Tandem Cycling - drag brakes

I just read this post:

You would think with over 5,000 miles on my Burley Samba tandem that I would know how to shift gears, but apparently I do not....
and am glad I'm not alone!

I've been using derailleurs since the 70's, and used to think I knew all about them, but since I started using internally geared hubs several years ago, I've gotten to really hate derailleurs. I am now so used to being able to shift any time, even when stopped, that I have become totally inept with derailleurs ever since; and on the tandem this ineptitude is really a problem. My solution: lose the derailleur!

So I rashly went ahead and got myself a Rohloff hub for my tandem. I have not yet built it into a wheel.

But now I'm wondering, what about the drag brake? My tandem has that bombproof Arai disk brake on the rear hub in addition to excellent rim brakes (cantilevers), but there's no way to use the Rohloff hub with the Arai brake. Is there another drag brake solution? I'm told a regular disk brake will not cut it; can't take the heat generated when using it as a drag brake. Worth doing anyway as a secondary brake for occasional emergency use? If so, is one type of disk brake better than another?

Also, I have the option of putting either a Shimano roller brake hub or a Sturmey-Archer drum brake hub on the front wheel. Would either of those be suitable as a drag brake, or would they have the same problem as the disk brake?

Is there another drag brake solution?

Are you sure you need a drag brake, i.e., you'll be riding in fairly hilly terrain with a total team weight over 400 lbs or pulling a trailer, doing loaded touring on unknown terrain, have a preference for riding brakes down technical descents, or plans to tour the switchback mountains of Europe?

I'm told a regular disk brake will not cut it; can't take the heat generated when using it as a drag brake.

A disc brake does not have the heat capacity afforded by the Arai drum brake, but is still far better at dealing with heavy braking than rim brakes. Therefore, while disc brakes aren't designed for use as a drag brake, per se, they will work fairly well on long descents under light to moderate demands.

Worth doing anyway as a secondary brake for occasional emergency use?

For lightweight teams, the disc alone has become the rear default for 'something better than just rim brakes'. For larger teams, or anyone looking for more brake power who is left without the option of a drag brake, it's feasible to use either the rim or disc as a primary rear brake with the other as a back-up.

If so, is one type of disk brake better than another

The Avid BB7 Road with 203mm rotor is the most prolific, easiest to set-up, and least costly.

A disc brake does not have the heat capacity afforded by the Arai drum brake, but is still far better at dealing with heavy braking than rim brakes.

For lightweight teams, the disc alone has become the rear default for 'something better than just rim brakes'.

The de-facto opinion here seems to be that disc brakes are superior to rim brakes; this has been discussed before and I still don't get it. Is it because of the pad material - rubber vs. whatever the disc pads are made of? Do disc brakes "squeeze" harder than rim brakes? Is there a greater mechanical advantage so that you can apply more pressure to the disc? Can you stop faster with disc brakes? Do they fade less? Since a rim brake is just a large-diameter disc brake, it would seem to me that the mechanical advantage of rim brakes is far greater than a disc, so there must be something else going on here. (A disclaimer: I have never ridden a tandem with disc brakes.)

... there must be something else going on here. (A disclaimer: I have never ridden a tandem with disc brakes.)

I'm reminded of young boys asking about sex and wondering what makes it so special... It's hard to explain in a way that is as compelling as the actual experience which is perhaps true of disc brakes. Moreover, first experiences can be somewhat awkward and may not produce the expected outcome for any one of a variety of reasons. Less I digress... before I get in trouble.

From this thread (http://www.bikeforums.net/showthread.php?t=285449) comes the following post that I have appended in it's entirety because, a) I'm lazy and, b) it's on topic relative to discs as drag brakes. I have highlighted the parts that talk to the features that make a rear disc desirable for certain teams.



I thought it was unsafe to use disc brakes as drag brakes (i.e., constantly applied) due to excessive heat build-up. Is this not true?l

Only if the operator is completely oblivious to or ignores all of the very obvious signs that they are exceeding the heat capacity of their brake system, which is true for all rim, disc, and even drum brakes.

