 08:38:53 PM

I also have to carry mine up and down stairs every time I use it, but do so by the seat tube, have done so with every bike without thinking about it. 

Maybe I don't get what you mean but if I do this then I end up with my legs banging into the handlebars! But minor gripes indeed.

Quote from: PH on June 12, 2021, 08:38:53 PM

Needing to clamp the seatpost tight doesn't sound good, is it the standard Thorn one that came with it?  Mine don't need much tightening, if they did I'd be inclined to add a shim.

Yes I'm using it as supplied with the plastic shim. I might try the foil and/or grippy compound suggested above because I do find the post can end up lower after long and bumpy rides and the tightening makes me a bit nervous.

Quote from: JohnR on June 12, 2021, 08:49:44 PM

Have you positioned the saddle with exactly the same saddle to handlebar spacing, saddle to handlebar height difference, saddle slope and saddle top to crank centre distance as on the other bike? I would try flipping the ahead stem to raise the handlebars slightly.

The bikes are so different that the spacings are totally different. I am at 'limit nose down' with the adjustment on the supplied Thorn seat post which actually feels like it should be about right but I would like the option to experiment by dropping the nose a bit more. I can't do that without buying a new post though since I don't have any spares knocking about.

This may sound like a daft question but did you make sure that the shim gap lines up with the seat tube gap?
If not the shim has a very hard time closing down on the seatpost.

The Thirn Touring Bike Bible covering the Mk3 Mercury is still on their website here

https://thorncycles.co.uk/resource