Brakes grabbing at low speed when wet

[cincidaddi]

I have a 2013 FFH and have been trying to figure out why my brakes grab when I'm almost at a complete stop. This behavior only happens when the brakes are wet, like when I'm driving in the rain or when I get out of a car wash. It forces me to have to release pressure on the brake when I nearly stop to avoid the car jerking at a stop. This is very peculiar and has occurred since taking delivery in Dec 2012. I've had the dealer mechanics look at it but they don't seem to understand why or think anything is wrong. I've simply been living with knowing I need to ease the brake pressure when I'm close to stopping with wet brakes but I can't believe this is normal. Has anyone heard of anything like this? Any suggestions?

[hybridbear]

I always ease up on the pressure right before coming to a complete stop so as to stop smoothly. That's something I was taught to do by my dad when he taught me how to drive. Since the friction brakes don't engage until about 5 MPH (when you get a 100% brake score) it could be that since the wet pads have less stopping power the car is automatically compensating for that and that is what you feel. We've been in such a drought here in MN that our FFH hasn't driven in rain in at least 3 months... From what I can recall in driving with wet pads I have not noticed any difference in brake feel.

[GrySql]

Mine have done that a few times, especially in cold weather, they get 'grabby' right at the final stop, like HB says - <5mph.

The last time was a week ago when I was in a DIY car wash on a cold morning and pressure washed the wheels (and brakes).

Otherwise, after a few stops, when the rotors and pads have warmed up it goes away.

 

If this continues happening even after the rotors/pads are warmed up then you need to impress upon your service department that something is amiss.

[lolder]

I have a 2013 FFH and have been trying to figure out why my brakes grab when I'm almost at a complete stop. This behavior only happens when the brakes are wet, like when I'm driving in the rain or when I get out of a car wash. It forces me to have to release pressure on the brake when I nearly stop to avoid the car jerking at a stop. This is very peculiar and has occurred since taking delivery in Dec 2012. I've had the dealer mechanics look at it but they don't seem to understand why or think anything is wrong. I've simply been living with knowing I need to ease the brake pressure when I'm close to stopping with wet brakes but I can't believe this is normal. Has anyone heard of anything like this? Any suggestions?

It's "normal" and all the 2010 and up do it the first stop with wet brakes. The best hybrid braking technique is to gradually reduce braking as you slow so the last 5 mph is almost coasting to a stop. Regen capability reduces with speed and if you do this, you will hardly notice it. Don't worry about it, Ford has the smoothest hybrid braking.

[cincidaddi]

Thanks for the replies. I feel a little better about it though it seems a little strange. Seems like standard fare.

[acdii]

The service brakes are very good, and since not used much until the final few feet, they will grab, plus when slowing to a stop with 100% brake score, the computer adjusts the pressure to apply the pads. Quite normal. I would rather they grab than not.

[Eddie Sessum]

Yea it all just has to do with the feel of the regen vs friction switch over.

[Sleddog]

I had it happen to me today. I never experienced it before, and it's been driven in the rain numerous times.

[cincidaddi]

I had it happen to me today. I never experienced it before, and it's been driven in the rain numerous times.

This is why I'm not convinced its 100% normal. It doesn't happen to me when the brakes are dry. Seems like the braking system should compensate better if transitioning when wet.

Edited September 28, 2013 by cincidaddi

[corncobs]

I would say it could the water film on the rotors. VW / Audi used to have a huge problem with that so they implemented an automatic water film removal sequence. The system would apply the brakes every so often to remove the film.

Maybe it's a similar problem that at first nothing happens while there is water but then it grabs really hard since you apply more braking force.

 

I'm not sure just a thought.

[kuzzi]

This has happened to me with every car that has ABS.

[GrySql]

This is why I'm not convinced its 100% normal. It doesn't happen to me when the brakes are dry. Seems like the braking system should compensate better if transitioning when wet.

When the rotors/pads are hot from being used evaporation quickly dries them.

The problem occurs most of the time when the rotors are cold, the water sticks and the cold/wet pads grab.

 

Forget what all your other cars have done, these FFH's are different.

Remember, the eCVT does most of the braking so a simple tap on the brakes when driving will not heat the rotors and dry the brakes.

It appears, from my last episode, that the slow, final stop is the only way to heat the rotors/pads and evaporate the water - so more of these 'final hydraulic braking' stops are necessary before the water is dissipated.

Just my 2 cents.

