Need a long cage FRONT derailleur

wtherapy

Hello,

I am using the new O.Symetric chainrings set 50/34 on my road bike, together with the new 105 5800 groupset 2x11 ( http://bike.shimano.com/content/sac-bik ... 0-b-l.html ). Using hydraulic brakes with corresponding ergopowers from shimano for hydraulic brakes (but I don't think this is relevant here).
The front dérailleur has a 16 teeth capacity which should be enough for the stock 50/34 round rings, but not for my o.symetric. They say that 50 extents to almost 55 when it's in vertical position and the small one drop to 31 when it's in horizontal position, thereby requiring a much bigger teeth capacity.
Because of this problem, the big 50T ring can go up to the 10th pinion on the cassette (I know, I don't go that far with it), but the small ring can only go down to the 4th biggest pinion. This is a serious limitation on long climbs. What actually happens is that the chain rubs the upper or lower limit of the derailleur cage when moving out of that limitation (let's say, for example, smallest ring of 34T with a little smaller pinion would rub the lower limit of the cage).
Currently I moved to 44/34 teeth of the o.symetric but this is not enough for long rides on flat areas.
I want to know if anyone here has any idea on how to overcome this problem and / or where to get a 'long cage' front derailleur for 2x11 system that would suit my chainrings. Can the cage be extended with a custom build?

arlowood

wtherapy wrote:

Hello,

I am using the new O.Symetric chainrings set 50/34 on my road bike, together with the new 105 5800 groupset 2x11 ( http://bike.shimano.com/content/sac-bik ... 0-b-l.html ). Using hydraulic brakes with corresponding ergopowers from shimano for hydraulic brakes (but I don't think this is relevant here).
The front dérailleur has a 16 teeth capacity which should be enough for the stock 50/34 round rings, but not for my o.symetric. They say that 50 extents to almost 55 when it's in vertical position and the small one drop to 31 when it's in horizontal position, thereby requiring a much bigger teeth capacity.
Because of this problem, the big 50T ring can go up to the 10th pinion on the cassette (I know, I don't go that far with it), but the small ring can only go down to the 4th biggest pinion. This is a serious limitation on long climbs. What actually happens is that the chain rubs the upper or lower limit of the derailleur cage when moving out of that limitation (let's say, for example, smallest ring of 34T with a little smaller pinion would rub the lower limit of the cage).
Currently I moved to 44/34 teeth of the o.symetric but this is not enough for long rides on flat areas.
I want to know if anyone here has any idea on how to overcome this problem and / or where to get a 'long cage' front derailleur for 2x11 system that would suit my chainrings. Can the cage be extended with a custom build?

There is the option to consider fitting a triple FD

http://www.wiggle.co.uk/shimano-tiagra- ... erailleur/

These can cope with up to a 20 tooth difference (say 50/40/30 triple chainset) so might go some way to dealing with your problem although at the extremes you seem to suggest a 24 tooth difference.

Some in the pro peleton are using O Symetric rings so the problem must have a solution somewhere.

wtherapy

Hi,

thanks for the answer, I was looking at https://www.rosebikes.co.uk/article/shi ... aid:516304
My ergos are https://www.bike24.de/p1141894.html - I don't know whether they will work together or not.

trailflow

Can you post a picture of the problem ? Do you mean the chain is touching the bottom bridge of the FD ? Is the FD positioned as close to the big chainring teeth as possible at the chainrings widest point ?

The 5800 long arm FD's are designed to be mated with the cable pull of the shifter. The ultegra FD-6703 is designed for a different cable. It may work but not optimally and the trim action may be effected. Also if the shifters have to work harder (no long leverage arm) the internals may be put under more stress.

svetty

Given that there is limited objective data to support the claims of improvement using oval chainrings - and you have detailed very clear real-world drawbacks arising from their use - the sensible option seems clear.......