Technical > Wheels, Tyres and Brakes

Brakes with heat capacity

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hendrich:
For some years, I have been a somewhat religious reader of Thorn literature. I more or less find everything Andy has written is spot on for tour bikes. Our new tandem has a Rohloff, sorry, not a Thorn....we considered but we are tall and sizing was difficult. Regarding brakes, we have good cantilevers (Andra rims) and a standard (non-hydraulic) rear disk (3 brakes). We find this is not sufficient for mountains when heavily loaded and walk down >10% grades.  Our old tandem had an Arai drum and we did >15% downhill without problem. I don't wish to mess with hydraulics. Recent posts have suggested Sturmley-Archer drums are good. We could use such a front drum and I suspect that it would have braking heat capacity similar to the Arai. It appears that adoption of a this front drum would not interfere with front panniers (Tubus/Ortlieb).

Clearly, Thorn literature talks about the problem of standard disks and poor heat capacity (I forget the test hill name that set the brakes on fire). Eventually Hope came up with a solution, but this solution is hydraulic. So my question...drum brakes are very reliable, have high heat capacity, and require a less complicated routing setup. Why did Thorn seemingly bypass this lower cost option?

PH:
I've never ridden a tandem so my assumptions may be wrong, but I thought the purpose of a rear drum brake was as a drag brake rather than deceleration?  Wouldn't doing that on the front seriously mess with the steering? 
I don't know what the Hope solution you refer to is? I know that some rotors and pads are better at dispersing heat than others, I'm doubtful that any would be up to being used as a drag brake on a long decent.  I've never had hydraulic brake fade, I've never pushed the system to anything like the point where that might happen.  The reports of it I've read are frightening, almost complete brake loss without warning!

mickeg:
Can you put on a larger rotor on your disc brake?  Or, are you already at the maximum size?

For your rim brakes, Koolstop Salmon are generally considered the most grippy of the rim brake pads.  I have them on some of my bikes.

I have had brake fade on a disc brake on my light touring bike, I have resin pads on that brake.   Before I do a bike tour with more weight on the bike, I plan to switch to semi-metallic pads.  I put the softer resin pads on for better braking, most of my riding is in areas without much relief so I almost never have to worry about overheating my brake.  Do you have the right type of pads for the best heat dissipation and high temperature performance on your disc brake?

I know you asked about drums and I was silent on that.  My only Sturmey Archer drum brake experience is I am quite sure irrelevant, as it is on a 1966 three speed hub.  And I would have no clue if such a front drum brake would have better performance than adding a disc to the front.

Does the manufacturer think that the fork is strong enough for adding a brake to the hub on that bike?  Does the manufacturer of your tandem have any other ideas? 

hendrich:

--- Quote from: mickeg on August 15, 2022, 12:53:01 pm ---Can you put on a larger rotor on your disc brake?  Or, are you already at the maximum size?
For your rim brakes, Koolstop Salmon are generally considered the most grippy of the rim brake pads.
Does the manufacturer think that the fork is strong enough for adding a brake to the hub on that bike? 
--- End quote ---

Yes, max 200 mm rotor with semi-metallic. Koolstop pads on cantis. I will discuss with the builder, but I am trying to gather information from knowledgeable sources before doing so. Thanks.

hendrich:

--- Quote from: PH on August 15, 2022, 09:55:26 am ---I've never ridden a tandem so my assumptions may be wrong, but I thought the purpose of a rear drum brake was as a drag brake rather than deceleration?  Wouldn't doing that on the front seriously mess with the steering? 
I don't know what the Hope solution you refer to is? I know that some rotors and pads are better at dispersing heat than others, I'm doubtful that any would be up to being used as a drag brake on a long decent.  I've never had hydraulic brake fade, I've never pushed the system to anything like the point where that might happen.  The reports of it I've read are frightening, almost complete brake loss without warning!

--- End quote ---

Your question regarding front steering is good (perhaps?). On a Rohloff, Thorn adopted a Hope hydraulic made for downhill mtb. The rotor has twice the thickness (2x heat capacity) and is ventilated. Thorn's hydraulic cable routing through detachable clips was innovative (I thought). The heat capacity is higher, but I know a drum is far superior (at least an Arai).

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