# Avid Mechanical discs for tandems?



## Bocephus Jones II

Starting to dream up a new tandem and read the santana and co-motion websites. Santana claims the Avid discs are no good for tandems (and says your fork will melt if you use a disc on the front) though Co-motion only seems to offer Avids. Anyone used the Avids on a tandem before and not died from brake fade? Since I'm in CO and there are a lot of long descents this would be a valid concern for me though I'm actually pretty easy on the brakes with my single bike.


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## MB1

My favorite rear brake of all time is the Arai Drum (with some additional machining to drop weight). If I was in Colorado that is what I'd be running.

I am running the WinZip disc now with the big rotor, I think it too would work well in Colorado (I'll note that the stock brake pads didn't last 1,000 miles) with a change out to downhill pads (which after 1,000 miles (lots of those miles loaded) show very little wear). We like climbing and descending and do a lot of it-I am very impressed with the WinZip.


On the Santana Danube trip there were quite a few bikes with the Avid disc-they seemed to work fine but very few of the teams were what we would consider strong and almost every team avoided hills like the plague. 

I just don't see the reason to put a disc on the front of a tandem-I want real stopping power up front and don't need a heat sink like we do on the rear. Still, an Avid up front and a WinZip (with the big rotor) on the rear would be a pretty styling setup.


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## thinkcooper

MB1 said:


> the Arai Drum (with some additional machining to drop weight). If I was in Colorado that is what I'd be running.


Machining the drum to lighten it sounds like a fab idea. Do tell...

That advice of the drum in Colorado seems spot-on.


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## Bocephus Jones II

thinkcooper said:


> Machining the drum to lighten it sounds like a fab idea. Do tell...
> 
> That advice of the drum in Colorado seems spot-on.


So you'd run a drum rear and a caliper front? Is the drum just for hills (meaning do you have a backup caliper back there also?) or is it the sole brake for the rear wheel? I have cheapo drum brakes front and back on my newest cruiser tandem and they are OK, but don't really stop you all that quick.


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## MB1

Machining the Arai Drum Brake. Pretty easy with a lathe....

#1) Machine the inner drum brake surface to a true round-this will reduce surging at low speed, not really done to reduce weight as only a few thousands will need to be taken off.

#2) Get creative on the outer. You can remove a lot of weight from the fins and reduce the OD quite a bit without harming the performance as a heat sink. Don't forget, at speed when you need the brake there is going to be a lot of wind flowing across the thing.

Arai used the same casting for the production life of the way overbuilt design (they always considered the thing a toy for the Japanese home market and never could understand why Americans bought so many). Santana is likely to have small parts available forever (or until they finally get bored and throw boxes of them out). The brake pads seem to last forever but will require deglazing every so often.


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## MB1

Bocephus Jones II said:


> So you'd run a drum rear and a caliper front? Is the drum just for hills (meaning do you have a backup caliper back there also?) or is it the sole brake for the rear wheel? I have cheapo drum brakes front and back on my newest cruiser tandem and they are OK, but don't really stop you all that quick.


If the inner surface of the drum was machined round I *might* consider it as the sole rear brake but I like the security of a caliper/canti/V rear brake with the drum as a really good heat sink.

FWIW The WinZip seems fine as the sole rear brake.


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## wooglin

thinkcooper said:


> Machining the drum to lighten it sounds like a fab idea. Do tell...


What MB1 said, or you can send in your outer drum to Tandems East along with $30 and they'll send you a machined one back as a simple exchange. I imagine other places make the exchange as well, but I just got a Tandems East catalog so that's the one that comes to mind.


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## TWD

Bocephus Jones II said:


> Starting to dream up a new tandem and read the santana and co-motion websites. Santana claims the Avid discs are no good for tandems (and says your fork will melt if you use a disc on the front) though Co-motion only seems to offer Avids. Anyone used the Avids on a tandem before and not died from brake fade? Since I'm in CO and there are a lot of long descents this would be a valid concern for me though I'm actually pretty easy on the brakes with my single bike.


A lot obviously depends on where/how you ride.

I've run the Avid discs on my single mtb, single cross bike, and tandem mtb, and would have no qualms about running them on my tandem road bike (don't have a rear disc tab on that bike tho). 

On my tandem mtb, I've got 8 inch rotors front and rear. The fork on my road tandem is only rated for 6" rotors, so I'm limited in that regard. On my tandem MTB, I'm running a 20 mm thru axle with the 8" rotor, so no concerns there, but I would be concerned about running a quick release fork with an 8" or larger rotor, as I've had the axle shift in the dropouts on several mtb forks running only 6 or 7" rotors. 

The other thing to realize is that the Avid disc brakes are NOT drag brakes. They can put up with a lot of heat, but not that much heat. I've had my Avid discs fade pretty bad on a single mtb, while dragging the rear brake w/6" rotor for several miles down a very steep (25+% grade) loose gravel fire road on a 102 degree F day. I've heard of the same type of fading on tandems when setting the Avids up as a drag brake. 

If you do loaded touring over long descents, and feel you need a drag brake, then get an Arai drum. I"ve got an Arai drum on the back of my road tandem, and it works great for the intended purpose. It's nice to be able to set partially on to check your speed on a steep descent when you know there is a tight turn coming, or you don't feel like pushing the limit and want to keep your speed reasonable. That, and it makes one heck of a nice parking brake.

Even with the Arai, you have to be careful about using the rim brakes too much and blowing out your rear tube. I did just that with the arai drum full on over a 2 mile very steep descent (avg 12% with numerous pitches over 20%) while hauling two kids in our trailer. 

