When running a 1X9 set up do you need a specific chainring spider that alters the chain line. I have taken the inner and outer rings off my Middleburn RS7 spider but the chainline in the lowest gear is way off. The chainring really needs to come in a bit so its straight when in the middle of the cassette. Is that a common problem.

I took one of my spacers from one side of my outboard BB and slotted it on the other side as I had similar issues, but mine was way out on the top of the cassette, not the bottom (if that's what you meant by lowest).

With an old style BB you may just want to get a shorter spindle length.

by lowest i meant lowest gear, ie, biggest sprocket. i need to get the chainring further in towards the middle of the bike. unfortunately i recently replaced the square taper bb with a rather expensive one from middleburn so don't really want to change that, Any other suggestions.

you could change bb length, but the way i have done it before was to use some washers on the chainring to move it in a bit

Aye, use your chainring bolts for middle and outer but just whack in a load of washers to space it in a bit. Not very elegant, but the best shot without swapping BB.

i'm using a 113mm axle at the moment, what would be he best alternative.

111m or 109 mm.
Have a look on the widgit web site.

a middleburn uno chainring may sit closer in as in replaces the spider and looks very neat . Not sure of they do a 3/32 one though .

You can get spacers to put between the crank and chainring. I got some with my MRP chainguide, but you can also buy them here: http://www.hubjub.co.uk/etc/etc.htm

Search for 'chainring spacers'

I'm running RS7s on my 1×9 and had to stick spacers between the ring and spider. Ugly, but works.

Can someone please explain the whole BB length thing. Is it only applicable when you have 'excess' space between the inside of the crank and the BB housing?

Having been out for ride today and shed my chain 3 times I'm gonna try the spacers from Hubjub and get me some sort of chain device. Whats the lightest least obtrusive chain device that utilises iscg tabs (Orange P7)? probably don't need a botton roller.

MRP or E13 both do a top guide style device, but I they only come in BB mount not ISCG as far as I can tell.

http://www.chainreactioncycles.com/Models.aspx?ModelID=47875

http://www.chainreactioncycles.com/Models.aspx?ModelID=40904

The most common 1×9 set-ups are the MRP 1.X, e13 XCX or the Paul's Chainkeeper. AFAIK it's mainly a matter of taste choosing between them. I have the MRP and it works fine. I haven't heard much feedback regarding the e13 one yet as it's a bit newer.

http://www.chainreactioncycles.com/Models.aspx?PartnerID=79&ModelID=40904
http://www.chainreactioncycles.com/Models.aspx?PartnerID=79&ModelID=47875
http://www.paulcomp.com/chainkeeper.html

MRP 1.X, e13 XCX or the Paul's Chainkeeper

Nothing against those but the N-gear Jump Stop used by many and around for longer.

I use an e13 XCX and it works fine , it came with some spacer washers which I used and that made a difference …love my 1×9 set up

N Gear jump stops are ok for xc rides, but I would want a little more that that to keep my chain on for anything more demanding.