Selecting a Front Derailleur for the Stoker tube
12-04-16, 11:12 AM
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Selecting a Front Derailleur for the Stoker tube
I just got a never-built steel Meridian frame, and I'm making plans for it. It has a very oversized tubeset from a vintage road bike point of view, and I think the stoker seat tube has OD around 35 mm, but I haven't measured it yet. It will need a 29.2 mm stoker seatpost.
I wonder if any special front mech or a front mech mount is needed, based on the OLD and hence chainline. I haven't tried to buy BBs yet, so I don't really know how the chainline will come out, but just based on the frame OLD, it should be about 7 mm more than the norm for a 130 mm road frame, so around 48 to 50 mm.
Is there a need for a special offset front derailleur to accommodate this width?
Do I have to watch out for a front derailleur with a cage that has a special wide range of motion?
I'll be building it with a Sugino XP tandem triple crankset.
I'm an experienced road bike guy, but brandem new to tandems!
I wonder if any special front mech or a front mech mount is needed, based on the OLD and hence chainline. I haven't tried to buy BBs yet, so I don't really know how the chainline will come out, but just based on the frame OLD, it should be about 7 mm more than the norm for a 130 mm road frame, so around 48 to 50 mm.
Is there a need for a special offset front derailleur to accommodate this width?
Do I have to watch out for a front derailleur with a cage that has a special wide range of motion?
I'll be building it with a Sugino XP tandem triple crankset.
I'm an experienced road bike guy, but brandem new to tandems!
12-04-16, 05:59 PM
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I don't know, but I don't think so. If that were true FD's would come with designations for their intended purpose and they do not as far as I am aware. Why not Google the spec sheets of some tandems and see what model FD's they are using?
12-05-16, 06:31 PM
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A 34.9mm seat tube is typical, so you will be able to find many road FD clamps that will fit that size.
You didn't mention which mfr/# gears you wish to run, but as an example, the Shimano Ultegra 9 or 10 speed mechanical triple FD has enough range to cover that chainline without need for a special offset. Santana frames with 160mm rear spacing and matching wide crank/BB widths are the only road frames I know of that may need a special wide offset clamp.
For seatposts, if you wish to use a more standard 27.2mm road seatpost, then don't sweat it and add a seatpost shim.
A 34.9mm seat tube is typical, so you will be able to find many road FD clamps that will fit that size.
You didn't mention which mfr/# gears you wish to run, but as an example, the Shimano Ultegra 9 or 10 speed mechanical triple FD has enough range to cover that chainline without need for a special offset. Santana frames with 160mm rear spacing and matching wide crank/BB widths are the only road frames I know of that may need a special wide offset clamp.
For seatposts, if you wish to use a more standard 27.2mm road seatpost, then don't sweat it and add a seatpost shim.
12-05-16, 06:52 PM
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Meridian has been out of business 16 to 17 years, based out of Bend,Or. most of there seat post at that time I believe where 29.8 hope this helps.
