newbie question about double chainwheel with triple shifter

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newbie question about double chainwheel with triple shifter

Postby pembo6 » Sun Sep 16, 2012 2:54 am

hi. im very new to riding. Just bought an old (2003) Giant OCR3 to try and get into some triathlons.

i have been trying to adjust the derailleurs and am not having much luck. i finally worked out that the front shifter is a 3 speed (shimano sora), but the previous owner must have removed the triple chainset and replaced it with a tracer f.i.s. double chainset.

so i have a 3 speed shifter with a double chainwheel/chainset. The inner chainwheel is missing. Other than making derailleur adjustment difficult, is there any major problem with this setup? Is the shifter indexing the same?

i cant seem to get the derailleur shifting perfectly and i dont know if i should keep perservering or give up because it wont work..

i am badically allowing the front derailleur to start on an 'imaginary' inner chainwheel, then move to the middle (which is actually the inner), and then to the outer. i use the low limit screw to stop the derailleur from throwing the chain off the inside chainwheel when shifting down. the large cage allows this to be done easily.

in the end i will probably just take it to a bike mechanic, but i was just wanting to know if i was waisi g my time because the indexing was diggerent, or something else.

thanks for your advice.
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by BNA » Mon Sep 17, 2012 1:33 pm

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Re: newbie question about double chainwheel with triple shif

Postby pembo6 » Mon Sep 17, 2012 1:33 pm

OK. So after googling for an hour or so, I came up with some answers. Honestly, I did try that before posting..... but I'm just learning some of the correct terminology for bike parts and I was googling the wrong things.

So it seems like there is no problem running a double chain-wheel with a 3 speed/triple shifter. Lots of people do it.

But I am unsure where to put the "ghost" chain-wheel in the gear sequence. On the inside, or the outside. There seems to be benefits for both.

If I treat the front inner shift as the 'ghost' and adjust the inner limit screw accordingly,..... then it is quite hard to set the gears up properly because I am starting off on on imaginary position.

If I set the shifting up so that the 'ghost' chainwheel is on the outside, then I run the risk of throwing the chain off the outside if I don't keep an eye on the cable tension and outer limit screw. But the benefit may be that the final ghost shift can actually be used as a 'trim' if required, to just push the cage out slightly if it rubs when moving the rear rear to the small cog.

Any recommendations would be Greatly appreciated. Thanks so much.
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Re: newbie question about double chainwheel with triple shif

Postby RonK » Mon Sep 17, 2012 2:21 pm

pembo6 wrote:OK. So after googling for an hour or so, I came up with some answers. Honestly, I did try that before posting..... but I'm just learning some of the correct terminology for bike parts and I was googling the wrong things.

So it seems like there is no problem running a double chain-wheel with a 3 speed/triple shifter. Lots of people do it.

But I am unsure where to put the "ghost" chain-wheel in the gear sequence. On the inside, or the outside. There seems to be benefits for both.

If I treat the front inner shift as the 'ghost' and adjust the inner limit screw accordingly,..... then it is quite hard to set the gears up properly because I am starting off on on imaginary position.

If I set the shifting up so that the 'ghost' chainwheel is on the outside, then I run the risk of throwing the chain off the outside if I don't keep an eye on the cable tension and outer limit screw. But the benefit may be that the final ghost shift can actually be used as a 'trim' if required, to just push the cage out slightly if it rubs when moving the rear rear to the small cog.

Any recommendations would be Greatly appreciated. Thanks so much.

Your problem is not with the chainset or derailleur, it is with the shifter, which is for a triple. I'm not aware of any way to make this work happily with a double chainring.
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Re: newbie question about double chainwheel with triple shif

Postby nickobec » Mon Sep 17, 2012 7:05 pm

Go with the ghost on the outside

pembo6 wrote:If I set the shifting up so that the 'ghost' chainwheel is on the outside, then I run the risk of throwing the chain off the outside if I don't keep an eye on the cable tension and outer limit screw.

The same can happen with a regular double shifter, if you don't keep an eye on the cable tension and outer limit screw.

Most double shifters, let you trim inside, for those times on the big ring and larger cogs on the cassette. you trim outside for big ring and little cog. One thing you will have to get use to when you upgrade. But until then set it up (and the first few times setting a FD is a fiddley nuisance) and ride the bike.
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Re: newbie question about double chainwheel with triple shif

Postby sblack » Tue Sep 18, 2012 12:32 pm

pembo6 wrote:I run the risk of throwing the chain off the outside if I don't keep an eye on the cable tension and outer limit screw.

As cables tend to stretch over time this is more likely to be a problem on the inner ring, the problem with the outer ring if the cable isn't adjusted for the stretch is that you won't be able to shift up into the ring at all and will be stuck on the small ring. For this reason I see the advantage being to setup the ghost shift on the outside as if you find yourself stuck mid ride with the cable having stretched to this point you could use the ghost shift to change up to the big ring.
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