Can a drive chain be "too tight"

locell

locell

Member
Can a drive chain be "too tight" and what can happen? I ask because I eliminated my chaiin tensioner on the drive side by adjusting the placment of the engine within the frame. The sprocket-to-sprocket alignment is really good and i like not having the tensioner (mo parts mo problems). I just want to know if i going to cause any problems on this as most people on here run tensioners.
cvlt1
 
Yes it can be too tight. If too tight it will cause noisy and rough running of the chain and put undue wear on the drive components.
You'll want 1/2" to 3/4" slack in the chain measuered on the top chain run with the clutch engaged and rolling the bike forward against a compression stroke.

Alignment is also critical as is chain tension.

Tom
 
Thanks, 2door i'll check it like you suggest. What drive components are in jepoardy? My alignment is "spot on"
 
Everything. Chain, sprockets, bearings, anything that rotates when the chain travels over them will be subjected to excess wear if the chain tension is too tight. This applies to any roller chain drive system, not just motorized bicycles.

Tom
 
Just a couple of details about no tensioner builds as I have been a real proponent of them for a long time but there are issues as well as solutions to them.

First lowcell what bike is it on, specifically your drive train. A geared bike? Vertical or horizontal drop-outs? Coaster brake bike and it's back wheel frame drop-outs?

In short if your drive train pedal side allows you to move the back wheel back and forth horizontally to adjust the pedal chain tension you are golden, but with a catch...

Your motor drive chain will 'stretch' which is a BS term for parts wearing in a lot at first but get stable so that back wheel has to be moved back unless you want to dink with moving the motor which is just silly in my opinion.

If you want to mount the motor solid and go from there with 2 chains, with some wheel movement for the drive side you can compensate for a chain mismatch if you use a tensioner on the pedal side as you won't be using that side much anyway and it has a lot less torque on it when you do.

It takes more to adjust the drive chain as you have to not just adjust a tensioner anyway you have to move the wheel. This sucks if you have caliper rear brakes too and with a coaster the brake arm as well.

As you mention however one less part to screw things up without a tensioner.
Let us know what your build and I'll bet we can give some advice and tips ;-}
 
some details about my setup:

Its a coaster brake cruiser frame with vertical "backslash /" dropouts

back brake is a "band brake" like this: http://www.kingsmotorbikes.com/bike-motor-engine-heavy-duty-axle-kit-free-wheel.htm my pedal side chain has been adjusted via adding a half link. Currently, there is no tensioner on either side.

The pedal side chain has more slack than the motor side chain, but neither have jumped off the sprocket in its current state.
 
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All good advice from KC. I will add this:

When using a pedal side chain tensioner the bracket that holds the wheel or sprocket MUST be securely attached and designed to absorb a lot of stress. When back pedaling to brake you might be surprised at how much tension is put on the pedal side chain.

I've built several with pedal chain tensioners and always securely weld the bracket to the frame so it can take the forces applied to it when braking. The wheel or sprocket must also be able to stand up to the task.

Tom
 
I've seen problems, but only after the chain slackens a bit after wear - a tensioner can both adjust this slack AND help point the underside of the chain up onto the rear sprocket.

As far as too tight goes, if the chain doesn't make funny noises when you roll the bike backwards & forwards for some distance, you probably can leave it that way.
 
i think ill be OK on that because I dont pedal backwards to brake, my setup is freewheel with hand brakes (front disc/rear drum)

My concern is wearing out anything on the engine-side. it seems like pulling on the drive gear more than is needed for the roller chain to seat on the small front sprocket may cause some wear.

I also appreicate all the advice!
 
I never ran with a tensioner but I don't have a china girl kit.

as someone above said you want X and X slack.

Personally I push on the chain, if it moves more then a quarter of an inch, but doesn't come off, thats a good start.

Chains do stretch and they also wear out from too much force, ask me how I'd know ;)
 
locell said:
i think ill be OK on that because I dont pedal backwards to brake, my setup is freewheel with hand brakes (front disc/rear drum)
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Excellent and exactly why I asked what you had;-}
My concern is wearing out anything on the engine-side. it seems like pulling on the drive gear more than is needed for the roller chain to seat on the small front sprocket may cause some wear.
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Drive chain tensioner or not the drive chain needs to be 'fairly tight' but you are in luck with your bike, you have some horizontal wheel movement and independent back band brake so you can always toss something on your almost now never used pedal side chain to match 'em up.

Just adjust your drive side chain to 'feel right' and either use the kit tensioner on the pedal side like this fairly recent build...

2_PacificJustinRight.jpg


Or spring for a smaller one like this other build I did like 3 years ago.
Sorry, I can't remember the brand name or model of that tensioner part.

2_1-MauiDoneRight640.jpg


Once again it all comes down to how easy want it to be to adjust your chains as they wear and for the majority of my customers they want quick and easy and why I usually put a drive tensioner on for them but place it where and how it is least likely to fail and even if it does not crash you like this staple build I do.

2_Macargi1200L.jpg


I can kick the tensioner and it won't move as it is on the meat of the chain stay but even if it did it would hit the tire or rim before it could ever go into the spokes. It all comes down to how easy you want things to be vs. less chance of failure and a pedal side tensioner if one is even needed is best in my book if you can.
 
Get rid of the kit chain and use an industrial/farm #41 chain and you wont have to worry about stretch/wear for a LONG time, like thousands of miles....
 
2door said:
Yes it can be too tight. If too tight it will cause noisy and rough running of the chain and put undue wear on the drive components.
You'll want 1/2" to 3/4" slack in the chain measuered on the top chain run with the clutch engaged and rolling the bike forward against a compression stroke.

Alignment is also critical as is chain tension.

Tom
Click to expand...


best reply award. helped me out.
 
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