Shimano chain length

[Lookrider]

I come across this official recommendation from Shimano
I'm not at all sure if the bike needs to have both wheels on the ground to do this
The diagram does not look like the chain stays would in fact be anywhere near horizontal

Thanks all

 

[Cycleops]

Don't know what the diagram is supposed to tell you but it's not chain length. It says 'stroke adjustment ', whatever that is. Something to do with the RD?
If you're asking how to calculate length there are a number of methods, my rule of thumb is big front to big rear (not through the derailleur) plus 2 links, one of which is the quick link.
There is also a mathematical method. Look on line.

 

[Lookrider]

Thanks for noting the stroke adjustment ...although that is printed on ..it belongs to the previous page in Shimano manual
It just came out like that on me printer
I have two Shimano diagrams so here is the other for a triple but the method is the same

 

[presta]

I have a copy of the same diagram:

 

[Lookrider]

And the commonly used big/big plus ...

 

[Lookrider]

Don't know what the diagram is supposed to tell you but it's not chain length. It says 'stroke adjustment ', whatever that is. Something to do with the RD?
If you're asking how to calculate length there are a number of methods, my rule of thumb is big front to big rear (not through the derailleur) plus 2 links, one of which is the quick link.
There is also a mathematical method. Look on line.

Sorry for not explaining better
But Shimano suggest to calculate chain length ( fir the described sprockets)
As to gauge the chain length by overlay until the rear jockeys are both plumb and 90° to the floor

But what position is the bike at relative to the floor
If it was on the floor then the chain stays would be roughly horizontal
The diagram if ti scale us nowhere near horizontal

 

[Ajax Bay]

Total overthinking. Also requires that the drivetrain is within the specs for that RD.
Just have the cage roughly vertical (and no further forward).
This is similar to the way Campagnolo says the chain length should be determined, btw: they go small-small and the return section of chain should be x mm away from the chain on the tension pulley: i.e. they are seeking to provide a guide by cage orientation as opposed to: large-large and at least one (inch) link, and then cut the chain there.
Which is the sensible and error free method.

 

[slowmotion]

People have already taken the hard work out of this little problem.....

http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html

 

[Ajax Bay]

People have already taken the hard work out of this little problem.....
http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html

Well not really. This requires data (length of chainstay, type of RD). Then you need to 'stretch' the chain out in a straight line and measure it. This is harder work (and less assured) than clicking the RD and the FD to large, threading the chain round large/large (not round pulley wheels), adding an inch, and cutting, threading back through the RD and joining with a quick link. Done: ride on.
But each to their own: a jar to night, iykyk.

 

[Lookrider]

Rather than open up another thread fir a "simple" advice

I just bought 2 tubeless tyres
Both same make and model but as they were last ones
One is a 2'25 and one is a 2:1
I would guess the 2'25 will be best on front for better grip
I'm not racer so it not matters much
But I'm all ears for advice
Thanks

 

[Ajax Bay]

There'll be more weight on the rear and if traction is important (ie not tarmac) then better have the wider one on the rear. And having the narrower one on front would mean you're more aero downhill.