Here's the deal: In the case of disc brakes, as the rotor approach the upper-end of the caliper & rotor heat capacity the operator will begin to hear and feel the distinctive effects of brake pad outgassing and glazing which will only get worse and is accompanied by the loss of braking power, aka. heat induced brake fade. The same thing happens with rim brakes, except that unlike the mechanical discs which limit the heat build up to the rotor, hub, caliper and cable/housing, rim heating migrates into the tires and tubes and can create a situation where a tire "blows off" a rim: a catastropic failure mode. If anyone is struggling to understand what I mean by the sound and feel of brake's outgassing most teams have probably experienced it on any hilly, regular ride where they apply maximum braking near the bottom of a steep hill: it's that 'griding' sound and vibration that occurs just before you've finally got it slowed down enough to either finish the stop or move on. It's not a bad thing near the bottom of a hill that you're familiar with; however, it is a problem when you're 1/2 way down an 5,000 ft descent that you're unfamiliar with.

The only way that I know of to create a catastropic failure mode with a mechanical disc brake is to continuously apply both front and rear brakes to the point where both brakes are allowed to acheive heating points where they can both suffer nearly compete brake fade before the tandem is safely brought to a stop. Again, this suggests that the captain was unaware of how to properly use his braking systems or of the warning signs associated with a brake system exceeding its heat capacity and the need to bring the bike to a stop so that the brake system can cool-off before resuming the descents.

IMHO, continuing to make a long and challenging unfamiliar descent on any brakes after there are obvious signs of fade is analogous to riding with tire that is going flat; you either figure out "something's not right here" or end up skidding around on a metal hoop with a tire jamed in your fork or rear stays. However, I suspect that many captains may not have received sufficient instruction or taken time to appreciate what brake fade is and how it works and assume that "discs" will simply work under all conditions... which is simply not true of discs or any brake system.

Since they were mentioned, let me note here, hydraulic brakes are different in that as they overheat they can transmit the heat into the fluid as well as the non-metallic hydraulic lines. As hydraulic fluid heats it expands and even in an open system you can reach a point where the expanding fluid will no longer allow you to release the pads from the rotor. In off-road conditions the affected wheel / brake simply lock up and drag you to a stop in the dirt. However, the high friction roads will keep that wheel turning on the outgassing, fully glazed-over brake pads (to no effect other than heat generation) and at some point a hydraulic line or seal will let go: that is a catastrophic failure mode, i.e., your brake is now inoperable. I bring up this little problem with hydraulic brakes to underscore that to my knowledge the only tandem disc brake systems in recent times to suffer catastrophic failures have been hydraulic systems, not mechanical. Yes, there have been all kinds of profound warnings and cited test results that suggested the Avid brakes were "not safe for tandems" but despite asking for real world examples over the past 4 years I have yet to hear of anything other than melted plastic knobs. Santana's introduction of the all metal WinZip mechanical disc caliper is, in fact, the solution to their Formula disc. The Formula, to its credit, when set up properly and given the necessary attention to routine adjustments, is an outstanding brake. However, in the real world, most owners neither had the knowledge or access to mechanics who knew how to work on those brakes and therein was the weakness in that system. The Avid is a no-brainer, the Winzip, from most accounts, is far easier to set up and adjust than the Formula, but not a no-brainer.

So, getting back to Avids, yes you can melt the red plastic knobs (they're replaceable and cheap, by the way), probably the nylon seal/cap, you can even melt the plastic cable housing and teflon liner but not the metal inner housing, you can end up with a warped disc, and although I haven't heard of it happening with a rotor, I suspect you might cook the grease out of your rear hub's bearings as has been reported a few times with drum brakes that were severely overheated. But, other than "losing both your brakes" due to rider-induced brake fade while still underway, the mechanical brake will not come apart UNLESS there is some type of plastic part sitting in the reaction arm, cams, or retention screw and nut that holds the whole thing together that I'm not aware of.

