Drum-Brake Reliable for Long, Steep Descents?

[James Thomson]

"Elisa Francesca Roselli" <[email protected]> wrote:

> Interesting discussion. I feel right in the firing line as I am a heavy, very cautious rider who
> doesn't know how to change or repair a tyre (I saw it being done once, but from there to practice
> is a long way).

As Robert says, tyre blow-off is very unlikely to be a practical problem for you on the local hills.

> The Giant Melbourne also is supposed to have "pneus anti-crevaison", "unpuncturable" tyres. What
> are those, and would they make a difference in the kind of blow-off situation you're describing?

"Unpuncturable" is an optimistic translation. These tyres have a thick tread combined with a breaker
layer, and are fairly resistant to intrusion by sharp objects. They can still be blown off the rim,
and they can still suffer from pinch punctures - where an impact with a blunt object pinches the
tube without penetrating the tyre.

> Another question: if a blow-off should happen, what does it feel like? Do you lose control? Or is
> it a decline in perfs sufficiently slow that a person with very slow reflexes can get possession
> of herself?

The tyre goes flat in a fraction of a second. Even so, it's usually possible to bring the bike to a
controlled halt, particularly if the puncture is to the rear wheel. If the tyre is a tight fit to
the rim, it's likely to fall back into place after the tube bursts, but a loose-fitting tyre can
separate from the rim and leave you riding on metal.

But to reiterate, it's very unlikely that this is something you need to worry about.

James Thomson

 

[James Thomson]

"Chalo" <[email protected]> wrote:

> If you are equipped and prepared to remove/replace a Shimano Nexus 7 gearhub wheel and its shift
> cable, which is the kind of wheel the OP is discussing, then detaching the brake hardware does not
> substantially complicate that process.

It's one further step that requires one extra tool. Elisa has said that she doesn't fix her own
punctures at the moment, but if she hopes to become mechanically independent in the long term and
hand strength is a problem, the differences in convenience in removing different types of wheels are
worth considering. It's possible to fix some punctures without removing the wheel, but it often
makes more sense to change the tube, and that generally means removing the wheel.

> If removing a screw to release the brake torque arm is too much of an operation for you, you will
> probably not be changing out a nutted hub or gearhub either.

I have nutted track hubs and Stumey threes, fours and a five, but I no longer have any bikes with
drum brakes. A torque arm attachment is one more small, grime-encrusted screw to monkey with and
lose in the cold and dark of a winter commute. I don't suffer from many punctures, but even so I
find the advantages of a drum brake don't outweigh this inconvenience.

James Thomson

 

[Chalo]

"James Thomson" <[email protected]> wrote:

> I have nutted track hubs and Stumey threes, fours and a five, but I no longer have any bikes with
> drum brakes. A torque arm attachment is one more small, grime-encrusted screw to monkey with and
> lose in the cold and dark of a winter commute. I don't suffer from many punctures, but even so I
> find the advantages of a drum brake don't outweigh this inconvenience.

I'm guessing you also don't run a full chain case like the one on the bike Elisa is contemplating.
That bike is apt to be easy to live with, and also inconvenient to strip of its rear wheel. "Ils ont
les fautes de leurs qualités", as they say.

Chalo

 

[James Thomson]

"Chalo" <[email protected]> wrote:

> I'm guessing you also don't run a full chain case like the one on the bike Elisa is contemplating.
> That bike is apt to be easy to live with, and also inconvenient to strip of its rear wheel. "Ils
> ont les fautes de leurs qualités", as they say.

I used to work as mechanic for a company whose major business was importing and reconditioning
old Dutch roadsters, so I'd say I have a more-than-fair appreciation of their qualities, and
their faults.

James Thomson

 

[Michel Gagnon]

Elisa Francesca Roselli <[email protected]> wrote in message
news:<[email protected]>...
> At the Paris Cycle Fair, the highest specified bike I saw in the category that interests me
> (Cannondale Street 800 Women's) had hydraulic disk brakes by Shimano. These brakes were an
> important component in its hefty price tag (nearly 1300 Euros). I was told they are the highest
> performing brakes on the market today.
>
>

I am not a fan of disk brakes, but that's mostly for the "if it ain't broke, don't fix it!" aspect.
In other words, v-brakes on aluminium rims work very well, and if you endulge yourself with Kool
Stop Salmon brake pads, you will have very good braking in the rain and even in snow. Besides, Kool
Stop pads seem to wear the rims much less than some of the Shimano pads.

The real advantage of disk brakes, I think, is for cross-country rides, where you sink your wheels
in so much mud that you brake and grind your wheels at the same time. Not a problem with Paris
streets, as far as I know.

The "hydraulic" part of the brakes, is, I think, good for very long bikes: tandems, but especially
triplets, quadruplets and the like. On those bikes, cable stretch is a real problem. Besides, with
hydraulic brakes, it is possible to adjust the pistons (or whatever they are called) to get the
proper pressure on both brakes, so it allows for operation of both brakes from a single lever
without constant fine-tuning. On a tandem, triplet and the like, applying both rim brakes with 1
hand would allow to use the second lever to operate a third brake and avoid brake overheating in the
Alps. Not a problem with a single.

