DubT

There is much talk and interest in disc brakes these days. I like to see real world test data before making a decision on what to use.

So the question, has anyone actually done a controlled study of the advantages/disadvantages of caliper/disc brakes? How about hydraulic caliper brakes.

One of the issues that I have heard is that calipers generate enough heat on a long downhill to cause the heat to build up and cause a blow out. Is this really true, if so would tubeless tires make a difference.

How about a study on how much braking force is generated by the front brake vs the rear brake.

There appears to be an area that needs clarification. Maybe it has already been done, is so it would be great to see the data.

What about the old drum brake? I believe a new company is making one, is that a viable option for loaded touring.

Here on the prairie all we need are stander caliper brakes, our bike stops just fine. However if we ever went to the mountains it would be nice to know if there is something that is actually better, with actual data to prove it is better.

Wayne

DubT

Interesting article: https://www.rodbikes.com/articles/disco-fever/disco-fever.html

reburns

I agree that it would be great to see actual data from carefully controlled tests. But there are an awful lot of variables that would need to be controlled for. In my experience I have seen more variation across brakes of the same type than I have seen between the best performing rim and disc brakes. So I've developed the opinion that the quality of the design, manufacture, materials and setup are more important than whether a brake works on a disc or a rim. Either can stop a fast loaded tandem very effectively provided that all of the elements are done well.

That said, if you are riding off road with knobby tires where you might encounter stream crossings, snow or other wet conditions, discs have an inherent advantage due to the higher pressure required on the smaller diameter braking surface. And if you need sustained braking to control speed down long steep hills due to mountainous terrain, a hub brake (either disc or drum) used as a drag brake keeps the resulting heat away from tires and rims.

ironhanglider

Hi Wayne,

I can't answer the other questions, but I can answer this one to an extent. We run tubular tyres on the race tandem. We are a heavy team at 200kg including bike, but at the time of this incident we were about 220kg. The section of road is a steep descent with lots of corners with poor visibility of the exit, and I wasn't very familiar with the road, so perhaps braked more than I needed to, although probably less than most. Here it is https://www.strava.com/activities/52205323/overview
It wasn't just us, there were at least 3 single bike riders who also had problems that day from rim heat, although they were on single bikes with carbon rims.

We managed to heat tubular rims with V brakes to the point that the glue melted. This meant that instead of being an adhesive it turned into a lubricant. The front tyre rotated around the rim and tore the valve out. I didn't hurry to get the wheel out to put the spare on since I was too busy recovering, but it was still plenty warm when I did.

I have heard of heat affecting tyres to the point that they blow off more easily before, so it is entirely believable. Tubeless tyre manufacturers on the other hand make their beads very tight and inflexible so that they make a good seal. I would expect them to perform better in this aspect.

Cheers,

Cameron

waynesulak

Sorry to hear about the crash. Must be a powerful 220kg race tandem team. Please post pics of team an bike.

twocicle

FWIW,

Look up some of Bill McCready's (Santana) blurbs on the various disc brakes he promoted over the years. He did try to provide real life tandem usage comparison info, but that often seemed overshadowed by a biased sales pitch.

Dean V

Not a scientific test but has anyone here ridden a tandem with front brakes powerful enough to skid the front wheel with a good tyre on a dry road? My rim brakes or BB7 discs have not been capable of this. BTW I am aware that locking the front wheel on a bike is something that should only be done with the utmost caution!

