Strange Front Brakes

[David Towle]

I have meant to post this since I first put on snow tires but kept forgetting, although maybe its been mentioned in a thread I missed. Took the snows off today, and was re-reminded of the very strange front brake design.

The pads do not contact the outer 1" diameter of the front ventilated rotors! I have been doing brake jobs and changing snow tires for about 35 years and I have never seen this on any car. There is a half inch wide strip of rust around the OD of the rotors. Do others have this?

It looks like the pads extend out to the full diameter of the rotors but they don't make contact. Do they put a bevel or cutout on the pads for some reason? (Stabilizing the pad material when its still very thick?) Is this something done on other cars that disappears as the pad wears in a few thousand miles, but because I use the brakes so little on this car its lasting years? (I have over 30,000 miles on the car) This design of course makes the brakes less powerful and fade resistant than they could be since the full area is not being utilized.

The rear brakes are smaller non ventilated, and the pads contact within a few millimeters of the rotor OD as is normal.

 

[Atkinson]

You may find that rust has worn the pads near where they used to touch the outer edge of the rotors so that there is insufficient contact to clean the rust.
Beveled pads would wear flat over time.
My pads are contacting (and cleaning) the full rotor diameter.
The combination of regen and light friction braking (and salt, if that applies) can allow the rotors to get a little rusty longer and more often compared to cars that are driven hard.
If hard braking doesn't help, try multiple emergency stops from highway speed in neutral.
The brakes will get hot.
I had to do this to fix a related issue: faint rust pulsation in the rotors due to my lack of aggressive driving.
Failing that, the rotors may have to be replaced or turned and new pads installed to break the cycle.

 

[insightman]

You may find that rust has worn the pads near where they used to touch the outer edge of the rotors so that there is insufficient contact to clean the rust.
Beveled pads would wear flat over time.
My pads are contacting (and cleaning) the full rotor diameter.
The combination of regen and light friction braking (and salt, if that applies) can allow the rotors to get a little rusty longer and more often compared to cars that are driven hard.
If hard braking doesn't help, try multiple emergency stops from highway speed in neutral.
The brakes will get hot.
I had to do this to fix a related issue: faint rust pulsation in the rotors due to my lack of aggressive driving.
Failing that, the rotors may have to be replaced or turned and new pads installed to break the cycle.

Following a two-week driving hiatus after driving in wet weather, the rust on our Clarity's front rotors was so entrenched that no amount of high-speed emergency-style braking could fix the problem (I was starting to worry about wearing out my front tires prematurely). I had to have the rotors turned.

 

[craze1cars]

Photo below I have about 29,000 miles. All looks very normal to me. Pad wear is barely measurable. I’m sure those who think they are “saving” the brakes by using regen paddles all the time and driving like little old ladies will be forced to replace rotors prematurely, especially in the rust belt areas, much like Insightmans experience. In CA maybe notsomuch I dunno. But here in Indiana winters I noticed some time back that you gotta drive these cars kinda normal to semi-aggressive to keep the rotors clean...More so than my other cars. Dont baby the brakes...the system inherently babies them too much already. These can be lifetime brake PADS on these cars, but for the sake of the rotors which are more expensive, you gotta cram on the pedals and do some good hard stops at times to keep the surface rust at bay. Don’t let them get deep pitted or you’re in for a repair bill. I don’t think I’d bother turning them...they’re only about $100 each and modern rotors can’t take much turning anymore they get too thin and warp easy. Pads are cheap too easy to find for only $45/set OEM from many sources. So for less than $250 in parts you can get new front factory pads and rotors. Add Labor maybe $100 at most shops if you don’t DIY.

 

[David Towle]

Thanks all for the advice. They've been like this for a year but I've never noticed any pulsation or other problems. I will try repeated high speed stops when traffic is light. Still not really sure how this problem can happen, seems like the pistons should push the entire pad to the rotor, but I'll report on any improvement.

