chucky

(this is a repost from the mechanic's forum that I thought might also be of interest here)

I would like to share with you an excellent technique I stumbled upon for tensioning single-cog drivetrains (ie with horizontal dropouts or eccentric/hubs).

First off, you are probably wondering that if we are talking about bikes with horizontal dropouts then isn't the only thing we need to do to tension the chain is pull the wheel back with the left hand while tightening the axle nuts with the right hand? Actually no, because one of the primary benefits of single cog drivetrains are that you can run the chains much much longer by really cinching down the chain tension to prevent severely stretched chains from jumping the cogs. By doing this you can forget about measuring chain stretch with a micrometer (and throwing out perfectly good chains) because no matter how stretched a chain gets you never have to discard it until it literally snaps in half! However, once the chain gets stretched to the point that it's more inclined to jump off the cogs than be driven around them, then you require a much higher chain tension than can be achieved with springs or arm strength and, until now, the only way I knew to achieve it was with a rigid tensioner/tug like this:


But chain tugs are annoying because:
1 Bikes almost never come with them...you have to buy it separately and many bike stores don't carry them.
2. They always come with the wrong kind of nut for tightening...you need a wing nut so you can cinch down the chain on the road without tools after it starts jumping off the cogs in the middle of your 30 mile winter commute on slushy salted roads. Of course you can get a wing nut, but it's yet another thing you have to buy separately and it's not like every store carries metric wing nuts.
3. The quality of many of the chain tugs is not good. I bought a fancy MKS chain tensioner for $30 and the tensioning bolt snapped in half before my chain did...kinda defeats the purpose of extending chain life when it would've been cheaper to just replace the chain.
4. There are many axle standards for single cog drivetrains...so whatever you end up getting probably won't fit without some filing. Even this is just a partial list of bike axle standards:
M9x1.0- Front "fixie" (fixed gear road bikes) hubs as well as front dynamo hubs (front generator hubs for bicycle head lamps)
3/8"x26T - Most axles including most department store bikes; Shimano Nexus and Alfine Series; 8FUN e-bike front hub motors. Very commonly used on road or bikes purchased at department stores that are not fitted with traditional quick release hubs.
M10x1.0 - European brands, SRAM, NuVinci, Rohloff; Bionx and some e-bike front hub motors
3/8"x24T - Rear coaster brake hubs found commonly on beach cruisers, Huffy brand, older department store bicycles.
13/32"x26T - most Sturmey-Archer hubs.
M12x1.25 - E-bike hubs - either 1.0 or 1.75 thread pitch.

So what's the alternative? Well, the technique is quite simple:
Step 1- Tension the chain with arm strength by adjusting the axle position with your horizontal drops or eccentric BB/hub. Carefully observe the axle position so you can remember it.
Step 2- Take the chain off the cogs, move the axle to a slacker position so you can derail the chain or whatever you gotta do to get it off.
Step 3- Set the axle position or eccentric a couple mm tighter than you had it in step 1.
Step 4- Put the chain around the rear cog and over a few teeth of the front chainring. You won't be able to get it all the way around because there's not enough slack.
Step 5- Turn the cranks with your hands so that the chain is forced to climb itself all the way onto the chainring. You might have to also push the chain laterally hard with your other hand to help guide it just as a derailleur guides a chain towards climbing onto a bigger cog.

So, in summary, the technique is to set the axle to a position that would be a little tighter than you can tension by hand (without the chain on) and then force the chain to climb onto the cogs like a derailleur does. With this technique you can get the chain just as tight as any rigid mechanical device.

Jaytron

I'd say good info, but why would you want your chain that tight?

Nagrom_

tl;dr:
How to over tighten your chain.

seau grateau

Scrodzilla

This.

It's not ****ing rocket science.

chucky

Because it's the only way to keep severely stretched chains from jumping off the cogs.

So if you ride a lot of miles and you don't want to send the bikeman's children to college by replacing stretched chains all the time...

Apologies...took me about 8 years to figure it out so if there's anyone else out there as dumb as me I thought this might help them because I don't see any of the books or wise gurus like you teaching it to anyone.

Scrodzilla

And overtightening your chain will cause any chain to stretch a lot faster than if you were just riding with a normal amount of tension.

FWIW - I've never had a chain "jump off" my cog.

