Cave

I'm considering upgrading my horizontal-dropout, bolt-on derailleur hanger tandem (rather than shelling out for a comotion or thorn).

2 options I'm considering:

1. Derailleur drivetrain.
1(a): Braze on derailleur hanger, keep horizontal dropouts, run 135mm freehub/cassette
1(b): Major re-work of rear triangle with vertical dropouts +/- respacing to 145mm

Planning to run XT (possibly XTR) in rear; deciding between Tiagra and XT up front.
Still deciding on single/double sided drive train and chain tensioning strategy.

2. Rohloff upgrade.
This may also involve frame work at the back.
Keen to use single-sided drive chain and eccentric BBs for tensioning if we go this way.


Thoughts, anyone?

(Thanks for previous comments on the Comotion vs Thorn thread.)

dbohemian

I would consider either leaving it as is or the Rohloff option.

Some of my thinking.

1. A brazed or welded on hanger would never be a strong as the rest of the drop-out. When I have seen this done in the past it is sometimes problimatic (it comes off) Also, the relationship of the hanger to the slot can be important. It should sit quite forward on the drop.

2. I never like re-spacing to such an extent. 130-135. That can work on non-heattreated tubing but 10mm can be a push on some rear-ends and in essense when I do that I am damaging the chainstays of the bike.

3. The Rohloff may work with your existing setup with very little modification. They have a torque plate that meshes with a brake disk tab. Even if you don't care to use a rear disk a framebuilder could weld on a disk tab, you could order the appropriate Rohloff and use one of the mounting points of the disk tab to secure the torque tab. It would be very clean, you would not have to change the drops or respace the rear end.

4. You may consider using the Saint system from Shimano. I don't have any direct experience with these but the rear deraillieur is attached not to the drop but the rear hub axle. Maybe this could work for you and it would cost far less than a Rohloff.

Your friendly framebuilder

Dave Bohm
Bohemian Bicycles

Cave

Thanks Dave, I might look at the Saint gears as well.

Re rohloff torque arm - sounds like your suggestion of adding a disc brake tab is the most practical, but:
(1) Can it just bolt to the chain stay, or is this not secure enough? (ie. some sort of clamp bolted around chainstay)
(2) How big a deal is it to remove the old dropouts and braze or weld new dropouts? (I think the frame is welded rather than brazed.) Rationale here is to use Rolhoff dropouts eliminating the need for a torque arm.

zonatandem

Rohloff system will set your back around $900 without any additional work needed.

dbohemian

Hi Cave,

1. There is a version with a torque are that can be bolted directly to the chainstay. (with a provided clamp) Certainly this would work.

2. It can be time consuming to remove a set of TIG welded drops and replace. Since there is no easy way to melt them out (like with a brazed drop) you have to surgically grind them out without damaging the existing stay. Then, hopefully your new drop will fit the existing angle of the chainstay to the seatstay.
It can be quite time consuming. I typically charge upwards of 200 dollars to do it, if that helps. Also you would be damaging your paint and if you wanted something other than a rattle can job you would have to add that in as a cost.

3. The disk tab would also damage the paint to some extent but it could be done so that a quick touch up job would make it largely unnoticeable.

Hope that helps.

Dave Bohm

TandemGeek

The frame is the heart & soul of a tandem, or just about any other bicycle for that matter.

Don't throw good money after bad. Your current tandem's frame does not sound like something that has much left to offer beyond any utility it has already provided, never mind being something on which to start hanging new components. Science project comes to mind and while sometimes enjoyable, they rarely yield a product that is worth the investment of resources and sweat equity or that is as reliable as a purpose-built machine of an equal investment of money and the value of your time... asuming you place a value on your time.

Therefore, and since you asked, I'd suggest you establish your budget, price your components and see what's left over relative to the cost of a frame. At that point, decide what your options are for obtaining a reliable, quality frame that will meet your needs. If the amount of funds available can be used to acquire a new steel frame built to your specfications, all the better. If you find that you could come out ahead by picking up a better-quality, second hand steel tandem and off-setting some of your component costs by simply using the ones already attached to the new second-hand tandem's frame, then that may be your path forward. If a new, purpose built 26" tandem with an OEM Rohloff hub from Thorn or some other builder was in reach, even if some compromises on paint or the grade of other components was required, then you're all set.

Regardless, predicated on what you've described as your future use of the machine, you truly want to start with a more contemporary, better quality steel frame. Thorn, Santana, or some other quality brand's frame should prove to be adequate. I'd include aluminum frames like those from C'dale; however, you sound like someone who would better off with an "easier-to modify in the future" material like steel.

As for the Rohloff, if I didn't already have a quality frame to hang one on and was committed to the design, I would definitely pursue a builder who has successfully integrated them into their tandems. Andy Balance and Thorn have obviously taken the lead in the UK by offering the Rohloff as an OEM fitment on their frames. Retrofitting is certainly doable but I would definitely run all of the numbers on material costs and labor before heading down that path given where you are today.

Bottom Line: You can't make a silk purse out of a sow's ear.

Cave

Sage advice.

We still have to test ride the Cannondale and a Raleigh tandem. I'm pretty much resigned to forgetting about the Co-Motion and the Thorn, perhaps we can reconsider in 3-5 years but not now.

Our frame is very stiff and fits us well, apart from the dropouts it is better than all of the sub-$3000 tandems we have tried so far (despite costing us just $350 second hand!), hence "heroic" efforts are justified if the cost stays below AUD$2000 or so.

The Rohloff will work with on our frame with a chainstay-mounted torque arm. An XT gruppo is about AUD$1300 compared to about AUD$1650 for the Rohloff ($33 for new brake levers, about $150 for rear rim/spokes/wheelbuild, extra for new BBs/cranks but can defer that cost), with a price that close I'll probably go for the Rohloff if we decide against the Cannondale (AUD$4500).

Maybe I should just look for a job in the US or UK.....

Cave

Sorry, I only work on livers, not bike frames...