Tandem rear 3rd brake query

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greyingbeard
Posts: 851
Joined: 24 Mar 2015, 10:41pm

Tandem rear 3rd brake query

Post by greyingbeard »

Im looking at adverts for tandems. Convinced that they ought to have a drag brake but many dont.
Whats involved in fitting one ?
Am I likely to need an entire rear wheel, rear triangle splayed, attachment point on lhs chainstay ?
In other words, not practical for a starter bike ??
Dave W
Posts: 1483
Joined: 18 Jul 2012, 4:17pm

Re: Tandem rear 3rd brake query

Post by Dave W »

Depends on what brakes it has whether you need a drag brake and where you intend to ride it. Our first Tandem had a drag brake and cantilevers. I had to take the drag brake off to stop Mrs Stoker squeezing it on. I upgraded it to Vee brakes. Our newest tandem came with cantilevers and no drag brake - I upgraded to big discs.
Most will tell you on here you must have a drag brake for alpine passes etc.

I have a nearly new Arai drag brake in the garage that is probably worth more than the bike if Ebay prices are anything to go by. You need a hub with the threaded part to screw them on to.
Brucey
Posts: 44521
Joined: 4 Jan 2012, 6:25pm

Re: Tandem rear 3rd brake query

Post by Brucey »

some machines come equipped for a third brake to be fitted but many budget machines don't come with this facility.

If you have no provision for a retro-fit brake then it is as you say, you need a load of stuff to have a third brake available.

However in all fairness buying a decent drag brake isn't that easy these days anyway. The Arai brake is NLA now and it isn't clear that alternatives to this are in the same league.

cheers
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rjb
Posts: 7200
Joined: 11 Jan 2007, 10:25am
Location: Somerset (originally 60/70's Plymouth)

Re: Tandem rear 3rd brake query

Post by rjb »

Our previous tandem a Dawes Super Galaxy of 1980 vintage came equipped with an arai drag brake operated by a barend gear lever. We are not heavyweights (combined weight of the 2 of us about 135kg) but i did not find it to be very powerful. Going down a 1 in 4 could be quite scary, the bar end lever pulled tight before the decent then using the front and rear cantilevers operated by individual levers on the handlebars. I had control of all 3 from the front.
We now have a Dawes Discovery tandem with just V brakes front and rear operated by the pilot. These are far more powerful than the previous galaxy and although it has provision for a drag brake (braze ons and a screw thread on the hub non drive side) we don't need it.
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
Brucey
Posts: 44521
Joined: 4 Jan 2012, 6:25pm

Re: Tandem rear 3rd brake query

Post by Brucey »

the Arai brake would originally have been set to work from one brake lever and both the cantis from the other, I think. That is how my Super Galaxy tandem came equipped originally IIRC. A conventional brake lever can generate much more cable tension vs a bar end lever, so the brake comes on that much harder. I would suggest that this arrangement may be better suited to shorter steeper hills.

The 'bar end lever on the drag brake' arrangement works best on alpine descents where the gradient is usually around 10%. It is best to leave this control to the stoker, unless you have three hands! On shorter steeper hills the stoker can apply more cable tension (more than the lever can be set to give in friction mode) as required, up to a point.

Considering the braking forces; a hard stop would be 1G and on a tandem the front and rear wheels might contribute about half each. On a 1:4 hill you need ~0.25G in order to hold the speed constant, which is a big ask from a drag brake alone, getting on for its full power when connected to a proper brake lever, (and vastly more than a friction gear lever would normally manage).

Other brakes can have a much higher Mechanical Advantage than a drum type drag brake and this may instil some sense of confidence. However such confidence is somewhat misplaced IMHO. On any kind of long descent it is not outright braking power that is the issue, it is heat build up in the brake. Rim brakes and disc brakes (alone) can have a surprisingly small heat capacity; on a tandem a pair of moderately large discs or a pair of rim brakes can overheat in about 500ft of vertical descent.

