right bear with me on this. I have a surly crosscheck im running with compact 34/50 chainset and 12/25 block i was thinking of running chainset as is but running two rear cogs on the back one to use with the 50 and one for off road on the 34 are any of the ratios suitable for those chainrings that will keep a similar chain length i have slidey dropouts but not sure how many link difference they will work with. Ta

That would be a really weird set up. Maybe you could have 2 chains, and with some quick links its not a hard job changing them between rides.

Else, think you would probably need a tensioner or mech to take the slack.

yeah prob its a lot of chain length between the two chainrings id guess

Cant see much advantage to having 2 speed, other then making it harder. I'd just keep the cassette and mech.

Flip flop hub? 2 cogs on each side?

I've been SS etc and now have my cassette and mech back on. Yeah it's a bugger to keep clean in winter with no garage etc but gears! makes the ride so much fun when fully laiden with shopping on the rear or just commuting light to work.

was just thinkin of running one gear for road and one for off road. I nearly did it when i built my singular up someone makes a dual single set up called dingle speed cant remember who

ive got a surly free free wheel i built up from my spares box i could use but its getting the chain near enough like to run the two ratios with my current chainset. That said like you say zasker im recently back to gears and the bits of road between the mud is great in the big ring lol. I just like fiddling 🙂

Mick, the dingle set up is for riding fixed and is made by Surly.

White Industries do a double speed freewheel, but if you already have a cassette hub that doesn't help you. You may as well use Surly single speed sprockets (conveniently spaced so you can run them side by side.

However, for this idea to work, the total number of teeth across the two chainring/sprocket combinations needs to be the same. If you wanted 38-18 for the offroad gear, then you'd have 40-16 for the higher gear, for example.

I doubt you could make it work with the 50 and 34 chainrings very easily, if at all.

yeah ive been hunting round adam i think im either needing a tensioner or new crank so i think it will be a pipedream (for now lol) and ill stick to gears for the moment. ta all

You need the same total number of teeth for it to work with the same length chain, which means that you'd need a 16t difference between the sprockets at the back!

Could you do it by running a chain with two quicklinks in it? Get the right length for the off-road ratio and then add extra for the on-road one.

34:18 for off-road and 50:?? on-road? I've a feeling that the sprocket for on-road with a 50 will need to be stupidly big though.

yeah mike i think its a no go other than tensioner or spare bits of chain shame really but always there when i need new drive train lol

I was thinking of doing something similar on my SS MTB. 32:16 for off road and 36:12 or 34:14 for getting to the trails, keeping the chain length the same for both. This would mean I'd just have to drop the rear wheel out to change the gear.

If you had a 34:18 for off road you would need a 2 tooth ring 😆 on the back to make up the difference in teeth between the big rings (50-34=16) to keep the chain the same length.

i've already tried it. 36:18 for off-road, 40:14 for the road. Little bit overgeared on the road but works quite well otherwise. same length chain.

cheers mate still need a new chainset for that tho so will just keep in on a backburner for now me thinks 😉

50:11 is the lowest you can go, so you could run 34:27 for off-road 🙂

now you just being silly mike lol get back to sorting out that distressed frame of yours lol

Dingles work really well if you have a long road ride before you get to trails, or you commute on the same bike you ride on trails or a whole host of other reasons you might want two gears on the same bike but don't want derailleurs and shifters. It's not quite true that you need to add the same number of teeth to the chainring as you lose from the cog – the teeth change the circumference of the circle but also its radius. A combination of the fixmeup calculator and sheldon's gear calculator is the best way of finding something which is going to work for you. In the past I've done 34-19 off-road gear, 39-15 on road gear. The cross-check has pretty long dropouts right? You will be able to get a pretty broad jump, but probably not 34-50. Just swap out your large chainring for a 38 or 39 and you'll be set.