zonatandem

Have ridden tandems with all types of brakes since 1975.
Centerpulls, cantis, side pulls, discs (front and rear) drum brake, V-brake and U-brake (rear).
All work fine to varying degrees.
In 1979 climbed/descended Kitt Peak in AZ with Mafac cantis (front and rear & NO 3rd brake). A curving 11 mile long 7% grade without any issues except fingers starting to cramp from on/off braking. Stopped about 2/3rds way down to ease finger issue for a couple minutes and felt the rims. They were warm but NOT hot. Had been told at that time by Bill McC (Santana) we could not safely descend without a 3rd brake. So much for that.
Much has to do in how you brake. Diving into a mountain switchback at 30 mph and grabbing both brakes is not the safest approach.
On long/steep descents we apply front brake . . . release, apply rear brake/ release and alternate rapidly. Rims with good tires will do just fine.
Have we ever blown a tire? Yes, but never yet while descending. Usually caused by debris, hitting a big chuck hole or even faulty tire.
Have ridden/descended many times from 9,000+ ft elevation with rim brakes. No issues for us.
Tried discs front and rear when they first became 'popular' and considered them to be overkill and bothersome to keep adjusted. Have seen plastic bits on discs that were melting, seen folks pouring water on the discs or just plain stopping to cool them off.
Hydraulics can have an issue with the fluids and ridden only one German tandem with Maguras. Do they stop? Yep, but so do our calipers.
For the last 40,000+ miles have used Dura Ace caliper front and Tektro Mini-V brake rear.
We are a rather light team, just under 250 lbs.
Just our input/experience.
Pedal on!
Rudy and Kay/zonatandem

ironhanglider

Hi Wayne,

We managed to stay upright but it was exciting moment nonetheless.

We had no problems this year. The bike now runs dual discs.

Looking for photos, there are not many around but I do recall one of us sprinting against one of the smaller riders. If I find it I'll post it in the happy tandem thread.

Cheers,

Cameron

vrooom3440

Brakes are the *last* thing I want to have to worry about. This is a good area to have lots of safety margin in the design. Thus it does not take many reports of tire blow offs or outs with rim brakes to swing me all the way over into the disc camp. I run two piece Hope rotors in 200mm with BB7s so, melting adjusters aside, heat will never be much of an issue. Comforting coming down 10% grades from Dante's View near Death Valley.

Mechanical or hydraulic probably matters less, once you can generate enough pressure you are going to get the same affect and mechanical never need bleeding nor can they boil the fluid.

Carbonfiberboy 

I once briefly locked our front in the wet with our Avid 7 V brakes. We stayed up. I was servicing our front wheel and had put on a single bike wheel with an Open Pro rim. Bent the rim a little, but pulled it back true with the spokes.

joe@vwvortex

The biggest variable would be team weight. What is effective for a 220lb team won't be near as effective for a 350+ lb team. Braking style and speed also will have a big impact as well.

Wilfred Laurier

Does anyone make dual disc hubs and forks? My understanding is that heat dissipation is the primary reason motorcycles do it that way.

gracehowler

Dual disc, ouch, more weight!
R

Team Fab

Also twisting force with single disk. I have suggested duel disk for tandems(and downhill bikes) on other threads in the past as I cant stand the twisting feeling.

sch

I think the stories about hydraulic discs locking up, plastic parts (BB7) melting and tire blowoffs are endemic to California where very long hills aren't hard to find. Our team
weight was in the 360-380 range and the first tandem heated up the rims to the point of not being able to touch them in the 0.2 mile 75' drop to the house. That was enough to
go to rear disc on the next bike. Last year on the single I had the pleasure of coming down the Cherohala skyway in a driving rain, no fun when I realized I had zero rim
braking for the last 10 miles, fortunately brakes were more or less optional until I did need them and they dried enough to start working, but it was scary (as well as COLD).

Sprout97 

From auto racing, the advances introduced -- disc brakes, vented discs, bigger disc, x-drilled, & slotted -- were to combat brake fade/degraded braking characteristics from repeated and/or long braking periods. But as I'm not an engineer, I talked a friend of mine who's a retired CSX engineer (CE, not a locomotive driver) on his thoughts. His response:

"Now this is a brain challenge. In theory, the tire to pavement issue is based on the direct weight load applied to the tire and the coefficient of friction between the tire and the pavement surface. But then there are so many variables, including the irregularities of the surface, the composition of the tire rubber, the tread style, stiffness/flexibility of the compound, etc. I would think that both the braking effort applied to the rim/rotor to slow the wheel assembly, and the effective transition of the slowing effort via the tire to the tire pavement contact area, are critical to the braking efficiency.

It appears heat could be a factor to both rim/rotor contact and rubber to road contact.

Well, for what it is worth (darn little), there is my two cents."

