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Chain Tightness & Loosness Questions

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So, I've been riding for 3-4 years.  Ive had 4 different bikes, 3 being Dirt bikes, and, since day 1, I've never TRULY understood the proper tension of the chain.  I have always kept it on the loose side, but i know im too loose due to the sprocket wear.  Im just too afraid to go too tight, in fear of it damaging my trans. and also snapping and breaking me or my case.

I know the manuals all tell you to pull it or push it up and measure. But i dont really get those instructions, and when i do it that way, the chain feels way too tight once pressure/weight is put on the back shock. Feels real loose and good on its stand but real tight when weighed down.  And that makes me worry its too tight while im on it and riding.

I just got a new chain and have it on the tighter side, to allow some stretching but this worries me and im riding way softer and slower because of it.

My chain right now, has all kind of play up and down when on the stand and in neutral.  Enough that looks perfect.  But when i test its tension with my weight on it, and the swing arm moves up closer to the seat, it feels really tight.  Not so tight that it wont budge.  But tight enough that it doesnt have much play, and the play it does have feels strong.

So i guess, what im not understanding and asking is; should i be measuring from the stand or with weight on?  AND should it feel loose when on the stand and then be tight with weight on?

Basically, is loose (per 3 finger rule/measurements) while in neutral and no weight, good? But then significantly tighter with weight and pressure on rear shock, still good?

Or should it always be pretty loose and floppy.  Because loose while weight is added, always feels WAY too loose without the weight.

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Compress the suspension so the axle, swing arm pivot and countershaft are all in line (tightest point of suspension travel). Set chain free play so it doesn’t bind or slap around and ride on. No fingers or measuring involved. 

 

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A loose chain will not cause sprocket wear, a tight one will. Grimlock pointed out how you can determine how tight a chain can be. You only need to do that once. After you move the suspension through its' entire travel, set the chain just loose enough at the tightest point, with the bike back on the shock, and the bike on the stand, pick a point (usual;y near the upper slider) and see how far up (how many fingers) you can fit. Then always set it to the measurement.

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I use a 2 finger rule at the back of the front rubber swingarm chain guard, never had a failure and my chain and sprockets last a very long time. That is checked with bike sitting on its own weight. Keep you chain clean and lightly lubed at all times.

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Never adjust the chain “on the tighter side” to allow for stretching.  A great way to wear on the sprockets, put undue strain on the countershaft bearing, and in extreme cases, crack the case at the countershaft.  Adjust as outline above, with the countershaft bolt, the swingarm bolt, and the axle all in line.  After adjusted, put the bike on a stand with the rear wheel elevated and measure the slack at a given point, usually at the rear end of the chain slider.  Record that measurement and use it whenever you adjust the chain.

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I have several bikes.  I adjust the chain as per the service manual on each.  The only reference I have come across regarding fingers is too keep they away from your chain and sprockets.  I adjust the chain to the minimum spec at the tightest point.  The chains on the bikes with little travel look pretty tight.  The ones with long travel look like they are gonna fall off on the stand.  You can do the whole thing with the swingarm in line with the countershaft but I find the service manual spec easier.

 

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3 hours ago, mikedabike said:

I have several bikes.  I adjust the chain as per the service manual on each.  The only reference I have come across regarding fingers is too keep they away from your chain and sprockets.  I adjust the chain to the minimum spec at the tightest point.  The chains on the bikes with little travel look pretty tight.  The ones with long travel look like they are gonna fall off on the stand.  You can do the whole thing with the swingarm in line with the countershaft but I find the service manual spec easier.

Well thats how they came up with their number so it works.  Do it once and you will know what that bike needs for slack.  Every bike is different.   Whar i mean is you dont need numbers if you do it this way, on the trail, wherever.  Once you do it you can do the finger measuring and get it close.

Edited by Spitz85
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2 hours ago, Spitz85 said:

Well thats how they came up with their number so it works.  Do it once and you will know what that bike needs for slack.  Every bike is different.   Whar i mean is you dont need numbers if you do it this way, on the trail, wherever.  Once you do it you can do the finger measuring and get it close.

Yes I agree if you have the starting point then you can do the finger thing.  Problem is most people want to skip the important parts!

 

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Remember also that you can do damage to the sprockets, chain, roller, etc. if your axel is not even on both sides.  If one side is off a bit the tension of the chain can still seem correct but the chain can be out of alignment causing quicker wear and tear on anything chain related.  Purchase a cheap caliper from Harbor Freight and measure the distance of the axel bolt on the swing arm on each side before you tighten the axel bolt.  Your chain, sprockets, roller, etc. will last a lot longer if the chain is in alignment as well as within proper tension spec.

https://www.harborfreight.com/6-in-digital-caliper-with-sae-and-metric-fractional-readings-63731.html

 

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If you have no one to help you. Just bend over the seat on your gut, one hand on the swing arm, and pull down, check the chain with your free hand [emoji3].


Careful, this is how I tore the cartilage off one of my ribs (costochondral separation). Pulled the swingarm up toward my gut while leaning over the bike until I heard a pop and quite a bit of pain. Lasted about 6 weeks.

Probably just an unfortunate occurrence but now I use ratchet straps and let those do the work for me.
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8 hours ago, ranga97 said:

3 fingers is pretty close just behind the plastic slider on the swingarm

3 fingers while compressed? Or while free standing? 

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23 hours ago, mikedabike said:

I have several bikes.  I adjust the chain as per the service manual on each.  The only reference I have come across regarding fingers is too keep they away from your chain and sprockets.  I adjust the chain to the minimum spec at the tightest point.  The chains on the bikes with little travel look pretty tight.  The ones with long travel look like they are gonna fall off on the stand.  You can do the whole thing with the swingarm in line with the countershaft but I find the service manual spec easier.

