Yet Another Cycling Forum
General Category => Freewheeling => Tandems => Topic started by: dat on 17 July, 2020, 08:58:49 am
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I bought a tandem (Dawes horizon) for me and my wife a month ago and we’re loving it. It doesn’t quite fit her though and the brakes are poor for the hills in Cornwall. We still did 50 miles yesterday though which is double anything she has ever done before.
We have just purchased a Thorn Raven S&S Rohloff bike and it’s fitted with XTR brakes and CSS rims. The Rohloff hub can also take a disc as can the frame. What would people normally do, use a thumb shifter like on my previous ICE trikes?
Small side question. We don’t drive and want to use the S&S frame to take it on trains I presume we can just book it in as two bikes?
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I've used a thumb shifter for drag brakes in the past, yes.
Round these parts (Sussex) there's no booking required (or available) to get a tandem onboard a train.
On services where booking has been required I had to book two spaces even though the tandem was in one piece. Services such as Great Western (or whatever they're called) to Cornwall have/had a guards' van which could easily accommodate a fully assembled tandem.
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Not got a drag brake on mine but I've seen a thumbshifter used. The other option is to fit a brake lever to the stoker's bars but that is fraught with communication issues.
Generally rail companies forbid tandems, but as they all have different rules you will have to check. If you are allowed on, in Cornwall you will have GWRs ICE abominations to deal with anyway. These have tiny bike compartments in which you are supposed to hang two bikes. It isn't impossible to do this, just inordinately difficult. Unless you are extremely lucky with the fold geometry it's not going to work with a folded tandem. If the folded machine is sherter and narrower than two solos you might be able to fit it in the space horizontally, but don't count on it.
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I have a Thorn Raven tandem with a similar specification to yours.
Most train operators will expect you book it on as two bikes, I've seldom had to actually split it for train journeys as the most of the trains that run through Newcastle have decent bike stowage, (*new trains just introduced on the East Coast Line might change that).
I've been considering a second thumb operated rear disc brake myself but haven't bothered fitting one yet as I've never felt the bike lacking in stopping power. I guess if I were tackling long alpine decents it would be useful but round here, (Northumberland) it doesn't seem essential.
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I remember, years ago, we had a work ride to watch the rowing bumps near Cambridge. Two colleagues, (6 ft plus, ex-rowering and ex-rugby players) rode a tandem, and seemed to be making hard work of it. Eventually the tandem suffered a rear wheel puncture, and as I had tools, I fixed it.
It was when I burned my hand on the hub, they realised they had had the drag brake on all the time. :facepalm:
That was a friction gear lever type. ::-)
Hope this helps. :demon:
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I remember, years ago, we had a work ride to watch the rowing bumps near Cambridge. Two colleagues, (6 ft plus, ex-rowering and ex-rugby players) rode a tandem, and seemed to be making hard work of it. Eventually the tandem suffered a rear wheel puncture, and as I had tools, I fixed it.
It was when I burned my hand on the hub, they realised they had had the drag brake on all the time. :facepalm:
That was a friction gear lever type. ::-)
Hope this helps. :demon:
I once struggled to get up Leith Hill under similar circumstances, although the drag brake was a thumb shifter type, operated by the stoker. I think that we got as far as we did is a measure as to how efficient the drag brake (Arai drum) was on that bike.
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I guess I’ll hold off on picking up the needed parts until I’ve given the brakes a go.
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I have just acquired a similar Thorn. It is my plan to add a mechanical disk such as an Avid BB7 and an extra brake lever for me, the stoker.
I haven't decided yet whether to make the disk the main brake with the XTR v brake the drag or just make the BB7 the drag.
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Curiosity, how much was yours? I feel I paid the higher end of what is reasonable at £2100 but it will hopefully last.
https://tandem-club.org.uk/forSale?cmd=view&id=444
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We bought one second hand early last year. We paid slightly less than that, but only slightly.
I too have been mulling over putting on a disk brake. For us though, it means changing the end cap on the Rohloff first. If we do, the disk will be the main brake, the V-Brake will get a thumbshifter, so it can be used as a parking brake, or an emergency brake. The CSS rims do not appear to be much good in the wet with the V brake.
I don't think I'd want to use either the V brake or a disc as a drag brake. Too much heat. Our old tandem has an Arai, and that is a big lump of metal, and has the stubby little cooling fins.
