Bike Friday Tandem Brakes….

5 04 2012

Note a front disc and v-brake posts...

I was asked about the brakes on our Bike Friday Tandem Traveller XL over at my Flickr site and thought I would share the answer here for wider dissemination:

My Bike Friday tandem was ordered with disc brakes and v-brake mounts. I haven’t felt the need for extra braking at this point so we only have the discs mounted.

Like for any bikes there is no magic in v-brakes vs. discs. They both work. So you can pretty much pick whichever you prefer and use them.

Neither v-brakes or discs can take prolonged application before they’ll fail. V-brakes will heat up the rims and your tube will blow. Disc brakes will boil their hydraulic fluid, melt the plastic parts of the caliper and warp the rotor if overheated. Neither outcome will be pleasant with your GF on the back bombing down a mountain!

On a tandem the extra weigh without as much aero drag = extra speed on the downhills which can be a problem.

Are you saying we are so fat we need 4 brakes????

My suggestions are:

  1. if the roads are good sit up, take the lane and let the bike run without braking or minimal braking [I do this with my loaded touring bike frequently]
  2. if you need to brake a lot use pulse braking….slowing hard with front brake, releasing and then slowing hard with rear brake…then repeat. You’ll speed up to a top speed each pulse and then slow down to your bottom speed. Note the fast top speed allows a lot of air to flow over your brakes to cool them very effectively.
  3. add if a 3rd or 4th brake..in my case a v-brake front and rear possibly. Use pulse braking, but now you have 3 or 4 brakes to cycle through so you can brake more frequently without overheating.
  4. take a break or 3 on a steep descent to snap a picture or nimble something while your brakes cool.
  5. if you need more braking than you can get with pulse braking or you can’t be okay with the faster speeds of a pulse braking solution you can get a rear drag brake that will keep your speed lower since it’s on all the time. Keep in mind only a specially designed drum drag brake will do this safely. A disc or v-brake applied even very lightly, but constantly will quickly overheat and fail.

Our tandem team weighs ~300lbs + gear + bike…so probably close to 400lbs total on a ride with a lock and a light load of gear. My main strategy is #1 above….I just let the bike run as fast as she wants and brake only when I absolutely have to – which is infrequently. For a tour with full camping gear I’ll do some test runs locally and determine if I need an extra brake. If  so I’ll put a stoker controlled rear brake on.


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7 responses

5 04 2012
Humanist Action Hero

Some disk brakes are better than others at distributing heat, think XTR trail brakes, though there are others. Most higher end ones use ceramic in the pistons to keep the pads from boiling the fluid, though it will happen eventually. Man, do those rotors get hot though! I’ve never had one get red hot, but even after a short downhill, say a 1/4 mile, they’re way more than hot enough to burn you. Don’t ask me how I know.

8 04 2012
Adam DZ

Larger rotors help dissipate the heat. Too bad many frames are limited to 160mm rotors (yeah, I’m look at you, Surly!)

8 04 2012
thelazyrando

I ride my Big Dummy fully loaded with only 160mm rotors and never had an issue. How you brake is far more important than the size of rotors. You can overheat a 200mm+ rotor no problem if your technique sucks.

10 04 2012
mike

mechanical discs solve that pesky boiling fluid issue. larger rotors help. pulse braking is a good idea. don’t use those super lightweight rotors with more air than metal…they overheat quickly…ask the guy from bikerumor.

10 04 2012
thelazyrando

If you are boiling fluid on a hydro brake you are melting the plastic parts in a BB7. Both kinds of brakes will fail from overheating. They key is not to overheat them.

18 08 2012
Ash L

Semi related BF question here; what are you using there for a front rack? Something for a Brompton? Does is take front panniers well or do they ride very close to the ground because of the 20″ wheel?

18 08 2012
thelazyrando

@Ash – the front rack on our tandem is a Bike Friday front rack.

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