The combination of the Avid's excellent performance and higher-than-rim-brake heat tolerance with non-catastrophic failure mode is why disc brakes have become very popular as a rear brake alternative for teams that don't need or want a drum brake on their tandem for any one of a variety of reasons. As for your original question about their use as a drag brake, let me be the first one to suggest that almost anyone with one of these Avid rear discs is already using it as a drag brake... it's hard not to because it just works so darn well. What I mean is, because a rear disc is so much more effective than a rear rim brake I know that I find myself biasing my downhill braking to 75% rear / 25% front, using the front only for more aggressive braking action in combination with the rear, particulary when it's wet. Now, while I'm not doing the "set-it-and-forget-it" drag brake operation normally associated with an Arai drum brake, in many cases and on very steep, twisty descents the effect is the same: that rear brake is on A LOT... as in a lot more than it would be if it was a rim brake as I still remain ever mindful of rim heating given that we run very high pressure, narrow tires. As the terrain gets steeper and more challenging, the brake use goes into alternating front on / back off then front off / back on brake use to make sure that neither brake is allowed to climb into unchecked brake fade, thereby ensuring that I always have sufficient brake capacity to bring our tandem to a stop if needed.

This then brings us full circle to the Avid as a drag brake. No, I wouldn't recommend the rear rim / Avid as a defacto "default" set up on any tandem or for any team that truly needs a drag brake: that's the realm of the Arai drum brake and always will be until something better comes along. However, what what you describe about yourself and the way you ride, the rear Avid with front caliper will be all you need for nearly all of your domestic riding. However, if you should happen to venture into the mountains where some type of supplemental braking system is recommended by the tour leaders or anyone familiar with the route, prudent use of a dual caliper braking system with an Avid disc judiciously employed as a "supplemental" brake should allow you to make the most challenging descents in a safe and controlled, non-stop manner if you so choose. Add 100lbs to your team weight or cut your experience level as a cyclist by 75%, and the recommendation quickly changes, as would steering someone who is rather large away from the authentic Chippendale side chair.

P.S. With regard to XTR V-brake vs. Caliper, while linear pull brakes have more stopping power it's almost a moot point on the rear wheel since either a caliper or linear pull brake will lock up the rear wheel under near panic braking with the front brake fully applied and heat capacity is the same for either.

So disc brakes are as good as sex? Wow, this is something I've gotta experience for myself. Are you saying that they are better because no matter how *hot* they get, they don't cause premature blow-outs? Or is it that they last longer before they start to fade?

Disc brakes can have their own issues. Break-in time. Some need adjustment quite often. Talk to the folks who have stop halway down a long descent to let that disc cool. Plastic parts melting from heat buildup.
As related to us, even Mr. Bill's tandem was not immune to heat buildup in Italy
Have used discs, calipers, cantis, self-energizing, U-brakes, V-brakes or combinations thereof. Yup, they all stopped our forward momentum on the tandem.
Have never had blowouts due to overheated rims; never have had our brakes fail to stop us properly in over 220,000 miles of tandeming.
Or maybe we are just lucky????

this is something I've gotta experience for myself.

That was and remains the point; you can't form an objective opinion until you have sufficient first hand experience... hence, the analogy. Therefore, the only way to appreciate the difference between a rear rim brake and a rear disc brake -- a rear disc brake that's actually set-up correctly and broken-in -- is to log a few hundred miles in the mountains or any other high-brake-demand terrain where prolonged use of rim brakes began to weigh heavy on your mind. If you don't have to deal with high-brake-demand types of riding conditions rim brakes are more than adequate. Conversely, if you're more inclined to ride the brakes all the way down technical descents or fall into the other heavy-brake-use situations described in my original reply to the OP, then you'd do best to stick with rim brakes and a rear drum: belt & suspenders, if you will.