My daughter and her husband bought one last year too, for very much less, but they have had it resprayed to fix rust that was developing on the frame, and they had to have the Rohloff reshelled, by which time they have spent pretty much what we did. Of course it does mean that they have the colours they wanted.
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I should add that price is hand delivered to my door that is a 170mile round trip! This was important to us as we choose not to drive which means getting any large bike can be a PITA.
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Curiosity, how much was yours? I feel I paid the higher end of what is reasonable at £2100 but it will hopefully last.
https://tandem-club.org.uk/forSale?cmd=view&id=444
It was a little cheaper than yours and it will be delivered on 9th August by a special courier known in these parts as The Velomancer.
Tandems are strange beasts because their spec makes them more difficult to shift. Ours is a L/L, not generally a popular combination.
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A word of caution! A disc brake is NOT a proper drag brake like the old Arai drums used to be. You have to use the disc for short intervals and let it cool down in between. Otherwise the disc will warp from overheating and possibly lock the rear wheel. On our tandem, the disc is operated from an mtb brake lever on the (flat) stoker bar. S use it only for short runs when I ask her. You really need to talk to each other!
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Maybe the drag brake on the rim then?
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I really would not use a rim or a disc brake as a drag brake.
The old Arai drag brakes were terrific for moderating speed on long descents, they were designed to produce a low but constant braking force and were able to absorb and disperse the heat produced by continuous braking.
Using rim brake in that fashion could overheat the rim and cause a blow-out. Using a disc in that fashion can warp the disc and boil the oil, (if not mechanical).
The best approach for a third tandem brake these days is to treat it as an alternative of redundant rear brake.
When used as an alternative brake descending big hills the idea is to moderate speed by alternating between all three brakes, thus ensuring that no one brake surface becomes too hot.
Used as a redundant brake means that its simply there in case of primary brake failure.
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Interestingly, we once owned an ICE tandem trike which was fitted with two rim brakes on the rear wheel which were both ratchet operated.
An odd arrangement really as;
a. recumbent trike rear brakes are only ever used as parking brakes, all the stopping power is in the two front brakes.
b. even if one was intended as an alternative or redundant brake it’s still acting on the same surface as the primary.
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When I had my Moulton ATB converted to a tandem with a central insert into the separable frame, a Rohloff hub with disc brake was also installed. The original rear rim brake was retained with the lever on the stoker's bars, as an emergency extra brake. This has never been used as we don't do major ascents and descents, but it provides reassurance.
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Deep section aluminium rims (non-ceramic) have enough mass and surface area to avoid overheating when used on tandems doing long descents. Ditto disc brakes with a 200+mm rotor.
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My daughter and her husband bought one last year too, for very much less, but they have had it resprayed to fix rust that was developing on the frame, and they had to have the Rohloff reshelled, by which time they have spent pretty much what we did. Of course it does mean that they have the colours they wanted.
We did the same a few years ago. Best bargain to ever come my way, Rohloff tandem with S&S couplings and many other extras for less than the price of a new Rohloff.
The paint was in a shocking state but once Bob Jackson had done their thing it was like new.
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Deep section aluminium rims (non-ceramic) have enough mass and surface area to avoid overheating when used on tandems doing long descents. Ditto disc brakes with a 200+mm rotor.
I have noticed that many tandems now seem to have rather large rear discs and wondered about their heat shifting abilities. I've only ever seen them set up with hydraulics though, anyone using a big disc with a BB7 or similar?
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Avoid tandem disc brakes with plastic components, both cable and hydraulic. They melt in severe terrain, killing the brake surprisingly quickly. BB7s use plastic adjusters, though the main mechanism is metal.
Last century, I had to walk out a disc MTB tandem several times after various brake and disc failures. It was a painful learning experience... Brake technology has improved but there are still many disc brakes with inherent weaknesses.
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OK, let's be more pedantic. Having read the jdtandems view on brakes as well as many others, I would prefer to swap my rear v-brake for a rear cable disk. The rear v brake will be left in situ as a backup brake and for any cheek-clenching extra duties.
I don't think that we will have the need for a traditional drag brake to be honest.
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We are just back tonight from a week in the Pyrenees, and I can now say two things for sure:
1)A third brake is an absolutely necessary item.