A third brake (of almost any kind) can at least be used to hold the speed for long enough for the main brakes to cool off and this will then allow the machine to be brought to a halt safely using the other two if necessary.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
tim-b
Posts: 2093
Joined: 10 Oct 2009, 8:20am

Re: Tandem rear 3rd brake query

Post by tim-b »

Hi

If there's one thing that a tandem excels at then it's going downhill. I've heard of (but never saw) instances where tyres have blown off tandems due to heat build-up from rim brakes, which is where a third brake comes in for me. I didn't want it to be a full brake, just something to take the edge off the speed and strain off the rim brakes

My 1980s Dawes SG Tandem also came with the front and rear canti brakes off one lever and the Arai drag brake off the other. I wanted separate levers for each brake but my son was too young to reliably use the drag brake
I used conventional F and R brake levers with the cantis and put the drag brake on a ratcheting gear lever. It made a useful handbrake when loading with an element of theft deterrence

If you accept Brucey's assertion on disc brakes (I don't have the information to hold a view either way) then you may consider a third brake necessary for that application as well and I'd recommend the Tandem Club Website for information. You can post on their discussion board without being a member

Regards
tim-b
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Brucey
Posts: 44521
Joined: 4 Jan 2012, 6:25pm

Re: Tandem rear 3rd brake query

Post by Brucey »

BTW there is a good reason for not having an especially powerful drag brake; if you have it set to drag strongly (either from a friction lever or via the stoker) there is an increased risk that the rear wheel might lock up momentarily (on water, diesel, ice etc) without there being a good chance to let the brake off quickly and correct the skid.

if you look at the disc brakes on a small-ish motorcycle, these are built to stop something about the same weight as a laden tandem. If your tandem brakes look like that, then maybe they won't overheat too much. But if they don't, I'd take it as read that there will be circumstances that will overheat them and it is just a question of when and then how benign the failure mode is.

A few years back a chum bought a posh new tandem (about 10Ks worth) that had a state of the art disc brake on the rear wheel. It was just junk; it was OK pottering about in the UK but on longer hills abroad it regularly overheated and gave trouble even when the machine wasn't fully loaded.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
reohn2
Posts: 45158
Joined: 26 Jun 2009, 8:21pm

Re: Tandem rear 3rd brake query

Post by reohn2 »

greyingbeard wrote:Im looking at adverts for tandems. Convinced that they ought to have a drag brake but many dont.

It depends on where you're riding,if you're planning on long steepish descents a drag is a boon as due to the extra weight on board tandems gather speed PDQ,and so the mass needs keeping under control.
A drum/drag is by far the best way to do that,with a friction lever controlled by the captain NOT the stoker.
The drag can set to keep things under control without fear of fading or burnout.Short descents can be handled without a drag especially if you're a light team,good V's or cable discs will handle it OK providing you don't drag them and use a pulse braking technique and alternate front and back.

Whats involved in fitting one ?
Am I likely to need an entire rear wheel, rear triangle splayed, attachment point on lhs chainstay ?
In other words, not practical for a starter bike ??

Most tandem spec hubs have threads on the NDS.Most tandem frames have a lug on the left chainstay to take the reaction arm on the drum,and cable brazeons throughout the frame.
If you planning on a drag/drum you'll need the brake itself(Arai are the best and now obsolete but available s/h or NOS)a friction lever that'll fit conveniently somewhere on the captains H/bars,inner and outer cables,and an anchor point for the outer with an adjuster incorporated(usually sold with a new Arai but can be fabricated.
Most later tandem hubs and frames are usually 145oln or more ie; Santana are 160oln,and are designed to take a drum/drag brake.
Last edited by reohn2 on 2 Apr 2015, 8:45am, edited 1 time in total.
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ChrisButch
Posts: 1188
Joined: 24 Feb 2009, 12:10pm

Re: Tandem rear 3rd brake query

Post by ChrisButch »

Our 1970s Bob Jackson had a very simple arrangement. The main braking was Mafac cantilevers (with longer, tandem-specific pads). The third brake was a simple sidepull bolted to the 'wrong' side of the seatstay bridge. It was stoker-controlled. Rarely needed, as it happened, (even going down the Tourmalet) since the Mafacs were so good (and I suspect we were a tad lighter in those days) Though we did have occasional problems with overheating rims. Anyway, the Bob Jackson solution, though obviously not ideal, is worth thinking about if dropout limitations etc rule out sme of the other options.
Last edited by ChrisButch on 2 Apr 2015, 12:58pm, edited 1 time in total.
reohn2
Posts: 45158
Joined: 26 Jun 2009, 8:21pm

Re: Tandem rear 3rd brake query

Post by reohn2 »

