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PostPosted: Mon May 10, 2010 1:56 pm 
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Posts: 995
I did try searching for info, and have read through the instructions that come with this FD....
I've never set up 7900 before, but about everything else...
Anyway, on initially setting it up, when I try to shift the from the small ring to big ring, I can't get the lever to hit the 'click' to go to the big ring, even though I have the limit screw pretty much wide open (I can move the FD by hand way out over the big ring).
I think I've taken the slack out of the cable......is it simply still too little cable tension?
Help!


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PostPosted: Mon May 10, 2010 2:45 pm 
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Simple Checks:
i) Did you 'release' the shifter before tensioning the cable? Can you achieve the "click" without the cable in tension?
ii) Is your limit screw set correctly ?
iii) Is your shifter a new one ? I have seen used ones with some jammed /broken cable ends inside, thus unable to shift properly.


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Posted: Mon May 10, 2010 2:45 pm 


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PostPosted: Mon May 10, 2010 6:04 pm 
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Posts: 333
As odd as it might seem, the best front shifting from 7900 STI shifters and front deraileurs is achieved with a little slack in the cable.

I can't recall where I read that, but once I made the adjustment, my front shifting improved greatly.

http://cycle.shimano-eu.com/media/techd ... 651777.pdf


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PostPosted: Mon May 10, 2010 9:46 pm 
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maxxevv wrote:
Simple Checks:
i) Did you 'release' the shifter before tensioning the cable? Can you achieve the "click" without the cable in tension?
ii) Is your limit screw set correctly ?
iii) Is your shifter a new one ? I have seen used ones with some jammed /broken cable ends inside, thus unable to shift properly.



Not sure what I've got going on....I just tried to fiddle with it again, tried tightening the cable by hand, and suddenly the large lever wouldn't move the derailleur at all, like it was jammed.
Even when I released the cable entirely from the front der., it was still jammed. Then I took the cable all the way out of the shifter, then it would move normally.
So yeah, when there is no cable in the shifter, it seems to move/click properly. The shifter and cable are new.
I put the cable in through the bottom as pictured in instructions, can see it coming up through the white plastic piece and into my cable housing.
What the hell am I doing wrong?!


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PostPosted: Sat Jul 03, 2010 7:28 pm 
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Joined: Wed Sep 03, 2008 2:42 pm
Posts: 87
Location: Aberdeen, Scotland
I have exactly the same problem, I have just put my bike back together after having to replace the frame, so same componets, new cables.

Try shifting up to th ebig ring and it will just not let me! I am about to explode as its just frustrating me why its doing this.

the only thing i can think of is i had the chain rings of to givethe bike a good clean, other than that should all be th esame as before.


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PostPosted: Sat Jul 03, 2010 10:24 pm 
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Location: Canada
That is one of the annoying things about the 7900 front. I have found that allowing a tiny bit of slack in the cable initially helped. Installing a Jagwire in-line adjuster was the other thing that I did that made a difference. The problem with setting up the bike without an adjuster of some kind is that when the cable stretches, you have to do it all over again.


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PostPosted: Sat Jul 03, 2010 11:30 pm 
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Joined: Wed Sep 03, 2008 2:42 pm
Posts: 87
Location: Aberdeen, Scotland
do i reset everything, release cable and leave a little slack when tightening?

Actually, just tried that and seems no matter what i do i can not get the chain up to the big chain ring!!! getting very frustrated!!!!!

same mech and shifters were fine before, just seems like the front mech wont go far enough up to ge the chain on, just rubs the inside and does not catch!!!


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PostPosted: Sun Jul 04, 2010 1:52 am 
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Check your limit screws if that is the case.
-Set your bike onto a workstand, with rear wheel off the ground.
- While maintaining some mild tension in the cable (When the FD is in the SMALL chainring position before changing gears.) Release your limit screws for the 'H' end bit by bit while you repeatedly try and see if the chain will get up onto the big ring.
- After that, shift to small/BIG for FD and RD. Adjust the limit screw for the L until there is no chain rub on the FD.
-After that, shift to the Big/Small for FD and RD. Adjust the limit screw for the L until there is no chain rub on the FD.
-Double check again for small/BIG for FD and RD combo. You should be good to go from there.


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PostPosted: Sun Jul 04, 2010 8:51 am 
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Location: Aberdeen, Scotland
The only way i can get it on the BIG is by screwing in the Lower Adjust Screw all th eway down (this is the one next to the frame?).

It will not then release down to the small CR.


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PostPosted: Sun Jul 04, 2010 3:52 pm 
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Location: Aberdeen, Scotland
Thats it working, its not pretty and may need fine tuning by a better bike mechanic than me!

Now to figure out why there is a loud clunk noise when applying pressure from the crank/BB/pedal area or it soundliek its coming fomr there.

Never had these issue in previous bike builds.


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PostPosted: Tue Jul 06, 2010 10:29 am 
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Location: Australia
sounds to me like you could be wrapping the cable around the pinch bolt on the FD the wrong way.

If you have cable wrapped anti-clockwise instead of clockwise on the pinch bolt then the leverage/angle will be wrong and would make it very difficult to up shift.

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PostPosted: Tue Jul 06, 2010 10:43 am 
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Location: Aberdeen, Scotland
It is clockwise, if you are looking at the back of the FD at the bolt the cable comes up from the left.


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PostPosted: Tue Jul 06, 2010 10:59 am 
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Location: Belgium
Could you take a pic of the fd setup? Just to have a look at it?
Are you mounting the whole 7900 gruppo or do you have another crank?

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PostPosted: Tue Jul 06, 2010 11:23 am 
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Joined: Wed Sep 03, 2008 2:42 pm
Posts: 87
Location: Aberdeen, Scotland
Crank is SRAM Red
Shifters are 7800

this set-ip was on my Giant TCR Adv 3, now on a Giant TCR ADV SL Team.

added some pics, i know the mech is probably higher than it should be, but have the same issue with it lower.


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IMG00139-20100706-1218 (Medium).jpg [ 116.08 KiB | Viewed 3906 times ]
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Posted: Tue Jul 06, 2010 11:23 am 


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PostPosted: Tue Jul 06, 2010 3:17 pm 
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Location: London
wymthg wrote:
Shifters are 7800


That would be it, then. 7800 and 7900 have different cable pull ratio for the front.

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