Are you saying that they are better because no matter how *hot* they get, they don't cause premature blow-outs? Or is it that they last longer before they start to fade?

What I'm saying is, having actually owned a couple tandems with rear discs and ridden them in the mountains and other high-brake-demand situations as have many of our friends who have similar brake configurations, rear discs provide an added measure of security FOR US when compared to the caliper and cantilever brakes we've used on our tandems (to include our current Campy dual pivots front & rear). Our Avid discs have consistently demonstrated superior stopping power, exceptional modulation which is a real plus on wet roads or when threshold braking is required, they don't fade as quickly when they're over-used under demanding conditions, and don't exacerbate rim/tire heating the way rim brakes do under those same demanding conditions.

Yes, they do add weight, but not as much as a drum brake. Yes, if you don't know how to set-up and dial-in disc brakes they can be more trouble than they're worth... particularly if you really don't need them in the first place. I mean, how many folks are running out to by Xtracycles or cargo bikes because they're the latest and greatest and evoke images of self-suffuciency when all they really needed was a rear rack and grocery panniers, rear baskets (do they still make those?), or perhaps a trailer every now and again. Instead, they're now riding around on a 50lb bike that they need maybe two or three times a year: no wonder they're called bicycle SUVs.

However, if you feel you want or need something more than a rear rim brake for those occassional trips to the mountains, pulling a child's trailer in hilly terrain, or some other high-brake-use conditions then you'll most likely trade off the benefits for the minor annoyances of the added weight, the need to true the rotor if it gets bent, etc. In fact, they're probably not that much different than mud guards which can also be annoying IF you don't see or derive any value in their use.

Disc brakes can have their own issues. Break-in time. Some need adjustment quite often. Talk to the folks who have stop halway down a long descent to let that disc cool. Plastic parts melting from heat buildup.

You know, I've heard all of this stuff time and again and have traced most of it back to the source and the number of these types of incidents that have actually occured on tandems fitted with the 203mm Avid BB7 road model discs on the rear wheel of their tandems can be counted on one hand. Santana's Forumula discs did indeed have problems which account for a lot of tandem disc brake urban legends, many of them being true. However, they have since been replaced by the WinZip brakes as noted in my earlier posting. So, lets limit the discussion to the tried and true mechanical disc system that has always worked well... the Avid BB7 and its variants like the WinZip.

Break-in time and frequent adjustment are often times coincidental: single piston disc brakes like the Avid BB7 don't achieve full brake power until the brake pads wear down enough to conform to the rotor's camber and will experience accelerated wear during the break-in process. If they continue to wear quickly then a different brake pad compound is most likely needed, e.g., Santana's WinZips apparently came with a compound designed for off-road bikes that was not well-suited for road tandems. List members like Bloomingcyclist have done a wonderful job of documenting their experiences with the OEM pads and suggesting replacements that they have actually used to solve early issues.

I've never encountered anyone with an Avid BB7 who has had to stop and let it cool and, aside from the German "MountainBike" magazine article written back in 2001 where it was first observed that you could heat up Avid disc calipers to the point where the plastic knobs would melt (which, incidentally, didn't result in a failure of the disc's functionality aside from the associated brake fade), I've only heard of three such incidents in the real world... despite soliciting such examples on several occassions and in several forums.

Have never had blowouts due to overheated rims; never have had our brakes fail to stop us properly in over 220,000 miles of tandeming. Or maybe we are just lucky????

I suspect a combination of the latter, lightweight, proper bicycle maintenance, good descending skills, and good judgement all contribute to your success. Now, how to we apply that standard to all tandem teams? After all, there are tandem teams that have done all the right things and who have still been run-down by logging trucks; luck and fate are indeed fickle mistresses. Fate and luck have also smiled upon us, as we've never had a tire blow-off (then again, we've never used wire-beaded tires and go through tires fast enough that they're never more than a few months old). However, I know teams who've had blow-offs and have personally heated up brakes on and off-road well past the point where brake fade (rim & disc) has become a factor on several occassions and one-time melted the pads off the rear XTR V-brakes on our MT3000. Therefore, like many things, while I haven't suffered personal harm due to brake-related issues, I've experienced enough to know that bad things do happen to sufficient numbers of teams related to brakes that cause folks to remain in search of better tandem braking solutions vs. simple rim brakes.

