Chain tensioner necessary?
- Thread starter teaviswalker
- Start date
On some bike models I have ran across you have no choice but to use one for various reasons; And others you do not.
if the chain has finished its initial few days of stretching and you now have good tension, and the alignment is good enough that you don't need the tensioner to help feed the chain squarely onto the rear sprocket, you can probably run OK till the chain stretches more
I used to use a chain tensioner on my drive chain, but after discovering that I could shorten my chain and not need it, I removed it. However, since I have a single speed bike, shortening the drive chain put too much slack on the pedal chain. Now, I had already removed my pedal side chain guard, and there was a tab on the bottom chainstay used to mount to, so I took the tensioner and put it on the pedal side where the tab for the chain guard is. The tab keeps the tensioner from sliding around, and keeps tension on my pedal chain. This is just my experience. I know some others have run similar setups, but it may not work for everyone. If you have a bike with gears, there is no need to place the tensioner on the pedal side, as the derailleur will keep tension on the pedal chain. Hope this helps a little.
From my experience, a spring-loaded tensioner on chains is just about necessary for long-term daily riding.
Without a true tensioner, the chain can be subject to misalignment at any time - especially when hitting a bump while leaning during throttle changes.
Without a true tensioner, the chain can be subject to misalignment at any time - especially when hitting a bump while leaning during throttle changes.
I have been riding for over a year without a drive chain idler, and never had a problem like that. I dont know if anyone else has ever had that problem, but I haven't.
I've had the problem over the long term with daily rides exceeding 30 miles. A spring loaded tensioner always takes up the slack.
On my Razor MX650 modded to 1000W the spring loaded chain tensioner worked fine unless you hit a rough trail, the momentum of the chain would be enough to overpower the spring and it would skip off the motor sprocket. I took a link out to see if more tension will help, it won't work without one because the dropouts aren't adjustable for the last little bit needed. I noticed that the increased tension on the spring makes the drivetrain less efficient. Running without a tensioner with a different sprocket that made the chain length right was much more efficient than with a tensioner, and because the teeth on the cogs are deep enough, it would be virtually impossible to skip the chain from bumps. I read somewhere that a tight chain is the most efficient, and it makes sense. Bearing this in mind, I'd use a tensioner for the pedal side to make both chains work out, which is less critical if you have a reliable motor, if. lol
Funny you find that a strong tensioner spring reduces drivetrain efficiency then go on to say a tight chain being most efficient makes sense.
As a longtime bicyclist, I've always found a tight chain to be less efficient than a chain with a touch of slack. Anyone who has made their chain tight on a single-speed bicycle has probably experienced the same. If you run a master link or half link, the chain will not have uniform tightness over the long term, either. Those parts simply don't stretch at the same rate as regular chain links. Chain drivelines are rarely uniform.
I've put 6-digit mile figures on bicycles over all kinds of terrain, I've found a spring-loaded tensioner is the best option for me.
As a longtime bicyclist, I've always found a tight chain to be less efficient than a chain with a touch of slack. Anyone who has made their chain tight on a single-speed bicycle has probably experienced the same. If you run a master link or half link, the chain will not have uniform tightness over the long term, either. Those parts simply don't stretch at the same rate as regular chain links. Chain drivelines are rarely uniform.
I've put 6-digit mile figures on bicycles over all kinds of terrain, I've found a spring-loaded tensioner is the best option for me.
Last edited:
I mean tight but not spring tensioned that last bit up against the sprockets, it should be free to float a tiny bit for best efficiency. The spring tensioner I'm using prevents chain skips, but a 1/2 link to get the chain length and tension right without it would be better.
I guess a weak spring tensioner could be tuned for a bit of slack, but the problem with that is if you hit a bump of go offroad it'll oscillate and kick the chain. If the chain is the right length in a fixed relationship it can not skip and isn't over tensioned. It's a difficult balance to achieve when you're concerned with pedal chains too.
I'd like to try a 1/2 link on my mx1000 to eliminate the tensioner, because running without one did net an efficiency gain that I was able to gauge by getting an extra couple miles to a charge and better performance.
I guess a weak spring tensioner could be tuned for a bit of slack, but the problem with that is if you hit a bump of go offroad it'll oscillate and kick the chain. If the chain is the right length in a fixed relationship it can not skip and isn't over tensioned. It's a difficult balance to achieve when you're concerned with pedal chains too.
I'd like to try a 1/2 link on my mx1000 to eliminate the tensioner, because running without one did net an efficiency gain that I was able to gauge by getting an extra couple miles to a charge and better performance.
Last edited:
I've also put on about 1.7K miles without a chain tensioner and haven't had that problem, or any problem for that matter. I'm running a #41 chain without a master link (and no half links), so far my chain hasn't loosened up on me at all. I tend to ride kinda hard, and weigh over 200lbs, although I only ride on the street for the most part.
I can't argue with the idea that a spring loaded tensioner is the best possible scenario really. Without a tensioner you need to have everything match up just right with the chain length and wheel/motor position, which may be easier on some builds than others to achieve. With a spring loaded tensioner the chain length only needs to be close, not perfect. A quality spring loaded tensioner should eliminate the majority of the negatives associated with running a standard tensioner, like excessive resistance and noise, and the chance of tensioner twisting into the spokes and sending you on a less pleasant sort of ride! That said, aftermarket spring loaded tensioners are sure selling for a pretty penny...
