Chain Tensioner Do I REALLY need a chain tensioner?

Discussion in 'Transmission / Drivetrain' started by Max-M, Feb 29, 2012.

  1. Max-M

    Max-M Member

    On my current MB build (my second), my bike's still inside my house, but it's road ready -- except for tweaking the chain tension situation. With the stock "Erector Set®"-style chain tensioner that came with my 4-stroke Hua Sheng/Q-Matic kit, I just can't seem to get the tensioner positioned in such a way that the chain doesn't eventually bind on the 56-tooth drive sprocket. (Despite all of the usual chain/sprocket/engine alignment activities.) And I'm a bit paranoid because of the frequent "chain throwing" habit that my first MB build had vexed me with. That was a major pain in the arse.

    This is how I'm testing it: I've got my bike standing on its double kickstand with the rear wheel free to roll, and then (by hand) I pedal the bike increasingly faster. With the chain tensioner mounted and carefully positioned and tightened in what looks like an appropriate position, the chain eventually binds on the rear sprocket. But when I remove the tensioner altogether, and rotate the pedals by hand, I can spin it as fast as I please, and the chain never binds on the sprocket. This latter situation happens with a rather loose chain. I mean, I can spin the heck out of that rear sprocket and the chain stays where it belongs -- slack as it is. I know I don't want it this slack on the road, though.

    What I think I want to do is to forget the tensioner altogether, and just "break" the chain down to a length where it's tight enough without a tensioner. I'm using hefty #41 chain with a master link, and I've got adequate experience with breaking and resizing these chains with my SmithTool B-5035 "Chain-A-Part" chain breaker.

    I think that my bike -- a 2012 Giant "Simple Single" cruiser with various upgraded motorcycle parts (brake lever, jackhammer throttle/grips, mirror, killswitch, etc.) looks better without that kit tensioner anyway.

    So my query to you guys on this forum is: what do you think of running a MB without a tensioner? The way I figure it, if it runs well without it, and resultingly looks good to boot, why do I need a tensioner? And in my way of thinking, ten feet of #41 roller chain at Fastenal or Tractor Supply or Grainger is pretty cheap, so I'm not worried about replacing it when necessary.

    I'd greatly appreciate any thoughts from forum members, and any comments on my latest build (pic attached).

    Attached Files:

    Last edited: Mar 1, 2012

  2. toojung2die

    toojung2die Member

    I tried to do without a chain tensioner. I didn't trust it to stay in place and heard sad stories of ripped out spokes. I got the chain tension right without one but the bottom slack side of the chain was slapping and wearing the paint off the chainstay. I put the chain tensioner on to lift the chain slack away from the bike frame. It has stayed put and no more chain rubbing.

    If I really want to make it right I'll weld a permanent chain tensioner bracket to the bike frame. I think the bolt-on tensioners that come with the kits are one of the worst designed parts of the whole mess. I have the four-bolt tensioner kit with a ball bearing wheel. Maybe a couple of tack welds on it will give me more reliability.

    I've seen some well designed spring tensioners. In my opinion a fixed tensioner is a better design. If you have the chain tension adjusted right you have no chance of the chain falling off.
  3. motorpsycho

    motorpsycho Active Member

    if you can get the engine chain and the peddle chain, both at the right tension, you'll be good. I ran one of my bikes for about a year with no chain tensioner, but then i changed the sprocket to a smaller one.
    this required me to go with a 1/2 link and to make a tensioner so that both chans woudl be set right. without the 1/2 link, one chain would be too lose, while the other woudl be too tight.
    you can make a much better chain tensioner out of almost anything....10 speed derailers work great, but you have to find one that has a metal gear (most newer ones have plastic gears).

    I made one out of a downhill bike chain tensioner that is designed for single speed bikes. It cost me $10.00 off e-bay and i i had to slightly modify (strip parts off of it) it to work, and hook a spring to it.
    Mine is held to the engine case by one of the side cover bolts and i have it on the top of the chain. the hole in the mouting bracket is slightly bigger than the bolt so it will pivot on the bolt.
    a lot of people say that having the tensioner on the top of the chain is innefective, or that it will cause problems. It's been on my bike for almost 2 years now with no problems with the chain or the tensioner. It does it's job because it's got spring tension pulling down on it. It moves up & down with the chain and keeps the chain at the same tightness all the time. these engine kits have the problem of the chain going "loose, tight, loose" as it rotates. this is due to the sprocket not being made perfect. so, as my chain goes loose, the tensioner pulls down on it keeping it at the right tightness. as the chain gets tight, the tensioner lifts up and takes pressure off the chain. it may not be the best solution to the problem, but it works for me.
    Look close in this pic and you will see the black arm bolted to the engine side cover, and you will see the gear on top of the chain.
    Last edited: Mar 1, 2012
  4. Max-M