Team weight has a lot to do with braking demands, too. Team Zonatandem doesn't weigh much more, the two of them together, than some big-guy single bike riders we've run across, so it's not surprising that they've been able to thrive on what amount to single-bike brakes. We are also lightweights, team weight 270 lb. or so, and the only time we ever really need any kind of third brake is in Europe. Even on supported tours with no baggage on the bike, the double-chevron descents with multiple hairpins ("lacets" in France) are just too steep and tight for us to rely on aerodynamic braking (and rim cooling) between the bends. With only rim brakes on our old tandem, typically after two or three lacets we would have to use what we figured was the last of the braking capacity to bring the bike to a stop and let the rims cool by walking the bike for 50 metres or so. (Good chance to enjoy the view, granted.) We never blew a tire off but we did have a valve stem let go (slowly: "psssssssst", not "BAM!") where it enters the tube just at the end of a precipitous descent into Hallein, Austria, from the German border.

The only terrain in North America we've ridden that comes close to this is the southern Appalachians of North Carolina and Tennessee. In the Canadian and American western mountains, the descents are longer but even as light unsupported tourists we always managed without a third brake. Perhaps the Sierras are tougher, you Californians would have more experience there.

On our new Erickson, we have an Avid BB-7 disc as the "primary", i.e., controlled by the captain, rear brake and a front dual-pivot caliper. There is a "reserve" rear caliper brake controlled from Susan's stoker bars that we would use (with the front caliper) to get the bike stopped if the disc ever got hot enough to fade, or otherwise failed during a long descent.

For us, the disc works superbly in this application. As TandemGeek does, we use mostly the rear to shed speed when we see a lacet coming up, then I punch the front a bit just before the lean starts. We do try to avoid braking entirely in the tangents so as to maximize aerodynamic braking and to give the rotor a chance to cool. This leaves us with two cool rims and a rotor which is hot only at the exit from a turn. Even when it starts to make outgassing noises entering a turn, so far it has always behaved as expected by the time the next turn approaches. You do need to carry spare pads in the mountains -- amazing how quickly that kind of braking wears them down -- and practice replacing them before you leave home. Don't forget a little pair of pliers to grab the tabs and yank them out, like pulling teeth.

The disc brake has allowed us to venture into mountains in Europe that we would not have tackled otherwise. It was just too frustrating (and too reliant on maintaining discipline when you're tired late in the day and suffering from "get-home-itis") to stop and walk periodically down those steep technical descents. Hard work gave us the fitness to climb the second-tier cols of the Pyrenees and the Alps; technology has given us a way to get down them safely and (also important) quickly. (You appreciate "quickly" when you've just beaten a thunderstorm over the summit and you've still got 1000 metres of descending to home base.)

But for all our other riding, a third brake is just an unnecessary boat anchor and it's one reason why we are hanging on to our old Santana Targa for quick spins up and down the Niagara Escarpment.

The common argument that a rim brake is a bigger disc brake and therefore has more nechanical advantage overlooks the actuation ratio part of the equation. A rim brake moves a lot in comparison the the brake lever, where the disc caliper pads move very little, resulting in more mechanical advantage for the disc.

I've used both types on a tandem, and there is no comparison- the disc is stronger. Also, the disc doesn't care if it is raining, snowing, or freezing. It just works well. My experience is with an Avid BB7 203.

The weather during the Bass Lake Double was so cold this year that it lowered the tendency for my rear disc to overheat on long/winding downhills. A small consolation for freezing to death all day.