Training.Wheels

It's actually not that hard to hand tension a chain... Also, If you ride fixed, especially brakeless, it's a good idea to own a chain tensioner anyways. The redline ones are like $10.

Jaytron

But what if you want DATTRACKSLACK for extra street cred when riding on the street?

chucky

And why should we care about chain stretch? Riders of chain driven motorcycles know that chains are supposed to have an initial break in of rapid stretching. Worrying about chain stretch is just a scam the bike industry uses to get you to buy more chains...and obviously they've got you hook, line, and sinker because if you've never had a chain jump off your cog then you're replacing before it's even broken in.

Try it and you'll see what I mean...there's nothing wrong with stretched chain, you just have to keep it as tight as it needs to be to prevent it from throwing itself off and the more it stretches the tighter you need to make it until after about 10-20k miles when it just breaks in half

Sure it's not hard if the chain is almost brand new...but if you don't replace it until it snaps instead of when your LBS needs more money for Christmas presents it gets pretty hard.

Also, as mentioned, it's often not possible to just buy a chain tensioner for $10 because the redline ones only fit certain axles and you have to also get a wing nut for them..so even after you buy the $10 redline you still have to make another trip to the store and then also spend a couple hours filing it to fit the axle which is a pain in the ass; not to mention that the width of the metal dropout (ie aluminum/steel) can make different tensioners incompatible with different frames.

Also if you don't have rear facing horizontal track ends but instead adjust the chain slack with an eccentric bottom bracket or some other method then the "chain tug" design simply can't be installed at all.

Nagrom_

I love grinding old chains against my expensive cogs and chainrings.

seau grateau

ha?

Training.Wheels

and that's why perfect tension isn't supposed to be super tight or super slack. It prevents abnormal chain stretch and the chain falling off. All of which could be done without special techniques.

swisscheese

^+1

I'd rather buy new chains than wear the **** out of my chainrings and cogs because of a stretched out chain. Not to mention it sounds horrible.

Nagrom_

Instead of replacing a 15 dollar chain every six months or so, I will instead grind it against 150 dollars worth of teeth.

Spoonrobot 

I thought it was a joke. Holy **** is that some bad information. Chain should be as loose as possible without derailing.


Also, why do you not know how to install a wheel?

https://sheldonbrown.com/fixed.html

chucky

You guys are pretty dumb...my cogs cost $2-$3 and I've never had to replace one for wear reasons. Same goes for chainrings if they are steel and, if you want to use an aluminum chainring then you should realize it is a disposable wear item that is also cheaper to replace than a chain.

Ok, then tell me what finally ends the life of your chains: chain stretch or chain snap? If it's stretch then, in fact, you are the one who is having trouble with chain stretch because you aren't doing what you are supposed to be doing.

The logic is irrefutable. With the right equipment and/or the right technique chain stretch ceases to be a problem and, therefore, there is no need to prevent it. Motorcyclists call it "breaking in the chain", but bicyclists are brainwashed to buy a new one.

Mumonkan

mom, the dog got into the bath salt again!

lubes17319

Once you go slack, you'll never go back.

Spoonrobot 

I can seriously believe you advocate using a part that is pretty critical to the safe operation of a bicycle until it catastrophically fails and then replacing it.

ETA: I've been reading through some of your earlier posts and threads. It's been real eye opening. :/

https://www.bikeforums.net/showthread...nsioning-chain

:\ :\ :\

Training.Wheels

No, I've never had trouble with tension, chain stretch, or chain snap. I always keep tensioners so that I don't run into those kinds of problems. Also, some people in this forum don't mind spending $50 on cogs and $200 on chainrings, so you can see why they would be wary of their chain condition.

GENESTARWIND

im confused.... is he trolling?

gregjones

I get tired of the color.

osiris419

So in using your method when my chain snaps I have to spend more money cause now I'm going to buy a chain cog and chainring since the extremely stretched chain will have worn the teeth out so bad that a good chain will not fit properly. Thanks I'll pass and just replace a piece at a time. Cogs and chainrings should outlast a few chains.

SpeshulEd 

If you're rocking a $3 cog, is dropping $4 on a chain really that hard? $4...that's less than a beer at a bar.
https://www.citygrounds.com/kmc/kmc-c...FSHhQgodmQUA9g