He's not a cyclist, just looking at it as an engineer.

TrekIrvine

Fascinating discussion. I've been right a mountain bike with hydraulic disc brakes since 2009. Never had a problem (>3,000 miles in last 12 months) and I'm just replacing the rear pads for the first time. To my mind the reason for banning disc brakes in pro road are probably more closely related to lobbying efforts of certain manufacturers than for the stated safety reasons. I just watched an entertaining video by GCN where one of the riders 'rode' down the entire 18km descent dragging his rear disc. While it did generate heat the performance never faded. One of the stated reasons for the ban is a hot disc might burn a rider in a pile-up. While true I believe the tarmac, speed, wheels and spokes present a greater hazard than a 120 mm disc.

Finally, once the weight issue is minimized you can't help but look at brake technology on other modes of transportation. Everything is going hydraulic disc.

Of course, all of this must be tempered with what type of riding you plan to do. If you're riding from Tierra del Fuego to the Arctic Circle then you would probably want the most simple system that can be repaired with basic local materials. For riding in an urban environment you can get much more sophisticate as the 'chase car' is just a phone call away. "Honey, come and get me, I've got a flat tire. I'm at the corner of PCH and Warner."

Carbonfiberboy 

I once descended from Artist Point on Mt. Baker on a rim-braked single in sleet. No braking trouble whatsoever, though I had trouble moving my feet in those funny little circles when I got to the bottom. The upper part of that road is all switchbacks at ~8%. Riding every winter in the PNW, I've never lost braking with rim brakes. They don't do much for the first 50', therefore I think ahead and ride defensively.

We haven't had any trouble with rim brakes on our tandem (283 team weight) since we went to deep section alu rims. Except that the rims wear out here in the PNW which is a PITA.

We have a spare rear wheel with a drum for loaded touring. If I were having a new Calfee built, I'd probably go with the same system: rim brakes and a spare drum wheel, except that Calfee wants $400 just for the little extra bits to be able to mount a drum. I don't get that, but it makes a disc a more attractive option.

shlammed

Though I don't have a lot of long decents here -similar with the climbs, for obvious reasons... our tandem with 140mm rotors brakes great.

I was out for a ride with a buddy of mine who isn't my normal stoker and he is a good 80-100lbs or so heavier than my wife... for a tandem loaded weight of ~450lbs and for giggles I did a quick stop from a downhill with us geared out at 70km/h. Stopping is just fine, but I might consider a 160 or 180mm upgrade or possibly metallic pads should I be doing it repeatedly.

merlinextraligh

I'd be concerned about heat dissipation with 140mm discs. There have been anecdotal reports of 140mm discs fading due to heat on long descents on single bikes. Depending on how you descend, I could see 140 rotors being a problem on long steep descents.

mkane77g

Try 10-15% grades for miles & miles. Rim brakes won't cut it. I live in Sonoma County. If you like hills and live here you know what I mean.

merlinextraligh

It gets back to descending styles. If you only touch brakes once for the entry of each turn, you don't have a heating issue even on steep terrain. If you want to control speed, and are putting them repeatedly on the straights, then yes rim brakes are an issue.

We did Everest challenge with 10 mile descents and 17 percent grades and never had a problem with calipers. Of cours we were also doing 65mph

mkane77g

Ever fall doing 50+. We had a blow out (new tire/tube, no brakes) at that speed on the rear around a bend in the road. The rear decided to try and change places with the front so, I laid the bike down instead of highsiding. The noise was incredible. I didn't get out of the drops the entire 175'. The grinding on the ground was so severe it completely ground down a ti speedplay to the mid way point on the spindle. My wife broke a shoulder and was banged up a bit. My hand now only has an index finger and a thumb with any knuckles. 300 stitches and it was ugly. We now decend at 40mph max. My stoker's to important to take any more chances. We have got away with some crazy things riding the tandem. Some get off lucky. I feel we did. Took a year to get back on.

merlinextraligh

I'm not arguing that going slower down descents is not a rational decision. I'm merely pointing out the way you descend has a lot to do with what you need in brakes.