V-Brakes Power Modulator

Peter Rosenfed said:

I just did some research on these things and found some of the older postings by Sheldon Brown
about what he regarded as the problem with the power modulator. Has the problem been fixed, or do
they still limit maximum braking force?

That's their designed function - that bug is a feature. If you're not likely to clamp on full force
and give yourself a free flying lesson, take the stupid thing out.

Quoted message said:

Also, what ias the worst case failure mode of the power modulators?

No brakes at all, I expect.

Quoted message said:

Are they more likely to fail than a cable without the modulator on the noodle?

Clearly yes, to some degree - it's just extra fiddliness.
--
David Damerell <[email hidden]> flcl?

Peter Rosenfed said:

I just got a new bike with Shimano V-brakes. The front brake has a "power modulator" on it. I've
been practicing emergency braking with this new bike and I can't get the back wheel to lift off
when using the front brake. I'm unsure whether this is due to the power brake or whether I'm still
getting use to the new bike's geometry and the longer pull on the V-brakes ( I'm used to center
pull and the older-style cantilever brakes).

Pulling as hard as I can, the lever doesn't bottom out, so I assume I'm getting full
braking force.

I just did some research on these things and found some of the older postings by Sheldon Brown
about what he regarded as the problem with the power modulator.

Has the problem been fixed, or do they still limit maximum braking force?

It's not a problem "with" the Power Modulator, the Power Modulator itself is inherently a problem.

It is designed to limit braking power so that you _can't_ lift the rear wheel. Shimano's legal
deparment seems to think that they are at a higher risk of getting sued if somebody overbrakes and
goes over the bars, than if they can't stop in time to avoid a crash.

The fundamental concept is fallacious, and my advice is to remove the power modulator, smash it with
a big hammer and throw it in the trash where it belongs.

Sheldon "Am I Making Myself Clear?" Brown
+--------------------------------------------------------------+
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Sheldon Brown <[email hidden]> wrote in message
news:<[email hidden]>...

Quoted message said:

It's not a problem "with" the Power Modulator, the Power Modulator itself is inherently a problem.

It is designed to limit braking power so that you _can't_ lift the rear wheel.

Does the modulator actually limit the maximum deceleration you can achieve, or does it simply change
the braking profile so that it is less "grabby"? In other words, does it require more pull to
achieve the same maximum braking force, or does it actually threshold the braking force?

I had thought that the mdoulator was simply an elastomer hooked to the cable that stretches when you
pull on the cable, adding a bit of non-linearity to the pull. In this is the case, if there is room
for enough pull on the lever you should still be able to reach the same force.

-Pete

"Sheldon Brown" <[email hidden]> a écrit dans le message de news:
[email hidden]...

Quoted message said:

... The Power Modulator itself is inherently a problem.

Quoted message said:

It is designed to limit braking power so that you _can't_ lift the rear wheel. Shimano's legal
deparment seems to think that they are at a higher risk of getting sued if somebody overbrakes and
goes over the bars, than if they can't stop in time to avoid a crash.

What happens in that Power Modulator? I looked at one of Shimano's instruction sheets (somewhere at
bike.shimano.combike.shimano.comOpen ↗) and noticed there are three settings:
- H (for high or hard?)
- normal, which is the preset
- L (for Low)

They say one could change the setting, but they don't even suggest what the two other settings do.
For instance, if one sets the Power Modulator to H, does it mean the Power Modulator is more
aggressive at preventing hard braking, or does it mean that one can brake more quickly?

Also, is the Modulator limiting pulling strength in the brake cable or is it actually controlling
the speed at which the bike decellerates? The latter could be a good thing: a bit like the car's
ABS brakes.

Regards,

--
Michel Gagnon -- Montréal (Québec, Canada) "][email hidden]