Carbon frame, crossed gear wires.

[roger72]

NOW FIXED,It was the cables crossing in the down tube. The bottom bracket and rear wheel were the same as on old frame,I have now found out how to get into the down tube on a carbon frame so I have leant something. Thank you very much to all who replied. Roger .
I have recently purchased a Planet X carbon frame.I have built it up into a complete bike but the gears will not change properly,I can get all the gears OK on the small ring but when I change to the big ring it will go from top to bottom gears alright but will not go back properly, it need 2or3 clicks to move to high gears.I am using Shimano ultegra gears.The gears worked OK on the previous frame with external cables. A friend in the cycle trade tells me this is because the wires are crossed inside the down tube causing friction.Can anyone help me please.Roger.

[pwa]

Just to be clear, when you talk of moving to a higher gear you do mean moving to a smaller sprocket at the back? If so, it does sound like a friction problem somewhere along the cable to the rear mech.

When you are on the small ring the front mech cable will be slack. It will be tense and could have moved the outer when on the big ring, so I guess it could be putting pressure on the rear mech cable housing. It does sound plausible.

[Brucey]

I agree it does sound plausible; is there any choice regarding the cable routing? Do the cables have to cross one another in one particular way ?

BTW if the rear mech is badly aligned (or the upper knuckle is too stiff) you will occasionally get a bad shift on one chainring where it is OK on the other, but your description doesn't really sound like that.

cheers

[Valbrona]

Presumably you are using some PTFE cable lining so they don't rub against one another.

[hondated]

Roger in the process of changing the frame have you fitted a new bottom bracket. I ask because I recently built up a bike and initially I too had a similar problem. Pondering over it I went out in the garage late one night and tweaked up the BB and bingo problem solved.

[nigelnightmare]

Check the chain line. middle of cassette to middle of chain rings should be a straight line( in-line with the cogs & rings)
The outer front chainring may be too far out.
Some bottom brackets are adjustable but you might need a different one or a different front chainset to get it lined up.





Why are the cables crossed?

[Gattonero]

I have recently purchased a Planet X carbon frame.I have built it up into a complete bike but the gears will not change properly,I can get all the gears OK on the small ring but when I change to the big ring it will go from top to bottom gears alright but will not go back properly, it need 2or3 clicks to move to high gears.I am using Shimano ultegra gears.The gears worked OK on the previous frame with external cables. A friend in the cycle trade tells me this is because the wires are crossed inside the down tube causing friction.Can anyone help me please.Roger.

Crossed wires can be only the tip of an iceberg.
You need to run trough the problem by exclusion. Anything that can create a problem must be checked: chain/cassette/chainrings/jockey wheels for wear, cables for correct routing and friction, cable ends for correct 90º cut and correct ferrules, absence of dirt in the entry/exit points of the wires, stiff pivots in the FD/RD, dropouts alignment, etcetc