2) For a heavy team with heavily loaded panniers, two rim brakes plus one disc may even not be enough.
Let me explain. On all long descents, we use the three brakes in turns to let them cool down in turns. On one long descent, where we lost 300m of altitude in 5 km, S told me that the disc smelled like it was toasted, but everything went fine anyway. Then, the next day, on a very steep and twisty secondary road, I had to keep braking all the time, until we blew out the front tube. Fortunately, only the tube was damaged, the tyre was fine, so we changed the tube and continued the ride.
What we didn't realize at the moment was that the overheating probably weakened the rim tape enough, so the next day, another puncture due to the rim tape collapsing through a spoke hole. I saved the day by putting a piece of old tyre between the tube and the punctured rim tape, and we kept riding while praying for no other spoke hole decides to swallow a tube before we reach the next bicycle shop. Then we bought new rim tapes, and nothing bad happened until the end of the tour!
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Velox rim tapes, rather than plastic, are the best option for tandems. They seem to be mostly immune to high temperatures.
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Yes, we had plastic rim tapes, and I think we will change for cotton tape as soon as we are back home.
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Our tandem does not have a drag brake. It was scary when all it had were the original MAFAC cantilevers. I upgraded to SunTour self-energisers, then added a third brake - an ancient Weinmann 500 sidepull salvaged from my old Falcon. It is controlled from the stoker's bar, and experience shows that it works ok so long as you have a trusting/compliant/obedient stoker. An autonomous stoker who thinks they can decide when braking is required is a disaster waiting to happen. DAMHIK...
Arai are hard to find, but do come up now and again on ebay. In their absence, SJS list as an alternative a Karasawa screw-on drum brake for 49.99. But don't be fooled: precisely the same thing can be found on Amazon for the princely sum of 14.60.
https://www.sjscycles.co.uk/brakes/karasawa-screw-on-tandem-drum-brake-replaces-arai/
https://www.amazon.co.uk/sourcing-map-Electric-Scooter-Bicycle/dp/B07L8PD2Q5/ref=sr_1_3?dchild=1&keywords=bike+drum+brake&qid=1598957626&sr=8-3
Compare and contrast..
I'm in the process of building another tandem so found some twin-threaded hubs with the aim of using one of those - not from SJS! - as a drag brake. The compromise will be being forced to use a screw-on freewheel too. It's a budget build for occasional use so I think we can get away with another part from the box of bits in the shed.
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I have never seen this^^ Karasawa brake for true, but judging from the photos, it is made of thin stamped sheet metal, while the Arai was a beefy cast metal thing. Calling this a substitute for Arai drum brakes is probably a bit optimistic.
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It certainly looks nowhere near as hefty as an Arai, which is a substantial lump with plenty of finning for heat dissipation. SJS include the warning that their Karasawa can get pretty hot, but that heat won't be anywhere near the rim so one of the principal reasons to have a drag brake - avoidance of popping the tyre off - is, er, avoided. If this can be achieved by shelling out a mere 14.60 I reckon it's worth a try. It reminds me of a screw-on alternative to Arai that aeons ago was available from the Richmond Cycles catalogue back when they were offering those oversize Balance hubs for tandems. Eek, that was a long time ago, around 1984 or thereabouts. (Have I really gone and got that old and how did that happen?)
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Somebody should molish one that fits to a disc brake mount...
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Somebody should molish one that fits to a disc brake mount...
:facepalm:
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The Amazon one is a '90' whereas the SJS one is a '108'. I believe that this refers to the drum diameter.
It looks like you can get the same model as the SJS one (BSZ108) from Aliexpress. Click on the second 'color': https://www.aliexpress.com/item/4000974788731.html
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Somebody should molish one that fits to a disc brake mount...
Oh of course, I quite forgot that carbon blingy-thingy with disc mounts lurking at the back of the shed. Silly me. I'll strip that down instead of rumaging in the parts bin for the old skool stuff...
Meanwhile, daft as it sounds, Kim, you're not the first to suggest this, as the Q&A on the SJS page shows:
Can this be screwed to a six-bolt disc hub?
By Jon
29 Jun 2018
Just wondering if the two holes either side of the threaded centre of this hub will enable it to be screwed to a standard six-bolt disc hub (I can't find any info online on the spacing and diametre of these two holes).
