[Trudeau89]

Hi,
This is mostly just to solve my curiosity. I know how to adjust a chain.
Anyway,
This weekend I swapped my rear wheel from my woods to MX tire. I have them mounted on OEM wheels with the same size sprocket so I wouldn't have to adjust the chain when swapping. After installing the MX wheel I noticed a great deal of slack in the chain. It took prob about 1/4" adjustment , way more than usual. I went ahead and adjusted it to spec. Rolled it a few times to lube the chain and I was on my way.

After hitting the track as I was loading the bike I noticed the chain had tightened up. Becoming way too tight.

This is prob the 2nd or 3rd time in my lifetime I have noticed something similar in the way of chain adjustment. Again I know how to adjust a chain I wondering if anyone can explain what type of black magic causes this phenomenon. Or if anyone else has ever experienced it.

Thanks.

[JimDirt]

What i am guessing you are experiencing is a stretched chain , when a chain stretches it does not ALL stretch , it depends on a lot of factors , like brand/quality of chain , and riding conditions , how its maintained , how its lubed all play a part in how and when and what part of a chain stretches

A brand new chain will start stretching from the minute you ride the bike , and it will wear the sprockets as it gets longer
(which is why your sprockets wear in a cup/hooked shape , because the longer the link gets the more space it needs to sit , since the sprocket is softer than the chain link , it wears the sprocket as the link's lengthen (actually its the rollers that elongate and wear not the sides of the link itself)


Now to your question..... If you happened to adjust the chain (prior to and after the rim swap) , and it happened to be in a tight/shorter part of the chain , or in a loose/stretched part of the chain , then it will affect how tight/loose it is at any given spot in rotation , so you could adjust it , and move the wheel a 1/4 turn , and it will be too tight or too loose now , even though it was fine when/where you adjusted it , if you did not check the entire rotation when you adjusted it , then it creates a issue with adjustment , on a stretched chain , you always adjust it at its tightest spot and hope the loosest spot is not so bad that the chain jumps the sprocket in the event of something hitting it , if it is noticeably different from tight to loose , then the chain (and usually sprockets , as they are a wear item and their longevity will be affected with a new chain , because they are "worn" to the old chain

No matter what , you will always have loose and tight spots in a chain , as torque is what does the stretching , along with improper adjusting or just lack of maintenance altogether **not implying this is the case with you** , my guess is the chain is either a cheaper chain , or its been on there a while (a season or more) , and this is the cause of the inaccuracy in tension

I swap wheels around on my 450R like you , for either practice and race wheels or trail riding , i buy $100+ chains (DID Gold Non O-Ring ER chains) about every 2 or 3 seasons , depending on how much i ride or how hard i ride each season , and i buy steel sprockets (because i am not worried about weight i am worried about strength and longevity)my chains wear very consistently , but when i notice the sprockets just barely cupping , i know its time and no adjustment is going to make it last any longer , its on a downhill slide just like once your valves start moving , its only a matter of time and your done

[Trudeau89]

Thanks for your reply,

It is a cheap chain I will give you that. Ordered on accident.

But on other points I did roll the wheel a few times after the swap and the entirety of the chain was way loose. I adjusted it and rolled it and it maintained its slack. It was only after riding that it tightened up and at that point it was/is the whole chain not sections.

My other idea was that using a different rear sprocket would have an affect and once under load the chain would 'seat' but that would lead to more slack not less.

Like I said I am just baffled how it all takes place. I like to know how and why things happen.

[JimDirt]

Not necessarily , if the old sprocket(the main one you use) is old , and the "spare" is new , or vice versa , then it would make a difference on the tension , a old sprocket would be looser when swapping FROM a newer one and a newer one would be tighter because even if slightly , the "newer" sprocket will be larger in diameter where the chain rides , whereas the "older" sprocket would be worn down where the chain rides and the adjustment would be different

Not sure why when spinning it was still loose then tightened up after/during riding , since usually the opposite is the result

Remember a sprocket does not have to be worn out , to be worn down

[Aussiecrf230]

If the chain got tighter after adjustment and then riding you would have to think either the axle has moved slightly to the rear or there is some wear/play in rear arm bushes.

Of course a build up of dirt, mud, etc could make the chain ride higher on the sprockets causing it to be tight.

At least you check your chain.
It is amazing the number of people who don't. Obviously they are richer than I, buying new chains and sprockets all the time.

[spaceboy]

Check your chain at multiple points for the proper slack. You will probably find that your chain links have stretched. It will be loose in some spots and overly tight in other spots.
You need to replace the chain and the sprockets together or it will prematurely wear out your new chain if that's the only part you change.