We've done some looonnggg descents on our tandem(upto 10miles) with cantis and V's and a drag,all up weight including bike=175/180kg inc bike.
With the drag set and adjusted now and again as needed during the descent,and using the v's or cantis to scrub off speed for the hairpins.
I've never had a problem with fade and never managed to lock up the rear,though I'm careful in the wet especially when cornering.
I wouldn't like to tackle the same descents without a drag.
Discs(BB7's 203mm rotors)are awesome stoppers for tandem use,but shouldn't be dragged as shouldn't rim brakes.
I've related the story before of our friends front tyre exploding at the bottom of (thankfully) a steep(10%+) 1mile descent into Ironbridge gorge,there were three tandems together two with Arai drags and our friends with two cantis,he was forced to drag the brakes,just at the bottom of the descent the front tyre went off like a rifle shot.Due to his good bike handling skills he remained in control but was very shaken,as we all were :shock:
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reohn2
Posts: 45158
Joined: 26 Jun 2009, 8:21pm

Re: Tandem rear 3rd brake query

Post by reohn2 »

tim-b wrote:Hi

My 1980s Dawes SG Tandem also came with the front and rear canti brakes off one lever and the Arai drag brake off the other. I wanted separate levers for each brake but my son was too young to reliably use the drag brake
I used conventional F and R brake levers with the cantis and put the drag brake on a ratcheting gear lever. It made a useful handbrake when loading with an element of theft deterrence

Regards
tim-b


Our early 90's one was similarly set up and no matter what I did I couldn't get the system to work effectively.
I concluded the idea was conceived by idiots,bought a pair of aero brake levers and a lefthand bar end lever,set the cantis up conventionally and put the Arai on the friction lever.Bliss,problem solved,and as you say also a good parking brake into the bargain :)
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Stradageek
Posts: 1657
Joined: 17 Jan 2011, 1:07pm

Re: Tandem rear 3rd brake query

Post by Stradageek »

I concur on all this advice. Our first tandem without a third brake and only Canti's could not be stopped on a hill steeper than 1 in 6. Our custom Orbit (V-brakes via travel agents and a rear disc) was miles better but when we had to use all three on a long fully loaded descent in the Scottish borders we had to alternate rim and disc to avoid brake fade and still managed to burn out the disc pads.

I've noticed that the rear disc on more modern Orbits is massive!
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foxyrider
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Location: Sheffield, South Yorkshire

Re: Tandem rear 3rd brake query

Post by foxyrider »

Stradageek wrote:I concur on all this advice. Our first tandem without a third brake and only Canti's could not be stopped on a hill steeper than 1 in 6. Our custom Orbit (V-brakes via travel agents and a rear disc) was miles better but when we had to use all three on a long fully loaded descent in the Scottish borders we had to alternate rim and disc to avoid brake fade and still managed to burn out the disc pads.

I've noticed that the rear disc on more modern Orbits is massive!


One issue is that you need more powerful braking on the front and of course tandems can go downhill much faster than solos! Double front brake might be more effective than double rear - just a thought. :D
Convention? what's that then?
Airnimal Chameleon touring, Orbit Pro hack, Orbit Photon audax, Focus Mares AX tour, Peugeot Carbon sportive, Owen Blower vintage race - all running Tulio's finest!
tatanab
Posts: 5033
Joined: 8 Feb 2007, 12:37pm

Re: Tandem rear 3rd brake query

Post by tatanab »

foxyrider wrote:
Stradageek wrote:One issue is that you need more powerful braking on the front and of course tandems can go downhill much faster than solos! Double front brake might be more effective than double rear - just a thought. :D
That's what I did in the 1980s. I had a tandem frame built for me at a time when cantilevers were just not available (post Mafac and pre Shimano) so I had the frame built for 3 Campag sidepulls with 2 on the rear. This was ok but the extra rear brake did not give any advantage so I removed it and put in a front hub brake. So I had a single sidepull front and rear plus a front hub brake. I operated them from normal drop levers for the sidepulls and a child's straight bar lever for the hub. The small lever was mounted underneath and at an angle to the rear brake lever. This meant that from the drops I could use 2 fingers on the rear brake and 2 fingers on the hub brake. This was all I used on Cotswold descents so I still had the front rim brake in reserve. Of course I was much younger in those days and probably braver, but it worked just fine.
Bicycler
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Joined: 4 Dec 2013, 3:33pm

Re: Tandem rear 3rd brake query

Post by Bicycler »

Anybody else think Sturmey Archer is missing a trick here? A tandem version of their drum brakes would fill a niche and they have shown they are capable of catering to small specialist markets. Anybody tried using a normal SA drum as a drag brake?
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