Carbon frame, crossed gear wires.

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roger72
Posts: 32
Joined: 10 Jun 2011, 7:21pm

Carbon frame, crossed gear wires.

Postby roger72 » 22 Oct 2016, 9:34am

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.
Last edited by roger72 on 23 Oct 2016, 3:26pm, edited 2 times in total.

pwa
Posts: 10460
Joined: 2 Oct 2011, 8:55pm

Re: Carbon frame, crossed gear wires.

Postby pwa » 22 Oct 2016, 9:42am

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
Posts: 35970
Joined: 4 Jan 2012, 6:25pm

Re: Carbon frame, crossed gear wires.

Postby Brucey » 22 Oct 2016, 10:08am

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
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Valbrona
Posts: 2240
Joined: 7 Feb 2011, 4:49pm

Re: Carbon frame, crossed gear wires.

Postby Valbrona » 22 Oct 2016, 6:00pm

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

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hondated
Posts: 2358
Joined: 27 Mar 2008, 7:59am
Location: Eastbourne

Re: Carbon frame, crossed gear wires.

Postby hondated » 22 Oct 2016, 6:16pm

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
Posts: 539
Joined: 19 Sep 2016, 10:33pm

Re: Carbon frame, crossed gear wires.

Postby nigelnightmare » 22 Oct 2016, 9:19pm

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?

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Gattonero
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Joined: 31 Jan 2016, 1:35pm
Location: London
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Re: Carbon frame, crossed gear wires.

Postby Gattonero » 23 Oct 2016, 1:22pm

roger72 wrote: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
It is by riding a bicycle that you learn the contours of a country best,
since you have to sweat up the hills and coast down them.
Thus you remember them as they actually are...