Thinking of building up my old GT as a rigid 1×8 for the odd (partial) ride to work, pub, shops and maybe some light off roading. Planning to use an 11-34 cassette

Do we think a 42t chainring is too big to allow the odd bit of off roading? Will anything smaller be too spinny? Think i can get up any road hill with 42t to 34 fine!

Oh and will I definately need a bash to keep the chain on? Or is a short cage mech, short chain, proper SS chainring and an ngear jump stop do it?

Usual answer when a 1×8/9 comes up is to use a bash and N Gear Jump stop to keep the chain on. An unramped (SS) chainring, short cage mech and properly tensioned chain will help things further.

More reading about this from the yanks here – http://forums.mtbr.com/showthread.php?t=469148

I'd run 38t, just about usable off road.

how fast will a 38×11 go at 80 rpm……off to try and work it out

I make a 38×11 at 80 rpm about 21.5 mph, that's not bad actually…off to spend some time in ms excel with gear ratios 🙂

Went the same way but really struggled steep uphill with shopping, panniers etc so I chucked cassette back on and 3 rings upfront-I never use Granny but hey it might come useful in a get me home way if injured or knackered/mechanical.

I reckon you should 1×8 to keep it mega useful for anything.

yeah i dont mean just an 11 at the back I mean an 11-34

Sorry thought you meant single 11 lol.

80rpm is that all, what are you running on diesel?