Any question answered...

what defines which combo can or cannot be used?

Front dérailleur is the main thing. Road fronts these days are mostly designed for a maximum difference of 16T, don't really have a minimum difference, but do like the big ring to be big.

Any combination of 32/34 inner and 46/44/42 outer will work, but at the lower end of the scale of outers the tail of the dérailleur cage will be a long way from the ring diameter so upshifts will be slow.

There are two limiting factors. The first is the PCD of the chainring bolt holes, which will define the minimum chainring size. 39t is the smallest (realistically) you can go with a 130mm PCD (standard), 34t for 110mm (compact). The second is the difference between the two chainrings in the number of teeth. This depends as much on derailleur design and geometry as anything, but a 16t maximum difference is a reasonable starting point.

Perhaps it's something to do with BCD (or PCD which is the same thing) and the capacity of the front derailleur?

I'm not sure

Hoping someone can help with a wheel question. I've just bought a pair of Mavic Ksyrium elite 11 speed wheels and I want to put my 10 speed Shimano 105 cassette on them (cs-5700). The wheels come with the spacer needed but I've read that you may also need another Shimano spacer for it to work properly? Does anyone know if this is required or fine with the just one spacer? Cheers

You need both.

Ok, thanks. Will this one be fine ?

Ah, oops photo doesn't seem to work

The 105 cassette come with the spacer.

Alternatively you can just get the cheaper Tiagra one (that doesn't required a spacer) and run that instead, you won't notice performance difference.

The spacer with your new wheel converts it to 10 speed.

10 speed cassettes also require a spacer as they are narrower than 9 speed: this spacer is supplied with the cassette.

Is it on your old hub, you'd have been using it there.

Yep, I've got it. Thanks. Does it matter which of the two spacers goes on the freehub first?

You need the Mavic spacer on first, so it now converted to 10 speed spacing, then you put the spacer that was provided with the cassette on after.

If a cassette doesn't come with the spacer (like the Tiagra one), you won't need it.

Really helpful, thanks a lot.

No.

Oh, it does?

Is that just for Mavic?

Mavic were doing 11 speed freehubs before anyone was going 11 speed groups.

^ Exactly what he said, they been doing it even before Campagnolo release the first 11 speed groupset.

Sheds. The community garden here needs a new one. Needs to be metal, reasonably sturdy, hinged doors (not ones on rollers that fall off and don't work) and roughly 7' x 3'. Any other companies to look at besides Asgard?

10 speed bar end shifters that will work with dyna-sys rear mech?

Anyone know of a front rack that might fit a 16" wheel (Early Rider Belter) kids bike? My young gun wants to carry stuff.

Something like this?

http://www.decathlon.co.uk/police-front-bike-basket-id_8246626.html

What does they want to carry? maybe a Klickfix system might be idea.

I've inherited a little stool, with flip down steps so you can use it as a mini step ladder.

The seat is a bit too weak to take my weight so I wanted to replace the seat and reupholster.

My question is this, what should I make the seat from?

The original is ½" thick, 300 x 300mm with the unsupported centre being 270mm.

I was going to use some 26mm MDF I've got knocking around, but after offering it up it looks way too thick - and this is before reupholstering. The total current thickness with material is 20mm.

I'd like it to last, but equally it's hardly a Chippendale so cost is a factor.

Cheers

Pick up an off-cut of plywood from a building site. Ask nicely rather than nicking it in the dead of night, you know it makes sense.

Cheers.

Will 12mm thick be strong enough?