I think that it should be noted that the fact that disc brakes do not perform well as drag brakes does not mean that they are a bad choice as a third brake. It just means you shouldn't use it in a "set and forget" fashion. The bike could be set up so that one lever activates both rim brakes and the other just the disc.

I have not done any steep descents with a drum brake, however my stoker has. Speaking of "set and forget", the captain did (forget that is) and was blaming the lack of performance on the stoker until he realized his mistake.

Thanks, all, for the comments here. Very interesting reading, and very helpful.

We're not a heavy team; 275 lbs of rider. I do want to do some loaded touring, though; perhaps 100 lbs of gear eventually, though that's pretty far off in the future. And of course being touring, it'll be on unfamiliar roads.

I plan to try a disk brake as a secondary brake, and may try a drum brake on the front wheel for the same purpose. I like the idea of carrying a few extra brake pads for the disk when on longer tours.

I should point out that the other way to get down a long steep hill with only rim brakes is to proceed VERY s-l-o-w-l-y. If you use the brakes immediately that you start rolling off the summit, just crawling at 5-10 km/hr, then the rate of heat input remains less than the ability of the rims to radiate and convect heat away, keeping them cool enough to save your tires. (At the limit, you generate no heat at all if you are stopped dead, no matter how steep the gradient.) But few of us have the patience to descend a hill at the same speed we crawled up it -- it becomes one of those "why bother?" experiences. But the point is that you can always get down a hill safely if you do it slowly enough. Good brakes allow you to do it faster!

......But few of us have the patience to descend a hill at the same speed we crawled up it ....

Let's see.... on a good day we could climb the toll house grade in 49 min. I do not know if can can keep squezing my brakes that long before my fingers quit.

Braking technique does play a big role in safe descents..
To go downhill full tilt and grabbing handfuls of brakelevers as you hit thecurve, works well some of the time.
Have only owned one tandem (our first one, a '75 Follis) that had a 3rd brake (Atom drum) that created some issues. We soon got rid of it and installed 2 back-to-back centerpulls (utilizing a longer bolt) for more pad to the rim. Worked for us.
However, in our advanced age, we no longer do 50+ mph descents . . . been there, done that.
Fortunately there's all kinds of choices and opinions and experiences on what has worked for other teams.

Let's see.... on a good day we could climb the toll house grade in 49 min. I do not know if can can keep squezing my brakes that long before my fingers quit.

Good point, so you would have to factor in the extra time needed to stop periodically to let your forearm muscles recover before you started crawling again.

Or you could cinch two toe-straps around the brake levers and handlebars to keep them almost fully applied. While this suggestion is made firmly tongue-in-cheek, this is actually how heavy freight trains used to get down the long grades in the Canadian Rockies and Selkirks during the era of steam locomotives (before the diesel-electrics came along with their dynamic brakes.) At the beginning of each descent, the train would stop and the brakemen would scamper along the tops of the boxcars to tighten the retarder wheels on each car's airbrake. This, in effect, kept the brake shoes in firm contact with the wheels even when the engineer wasn't using the airbrakes from the cab and so restricted the speed to what the locomotive could handle for curves and emergency stopping. Even at that, the trains would still have to stop periodically to prevent the wheels from overheating and fracturing or burning the oil out of the axle bearings, a "catastrophic failure mode" if ever there was one.

Just another parallel between bicycles and trains for your historical viewing pleasure. :)

I used to do a long tiring offroad ride and one of the problems we had with V Brakes was that the pilots hands gave up after about 8 hours. That and wearing out one set of rims a year and I made the change to Disk brakes. Hope Mono M4's with 203mm discs F & R. That hand fatigue disappeared. We still had some steep descents to make and on one night ride- The following riders remarked that they could see the discs glowing a Dull Orange. Never affected braking and even on long road rides- we have yet to come across a steep enough- long enough hill to cause any problems with the brakes. I must stress that we do not tour with heavy panniers- but that Tandem is ridden aggressively with an all up weight of 400 lbs.