Correct BB axle length????

matt24777 · Nov 4, 2013

width of shell is 68mm.

I've got a 110 on the way so will have a play when it arrives.

It's weird (or I'm just being dull, which is quite possible) I can get it so that the chain shifts up and down fine, but if I adjust it such that it doesn't rub when I'm in 1st on the back and middle ring it then rubs in 8th and big ring! but if I get it to clear the 8th/big ring it rubs in 1st/middle ring :facepalm:

RobMac · Nov 4, 2013

M737 is 8 speed yeah? Well are you aware that Shimano advise not to have the chain run
going to extreme (wee sprocket at the back with the wee sprocket at the front)(big sprocket
at the back with the big sprocket at the front) excuse the muppet like explanation but you
know what I mean. So your gears might not be as bad as you think :?

matt24777 · Nov 4, 2013

RobMac":2o28lzqg said:
M737 is 8 speed yeah? Well are you aware that Shimano advise not to have the chain run
going to extreme (wee sprocket at the back with the wee sprocket at the front)(big sprocket
at the back with the big sprocket at the front) excuse the muppet like explanation but you
know what I mean. So your gears might not be as bad as you think :?

yeah I generally work on the basis of:

Granny ring + any cog on the cassette down to 7th
Middle ring + any cog on the cassette
Big ring + any cog on the cassette from 2nd down.

Thing is it's rubbing in gears that shimano would definitely approve of!

FluffyChicken · Nov 4, 2013

You should be able to do that with no problem.

Is the front mech fine.
Slight re-alignment may help.

Rings all good?
Do it rub all the way around.
Are you the 2-3mm above the front cog tops.

Can we have some pictures in case of anything obvious.

RobMac · Nov 4, 2013

matt24777":3n0zasmu said:
yeah I generally work on the basis of:

Granny ring + any cog on the cassette down to 7th pushing it a bit
Middle ring + any cog on the cassette yeah that sounds about right
Big ring + any cog on the cassette from 2nd down. mmmmm

Thing is it's rubbing in gears that shimano would definitely approve of!

Understand Im accessing this from afar without seeing the bike :?

matt24777 · Nov 4, 2013

Ok bit difficult to photo but here we go....

In middle ring/1 on cassette

In middle ring/1 on cassette

In middle ring/1 on cassette

In Big ring/8 on cassette

Rings are 150 miles old, as is the Chain and the mech is about 50 miles old NOS

rider · Nov 4, 2013

What shifters do You use?
Is it 113mm BB axle length in those pictures?
Even if You use Rapidfire then some tweaking is posible to avoid that chain rub in middle ring/1 on cassette.
Please oil Your chain! :shock:

matt24777 · Nov 4, 2013

rider":2ff4zirt said:
What shifters do You use?
Is it 113mm BB axle length in those pictures?
Even if You use Rapidfire then some tweaking is posible to avoid that chain rub in middle ring/1 on cassette.
Please oil Your chain! :shock:

Yeah It's 113 here and its using XT M739 rapid fire.
It's been washed off after a quick poodle yesterday but not oiled yet

WD Pro · Nov 4, 2013

Non standard chain rings = non standard spacing / thickness etc ?

Check tooth to tooth pitch ?

WD

rider · Nov 4, 2013

If You do lot of road riding, then I would use it as is, otherwise shorter BB axle as was already recomended.
By tweaking I meant fine tuning with thumb shifter of rapidfire,as forefinger is just for downshifts.
But careful operation with Your thumb can adjust just that little bits needed.

Correct BB axle length????

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