    Max-M Member

    Thanks, gents. Yeah, I guess that going without the tensioner isn't such a good idea. I like the idea of the derailleur with a metal sprocket because I have one in my miscellaneous parts box. I may just attach that to the kit tensioner bracket to start, but I'm going to try to come up with something spring loaded eventually.
  5. motorpsycho

    motorpsycho Active Member

    just be aware that the stocl tensioner bracket can and will rotate. which can cause it to end up in the spokes of the rear wheel.
    Bolting it to the frame isn't the best idea because it won't grabe the frame tight rnough to keep it from rotating.
    I did ride this bike without a tensioner for quite a long time and everythign was fine.
    the hard part is getting both chains to be not too tight or not too can be tricky.
  6. I bought a spring tensioner from LiveFastMotors this morning, last night when I got back to my lair, I seen my new sprocket came in The mail, so I added it to my new sprocket adapter, went outside around 10ish lol. And then again my chain poped off! I knew that was the old problem which I blamed the ragjoint setup before, but I was wrong. Oh well yet another great weekend comeing but not able to go out for a cruise. :veryangry: hopefully This is the key to my bikes success comeing in the mail......:thinking:
  7. Max-M

    Max-M Member


    I feel your pain! My first build was really plagued by those danged chain derailments. And I had a hub-mount sprocket adapter on that first build right from the start (I have the same adapter on my current build). Before I take my new beauty out on its maiden voyage (which may take a few weeks, as I live in currently-chilly Southern Connecticut), I want to get the chain alignment/tension situation perfected. I'm going to take a look at what you bought on LiveFast's site.

    It seems like it should be a rather simple thing to: size and break and attach your drive chain, align it, tension it, and then be set for a long period of trouble-free riding. But this aspect of the MB experience has been the biggest pain in the arse for me!

    Let us know how things work out for you, via this thread, OK? I'll do the same.



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  8. Hey Max-M, yeah of course once I receive the tensioner I will add some pics to my album with all the new upgrades I've already added to my cruiser like the HD 12g rim set. Red tires and now a pull brake set. Along with the adapter I just got, the sprocket that fits and now this new tensioner coming, MB is getting expensive lol.

    I cant wait to go outside! My hopes are for next weekend lol!


  9. motorpsycho

    motorpsycho Active Member

    it's not so much the tensioner that causes these's poorly made parts.
    if you get a sprocket that's not machined almost perfectly, you will have issues. almost every kit comes with a poorly made sprocket.
    Chain alignment, and perfectly centered sprockets are the key.
    if you get a really nice, perfectly made hub adapter, but bolt a non perfect sprocket to it, you'll still have the same problem.
    it is possible to use the rag joint and stock kit sprocket, and never have your chain come off.
    it just takes a little tweaking, and A LOT of patience.
    I've built 3 bikes now, all using the stock kit supplied sprockets and rag joints, and I have not had a chain come off yet.
    the first m.b. i built with a friend (this was the guniea pig build) is going on 4 years old, still with the original rag joint and sprocket....but no chain tensioner at all. beleive me, this bike has been BEATEN and riddden HARD,. burnouts, doughnuts and all kinds of crazy stuff....and the chain, sprocket and rag joint are still hanging in there.
    Last edited: Mar 3, 2012
  10. Alright then, I've had it with the tensioner. I just had to remove a few links off my chain, after another session with my bro working on the bike, we found out my new chain tensioner didn't quite clear the frame when bolted on to the chain. Lol but its up and running. Now I'm just fine tuning everything and other small tweeks for a good ride coming.:helmet:

    We stoped working on it around 8pm, I took it for a test run down the road and back. Now I can feel how smooth the ride is with the heavy duty wheels. And the sprocket adapter works like a charm. Feels good to ride again! Now I just need a day off.
    Last edited: Mar 6, 2012
  11. Max-M

    Max-M Member

    Questions for motorpsycho...

    it's not so much the tensioner that causes these's poorly made parts. if you get a sprocket that's not machined almost perfectly, you will have issues. almost every kit comes with a poorly made sprocket. Chain alignment, and perfectly centered sprockets are the key.