 

[David Towle]

I did 5 hard stops 80-10 on a state road with few other cars around. They did make my rotors look more uniform, but you can still see the division line where I only got contact on these hard stops. Not near as rusty as they were . I guess I have to do this regularly. Thanks again. Everyone please take a look at your brakes once in awhile to check for this.,

 

[insightman]

When our rotors got really bad I could hear the rusty spots on the rotors as they passed the brake pads. The slightest touch on the brake pedal changed the swish-swish-swish sound, so now I believe the Clarity doesn't activate regen braking first and calipers second.

 

[PHEV Newbie]

Following a two-week driving hiatus after driving in wet weather, the rust on our Clarity's front rotors was so entrenched that no amount of high-speed emergency-style braking could fix the problem (I was starting to worry about wearing out my front tires prematurely). I had to have the rotors turned.

There's no regen when you go in reverse so instead of adding wear and tear on your car by making hard stops, just ride the brakes a bit while reversing on a slight downgrade (some place that's safe of course). The rust will come off rather quickly (and more safely) that way. Your experience just goes to show how "aggressive" Honda's regen braking is. Unless you brake hard, it's all regen except for the last second or so. A lot of hybrids and EVs combine friction braking with regen under most conditions.

 

[insightman]

There's no regen when you go in reverse so instead of adding wear and tear on your car by making hard stops, just ride the brakes a bit while reversing on a slight downgrade (some place that's safe of course). The rust will come off rather quickly (and more safely) that way. Your experience just goes to show how "aggressive" Honda's regen braking is. Unless you brake hard, it's all regen except for the last second or so. A lot of hybrids and EVs combine friction braking with regen under most conditions.

Really, I could hear the rusty spots go swish-swish-swish past the pads and the slightest touch on the brake pedal changed the sound, so I firmly believe that the Clarity combines calipers and regen and for braking from the start. It may stop the regen part at the end of a long stop, but it always starts with calipers + regen. I'll definitely try the reverse, caliper-only braking when the next crop of rust starts growing on the rotors.

 

[rodeknyt]

There's no regen when you go in reverse so instead of adding wear and tear on your car by making hard stops, just ride the brakes a bit while reversing on a slight downgrade (some place that's safe of course). The rust will come off rather quickly (and more safely) that way. Your experience just goes to show how "aggressive" Honda's regen braking is. Unless you brake hard, it's all regen except for the last second or so. A lot of hybrids and EVs combine friction braking with regen under most conditions.

Or, just coast in neutral and use the brakes. Then you know your not getting regen.

 

[PHEV Newbie]

Really, I could hear the rusty spots go swish-swish-swish past the pads and the slightest touch on the brake pedal changed the sound, so I firmly believe that the Clarity combines calipers and regen and for braking from the start. It may stop the regen part at the end of a long stop, but it always starts with calipers + regen. I'll definitely try the reverse, caliper-only braking when the next crop of rust starts growing on the rotors.

I have a different experience in normal braking. There was a time my brakes were really noisy so I heard them clearly whenever they engaged. In normal braking, I never heard them until the last few feet before a stop. Exceptions: 1) hard braking; 2) full battery -- friction brakes engage as soon as I step on them to protect the battery; 3) going in reverse. I had read an article by Honda that the Clarity's regenerative braking system differs from others by using regen for as long as possible to maximize efficiency. I couldn't find the link again but I'll keep looking. If friction brakes normally engage at the press of the brake pedal, no one should have any issues with rust on their rotors.

 

[Atkinson]

Really, I could hear the rusty spots go swish-swish-swish past the pads and the slightest touch on the brake pedal changed the sound, so I firmly believe that the Clarity combines calipers and regen and for braking from the start. It may stop the regen part at the end of a long stop, but it always starts with calipers + regen. I'll definitely try the reverse, caliper-only braking when the next crop of rust starts growing on the rotors.

This is a much better description of the the rusty brake sounds that drove me crazy!
Hard braking cleaned the rotors enough to stop the swish-swish-swish.
From an engineering perspective, I'd bet that Honda just takes up brake slack (touches pads to rotors) and applies regen for normal braking.
This prepares the system for full friction braking if needed.