By the way, you could check "Magura" and "Magura Julie" on the web for more info on these kinds
of brakes.

In other words, as others have said, no need for hydraulic brakes, and no need for disk brakes.

Michel Gagnon

 

[Cathy Kearns]

<[email protected]> wrote in message
news:[email protected]...
> [email protected] wrote:
>
> : I think you are hypothesizing rather than working from experience.
>
> That's correct, we don't have real hills so I'm descending in an armchair, if you will. Thanks for
> corrections
>
> : The real reason for stopping is if the primary front brake, rim or drum failed. Without a front
> : brake, hard braking is gone on a single. Descending fast uses primarily the front brake, the
> : rear one being largely ineffective in any hard braking because it skids so easily.
>
> How about a straight, long descent that isn't too steep? That wouldn't require hard braking. One
> would pick up speed, one would have to brake for an extended period. Still, could overheating be a
> problem - would the braking cause more heating than the cooling factors would handle? What if we
> have HPVs with different aerodynamics: a touring bike vs road bike (guess one doesn't need to
> descend in the drops though vs a recumbent vs a fully faired recumbent?
>
> As a side note, bents could really make a difference as comes to overheating. A two-wheeled bent
> with a front rim brake and 20" front wheel would be especially prone to the problem because of
> faster descending and the rim is smaller so it takes less energy to heat it up. On the other hand
> a tadpole trike with disc brakes on the front wheels would be quite well off on a descent that
> requires hard braking.
>
> Hmm anybody suggested air brakes as drag brakes yet?

Sure, any stoker worth her salt knows she can sit up and open her jacket and the bike will
immediately slow back into comfort zone.

>
> --
> Risto Varanka | http://www.helsinki.fi/~rvaranka/hpv/hpv.html varis at no spam please iki fi

 

[Cathy Kearns]

"James Thomson" <[email protected]> wrote in message
news:[email protected]...
> "Chalo" <[email protected]> wrote:
>
> > If you wish to use a gearhub, I recommend a linear-pull brake in front and a drum brake in the
> > rear. That gives you the braking power advantages of the linear-pull with the wet-weather
> > predictability and cleanliness of the drum brake, and the cost is reasonable.
>
> One disadvantage of a rear drum brake is that it can complicate rear wheel removal. Hub gear/ drum
> brake is the least convenient combination to deal with when mending a puncture at the roadside,
> and for me the advantages of a drum brake don't outweigh this inconvenience.

We have an Arai drum brake on our tandem. Changing tires is the same with and without the drum
brake, it stays on the wheel. Perhaps older models don't have the quick release on the brake cable?
(Though I admit, replacing a spoke would be a pain in the neck.)

>
> James Thomson

 

[Chris Phillipo]

> > faster descending and the rim is smaller so it takes less energy to heat it up. On the other
> > hand a tadpole trike with disc brakes on the front wheels would be quite well off on a descent
> > that requires hard braking.
> >
> > Hmm anybody suggested air brakes as drag brakes yet?
>
> Sure, any stoker worth her salt knows she can sit up and open her jacket and the bike will
> immediately slow back into comfort zone.
>

Or open her jersey and stop oncoming traffic.

--
_________________________
Chris Phillipo - Cape Breton, Nova Scotia http://www.ramsays-online.com

 

[James Thomson]

"Cathy Kearns" <[email protected]> wrote:

> We have an Arai drum brake on our tandem. Changing tires is the same with and without the
> drum brake, it stays on the wheel. Perhaps older models don't have the quick release on the
> brake cable?

Most drum brakes use a torque arm bolted to the chainstay. It needs to be unbolted to remove
the wheel.

> (Though I admit, replacing a spoke would be a pain in the neck.)

That's a drawback of tandem drag brakes that thread onto the left of the hub shell. The drum brakes
we're talking about are integrated into the hub, and don't impede spoke replacement.

James Thomson

 

[David]

"Elisa Francesca Roselli" <[email protected]> wrote in message
news:[email protected]...
>
>
> Pete wrote:
>
> > Not necessarily bad. After all, you use the front and back completely different. It's just a
> > matter of getting used to the differences.
>
> I'm not sure I do use them so differently? When I want to stop, I slam them both on.

They respond differently, whatever kind they are, and however you use them. When you brake hard,
weight is transferred from the back to the front wheel. Too much back brake and you will skid. Too
much front and you will endo. It may be hard to do completely by accident, but it's pretty easy to
send yourself over the bars with the front brake (if you try anyway).

There's nothing wrong with different types of brakes at each end of the bike. On modern bikes, I've
only heard of drum brakes as extra "drag brakes" for tandems on long descents. This being in
addition to rim brakes front and rear.

As far as brakes for long. steep descents, I've read on r.b.t. that rim brakes are better than discs
(backed up by a theoretical argument), but my experience is the opposite. I've had serious fade from
rim brakes several times. Got a flat from overheating once. Never had a fade problem with my front
disc brake. If I did, I suppose I could switch to one with a bigger rotor.