Brakes grabby when wet? - Page 2 - GreenHybrid - Hybrid Cars

Brakes grabby when wet?

  #11  
Old 07-18-2007, 01:52 PM
Omnia Gloria Fugit
Join Date: May 2007
Location: College Station Texas
Posts: 744
Default Re: Brakes grabby when wet?

TSB 05-13-8 (the one refered to above) applies only to the 05 year model and is specific to the rear brakes. I have noticed the grabbyness on my 07 and its definatly cold wet brakes. A change of pad material might relieve this symptom. But one or 2 aggressive warm up stops will also.
 
  #12  
Old 07-19-2007, 12:09 AM
gpsman1's Avatar
Hybrid and Ethanol Expert
Join Date: Apr 2005
Location: All over the Central U.S.
Posts: 3,589
Default Re: Brakes grabby when wet?

Umm.. the part in red is impossible, but I get what you are saying.
If your pads touch, they are slowing you down. Maybe just 1 MPH, but they are slowing you down ( else you are burning more gas to keep speed steady ).
Sounds kind of pointless though, and just something else for the "person who has everything" and needs to spend more money.

Originally Posted by livvie View Post
Audi (I also think BMW) has a system in place where it detects rain and will auto apply the brakes (without slowing the car down) to dry the brakes in case of an emergency. Very clever.
 
  #13  
Old 07-19-2007, 09:23 AM
Active Enthusiast
Join Date: Mar 2005
Location: Dearborn, MI
Posts: 246
Default Re: Brakes grabby when wet?

Originally Posted by Mark E Smith View Post
It is a function of cold wet brakes. One of the service trade journals sugestes that you periodicaly do some aggressive braking to clean the pads and rotos. The claim that alot of the prius' rotors were rusting and pitting due to little use.
BTW, if you switch from drive to neutral and then apply the brakes, the FEH wont use regenerative braking. This forces the use of the disk brakes.

Ford says you don't really *need* to do this. The coefficient of friction is higher because of moisture. The brakes will naturally dry themselves as they are used, but if you want to force the drying you can use this trick.
 
  #14  
Old 07-19-2007, 04:26 PM
gpsman1's Avatar
Hybrid and Ethanol Expert
Join Date: Apr 2005
Location: All over the Central U.S.
Posts: 3,589
Default Re: Brakes grabby when wet?

Okay, now I'm really going to split hairs, but the coefficient of friction is LESS when the brakes are wet. When they dry off, the friction goes up, and they "bite" harder than you were expecting, since moments ago you needed to press the brakes a tad harder to overcome the wet & slipperyness.
-John
 
  #15  
Old 07-19-2007, 06:07 PM
Active Enthusiast
Join Date: Mar 2005
Location: Dearborn, MI
Posts: 246
Default Re: Brakes grabby when wet?

Originally Posted by gpsman1 View Post
Okay, now I'm really going to split hairs, but the coefficient of friction is LESS when the brakes are wet. When they dry off, the friction goes up, and they "bite" harder than you were expecting, since moments ago you needed to press the brakes a tad harder to overcome the wet & slipperyness.
-John
Not true! Water can behave as both an adhesive AND a lubricant. While a large amount of water will tend to act as a lubricant, a small amount of water will tend to act as an adhesive. Once excess water is spun (or wiped) off the brakes, the remaining moisture on the pads or discs will increase the coefficient of friction, not reduce it.

There are all sorts of physics experiments you can do to demonstrate this.
 
  #16  
Old 07-20-2007, 04:28 PM
Omnia Gloria Fugit
Join Date: May 2007
Location: College Station Texas
Posts: 744
Default Re: Brakes grabby when wet?

Just a word of caution. If you EVER remove the brake pads, calipers or rotors you MUST disable the ABS system. (battery disconected, Maxi fuses #24(50a) and # 31 (50a) removed) These systems on the Hybrid are ACTIVE even with the key off in park! The system does periodic pressure ups to test the system and fill the ABS accumulator. This means that with the pads removed IF the system does one of its automated tests it will push the pistons out of the calipers! And it will do a test when the dome light is activated! I.E. open the door and oh s*#t
 
  #17  
Old 07-20-2007, 05:53 PM
GatorJ's Avatar
Pretty Darn Active Enthusiast
Join Date: Apr 2006
Posts: 402
Default Re: Brakes grabby when wet?

Originally Posted by Pravus Prime View Post
https://www.greenhybrid.com/wiki/ind...ape_Hybrid_FAQ

Part II: DRIVING THE ESCAPE HYBRID

9. Why is it after it rains, my brakes get all grabby?

Short answer, because you're not using them. Most of your deceleration, outside of stepping hard on the brakes isn't actually braking, it's the regeneration system taking your motion and turning it back into energy to use, which means that your wet brakes don't get a chance to friction dry when you apply light braking pressure (like in a conventional vehicle), which means your brakes are still wet when they are used when stopping. Wet brakes grab hard, hence the grabbyness.
Do you have a point of reference for this opinion? Have you changed your pads?
 
  #18  
Old 07-21-2007, 10:17 PM
gpsman1's Avatar
Hybrid and Ethanol Expert
Join Date: Apr 2005
Location: All over the Central U.S.
Posts: 3,589
Default Re: Brakes grabby when wet?

I think even the owners manual says not to change your brakes with the car "powered up". I know I have read this in official Ford documents more than once. Plus you can just tell by observations also.
 
  #19  
Old 07-23-2007, 04:39 PM
GatorJ's Avatar
Pretty Darn Active Enthusiast
Join Date: Apr 2006
Posts: 402
Default Re: Brakes grabby when wet?

Originally Posted by gpsman1 View Post
I think even the owners manual says not to change your brakes with the car "powered up". I know I have read this in official Ford documents more than once. Plus you can just tell by observations also.
You can change the pads and rotors, but it is absolutely impossible to bleed the system "powered up".
 
  #20  
Old 07-24-2007, 11:19 AM
08FEH's Avatar
Pretty Darn Active Enthusiast
Join Date: May 2007
Posts: 368
Default Re: Brakes grabby when wet?

This is cut and paste from my 08FEH owners manual.

The Regenerative Braking System checks the integrity of the brake
system at times when the vehicle is parked. This is done by developing
brake pressure for short periods of time. In order to change the brake
pads, it is necessary to enter the Pad Service Mode. This will prevent
brake pressure from being applied.
To enter the Pad Service Mode, perform the following with the vehicle
stationary:
1. Place the vehicle in Park and turn ignition to the ON position.
2. Apply the brake pedal.
3. Turn the ignition OFF, then ON three times and then release the brake
pedal. The total time elapsed for the three ignition cycles and brake
release must be less than 3 seconds.
The brake warning lamp will:
• flash as stored hydraulic pressure is released.
• remain illuminated once the pressure is completely released.
• flash if the brake is applied.
To exit the Pad Service Mode:
1. Apply the brake pedal and turn the ignition OFF then ON. This will
cause brake pressure to be developed within the brake system. Once
brake pressure is developed, the brake warning light will turn off.
2. The Pad Service Mode will also be exited if the gear shift lever is
moved from the (P) Park position, the vehicle is moved (wheels rotate)
or the ignition is turned OFF.

Hope this info helps

08FEH
 

Thread Tools
Search this Thread
Quick Reply: Brakes grabby when wet?


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.