Azrael71

Hello,
Had our offroad tandem a couple of years now and are just getting back into it after a break.
I am looking to upgrade the groupset from a mix of slx 3x9 speed and the original chainsets mainly for a larger range.
I am hitting a wall with finding decent offroad tandem cranksets.
Would ideally love to run XT 2 or 3x10 or 2x11 speed but really not sure how to achieve this.
Any help, advice or guidance, greatly appreciated.

Thanks in advance

twocicle

Middleburn cranks. go to mtbtandem.com and/or call Alex Nutt.

Another choice is davincitandems.com (Todd).

Azrael71

Thanks, seen the middleburns, even had a pair back in the day, not really what I am after for this bike.
Seen others on here using di2 so thought they may have been using hollowtechII cranksets.

akexpress 

The RS8 new middleburns use standard hollow tech BB in 24mm I have the old style square taper on our full suspension Ventana mountain tandem and new version is a complete redesign. I am putting the new ones RS8 on a new Calfee DI2 adventure tandem and they are very versatile 1x,2x,3x because of the their modular design. Call Alex at MTBtandems.com

twocicle

Yeah, I should have been more clear about the newer Middleburn RS8 tanden setup not being the old square taper. I believe the 24mm axle is a ISIS interface at both ends and the crank arms attach to that. It uses standard external bearings such as with the Shimano HollowtechII. You can get the axle in various lengths. I think this would be the best setup for a mtn bike. Santana should be doing the same thing with their carbon tandem cranks, but Billyboy diehard is sticking with the obsolete Octalink BBs which are a rare thing in tandem sizes.

Alex @ mtbtandems puts together lots of mtn tandems and provides these cranksets to various builders (like Calfee for one).

Azrael71

Cool, thanks all.
Just read that middleburn have closed so best get a wriggle on.

Thanks again
Mick

akexpress 

Where did find that info?

Azrael71

Their site has been shutdown and the news is all over the Internet this side of the pond

Azrael71

https://cyclingindustry.news/uk-cycl...s-closes-down/

twocicle

Freekin' hell. There goes another source for tandem cranks. The RS8 w/isis axle looked like a winner.

Good catch on the 1 day old news.

This isn't April fools day is it?

fietsbob

Put in a Rohloff and you can use 2 regular cranks , dont even need the cross over drive..

twocicle

True, you can go with same-side drive for a non-triple or Rolhoff setup. The compromise is usually having to use bigger steps between the gearing. If you can deal with 2.5mph differences, then ok.

fietsbob

Obviously don't own one..

Since the ratios are a % of the next higher gear, the lower gears are closer together than the higher ones .

twocicle

Correct, not sold on it. As the specs show, the ratio/% steps are still very gappy, even with their 14 gear version. No way can anyone say with a straight face that it provides a close ratio. Across the board trend is super wide range at the expense of close steps, even with Rolhoff.

justcrankn

??? 13.6% is 13.6% regardless of which side of the range it's on.
If the OP is okay with SLX and XT then he'll be okay with the jumps on the Rohloff. But the Rohloff has other drawbacks and it's not straightforward to mount onto 145mm dropouts.

fietsbob

with a 3 speed you have bigger 'gaps' It's simple to adjust your speed to make the gear you are in Feel right

Feel too low, slow down a bit , next higher one too big, speed up a Bit.

really OCD ? fit 2 chainrings 6.8% apart.. half the 13.6% of the hub engineers design.

twocicle

Adjusting your speed to suit your gappy gears does not work when riding with others in a group.

Shifting front rings back and forth in order to half step big gaps in your rear cluster/hub is impractical and nobody does this IRL.

mtseymour

The Rohloff is a good option for city riding and touring due to its low maintenance and ease of use. But the Rohloff is not suited to off-road tandems because of its large gear jumps (compared to 2x11 or 3x11), heavy weight, and sluggish shifting. The Shimano and Sram 11sp drivetrains are popular for fast and technical riding for good reasons.

fietsbob

Oddly enough people take their tandems on long adventure tours like to pre Columbian Peru & the Andes.

but they are all probably Germans and dont seek prior approval here..

the 36 hole hub shell was added as an option because tandems were seeing use like that..

twocicle

Perhaps post some realistic suggestions that could be taken seriously instead of recommending using 2 chainrings of only ~3 teeth difference (6%) and shifting those between each rear ratio.

For sure Rolhoff has its upsides, but close ratio is not one of them. The ratio steps are not all that different than with a SRAM 11-36 cassette (has a swing of 15-16rpm from one cog to the next in some positions) which we have used for very hilly, steeper terrain. It is definitely not ideal for riding in a group when the pace dictates either 90rpm or 105rpm cadence. Off on our own the gaps were somewhat easier to adjust to.

twocicle

Reposting new announcement. Middleburn will live on...

Middleburn | Mountain bikes & components by BETD