 

My manual tells me to push the chain up to the bottom of the swing arm near the chain guide.  How youre supposed to accurately measure 8-10mm in that weird spot is my issure. I measure what looks to be no more space than 1cm.  But then when compressed it seems too tight to me.  

Once compressed, should it be somewhat tight? Or should it still be floppy? 

I cant seem to find the middle ground.  Ill make my chain nice and floppy while standing, then when compressed it tightens like crazy.   So i make it loose as hell while standing (which looks and feels WAY too loose) and then when its compressed it stays pretty floppy, but like i said, it feels way too loose when just standing.

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With the 3 points in line thats the tightest the chain ever will be, should be just a slight bit of slack.  Whatever it is after that doesnt matter how you do it, just as long as its consistent.    I tried goin by the manual and it still left me concerned, so you do it this way once and youll have a better feel with whats correct, you have directly seen it, just puts it in perspective more so than a number.  Just my opinion.   You could also make a gauge after doing this like a no go gauge for easier accurate checks, most people use a few fingers at a specific point they can replicate easily.  Not rocket surgery by any means.

Edited by Spitz85
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5 hours ago, Ktm400EXCRacing said:

3 fingers while compressed? Or while free standing? 

On stand no load

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5 hours ago, ranga97 said:

On stand no load

Thanks, i definitely rode way loose before, then. You could have probably got 3 fingers in between while loaded.  Now im 3 fingers and a little bit more, with this new chain.  I think it might be on perfect then

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On 9/27/2019 at 8:32 PM, Grimlock said:

Compress the suspension so the axle, swing arm pivot and countershaft are all in line (tightest point of suspension travel). Set chain free play so it doesn’t bind or slap around and ride on. No fingers or measuring involved. 

 

 

On 9/27/2019 at 8:39 PM, William1 said:

A loose chain will not cause sprocket wear, a tight one will. Grimlock pointed out how you can determine how tight a chain can be. You only need to do that once. After you move the suspension through its' entire travel, set the chain just loose enough at the tightest point, with the bike back on the shock, and the bike on the stand, pick a point (usual;y near the upper slider) and see how far up (how many fingers) you can fit. Then always set it to the measurement.

These are the best advice.  The chain is at its tightest when the countershaft, swingarm pivot point, and rear axle are all in line with each other.  Make sure there is enough slack when these three points are aligned and it doesn't matter how much more slack there is for other positions (as long as the chain isn't too worn out).

Start by adjusting your axle blocks so that the chain seems to have approximately the correct amount of slack.  (On a stand or wheels supporting the weight of the bike are both fine.)  Then make sure that the rear sprocket is vertically aligned with the front sprocket.  This can be done with an alignment tool (e.g.: Motion Pro 08-0048), tape measure from swingarm pivot centre to rear axle centre on one side and then the other, or by marks on the swingarm at the axle blocks if you have already determined that they are correctly stamped on your swingarm and axle blocks.

Now take the bike off the stand and compress the rear suspension and run a tie down strap under the swingarm and over the seat and connect the two ends.  Tighten the strap until the centres of countershaft, swingarm pivot, and rear axle are in line with each other.  This may take some fine tuning with the strap -- especially if you are working on this by yourself.  Once the three points are aligned, move the rear axle blocks on each side equal amounts until you get some slack in the chain.  Once the axle block adjuster screws and axle nut are tightened, this will be the minimum slack that the chain will have for any wheel position through its travel arc.  For the amount of slack, something around one or two finger widths worth of lift of the chain at the rear end of the upper side of the swingarm chain slider will probably be enough.

Your chain will now be adjusted for optimal slack and you can remove the tie down strap after the adjuster bolts and axle nut have been tightened.  Now put the bike back on the stand so that the rear wheel is off the ground and the shock is at full extension.  Lift the chain at the rear of the slider again and measure how far it is above the swingarm at that location with the rear unloaded.  Now you can just use that measurement for future adjustments without having to go through the long initial procedure above.  If you want to make things really easy for future maintenance or changing wheels or sprocket sizes, etc., cut a small block of wood or other suitable material to a height to match the pulled chain height at your preferred measuring location (somewhere near the middle of the top run of the chain) to the height you just measured.  If the block you cut isn't a perfect cube then mark which face to use on it and mark which bike it is for.

This block will not necessarily be the correct height for adjusting chain tension on other bikes but it should always stay correct (assuming no wear or deformation) for the bike you made it for.  It will not be affected enough to matter for changes in sprocket size or sag settings.

Bike on the ground and weighted is better than bike on the stand only if you don't use the initial determination method above.  This is because the weighted rear will have the suspension compressed closer to the point of CS/pivot/axle alignment.  It's not ideal but just better.  The problem with this method is that the chain tension will change if you change your sag such as when changing from an MX set-up to one for trails.  With the first method you can set the chain tension and then just occasionally check it for chain wear.  When setting the tension with the bike on the ground you need to reset the chain tension every time you change the sag settings.  Plus, setting the chain tension when the bike is on the ground is only approximate whereas the first method is fairly exact.

The first method is only a bit of a hassle the first time you do it and afterwards it's actually the quickest and easiest way.  It also makes your chain and sprockets last longer.  How much longer depends on how accurate you would be with another method but to me it's worth it.  I use one bike for both track and trails so I swap between two sets of wheels frequently and this makes changes faster and easier.

Congratulations if you read this far!  I hope it will be useful for someone.

Edited by Max17
typo

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