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View Full Version : travel ratio = m/c push rod travel/pad travel


counter
10-29-2010, 09:03 AM
If the front and rear calipers have different diameters, then the travel ratio will also be different. what would the effect of this difference on brake assembly or on performance(if the difference is too much)?

what typical value of travel ratio is good for a braking system? I think higher travel ratio would make pedal spongy. Any ideas please suggest...
counter
10-29-2010, 09:03 AM
If the front and rear calipers have different diameters, then the travel ratio will also be different. what would the effect of this difference on brake assembly or on performance(if the difference is too much)?

what typical value of travel ratio is good for a braking system? I think higher travel ratio would make pedal spongy. Any ideas please suggest...
Old Greg
10-29-2010, 10:18 AM
It also depends on the difference in size between your master cylinders. All that is going to happen is that you'll have more travel in one MC than the other. Just adjust the clevises on the MCs so that the balance bar is perpendicular to the pedal under full braking and you'll be fine.

As for pedal ratio, that depends on everything else in your braking system. Decide out how hard you want to have to step on the pedal to slow down at 1g, figure out how much clamping force it will take to slow down at 1g and then connect the dots based on your calipers and MCs.
counter
10-29-2010, 11:23 AM
Is there any correlation between selection of caliper and master cylinder diameter e.g. a combination of very smaller diameter master cylinder and comparatively very larger diameter of caliper can apply required resistance torque to lock the wheel. But I heard it may create bleeding problems and pedal becomes spongy. CAN ANYONE LITTLE ELABORATE ON THIS ?
Carlos289
10-30-2010, 04:36 AM
Hi Counter,
Forget all about travel, brakes has nothing to do with travel.
Travel is important for a clutch but not for brakes.

For brakes what matter is "Pressure"

If you use very small MC you will have more difficulties with filling and bleeding, just because the volume displacement is lower, so if you bleed the system via the classical feet push you will need more push's to get the same result with a larger cylinder.

Pressure that is all about. [Balance in pressure]

First you bring the system to pressure [fill it and bleed it] after you lift the feet of the pedal, the system will have a "residual" pressure [depends of weight, gravity, etc.] That is why the pad will have a gap with the disk.

But when your MC are located lower than the calipers you can run in problems.
Say the fluid will go to the lower point and you will loose the required "residual pressure"
If that is the case, you need to install a "Pressure Residual Valve" of 2 PSI.
counter
10-30-2010, 09:48 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Carlos289:

Forget all about travel, brakes has nothing to do with travel.
Travel is important for a clutch but not for brakes.

But "travel to cut off" is necessary to uncover the transfer port which acts as "free play" after which pressure start to built up.

But when your MC are located lower than the calipers you can run in problems.
Say the fluid will go to the lower point and you will loose the required "residual pressure"
If that is the case, you need to install a "Pressure Residual Valve" of 2 PSI. </div></BLOCKQUOTE>

But our reservoir is open to atmosphere, which will also exert the residual pressure.
Adambomb
11-02-2010, 05:52 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by counter:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Carlos289:

Forget all about travel, brakes has nothing to do with travel.
Travel is important for a clutch but not for brakes.

But "travel to cut off" is necessary to uncover the transfer port which acts as "free play" after which pressure start to built up.

But when your MC are located lower than the calipers you can run in problems.
Say the fluid will go to the lower point and you will loose the required "residual pressure"
If that is the case, you need to install a "Pressure Residual Valve" of 2 PSI. </div></BLOCKQUOTE>

But our reservoir is open to atmosphere, which will also exert the residual pressure. </div></BLOCKQUOTE>

1. WHY??????? a.) fluid spillage; b.) fluid contamination; c.) fluid absorption of water

2. How will the atmosphere exert residual pressure? Are your calipers mounted in a vacuum?