[yewweng]

Got a 44T in the front and a 11-34T in the rear.
XT 04 cranks and XT 03 rear de regular length cage (I wanted non-rapid rise ).
XTR 04 front de (seems to be what has been recommeded to not hit the swingarm)
Currently have the chain length at 54 links (108 pins).
In the static position (bike unladen), everything looks fine....

But I noticed 2 things:
1. In the big chainring (44T), big cogset (34T), the swingarm will not be able to go through the full 5.5 inches of travel. The chain will simply not be long enough and will stop the swingarm about halfway through the travel. This I guess is due to 'chain length growth'.
I am afraid that if I happen to encounter a big enough hit in this gear, I might snap the chain.

Q1: What is the length of chain you guys are using? 54? 56?

2. I am not able to keep the bike in the big chainring, big cogset when riding. It will simply flip flop back and forth between the largest and second largest cogset. The shop mechanic explained that the chainline on the 5.5 was not optimal and that was causing this. (He had put in a spacer (2.5mm) on the BB otherwise the FD would not clear the seat tube in the granny gear).

Q2: What the size of the spacer you guys put in? or translated the spindle length?

PS: I am not blaming the mechanic, I think he's doing a decent job in the absense of a manual... I just want to get this sorted...

 

[phatbiker]

Regular length?

Got a 44T in the front and a 11-34T in the rear.
XT 04 cranks and XT 03 rear de regular length cage (I wanted non-rapid rise ).
XTR 04 front de (seems to be what has been recommeded to not hit the swingarm)
Currently have the chain length at 54 links (108 pins).
In the static position (bike unladen), everything looks fine....

But I noticed 2 things:
1. In the big chainring (44T), big cogset (34T), the swingarm will not be able to go through the full 5.5 inches of travel. The chain will simply not be long enough and will stop the swingarm about halfway through the travel. This I guess is due to 'chain length growth'.
I am afraid that if I happen to encounter a big enough hit in this gear, I might snap the chain.

Q1: What is the length of chain you guys are using? 54? 56?

2. I am not able to keep the bike in the big chainring, big cogset when riding. It will simply flip flop back and forth between the largest and second largest cogset. The shop mechanic explained that the chainline on the 5.5 was not optimal and that was causing this. (He had put in a spacer (2.5mm) on the BB otherwise the FD would not clear the seat tube in the granny gear).

Q2: What the size of the spacer you guys put in? or translated the spindle length?

PS: I am not blaming the mechanic, I think he's doing a decent job in the absense of a manual... I just want to get this sorted...

non rapid rise rear derailer are available in short, medium and long cage versions. if you run a 34 tooth cassette you should be running a long cage rear derailer. i suspect that you're either running a short cage or med cage. i have not had any shock travel issues with this set up.

phat

 

[Hecubus]

You should be using a long cage derrailleur on a 34t cassette to pick up the extra chain slack. This should address the issue of your chain being too short. Second, you *ALWAYS* have to use a 2.5mm spacer on the drive side of the outboard bearing type cranks from shimano. This has nothing to do with the 5.5, shimano made it that way by design. If you don't the derraelleur will not clear the seat tube in the granny. The only reason you should not use that spacer is if using an E-type front derr. If the BB shell is 68mm you should use 5mm of spacers on the drive side and 2.5mm in the non drive side. Failure to use the spacers as specified will cause he plastic shield that goes inside between the cups to get crushed and the cranks will be extremely difficult to turn and the spindle will rust. Its amazing how many mechanincs still don't understand how to work this spacer issue because they can't read a lousy instruction sheet.

 

[E-man]

In the big chainring (44T), big cogset (34T), the swingarm will not be able to go through the full 5.5 inches of travel.

Trying to calculate chain length and suspension travel while cross-chaining (big ring/big cog) is insane. Unless you're a sponsored pro and drivetrain components are freely supplied, there is NO reason that you should ever cross-chain a driveline as this put severe, un-needed stress on both the chain and the rear derailuer.

Personally, I calculate proper chain length while in granny/granny (24/34), making sure that the chain is short enough to allow for a 1" gap between the chain and the main pivot on the rear deraileur. Any longer and the deraileur won't be able to take up enough slack, and any shorter and you risk damage to the deraileur when in big/big (44/34)

Eric

 

[Blaster1200]

I agree with E and Hecubus.
But in addition to checking granny/granny, I also check big/big (there has to be some slack, and I'll cycle it with the air out of the shock).

But most importantly as E mentioned, you should never cross chain. I bet when you back pedal, the chain really comes off!

Not to try to make you feel dumb (on the big/big combo), learn not to ride in this gear combo. There is no good reason to, and even better reasons not to. I know that it may happen occasionally by accident, and that's why you want to provide for it, but you shouldn't complain about chainline issues in this gear. It's just all bad on all bikes.

 

[yewweng]

thanks

Thanks for the input guys.
Was going thru the Shimano instructions for the crank and it confirms with you guys that with a 73mm BB a 2.5mm spacer should be used. So that is closed.

With regards to the big-big combo thing, I was expecting to get some flak from you guys so no worries I just wanted to make sure that the bike is set up to comfortably handle a situation that can happen

The XT Rear De M750 comes in long (GS) and super long (SGS) but I can't find any markings to identify which one I have. In the worse case I am having the GS but that can be rectified....
Anyway, still it would be good to know what is the length of chain you guys are using so I have a point of reference to start with.
Information along the lines of : largest cog, largest chainring, chain length

Cheers!
Yew-Weng

 

[yewweng]

done!

Went down to the LBS and added in 1 inch to the chain, now its 55 inches.
This was done after deflating the shock and compressing the rear swingarm all they way.
Shifting is perfect now and the chain will not restrict the suspension at any gear range.
Case closed.