Author Topic: Tandem Gearing  (Read 883 times)

Tandem Gearing
« on: 20 February, 2021, 06:55:08 pm »
Originally posted in 2017 about replacing a Dawes Galaxy Twin, which never happened though hopefully that plan may come to fruition later this. The big questions is what to do about gearing. The Dawes originally came with 48/38/28 chainrings and a seven speed 13-30 freewheel, The freewheel remains the same however the chainrings are now 48/34/24 to give lower gearing. The question is whether to remain with a triple and similar or even lower ratios or go for one of the newer doubles with a much wider range cassette. My concern about a wider range cassette is the jumps between sprockets and also the jump when dropping from the large to smaller of the two chainrings, just wondering what experience people have of this and whether it will be an issue. It respect of a double chainrings have noticed that it is now possible to get a 46/30 tandem combination, thus would probably go for this rather than the more usual 50/34 or 48/34 which would mean not needing such a big  large sprocket, If sticking with triple again probably something like 48/34/24, most cassettes starting at 11 give a top gear of around 100+ ins, not certain anything higher than this is needed. Looks forward to comments

LittleWheelsandBig

  • Whimsy Rider
Re: Tandem Gearing
« Reply #1 on: 20 February, 2021, 07:04:46 pm »
If you run a double on your tandem, you will probably be on 11sp or suchlike. If so, you can have similar jumps to your current 7sp setup with a much wider range cassette e.g. 11-12-13-15-17-19-22-26-30-36-42. Most modern front mechs are rated for 16t double, so the rest of your gear range has to come from your cassette. Triples are virtually dead unfortunately. Bar end shifters or the orphan Tiagra 3x10 and not much else.

Personally I like a road tandem to top out somewhere north of 120” but you can choose whatever you want with suitable chainrings.
Wheel meet again, don't know where, don't know when...

Re: Tandem Gearing
« Reply #2 on: 20 February, 2021, 08:33:02 pm »
It's very hard to give any advice on gearing when I don't know exactly who you are, what is your level of fitness, what kind of rides do you enjoy most. On our tandem, we have a single 40t ring, and an 11-40t cassette. We are very happy with that setup, as it eliminated all front mech related problems, but I am not saying that everyone will be happy with the same setup.

A

Re: Tandem Gearing
« Reply #3 on: 21 February, 2021, 05:55:42 pm »
My tandem (new Oct 20) has 46/30 on the front, and I believe 11-34 11speed on the rear.
Mechs cope perfectly well, using a double on the front is a lot easier than a triple, and I'm surprised how much we can use the 30, on the smaller cogs at the rear, we can spin quite nicely up to 14/15mph.
On my road bike, riding a triple over 20 years, I simply used the 30 for hills, and then on the largest 2 sprockets of the cassette. So effectively there was significant redundancy in the gear combinations.And when in the 50t ring, I never used the two largest sprockets. So 3*11 = 33 gears less 9
unused ratios less another 2 unused ratios = 22 ratios used on my triple. Hence my de-tripling, and moving back to doubles.
Another factor is the advent of the 11tooth sprocket which has made chainwheels over 50t redundant for me, in fact, I'm happy with a 46 - it's a 113 inch gear.
Versus your existing setup, I think you will be very pleased with the performance of a compact double and 11 speed cassette. I cannot comment on durability, but I'm always pleased to wear something out, makes me feel like I've been riding enough!

Re: Tandem Gearing
« Reply #4 on: 22 February, 2021, 09:54:13 pm »
As above, it depends on your fitness level and what you use your tandem for. We use a 3x10 setup with 26/39/50 and 11-36 and use all the gears, although I'd be happy to not have such a high top gear. We're planning on building up a new tandem this year and will probably go for 24/36/48 with 11-36. IMO you can't have too low a bottom gear, but we do most of our riding in the Yorkshire Dales. What I do like about triple setup is that you get close ratios and good chainline. (I should add that I once got a pre-war tandem with a 54" bottom gear up Ditchling Beacon. I was 35 years younger but I would have loved a proper low gear - it's the closest I've ever got to having a coronary on a bike! Going down the other side into Brighton was just as eventful as the brakes were useless). 

Re: Tandem Gearing
« Reply #5 on: 23 February, 2021, 09:54:53 am »
I'm another fan of the triple set-up - in the past, I've converted twin chainsets to triples on some solos just because I like the range of gears offered and that you can maintain a decent chain line.  On the tandem, a wide range of gears is a key factor for me.