SJS Customer Service:
No, this will not fit a 6 bolt disc hub.
Thanks
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ISO disc brake BCD is 44mm, considerably smaller than the existing holes. It looks at first glance like the ISO holes would end up on the dished area of the backplate, given the threads are about 35mm. You would need a tapered adaptor as a minimum. Who knows whether there is enough frame clearance at the edge of the drum though. The drum is a bit wider than a disc.
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Just a point about the CSS rims DaT says are (or were?) on both wheels of the Raven Twin.
I put one on the back of our Thorn Adventure to replace a worn out Sun Rhyno (using the old spokes) and it has been a great success but I would not want them for both wheels. Once they have been used for a while, not so long a while with a tandem, they get smoothed off and after that although they still give very good braking in the dry and in light rain, they are less good once there is heavy water around. The Kool Stop special CSS blocks are a bit better once the rims are smooth than the Swiss Stops blues and SJS has the thicker R16 V2 version of the Kool Stop blocks which are good with the Andra 30 rim width.
With the CSS and appropriate blocks the rim looks like it should last for many X 10,000s and the blocks last well too making the combination good long term value compared to a normal alloy rim.
An option for control of a cable disk is to use a road type disk brake and one of the auxillary levers (cross levers) as a primary lever so you have two brake levers on the left of the captain's bars. I've found road BB7s work well with this set up and it has the advantage that you are sitting more upright on braked descents to aid air braking. I guess with flat bars you could just add a second lever with the appropriate pull for a V brake and use the MTB version of the disk brake but I've not tried that.
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HK found much the same with discontinued DT ceramic rims on the front of her upright trike and her foul-weather commuter. They ate brake pads for a while, regardless of being standard material or ceramic-specific. Once the rim coating smoothed out, she started complaining about wet weather braking with ceramic pads. Scrubbing the rim with a synthetic dish scourer improved matters but I ended up building a Al rim for her foul-weather commuter despite the additional grot. The trike has two V-brakes on the front rim, so one brake dries off the wet rim for the second brake.
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more than one person has told me that once CSS rims have smoothed off properly, you can change back to standard 'salmon' type Kool stops and wear rates are acceptable. I've not BTDT myself though, and maybe DT rims are different to that.
Using a threaded freewheel on a tandem of course means that the spectre of axle breakage may raise its ugly head. To combat this, it is possible to install an 'outrigger bearing' beneath the freewheel. In combination with a decent quality CrMo axle the whole arrangement seems to be pretty reliable. Since a threaded brake mount can be converted to disc if needs be, it is probably the more flexible choice in the long run. The rise of e-bikes with cheap wheel motors has meant that the screw-on freewheel format -instead of continuing to die a death- has remained a viable format. You can buy 8s, 9s, and 10s screw on-freewheels and they can come with 11T top sprockets.
I've not used the Karasawa brake on a tandem but I've got one in the spares stash just in case the Arai spits the dummy and I need it. I am pretty sure the karasawa is going to get super-hot on a tandem. One of my mad ideas is that it might be possible to add a bolt-on aluminium heat sink to the back of the karasawa drum. Another is that it may be possible to water-cool the brake drum using a drip feed of water from a nearby bottle cage, using a modified bottle with a tube and bleed valve.
I note that it is also possible to squeeze a suitable rear hub (eg which is threaded for a freewheel one side and has a six-bolt disc mount on the other) down to 100mm OLN, at which point it should go into a front fork. I don't know how easily the clearances work out (because I have yet to try this out in anger) but in theory if the threaded end of the hubshell is used on the left side with a threaded disc converter on it, this means the six bolt mount can be used on the other side and you can have twin discs up front. Or a drum on the left and a disc on the right. A significant worry on a tandem is that (because the CoG is so much further backwards) you might get into a situation where the increased front brake torque might either overload the fork or cause a front wheel lock-up.
However provided the second brake is only ever used as a drag brake, and/or alternately with the other one (there may be a clever way of doing this BTW) then you may not be in danger of overloading anything, more than you usually are, anyway.
cheers
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Using rim brake in that fashion could overheat the rim and cause a blow-out.
Been there and got the gravel rash. Luckily we were down to walking pace but it was still bad enough and the wheel was totaled.
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https://youtu.be/-obLQbhdNrI is what you need ;)