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Guaranteed 100% fix for leaking Hayes Calipers on R1250RTs

WWeldin said:
wemi, thanks for the reply.

I should have asked this in my first inquiry about your fix, but did you have the leaking (weeping) calipers to begin with? During my 12k service at the dealer, they did the inspection on the calipers with "no issues found." I have about 17,xxx miles on it and keep checking for signs of weeping. So far.....so good.

I bought my '19 model in Jan, 2019, for what it is worth.

Congrats on getting it sorted.
Click to expand...

the Hayes calipers on my 2020 were rebuilt/changed at the dealer when they uncrated the bike. They were leaking and apparently had done so since the bike left the factory. Since they also had ruined the rim with brake fluid the front rim was also replaced before delivery. My Hayes calipers never leaked since delivery. They performed just fine. I was just nor ready for the eventuality of them failing as well as the endless fix, stop sale, recall issues. As far as my survivability is concerned I don't do too many compromises. At this point I am quite happy with the total Brembo system, front and back. Professionally installed (albeit quite expensive) and guaranteed.
 
interesting observation after first 400 miles w/ Brembo brakes

A deeper look at why the brake feeling is significantly different with the new Brembos as opposed to the original Hayes brakes.

If you closely look at the the picture of the Brembo disc and the ruler you can see some interesting observations. The old Hayes brake swept the disc from about 4.5 to 25.5 whereas the Brembo brake is sweeping from about 1.5 to 29.5. The Brembo sweep goes right to the angled edge of the disk while the Hayes brake sweeps a significantly smaller area. This explains the additional force required on the lever for the same braking effect with the Hayes setup.

The Hayes brake pads are significantly smaller than the Brembo pads resulting in the smaller swept area or to put it another way the Brembo discs are quite a bit bigger (wider) than required for the Hayes brakes. So in time the Hayes pads will wear groves into the disc as opposed to the Brembo brakes which sweep the entire width of the disc for uniform wear.

The OEM of course lists the swept are as the entire surface of the disc which in the case of the Hayes brakes is incorrect, whereas in the case of the Brembos it is correct.

IMHO the Brembo discs are made for the Brembo brakes. Maybe BMW had a few 1000 of them on hand and just used them. No harm in that. Had they used Hayes discs we wouldn't be able to simply switch to Brembos.

YMMV
 

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Engineering Physics

It's been quite a while since I took my engineering degree, but from what I remember Frictional force (braking force in this case) is the product of the coefficient of friction between the two surfaces and the pressure. Area does not affect the force developed. Area will affect heat dissipation (which could alter the frictional coefficient) and the wear of the pads, but a bigger swept area does not mean more braking force. That comes (assuming the same brake pad material) from increased pressure. It'd be good to know if the pistons in the calipers have the same surface area and/or if the master cylinder plunger and lever geometry is the same.


wemi said:
A deeper look at why the brake feeling is significantly different with the new Brembos as opposed to the original Hayes brakes.

If you closely look at the the picture of the Brembo disc and the ruler you can see some interesting observations. The old Hayes brake swept the disc from about 4.5 to 25.5 whereas the Brembo brake is sweeping from about 1.5 to 29.5. The Brembo sweep goes right to the angled edge of the disk while the Hayes brake sweeps a significantly smaller area. This explains the additional force required on the lever for the same braking effect with the Hayes setup.

The Hayes brake pads are significantly smaller than the Brembo pads resulting in the smaller swept area or to put it another way the Brembo discs are quite a bit bigger (wider) than required for the Hayes brakes. So in time the Hayes pads will wear groves into the disc as opposed to the Brembo brakes which sweep the entire width of the disc for uniform wear.

The OEM of course lists the swept are as the entire surface of the disc which in the case of the Hayes brakes is incorrect, whereas in the case of the Brembos it is correct.

IMHO the Brembo discs are made for the Brembo brakes. Maybe BMW had a few 1000 of them on hand and just used them. No harm in that. Had they used Hayes discs we wouldn't be able to simply switch to Brembos.

YMMV
Click to expand...
 
Frictional swept area does not affect the force developed within the hydraulics, true, but it certainly Does affect how much slow-'er-down you get as a result. Harken back to drum brakes... bigger was/is always better. And even with disks, observe that racing vehicles (and even the hot-rod street cars in the showroom, like a 'Vette or Cobra) usually have larger disks (and pads) than street vehicles.
 
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but a bigger swept area does not mean more braking force.


Don't know what that means and that's not what my post says. A bigger sweep area in conjunction with larger pads, to access that larger surface, provides more braking (friction) surface due to a larger contact area and for the SAME lever pressure (with the same inline components, like actuator, etc.) provides more braking or faster deceleration. Conversely, the smaller the swept area/pad the more force (lever pressure) is required to achieve the same deceleration.
Too much deceleration, however, is not desirable either, since it can lead to wheel blockage and sudden death. The ABS would/should be engaging to alleviate that issue. So the size of the rotors, pads, the swept area, the brake pressure components, the electronic monitors etc. all play an important role and need to be engineered to harmonize.
 
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