We currently have a nine speed cassette (12 - 36) with 46 x 36 x 24 chainrings which gives us a gearing range from under 20 inches to over 100 inches.  As we're at the 'wrinkly' end of the age spectrum, this works well for us.  We can cope with the hills and headwinds with this configuration, which for us is a more important factor than speed.

Spa cycles still offer triple chainsets and I recently bought one from them to replace a Thorn set.  Pretty good value I thought:
https://www.spacycles.co.uk/m8b0s109p4061/SPA-CYCLES-Tandem-Triple-Chainset

I think a triple with a 10 speed cassette would be ideal and would give close ratios, but we've stuck with our 9 speed configuration as changing over to a 10 speed didn't really seem worth it.  If you are replacing the drivetrain, then 10 speed (or more) is a sensible choice.


Re: Tandem Gearing
« Reply #6 on: 25 February, 2021, 05:43:37 pm »
Thanks for all the comments, just for context my wife and I only do day rides and living in central Hampshire that can vary from the hilly South Downs to the relatively flat New Forest. In respect of the current set up we certainly do not need any higher gears if anything something lower would be useful !
Entirely see that going form a 7speed to a 10 or 11 would not necessarily increase the jumps between cogs though could quite easily increase the range, even a 9 speed 11-32 would achieve similar jumps and a wider range !
The uncertainty I have about a double is the effect of dropping from the large to smaller chainring, the difference being greater is it more difficult to maintain momentum which is so much more important on a tandem than solo, any thoughts ?

LittleWheelsandBig

  • Whimsy Rider
Re: Tandem Gearing
« Reply #7 on: 25 February, 2021, 06:00:41 pm »
It depends.

Changing both derailleurs simultaneously during a change isn’t a major drama with STI levers, though you still need to tap the rear upshift lever several times. Compared to barend or downtube shifters, using STI is trivial.

If you run Di2, then you can set it to sequential shifting and pretty much ignore when the front shift occurs.

All the above assumes you aren’t running outside Shimano spec. STI and the rest can get quite sensitive with non-spec gearing. You also need to stay on the ball with hanger alignment and clean gear cables.
Wheel meet again, don't know where, don't know when...

Re: Tandem Gearing
« Reply #8 on: 01 March, 2021, 04:10:13 pm »
Shifting between chainwheels between the 46 and 30 requires several taps on the rear mech to get the next gear in sequence, so yes, a 16 tooth chainwheel difference does take a little getting used too. After 2 or 3 rides, it is second nature. Absolutely not a problem, just a feature.

Re: Tandem Gearing
« Reply #9 on: 10 March, 2021, 03:37:29 pm »
The venerable Rob van der Plas in the Penguin Bicycle Handbook (1983) had this to say about tandem gearing:

"...you will certainly need those gears! It may not seem logical but uphill riding becomes extremely painful on a tandem and the lowest gear never seems to be low enough. However, I feel that for mountain riding it's not so much the number of gears that is important but the 'depth' of the lowest gear. So perhaps the increase in popularity of machines with fifteen-speeds does not really provide the best solution for tandem riding. A ten speed or even a five speed, provided it offers a wide range between the gears may well do just as well and will at the same time offer the additional benefit of less elaborate components which are easier to maintain and more readily available."

When I rebuilt our tandem re-gearing was high priority as it was running an ancient 14-28 Atom 5-sp freewheel and the odd combination of 42/50 rings. The chainset is a Stronglight triple with TA chainwheels running an inner 34T ring for the same-side drive chain. The new gears are 11-36 at the back and 36/52 at the front giving a theoretical range of a 27" bottom gear and a 127" top. However, frame clearance is so tight I've set the rear mech not to use the 11 sprocket so without going back to count teeth as I can't remember if the next one up is 12 or 13, we have a top end of either 117" or 108".  It matters little. We're not a fast team so the upper end stuff is rarely visited. But as Mr van der Plas noted, low enough is never low enough. While 27" is a big improvement on the 40'5" bottom we had before, it would be better if were lower still. 
Meanwhile, shifting between the rings with a 16 tooth difference is within the real if not the quoted capacity of the Tiagra front mech. I had to add a Jtek adapter to make the bottom-pull mech into a quasi-top-pull mech because of the cable routing.  Shifting is from bar-end levers, no indexing.  We have had a few mishaps and thrown chains but I think that's hamfisted spanner twiddling rather than faults in the system.
They laughed when I said I was going to be a stand-up comedian. They're not laughing now.