Single speed MTB project

[battered]

Fixed will not work with a chain tensioner. The forces are too great, when you stop pedalling the bottom run of the chain will be pulled straight by your momentum. This means that the tensioner is holding the chain in a bent position, and it has as much chance of doing this as you would of putting a bend in a car towrope while it's between 2 cars and going uphill.

Next question (inevitably) - which gear ratio? I favour 32 front 16 rear, which is the same as 34/17 above on a 26 wheel. It gives about 51-52 gear inches. It's just about liveable with off road and great for easy off road like canal towpaths. You can use an old derailleur as a chain tensioner, it's as ugly as sin though.

 

[HaloJ]

Wouldn't fixed on a vertical dropout be better achieved with an eccentric hub? Which in turn is a damn site cheaper than an eccentric bottom bracket.

 

[Zoiders]

51 inches on a tow path?

I can see the need for being spinny off road, 51/52 ish would be fine somewhere like the chase for example but on a tow path I can't see the need for running it that low, it would make for tedious riding to say the least.

On the subject of fixed, while it's only do-able on a vertical drop out frame with a magic gear or the ludicrously expensive Phil Wood hub which isnt even that good there is another option.

Do you have a picture of the drop out plates?

If there is enough meat there people have before now created a bit of wriggle room for creating tension in a limited amount of ratios by simply filing the drop outs slighty into a semi horizontal format. You do need a real chunky flat plate of a drop out to get away with this though.