Differential brake pressure? - 600RR.net
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post #1 of 17 (permalink) Old 09-13-2010, 03:25 PM Thread Starter
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Differential brake pressure?

I hope the title is accurate for what I'm encountering. Couple days ago I was inspecting my brake pads for wear. While doing so I noticed that when I pumped the brake lever that all the pistons did not move in sync, one of the lower ones took atleast 2 pumps to produce any travel.

Now I remember seeing a video regarding brake care( it was done by David Moss). This was refered to as differential brake pressure, I think this is what causes a slight pulsing in the lever when stopping at times. Am I accurate in my assumptions? I think I may have to rebuild the calipers and i don't really have an experience with that. Any insight would be really helpful.
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post #2 of 17 (permalink) Old 09-13-2010, 03:28 PM
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you are checking for movment with no pads installed?

yea, all 4 pistons are not going to be as movable as each other, and when squeezing the level the fluid is moving the easiest to move part, and free floating pistons, you may be talking as little as .0002 psi difference causing one to move and the other not...


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post #3 of 17 (permalink) Old 09-13-2010, 03:31 PM Thread Starter
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No i was checking with the pads taken out of the caliper.
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post #4 of 17 (permalink) Old 09-13-2010, 03:39 PM
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Quote:
Originally Posted by aceof84 View Post
No i was checking with the pads taken out of the caliper.
right, so your checking with free floating pistons, and no way for the various pistons to equalize pressure....


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post #5 of 17 (permalink) Old 09-13-2010, 03:48 PM Thread Starter
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Hmm, I guess in Moss's video he must have meant with the pads in. Thanks for clearing up this issue. I'm happy to know that rebuilding the calipers won't be nessecary.
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post #6 of 17 (permalink) Old 09-13-2010, 03:59 PM
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Quote:
Originally Posted by aceof84 View Post
Hmm, I guess in Moss's video he must have meant with the pads in. Thanks for clearing up this issue. I'm happy to know that rebuilding the calipers won't be nessecary.
i would guess to determin if what your talking about he mentioned was happening, the proof would be within the pad wear it self

one side worn more than the other.. type of a deal.


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post #7 of 17 (permalink) Old 09-14-2010, 03:11 AM
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I'm with Tenjin, you would expect one to move and not the other, the oscillations in the lever are most likely going to be caused by a slightly warped disc, as it turns it will push the pistons back into the calliper which will translate into pulsing at the lever.
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post #8 of 17 (permalink) Old 09-14-2010, 08:30 AM Thread Starter
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Quote:
Originally Posted by Nico View Post
I'm with Tenjin, you would expect one to move and not the other, the oscillations in the lever are most likely going to be caused by a slightly warped disc, as it turns it will push the pistons back into the calliper which will translate into pulsing at the lever.
That sounds accurate, but wouldnt the pulsing be present any time I pull the brake lever? Its an intermittent issue and only occurs when the bike is about to come to a complete stop. If one of the rotors is slighty warped then i'm willing to live with it for a little while, when i have the oppertunity i'll buy a front stand and stop the front wheel and check the rotors with a feeler gauge to see what the issue is.
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post #9 of 17 (permalink) Old 09-14-2010, 09:29 AM
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The amount of runout on the disc will change when you feel it, if its only a small amount you will only notice it at low speeds, if its a large amount you will notice it all the time and you will have to pump the brakes back up before they actually work.

All rotors will have some kind of warp in them simply due to the fact that they are subjected to high heat differentials across their surface, the point contacting the pad will be hotter and if they happen to get wet then this issue will be exacerbated due to the cooling effect of the water. That difference in temperature will cause some parts of the disc to have expanded relative to the rest causing a slight warp. Its completely normal and nothing to be worried about unless the runout exceeds 0.3mm (0.012") which is quite a lot.

To check the runout you should be using a dial indicator mounted to the fork leg and running along the surface of the disc, using a feeler gauge will not give an accurate result due to movement of the calliper and the pads. You should also either remove the callipers or compress the piston a little so that the pads running along the surface of the disc doesn't interfere with the measurement.
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post #10 of 17 (permalink) Old 09-14-2010, 10:10 AM
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Quote:
Originally Posted by aceof84 View Post
Its an intermittent issue and only occurs when the bike is about to come to a complete stop.

your rotors aren't warped.. this is a symptom of floating rotors - everyone will experience this on the 07+ RR's I know I have since the day I picked up my bike brand new.. (not too sure about the 06's and earlier)

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post #11 of 17 (permalink) Old 09-14-2010, 01:36 PM Thread Starter
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Seems like there is two different camps of thought on this issue. My Bike is an 07, so it very well could be caused by the floating rotor. Could a rotor get warped due to day to day operation? I've never have a tip over or accident with this bike. The previous onwer did tell me she tipped it over two, once one each side. Thankfully it doesnt have any affect on stopping power or feel.
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post #12 of 17 (permalink) Old 09-14-2010, 01:57 PM
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your rotors aren't warped.. this is a symptom of floating rotors - everyone will experience this on the 07+ RR's I know I have since the day I picked up my bike brand new.. (not too sure about the 06's and earlier)
Honda doesn't put floating rotors on our bikes stock, so it can't be that for the issue. 03-10 are all semi-floating rotors. The actual rotor and the carrier are firmly attached by the pins.

I'm starting to think it's a characteristic of the stock master cylinder. Ever since I put my Brembo one on, my chatter when coming to a complete stop vanished.
post #13 of 17 (permalink) Old 09-14-2010, 02:20 PM
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^ right..

I have heard that floating rotors cause that exact feeling so I assumed that since almost everyone experiences this on the 07+ rr's that this was the cause and maybe semi floating rotors do the samething - I don't see how the MC could cause it, but if you are saying that your Brembo MC has eliminated it all together I am thinking that maybe you are right (usually are LOL)

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post #14 of 17 (permalink) Old 09-14-2010, 02:22 PM
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Quote:
Originally Posted by aceof84 View Post
Seems like there is two different camps of thought on this issue. My Bike is an 07, so it very well could be caused by the floating rotor. Could a rotor get warped due to day to day operation? I've never have a tip over or accident with this bike. The previous onwer did tell me she tipped it over two, once one each side. Thankfully it doesnt have any affect on stopping power or feel.
you would know if your rotors were warped - they will vibrate the lever (and the whole front end for that matter) from the moment you hit the brakes all the way to a stop.

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post #15 of 17 (permalink) Old 09-14-2010, 02:37 PM
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^ right..

I have heard that floating rotors cause that exact feeling so I assumed that since almost everyone experiences this on the 07+ rr's that this was the cause and maybe semi floating rotors do the samething - I don't see how the MC could cause it, but if you are saying that your Brembo MC has eliminated it all together I am thinking that maybe you are right (usually are LOL)
To be honest, I don't know if it's the placebo effect or not. Just haven't felt it ever since switching. Only reason that I could think of as why it'd be doing it is because of the bore/stroke on the stock one.

Edit: You know what, it might be the brake pads moving back and forth as the speeds decrease.

Last edited by Demented; 09-14-2010 at 02:42 PM.
post #16 of 17 (permalink) Old 09-14-2010, 03:46 PM
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^ That is a good thought - My brake pads do have a very slight bit of back and forth play in them.

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post #17 of 17 (permalink) Old 09-15-2010, 02:51 AM
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Either way, the lever pulsing a little at low speeds is perfectly normal...
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