    I've finally got my chain tensioning problems under control. I used the kit tensioner bracket. But I attached a 17-tooth idler sprocket from Tractor Supply Co., made specifically for #40 and #41 chain (SKU #: 1182009, $19.99). The idler sprocket has a 1/2" bore, so I had to drill out the top of the tensioner bracket's slot to 1/2" and attach the sprocket with a 1/2" x 2" bolt. On the opposite side of the bracket, the bolt got fitted with: 1) a flat washer, 2) a lockwasher, 3) a nut, 4) a push nut (to hide the end of the bolt).

    The sprocket can't move up and down in the bracket's slot because of the larger hole that was drilled in the top of the slot: Now, adjustment of chain tension is done by moving the bracket horizontally on the chainstay.

    The kit bracket won't rotate into the spokes because, on my bike, the chainstay portion of the frame that it attaches to is oval-shaped. And, so both the upper and lower bracket fasteners can be tightened evenly, I took up the gap between the two sides of the bracket with flat washers (4 each on the top and bottom).

    The black finish that you see on the bracket in the attached picture is tough plastic sheet material (cut from the cover of a 3-ring binder) that is firmly affixed to the bracket with 2-side rubber contact cement. I did the same thing to both sides of the 56-tooth drive sprocket. This is strictly for appearance sake.

    Finally, my questions: When you say that a poorly-made sprocket will cause issues, are you referring to the overall production of the sprocket, the accuracy of the drilling of the hub adapter (or rag joint) holes, or both? I've got an aluminum hub adapter that attaches to the sprocket with three bolts. And I DO experience varying tension in the chain as I rotate the rear tire: at one point it's got about an inch of play on the upper run of chain, and at the other extreme it's got virtually no tension at another point in the rotation.

    Do you think this is the fault of the sprocket? The chain? And should I be concerned about it?

    Thanks for your attention!

    Attached Files:

  12. jeffuehrer

    jeffuehrer Member

    I use the two bolt tensioner design on the 410 pedaling chain. You won't have to worry about it going into the spokes on that side. I use the four bolt tensioner design on the drive train side using 10.9 (Grade 8) steel nuts and bolts as well as a 1/2" hex head bolt for the wheel allowing for sufficient torquing. To adjust your sprocket alignment, advance your bicycle until you reach the tightest area of the chain, loosen all of your sprocket bolts until you can adjust the position. Carefully tighten all the center bolts, then right of center bolts, then finally left of the center bolts. It's also a good idea to take a mental note of the tightest and slackest areas so you know where the sweet spot will be. This method has proven to work well for me.
  13. motorpsycho

    motorpsycho Active Member

    wait what?
    the chain tensioner didn't clear the frame when it was bolted to the chain?
    you're supposed to bolt the tensioner to the frame, not the chain.
  14. Yeah I guess I forgot to edit! What I meant was the frame. I wouldn't even know how to bolt it on to the chain lol. But I guess it was due to my chain being shorter since I took some links off.
  15. DanTheDIYGuy

    DanTheDIYGuy Member

    Old thread, but worth sharing.
    I made my own spring tensioners. Only cost about $10, and was very fun :)

  16. butre

    butre Well-Known Member

    as long as it doesn't rub you can go without a tensioner.
  17. skyash

    skyash Active Member

    If it gets tight and lose bad / bent Axel sprocket not centre then the self adjusting tensioner will fix that.
  18. Legwon

    Legwon New Member

    IF you can run it straight chain, DO IT!!!
    less contact = faster speed, faster excel.
  19. KCvale

    KCvale Motorized Bicycle Vendor

    I totally agree.
    IF the bike has a derailleur on the right it already has a tensioner.
    IF the frame has a J slot for adjusting chain slack for the left side that is by far the best way to go...
    You can adjust the chain tension buy moving the wheel.
  20. Nanonevol

    Nanonevol Member

    Tinkering around with my chain tensions tonight (who isn't, right!) trying unsuccessfully to get both sides tight without a tensioner using half-link. Then it occurred to me that tensioners for the pedal side are cheap (used), good quality, and readily available in the form of an adapted derailleur. Toss that other dangerous, cheap piece of junk! I think for a lot of us, the pedal side is really mostly the starter and we don't do a lot of unnecessary pedaling around. I'm gonna do it.