Any question answered...

I have enough p clips to do it already, but I'm willing to pay a bit more for something a bit nicer?! Surprised if there isn't somethjng.

@roboto, yeah that'll do, cheers.

Ah-ha, was expecting something like this:
Delta Cycle Rear Rack Center Mount/Brake Bridge Hardware https://www.amazon.com/dp/B000650WWK/ref=cm_sw_r_awd_jCbovb0Q4SK0B

but I'm willing to pay a bit more for something a bit nicer

P-Clips keep the rack stays short and spread apart, which is much the best thing for stability.

If I have a 12/25 105 11 speed cassette and wanted to change it to a 11/28 or even an 11/32 would I have to make any major changes on the rest of the groupset (deraileurs/chain)
#missingmygrannyring

You'd have to change the chain length but the derailleur will most like stay the same. What groupset is it?

@clefty so long as the rear mech is long enough drop it should just be swapping the wheel/cassette and checking it's shifting well.

I think a 32 may require a longer cage derailleur, but 28 should be fine.

so long as the rear mech is long enough drop it should just be swapping the wheel/cassette and checking it's shifting well.

That's an excellent way to rip a dérailleur hanger off your frame. Switching up from 25 to 32 will certainly need a longer chain unless the chain was already much too long

I think a 32 may require a longer cage derailleur

Almost certainly. Nominal maximum tooth on a short cage Shimano has been 27T since about 1741, they could always be pushed a bit as the hanger geometry assumed by the spec was quite conservative, but only as far as 29 or 30.

Rear mechs have various restrictions based on "capacity". For example:-

http://www.wiggle.co.uk/shimano-105-rd-5700-rear-derailleur/ gives:-

Short cage:

Maximum low sprocket 30T
Maximum front difference 16T, total capacity 34T

Medium Cage:

Maximum low sprocket 32T with double chainset
Maximum front difference 22T, total capacity 40T

The "total capacity" is the maximum difference between smallest and biggest gears. i.e. for a 50-34 and 11-28 you've got (50-34)+(28-11) = 16+17 = 33T

So front difference is 16T and total capacity is 33T, within the specs for that short cage mech.

An 11-32 would have a total capacity of 36T, more than a short cage RD-5700 could handle safely.

So it'll depend on what front chainring setup you have too. Find out that, and the rear derailleur model number and then check the specs.

On this topic, is there a good rule of thumb for chain length related to the angles of the cage on your rear mech when in a certain ratio? I'm sure I've seen something on that somewhere.

On this topic, is there a good rule of thumb for chain length related to the angles of the cage on your rear mech when in a certain ratio?

No, but there is a very simple set of proper instructions for setting chain length supplied with every retail boxed rear dérailleur, and if you've lost yours you can download it from the manufacturer's website. All the suggested rules of thumb based on cage angle are bullshit.

25.8mm carbon seatpost for peanuts for sale on ebay, is possible to shim to 27.2mm safely? any recommendations for a shim?

Like. Thanks.

Something like this but due to the odd sizes choose something like a 25.4 to 26.8 to give you the same 1.4mm difference.
http://www.sjscycles.co.uk/humpert-seat-post-shim-254mm-id-prod32253/

Unless you can find an exact match.

@Soul It's a 5800

Thanks guys @Greenbank it's a RD-5800 short cage with a front chainring of 36/52. I'd like to change as little as possible component wise, so if I can go with a 11/28 I can live with that.

Shimano polymer coated cables come with ferrules that have a little tail. I need to recable my nice bike that has inline barrel adjusters. Should is just use normal ferrules for when the cables enter and exit the barrel adjuster? Am assuming the little tail end will just get jammed up against each other inside the adjuster.

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Should is just use normal ferrules for when the cables enter and exit the barrel adjuster?

Yes. The tails are just for use at stops where there is bare wire on the other side, to reduce dirt ingress.

King cage iris cages. Yay or nay?

and

SRAM quickview garmin mount. Any worth spending the extra money on?

Where's a good place to get a leather saddle fixed? Bust the metal piece that works on the nose of the saddle...

As a rule of thumb I go big to big not through the derailleur, see where I could join the chain and add a link, remember how many links I could remove. Then go small to small through the derailleur and see what the fewest links I can remove while there is still tension on the chain, usually the cage is horizontal. Somewhere between the two will work, I err on the shorter side but a lot of the time it's the same length with both methods. If you use all the fancy maths and whatnot it tends to be the same.

As a rule of thumb I go big to big not through the derailleur, see where I could join the chain and add a link

That's not a rule of thumb, it's the correct method described in the Shimano Service Instructions

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Yeah, but I use my thumb.

The inch, which is the amount of extra chain you have to add, is not really derived from the thumb; there is some weak suggestion that the Scottish inch may have been defined in relation to the thumb, but the English and succeeding Imperial inches never were.

Where's the Foffa thread?

Spell it "f0ffa"