Chain adjustment

[Gramps99]

I have been reading here about chain adjustment, and while not a mcycle mechanic, I feel my engineering background permits a little input.
Mr. Honda does make an exceedingly good bike,  although occasionally he does muddy the waters in his manuals.  Like a lot of  far eastern bikes, the settings are often for people who are quite light, and may need adjusting for our western stature (porkiness).

As weight is applied to the bike, the chain tightens due to the frame geometry. Blindly following the manual could mean that your loaded bike may  have an overtight chain. This overloads the chain, sprockets, front sprocket drive shafts bearings and in extreme cases prevents full  suspension movement. This can cause expense on any bike.
Happily all you have to do is load your bike as per normal and then have a quick feel of the chain, making sure there is slack.  Tight like a steel bar is bad....

[Scimitar]

As you correctly state, the chain tension will increase as payload is added to the bike - but only until the swing arm has the front sprocket, front swing arm pivot and rear sprocket all in a straight line. Adding further load will then slacken the chain tension again. So the tightest point is when the front sprocket, front swing arm pivot and rear sprocket all align. Either side of this the chain will be slacker. The tension does not progressively increase as payload increases. It increases initially and then decreases again at full suspension compression, in a sinusoidal way.

Bike manufacturers realise that to simulate the "alignment" mid-point is virtually impossible for the workshop/owner. So they stipulate what the chain tension should be with the bike unloaded, either on its centre or side stand. They have calculated this 'slackest' position so that the chain will never be over-tight, irrespective of load. So you need not worry if you weigh 8 stones or 20 stones. Just set the tension as per manual and all will be well.

[Gramps99]

Hi Scimitar,

You are right that its all about geometry  , I  was aiming at the  less experienced owners among us.
At 30mm slack on the side stand my chain is overly tight when under normal load, IMHO. At 35 to 40  mm I am happy.

  My point was really that for those relatively new to biking and the crossrunner,  all it takes to prevent damage is to reach down When Not Moving and  feel the chain has some  slack when  the bike has its normal load.

As an aside, what a bike, its the best all round bike I've ever owned.

[Skids]

Originally Posted by Gramps99

Hi Scimitar,

You are right that its all about geometry  , I  was aiming at the  less experienced owners among us.
At 30mm slack on the side stand my chain is overly tight when under normal load, IMHO. At 35 to 40  mm I am happy.

  My point was really that for those relatively new to biking and the crossrunner,  all it takes to prevent damage is to reach down When Not Moving and  feel the chain has some  slack when  the bike has its normal load.

As an aside, what a bike, its the best all round bike I've ever owned.

But surely, if you are stopped to measure the slack, some of the weight of the bike/rider is taken by your feet so the tension on the chain will not be the same as when you are riding? 

[Scimitar]

  
I think we are all singing from the same hymn sheet really. I totally agree that it is much better to run the chain on the slack side - it’s a disaster to be tight and punishing the bearings.
When on its side stand I lift the bike towards me on the left side, so as to fully extend the forks and rear shock. With my Nitron/RaceTech set-up the bike stays there. On standard suspension it tended to sink back down a bit.
The layout of the CR makes chain sag measurement difficult. My chain lifts up to (just) touch the swing arm guide, which is probably close to 40 mm.
I agree it is wise to err on the slack side, as Gramps suggests.

[Scimitar]

p.s.  If I reached down to feel the chain I’d fall over with bike on top of me. I love the CR when it’s moving but at standstill I still find it appallingly top heavy, exacerbated by my meagre 10 stone geriatric physique.

[andrewbettany]

Interestingly my 2015 CR had an MOT this week and gained an advisory for the chain been tight.  The assessor explained how the chain gets too tight when the bike is sat on.  So I slackened it off a little and he was happy.

[Gramps99]

Originally Posted by Skids

But surely, if you are stopped to measure the slack, some of the weight of the bike/rider is taken by your feet so the tension on the chain will not be the same as when you are riding? 

With practice it is possible to static  balance the bike  with feet up.

[Gramps99]

Moving on  from my last post and going off topic a tad,  Being an oldie myself I know what scimitar means about weight, its a big old fuel tank and I prefer not to  completely fill mine to keep the weight  a little lower. It used to catch me out when slowly carrying out awkward manoevres.  Although I am 6ft I prefer to  have the saddle on low setting , it gives me a little more wriggle room for my aged muscles. Its nice to think that the NC750 is there for when the Crossrunner gets too much for me.

[Skids]

Originally Posted by Gramps99

With practice it is possible to static  balance the bike  with feet up.

And when you bend down to feel how tight or slack the chain is?