Since they are so costly I would probably fabricate something myself, which would take a bit of effort but less expense. Since my chain is still running perfectly after 1.7K miles with no tensioner I see no need to go down that road, if one day it does loosen up I'll just put a tight new #41 chain on there for a couple bucks and ride a couple thousand more miles...
After an initial stretch it should take a set at a length and stay that way, if not the chain is cheapo.
I think the sprocket style tensioners like the Pirate one are better in efficiency, and rollers are okay with the straight cross section chain with rectangular links that don't have a dip in each side. The #25 chain on mine doesn't have that so it would benefit from a sprocket roller. 05t chain would be okay with a plastic roller.
This last step on a bike getting the chain tension right is a huge pain unless you've only got one chain and dropout tensioners, on bikes like my mx with vertical dropouts so no adjustment there really, a spring tensioner makes it way easier to get the wheel on and runnable after a service, and obviously no 1/2 link too. That's something to consider if you get a flat on the road and need to take the rear wheel off, spring tensioners make it easy to do.
I think the sprocket style tensioners like the Pirate one are better in efficiency, and rollers are okay with the straight cross section chain with rectangular links that don't have a dip in each side. The #25 chain on mine doesn't have that so it would benefit from a sprocket roller. 05t chain would be okay with a plastic roller.
This last step on a bike getting the chain tension right is a huge pain unless you've only got one chain and dropout tensioners, on bikes like my mx with vertical dropouts so no adjustment there really, a spring tensioner makes it way easier to get the wheel on and runnable after a service, and obviously no 1/2 link too. That's something to consider if you get a flat on the road and need to take the rear wheel off, spring tensioners make it easy to do.
Last edited:
The #41 industrial/farm chain I am using said it was "pre-stretched", so it should be at it's final length before it's installed on the bike, which has been my experience...
My vote is for the Spring loaded tensioner. keeps chain nice and snug, but if for whatever reason chain becomes mis-aligned it wont snap the chain. but thats just my 2cents
Roller chains don't 'stretch'...they wear. Chain stretch is a misnomer. The cheaper the chain the faster it will wear due to the materials it is made from and the quality of the way it is manufactured. Typically the kit supplied chain does wear faster than a good quality industrial chain. The rollers and pins wear due to the abrasive action of dust/dirt that a chain is naturally subjected to. If low quality materials are used, the chain wears faster than one that has parts made of harder material. Sprockets also wear. This is the reason chains need occasional adjustment...not because they "stretch".
The wear of the parts of a chain can be measured in hundreds or thousands of an inch over time but you have to consider that each link/roller/pin will all wear at approximately the same rate you have to multiply the amount of wear times the number of components. A few thousands of an inch isn't much but multiply it by the number of links and you start to see an appreciable loosening of the chain (loss of tension)
Tom
The wear of the parts of a chain can be measured in hundreds or thousands of an inch over time but you have to consider that each link/roller/pin will all wear at approximately the same rate you have to multiply the amount of wear times the number of components. A few thousands of an inch isn't much but multiply it by the number of links and you start to see an appreciable loosening of the chain (loss of tension)
Tom
New chains DO go through an initial stretch, that is why quality industrial chains are "pre-stretched" to eliminate that initial stretch. These china kit chains, however, are not pre-stretched, and are made from such poor material the initial stretch and wear can be pretty serious.
I've got near 2000 miles on a (pre-stretched) industrial #41 chain and so far there has been no significant wear or change in tension. IMHO a good quality industrial chain will out last a china 2-stroke motor, probably several. Besides that, I got enough chain to outfit my bike twice for about $10 bucks, so if this chain does ever wear on me I have no problem putting the other half on my bike. I'm sure to get at least 4000 miles from $10 worth of chain, so the way I see it chain stretch/wear is a non-issue as long as you're using quality pre-stretched industrial chain...
If a chain did ever actually "stretch" I'd throw it away immediately & wonder what they were thinkin' when they started makin' them outa bungees heh - but as Tom said it's essentially the same thing, a semantic technicality - just a minor misnomer as the chain's side plates, pins & rollers themselves don't actually "stretch" yet due to the wear of these individual components "breaking in" through use, the chain gets looser as it's fractionally longer. Add in the sprockets' wear & tear and such loosening is an inevitability no matter what it's called lol
Chain stretch, chain wear *shrug* the only difference is clarity really.
Chain stretch, chain wear *shrug* the only difference is clarity really.
That is my point, the chain that comes with these kits from china (that I have received) are so poor that you should do yourself a favor and throw it away and get a real chain. They do "stretch" when initially stressed because they have not been pre-stressed and are poorly manufactured with low quality materials. I had links elongate and snap, at least a bungee snaps back! LOL
If you visit the website of any industrial chain manufacturer they will explain about how they pre-stress the chains so they are "stretched" to their final length before you receive them, from there they wear as you describe obviously..