I haven't used the WinZip disc, but with the size of that rotor, it ought to be able to take some heat. I agree with MB-1 that would probably be a pretty sweet setup with an Avid disc up front.


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## J_T

TWD said:


> A lot obviously depends on where/how you ride.
> The other thing to realize is that the Avid disc brakes are NOT drag brakes. They can put up with a lot of heat, but not that much heat. I've had my Avid discs fade pretty bad on a single mtb, while dragging the rear brake w/6" rotor for several miles down a very steep (25+% grade) loose gravel fire road on a 102 degree F day. I've heard of the same type of fading on tandems when setting the Avids up as a drag brake.


Not only fade but rotor warp is common too.

We ride serious hills (Mtns.) and total 325lbs of captain/stoker mass. The Arai drum-drag brake and good rim braking is essential. The thought of descending Monitor Pass without the drag brake gives me cold-sweat nightmares.


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## Jeffh

I love the Avid mechanical discs brakes on our 2007 Cannondale tandem.

I just recently modified the rear to a 220mm Formula rotor with aluminum carrier.


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## ignacious

We have a 2007 Cannondale Road Tandem, as well, just like the pix above. I have had zero problems with the Avid BB7 front and rear installed stock. We have done our share of hills (mountains) on it and had no problems with fade. I am thankful for the disc front brake. If I need to stop 100 feet ago, like when a bluehair snowbird turns in front of you while you are doing 25 mph, I like being able to wail on the front brake (and rear) to get some real stopping power.


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## dir-t

My wife and I are planning to buy a MTB tandem next spring. After reading about drag brakes/heat sinks over here I posted on MTBR about why those folks never mention using such brakes. Alex, the owner or MTBTandems.com posted this reply. It's a bit long but I'd be interested to hear what you all have to say about his take on the subject.

Oh boy, you've opened the proverbial can 'o worms now! Nothing gets folks on road tandem boards in a tizzy quite as much as a disc brake vs drag brake discussion.

As others have posted, prior to the introduction of appropriately-powered disc brakes to the bicycle market, drag brakes were necessary (and may still be) to keep the speed of heavily loaded tandems in check on long descents. In extreme situations, a drag brake might actually still be appropriate, but those circumstances would be something along the line of a fully loaded (meaning expedition-sort-of-loaded) tandem, with maybe a trailer behind it, in the Alps, etc etc. Sherwood and I actually discussed putting a drag or disc brake on a Bob trailer recently, but we haven't actually done. 

OTOH, as stated above, there are disc brake systems available for tandems that are very capable of keeping a speeding tandem in check in virtually all typical off-road tandem situations: The manufacturers that approve their disc brakes for use on tandems are Avid (BB7 brake with 203mm rotors F&R only), Magura (Gustav M with 210/190mm rotors, and Louise Tandem with 203/203mm rotors), and Hope (M4, M6 and Moto, 203/203mm rotors). Each manufacturer's "tandem rating" is contingent on specific minimum rotor sizes being used, and in some cases, different linesets (braided lines vs regular). When spec'd according to the above-specified parameters, there have ben very few (if any) documented cases of brake issues or failures on tandems, at least in the recent past. I do know that Chris Timm managed to melt a line off a Gustav rear brake several years ago, but that was a 160mm rotor, which isn't large enough for tandem use anyway.

However, if one searches among tandems for sale, one can find some entry-level tandems from some name-brand companys that are spec'd with 160mm rotors front and rear, and one will also see all sorts of brake combinations used on tandems by individual folks who either don't know or aren't concerned with the manufacturer's clearance for use on tandems. If there were a disc brake issue with tandems, I suspect it'd be that sort of situation.

That being said, one can use improper braking technique and overheat virtually any brake that's practical to put on a bicycle, so disc brakes don't relieve the operator of the responsibility for proper braking technique. The difference is in the failure mode; some disc brakes will lock up completely, others will get softer levers to the point of being scary, the Avid might melt an adjusting knob off, and I'm sure it's still possible to melt a line off a hydrualic brake if one tried hard enough. But on a rim-brake equipped tandem, the heat buildup on the rim would probably have blown the tire off the rim well before the point of failure for a PROPERLY SPEC'D disc brake.

I can tell that from our own experience of having started riding tandems off-road just prior to disc brakes, that the introduction of disc brakes to off-road tandems has, dare I say it, revolutionized off-road tandeming. Now some place with dry weather and no steep or long descents may argue that point, but in our experience, it made the difference between even being able to ride in less-than-ideal conditions or not. We have personally melted V and hydrualic rim brake pads trying to slow a tandem down, and the performance of any rim brake in less than ideal conditions is virtually always inferior to a properly set up disc brake. 

(here come the flames... )
For road tandems, there are, apparently, different laws of physics at work. If you peruse road tandem forums long enough, it will become apparent that one should never use disc brakes on road forks at all, and never use disc brakes on tandems as the only means of braking, or disaster will surely follow. I've never figured out what's actually different on a road tandem that invokes those other laws of physics, but it must be true, 'cause I read it on the internet! 

FWIW, our next road tandem will be dual disc brakes. There are quite a few road tandems with dual discs running around out there successfully flaunting said laws of phsics.

Personally, I wouldn't mind seeing even larger rotors available for tandem disc brakes (Santana makes a 10" rotor version of their Winzip brake). Hayes had/had a 9" rotor kit available as well. Larger rotors would still provide plenty of clearance for trail obstacles, but increase braking capacity/heatsink capabilities measurably. Seems like a 9" or 10" rotor setup would be ideal.


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