[horriefic]

I am new to mountain biking (started like 7 months ago). I have a totally newbie SS question. Please excuse my ignorance if my question sounds daft!

I currently ride a full sus. But thinking of buying an all mountain steel hardtail. Trying to understand more about single speeding, and the thing that puzzles me is the need for a chain tensioner for vertical drop-out bikes.

Can't the chain be tensioned by shortening the chain so that a tensioner is not required? I understand that a new chain will stretch. But you can continue to shortened the chain until the point where the chain does not stretch anymore? On horizontal drop-out bikes, my understanding is that you can pull the wheel back to tension the chain. Can't this be achieved by shortening the chain ie. removing links to keep the chain tension?

Or, is it such that no matter how tight you can get the chain to be (but not so tight as to lock-up the bearings), and assuming no chain stretch, there will always be some chain slack that will cause the chain to potentially come up the chainring and/or sprocket?

Thanks!

 

[Sheepo5669]

Can't the chain be tensioned by shortening the chain so that a tensioner is not required?

What you are reffing to is a "Magic Gear". Not all frames have a usable ratio of chainring/cog that allow perfect chain tension even with a half link. You will need a tensioner of sort unless you get super lucky with your gearing.

Sheldon Brown will tell you
http://www.sheldonbrown.com/singlespeed.html

 

[sunset1123]

White Industies ENO eccentic hub. Here.

No tensioner, no magic gear, no worries about chain stretch.

EDIT: only presenting this as an option to make a vertical dropout frame work without a defailleur style tensioner. Not an advertisement or official product endorsement. Just an FYI.

 

[mack_turtle]

if you set up a bike for a SS combo and the chain is just a little too loose, just enough tht the chain will fall off, and then you take a full link out, it will likely shorten the chain too much so that the axle won't reach the dropout slot. you might get lucky with a half-link in the chain, but that's a "magic gear" situation. the subtleties of chain length as they are affected by seemingly small changes in chain length are too big to make a chain fit just right.

My first mountain bike was a second-hand hardtail that had been converted to SS using a Paul hub and a 32/18 ratio and the chain was just a little loose. I replaced the chain and there was NO WAY the new chain would work. the old chain only worked because it was stretched as hell.

concerning tensioners, I tried a Surly Singleator and the spring died in the middle of a ride. maybe this was because I made it too tight, but I didn't trust the product after that. I later built another SS bike using a DMR tensioner and I like that design a lot more.

 

[horriefic]

Ok. I am beginning to understand. So eg. your chain is too loose. And changing to even a half-link chain may make it too tight. And you have the added variable of chain stretch. So a tensioner is a good and easy solution.

If only there was a 1/4 link solution!

Lastly, for horizontal drop-outs, on a new chain, how frequent do you need to undo the bolt/quick release axle to 'pull back' the wheel to tighten the chain to cater to the chain stretch?

Thanks.

 

[perttime]

So eg. your chain is too loose. And changing to even a half-link chain may make it too tight.

Yes.

If you are lucky, there's a "magic gear" that works on your frame, when the chain is new.

Chains are not all created equal either. I've had a cheap chain stretch in very little riding. Now I've been buying Shimano's CN-7701 (XTR level 9 speed chain), whenever I find them at non-outrageous prices. It seems to last well in my use.

 

[1SPD]

I have found that my KMC chain has held up well and never really had to adjust tension. However, I did have a few flats so by removing the wheel to fix that, I am sure I ended up taking care of any slack when I put the wheel back on.

As mentioned, you have to run a tensioner of some sort unless you have a magic gear ratio on a vertical dropout. There are lots of options out there, Eccentric bb, hubs, derailleur style tensioners to name a few.