[hybridbear]

Now that I think about it... back in winter when we were driving in freezing rain/sleet/snow on wet roads but with the temperature below freezing we experienced some strange brake behavior when stopping hard or at low speeds. I always just attributed it to slippage on the snow/ice. Perhaps some of it was the pads slipping on wet/ice coated rotors which were cold as ice from their limited use. I will pay more attention this winter.

[acdii]

All my Hybrids did this, so did my 2010 Sport when they were cold, when stopping while going under 10 MPH. The pads are just grabby, thats all, nothing wrong with them. If you think its bad, you should feel how strong EBC pads are when cold. Put you through the windshield!

 

 

There is a lot involved with how brakes actually work. More to it than a friction pad against a hunk of iron. Brand new brakes dont work very well until they are bedded into the rotor. There is actually a transfer of braking material applied to the rotor surface. Its this material that will cause the grabbing when cold.

 

One other thing to consider, when slowing down in a non Hybrid, 100% of braking is done with the brakes, so by the time you stop, the rotors and pads have heated up, so you dont get that grabbing, but since nearly all braking is done using the generators, the rotors and pads rarely heat up, and since they usually get applied under 5-10 MPH, they will be a bit grabby.

 

IOW dont worry about it, perfectly normal.

[hybridbear]

With all the rain we've had lately the changes in brake pad response due to water become really noticeable. Normally the transition from regen to brake pads is so smooth that it's imperceptible. However, when the pads are wet they will noticeably grab when they engage.

 

My point is, the recent experience of often grabby pads due to rain has caused me to be even more impressed with the regen programming by Ford in the FFH. They did an excellent job. Many car reviews talk about how well Toyota has smoothed out the Prius brake transition. I always found the FFH brakes to be more smooth in their transition.

 

Well done Ford!

[bcoil]

I suspect that the hard braking at 5MPH when wet is worse on some cars that others. My 2015 is practically schizophrenic between dry and wet. Normal gentle regen braking doesn't work when wet. The car is yanked to a stop at 5MPH if there is a light mist around. If you are driving after a rain, you might get hard braking or normal gentle braking, depending on the amount of moisture around the wheels. Those who talk about easing up on the brake as you approach a stop are right when it comes to normal braking. The problem is that the braking characteristics change unpredictably. I guess I can deal with it as long as I drive in either dry weather or wet weather, but the in between conditions make driving an aggrevation.

I appreciate people posting their experience so I know it is not just my car that acts this way.

 

I can only hope that someone has some success with a solution, such as a change to a certain kind of brake pad, or a reprogrammed onboard computer.

 

[Waldo]

 

I can only hope that someone has some success with a solution, such as a change to a certain kind of brake pad, or a reprogrammed onboard computer.

 

 

To understand the solution, you must first understand the problem. The problem is that at low speed braking the system is really a brake by wire. The computer has to guess at how much hydraulic pressure to apply to the brakes in order to match the decel rate you are currently experiencing in regen. To make that guess, the computer knows your decel rate and it has a formula that can calculate how much hydraulic pressure to use to match that decel rate, but the key is that it has to assume a co-efficient of friction between the pad and the rotor. The problem is this co-efficient is always changing, especially so when it's wet. Since the computer has no way to measure the co-efficient directly, it has to be pre-programmed and this pre-programming is based on the most usual co-efficient, which is when it's dry.

 

So the only way you're ever going to "fix" the problem is to develop some kind of sensor that can accurately predict friction or find a brake pad that always has the exact same co-efficient of friction in all conditions.

As an aside, this is also exactly the same scenario as to why the dual-clutch transmissions in the Focus and Fiesta got such a bad rap for smoothness, because there's no way to accurately predict the friction of the clutches in a dry-clutch system.

[Texasota]

As an aside, this is also exactly the same scenario as to why the dual-clutch transmissions in the Focus and Fiesta got such a bad rap for smoothness, because there's no way to accurately predict the friction of the clutches in a dry-clutch system.

Thanks, Waldo, for helping me to better understand the bad experience I had with the dual-clutch transmission in my 2012 Focus. It was the third Focus I have owned but will not consider another one until they jettison that miserable transmission.

[mwr]

I've noticed this when starting up on a wet morning.

[acdii]

The day I got rear ended, the brakes were grabby, so the car was stopping fast, which probably led to getting rear ended. Waldo's explanation makes total sense now as to why the brakes do what they do under different conditions.

 

+1 to Waldo!