benefits/ disadvantages of tensioner-less chain?

It's been advised, discouraged & discussed a bunch TBH... If you've horizontal dropouts chain adjustment is not as much of a problem & you can ofc use a 1/2 link as well, but aside from those bikes there's also the unfortunate fact some frames need a tensioner to act as a redirect (so the chain will clear the lower chainstay).

While the simplicity of running w/o a tensioner seems attractive & looks great sitting in the garage, it just isn't practical for bikes ridden frequently. The sprockets and chain will always continue to wear, requiring periodic adjustment of chain tension & w/o a tensioner this becomes a chore to say the least, often entailing more problems than simply making a better tensioner than the stock kit one;

On my first bike it was my intention to start with the standard setup: pedal chain adjusted to proper length & tightness - drive chain adjusted with the basic guide wheel/tensioner. This was only until I could get hold of a master link and chain breaker for the pedal chain.

While I had the basic setup, I was not surprised to notice after my first ride that the bracket for the tensioner was doing some creeping. The drive chain does place a lot of leverage on it, after all. So I tightened it down as much as I could, and that helped. But I watched it like a hawk, every time I got on.

Later, I was able to adjust the pedal chain with a master link, so I oriented the whole setup to the drive chain and put the guide wheel/tensioner on the other side with the pedal chain. I was lucky: the drive chain passed by the chain stay on the frame with plenty of clearance.

I am not lucky with my new bike (it's not really new, it's an old Higgins). I tried subtle changes in the way I mounted the engine, but nothing I could do would give the clearance I need between the drive chain and the frame. Under load, that chain would beat the chain stay raw without a guide wheel back there. At least, on the Higgins, the chain stay has a VERY oval-shaped cross section. With the bracket bolts tightened down, that tensioner does not move. At all.
I say, if you can install the engine and drive chain such that the chain does not try to saw through the chain stay - you're golden! That is, in my opinion, the ideal setup. Otherwise, do the best you can. Beware of leverage, don't underestimate it.

I build all all of my bikes without the roller tensioners... It's the only way to go!

I use special made shims that fit between the engine & rear mount to move the engine forward.

It's true that when a bike is new, the chain will stretch a bit & the sprocket will also wear in; so you can just add another shim to adjust when needed; but after some riding time, it will not need it for a good long time.

I have bikes that are daily riders & have been on the road for years using this method!

Yeah- NEVER use one. Never a problem- but that's with a cruiser frame that has clearance. The modern frames are almost as light as a vintage steel roadframe anyway, and with light wheells theres practically no difference in the roll.

Coaster brakes are PREHISTORIC! Get a freewheel wheel. You'll have to set up brakes then, with a dual lever.

I set the motor chain first- with a derailleur on the pedal side it totally takes away allignment between chain problems, but I've also got another build I matched up without any tensioner- you can use half links- on the pedal side the smaller chain is MUCH easier to split and work with- or you can also sometimes vary the freewheel on the pedal side- single freewheels aren't expensive -BEWARE OF CHEAP CHINESE THAT HAVE NO SLOTS FOR A REMOVER!- Also make sure it is compatable with your chain- if it's 3/32 it will work with either a 1/8" pedal chain or a derailleur chain- but you can't put a derailleur chain on a 1/8 inch sprocket- 3/32 has become more the standard, but they are both still common.


Or you could even have a multi-speed cog set on just one and then maybe vary that-

when you make changes on either side- you have to divide the changes in the teeth by two- because the chain only contacts the back half of the sprockets-

if the change is an even number- once divided by two- it will sit about the same in the chain stay- if it's an odd number, it will move one way or another by half a link- if you want it in the same place, you have to use a half-link with an odd number change. Once you get this concept down you can pretty much predict the results-

also if you are mounting a kit, or putting on a new motor chain- yes it will probably stretch more in relation to the pedal chain- so a little bit more play on the pedal side will disappear when you later pull the chain back in the stay a bit for the stretch- Don't start at the far end! Always try to be in the middle, or just a bit on the near end with a new motor chain. But be careful, a too lose pedal chain could come off, especially with cheap chainwheels.

I like to convert to lightweight well-made three piece alloy cranks- but I have used a low rider 36 sprock on the front, which gives you an easy peddling gear for a bike that's heavy with a motor. You can change steel front sprockets for under $20 if you shop around.

A bike with verticle dropouts will prove difficult without a tensioner or derailleur, but the frame clearances are also a factor- that's why I always use a modern lightweight cruiser.

here's when I still had on the low rider 36 steel sprock with a 22 freewheel on the back- light light gear- not fast but very comfortable in parking lots and pedestrian ways.

Yup.
A tensioner is just a fix for something that was engineered improperly.
...just one more thing that can fail...

Far better if you can adjust the axle or move the engine to make the adjustment.
...and have less mechanical drag...

Good luck
rc

i never use tensioners. venice's shim method works great, and i have a stock pile of different toothed rear cogs for coaster brake hubs, as going up or down a tooth will take up a half inch of chain.

i find it smoother, cleaner looking, and less drag. not all bikes will work, sometimes the chain will drag on the frame's chainstays, but with some patience and experimentation, most can be made to fit.

The best thing I ever did to my bike was remove the tensioner. It seemed I was adjusting that thing every ride, it was very frustrating. Not to mention all the noise and drag it added to my bike, specially when pedaling without the motor running, the drag it added was simply unacceptable to me.
I adjusted the motor mounting angle a bit and put a very small shim between the motor and rear motor mount to tighten the chain just a bit and never looked back. The ride is super smooth and quiet, there is MUCH LESS drag when pedaling, and I have never once had to worry about my chain tension since I got rid of the tesnioner....
Some people will chant you down, tell you that you need the tensioner for adjustment later etc. I put over 500 hard ridden miles on my bike and the chain tension was still fine when I disassembled the bike for the winter tear down. If you use the kit chain, or any bicycle chain for that matter perhaps chain stretch might become an issue requiring a tensioner, but if you run an ANSI pre-stressed industrial #41 chain I dont think it will be an issue. These chains are MUCH stronger than any bike chain, and they are pre-stressed/stretched before you buy them so stretch shouldn't be an issue IMHO.
Not every bike can be setup to run without the tensioner, but if you can I would encourage you to get rid of it. If you can't I would suggest you look into the rollor blade wheel tensioner, they seem to work better than the stock plastic thing...

I always run a tensioner. A proper spring-loaded tensioner keeps things going without headaches for a long time.

It can also aid in maintenance, sometimes facilitating easier removal of the rear wheel or components.

A tensioner is just a fix for something that was engineered improperly.

Click to expand...

Almost every automotive timing belt or chain system designed for longevity uses a tensioner

I forgot about chain tensioners on timing chains or belts. But I have never seen one on a motorcycle or dirt bike as part of the drive chain. There's a lot of engineering that goes into those bikes so I feel that tensionerless is how it should be in that case. Just my thought on it, others probably disagree.

I have been tensionerless the past few weeks. I just removed some links, took off the tensioner, put the wheel on as far back as I could (1-2cm till all the way back) and have been great since. With a perfectly true sprocket and frame clearance, you should be good to go without a tensioner. Your chain will stretch though especially if its a cheap china one. Only mostly during break in though.