02GF74
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| posted on 20/5/11 at 08:17 AM |
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brake bias
Mountain bike related question but principple can equally apply to motorcycles and cars.
Let's say you have one arm and want to have one brake lever to operate both front and rear hydraulic brakes.
Just like in motor vehicles, the majorty of the braking is done by the front wheel(s) so you don't want to be locking up the rear end each time
the brake is applied.
There is no bias bar so bias has to be done by caliper piston diameter.
Should the diameter at the rear be bigger, the same or smaller diameter than the front one?
Or some other way such as fitting restrictor* in the rear brake hose?
* by this I mean some means of reducing the dameter of the brake hose.
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daviep
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| posted on 20/5/11 at 08:26 AM |
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Rear caliper needs to be smaller. Reducing diameter of hose has no effect.
Davie
“A truly great library contains something in it to offend everyone.”
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daviep
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| posted on 20/5/11 at 08:27 AM |
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Or get one of those old fashioned drum brakes that applies the brakes when you pedal backwards 
“A truly great library contains something in it to offend everyone.”
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matt_gsxr
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| posted on 20/5/11 at 08:46 AM |
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rear disk should be smaller diameter if you want less braking at the rear. (torque is force times distance from axis. The force is the frictional
force between pads and disk)
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02GF74
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| posted on 20/5/11 at 09:36 AM |
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quote:
Originally posted by daviep
Rear caliper needs to be smaller. Reducing diameter of hose has no effect.
Davie
ok, so I have misunderstood how these pressure proportioning valve devices work -
these:
how do they work - spring loaded valve that changes size of orifice through whcih the fluid flows?
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britishtrident
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| posted on 20/5/11 at 10:07 AM |
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quote:
Originally posted by 02GF74
quote:
Originally posted by daviep
Rear caliper needs to be smaller. Reducing diameter of hose has no effect.
Davie
ok, so I have misunderstood how these pressure proportioning valve devices work -
these:
how do they work - spring loaded valve that changes size of orifice through whcih the fluid flows?
That is not a proportioning valve but a simple pressure limiting shut off vale, it just stops any further increase in pressure getting to the rear
once the pre-set pressure is exceeded.
Proportioning valves are a bit more complex: The front and rear pressures the the same up pressure X but above pressure X the pressure in the
rear line increase in a prre-set % of the increase in the front brake line.
One of the difficulties with brake proportioning on mountain bike is the effects of weight tranfer on steep gradients
[Edited on 20/5/11 by britishtrident]
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speedstar
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| posted on 20/5/11 at 11:44 AM |
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Why would you want them on the same circuit? Surely the ability to inifintely adjust your bias on the fly and whilst braking is worth keeping!! I know
how much you use it on a motorbike, so can only assume a mountain bike is the same?
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matt_gsxr
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| posted on 20/5/11 at 12:06 PM |
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quote:
Originally posted by speedstar
Why would you want them on the same circuit? Surely the ability to inifintely adjust your bias on the fly and whilst braking is worth keeping!! I know
how much you use it on a motorbike, so can only assume a mountain bike is the same?
quote:
Originally posted by 02GF74
Let's say you have one arm ....
I think that is a good answer!!!
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adithorp
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| posted on 20/5/11 at 12:26 PM |
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To do it with one lever you'd need the rear disc or piston to be smaller, or both. given variable grip surfaces though and undulations off road
it'd be very difficul to stay in control.
I've raced with a few one armed guys on the road (and on the velodrome but threre's no brakes there!). The usual way they do it on a raod
bike is both brake levers mounted on one side. One pointing down in the normal position and the other fitted upside down pointing up so the tips of
the levers are almost touching.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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britishtrident
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| posted on 20/5/11 at 07:18 PM |
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Whats needed a a simple light anti-lock device, only thing I can come up with is viscous coupling between the rear wheel and the disc.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 20/5/11 at 07:28 PM |
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Bud Brake
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 20/5/11 at 07:34 PM |
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I just found the patent for the above ---- not impressed.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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HowardB
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| posted on 20/5/11 at 08:18 PM |
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can you post the link to the patent, I'm interested to see what's in the box,..
thanks
Howard
Fisher Fury was 2000 Zetec - now a 1600 (it Lives again and goes zoom)
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britishtrident
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| posted on 20/5/11 at 09:06 PM |
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Patent link
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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