Brake talk again! - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Wrangler Forums > JK Wrangler Technical Forum > Brake talk again!

Savvy Billet LED Tail LightsLight up the holidays with LED lights from JeepHutIntroducing MONSTALINER™ UV Permanent DIY Roll On Bed Line

Reply
Unread 09-29-2014, 05:54 AM   #1
Wrigley
Registered User
2013 JK Wrangler 
 
Join Date: Oct 2006
Location: fLORIDA
Posts: 263
Brake talk again!

I went into my local auto parts store on Saturday to get brake pads for my 2013 Wrangler Sport. I just turned 50,000 miles and really have no braking issues, but was going to change the pads anyway. I have replaced brakes on virtually every car I ever owned but this was the first time on a Wrangler. The parts manager waited on me. He was an old crusty fella that looked like he had been around the block a couple times. I've read numerous times on this forum that the primary braking on the newer Wrangler models comes from the rear. During our conversation I had mentioned this to the old crusty fella and he looked at me like I was crazy. He told me there was no way in hell that the dominant braking occured in the rear. He said if that was the case you would experience what he described as "hydroplaning" everytime you applied your brakes. He went as far as to show me the difference in size of the front pads compared to the rear pads. The front pads were "beefier and thicker" then the rear pads and that, according to him, was because the primary braking occurs in the front. I had no other ammunition for this discussion other then what I read on this forum. Can anyone link me to articles, tech manuals, that support this theory.

Thanks
Mike

Wrigley is offline   Reply With Quote Quick reply to this message
Unread 09-29-2014, 06:52 AM   #2
RockyClymer
RedRock4Wheeler
 
RockyClymer's Avatar
2008 JK Wrangler 
 
Join Date: Apr 2008
Location: Colorado
Posts: 4,489
IMO braking bias (percent of brake in front to rear ratio) is controlled by the ECU and I am not sure what it is set at, but in general, yes most braking is accomplished by the front and is heavier due to shift of weight (front dip) on the axle under heavy braking...the weight does not shift, but the force (momentum) c auses the front to dip and apply more of the vehicle weight to the front.....that being said, the ECU also causes the rear brakes (front too) to sometimes activate during ESP activation and most often when off roading when the so called Brake Lock Differential is activated (you can look that up).
My reality - when I changed my brakes at about 60k, I did noticed more rear brake wear than the front and attribute it to smaller brake pads and BLD actions while the larger front pads were not as worn and perhaps (no proof) ran cooler during heavier braking. I did replace my rotors with drilled/slotted rotors and heavy duty ceramic pads because I do run 35s.
__________________
08 JK 23S - Colorado Jeep Club No. 204
Too much to list - see my profile for details on build
NRA Life member
"It takes a special kind of stupid to believe criminals will follow gun laws."
I do not consider myself a smartass. I point out the obvious, search for the truth, and speak fluent sarcasm. I am, by experience, an accomplished curmudgeon.
RockyClymer is offline   Reply With Quote Quick reply to this message
Unread 09-29-2014, 09:07 AM   #3
ronjenx
Web Wheeler
 
ronjenx's Avatar
2008 JK Wrangler 
 
Join Date: Jan 2009
Location: Maine
Posts: 3,968
The JK rear brakes are biased to the rear during normal, light braking such as when approaching a stop sign or light. They do this to provide more stable stops under normal conditions.
When heavier braking is needed, the bias goes to the front as the front can do more braking than the rear.

This is possible in more modern vehicles because of the computers that control the ABS which are more able to prevent rear wheel skid.

ESP and traction control do kick in sometimes, but not very often compared to regular braking, and not with enough energy conversion to make much difference in brake pad wear rate.
__________________
2008 JKU Rubicon
42RLE Auto
ronjenx is online now   Reply With Quote Quick reply to this message
Unread 09-29-2014, 03:58 PM   #4
jwmbishop
Registered User
2011 JK Wrangler 
 
Join Date: May 2011
Location: corsicana, tx
Posts: 3,728
60/40 bias was dialed into the static configuration of cars past because - in low traction (wet road) environments, that 40 was all it could handle before lock up risk was increased (and even on dry road hard brake while cornering can have the rear end swap with the front if back brakes get applied too hard). On dry roads that left the vehicle with less stopping force than the dry road could handle - but still more than wet road, and still within reasonable stopping distance. An engineering tradeoff. That "unused" back brake was simply wasted - or more precisely returned a longer life span in the linings.

With the computer the tradeoff becomes unnecessary (except in system failure - see below) - the brakes can be used at maximum, independent of each other - front rear AND left right biased - at all road conditions. This causes the wear to be greater in the rear - compared to a static biased non ABS system! This does NOT make the rears the predominate brakes. Weight will always transfer fwd in braking and the rear end will thus always LOOSE weight and can never be the predominate brake (the harder you brake the more weight comes off the rear the lower the traction available). What this means is a wet stop can be 60/40 while a dry stop is 51/49 Or even better than 50/50 - depending on how hard you are asking the brakes to work.

Further with computers traction control can be made to use the brakes (and the JK does this) - and applies one or both rear even when on the gas - if slippage or slide is detected by the wheel speed monitors and Gyro.. This also adds to wear - comparative to a non TC system - and again its simply using brake potential that would be left on the table if it was simply a 60/40 non ABS, non TC! Does not make rears predominate!

There is still a 60/40 mechanical bias in the brakes. That's the "failsafe" so that if TC and ABS do fail leaving you suddenly with only hydraulics brakes - you wont have an end swap when braking under a corner. The abs and tc system merely "equalize and maximize" the brake force at the tire contact by a strategy of bleedoff and individual wheel PSI increases.
__________________
J Wm Bishop EA, ASADE
Alcohol - because great stories never run on gasoline...
jwmbishop is offline   Reply With Quote Quick reply to this message
Unread 09-29-2014, 04:06 PM   #5
Hittnthebz
Registered User
 
Join Date: Jan 2011
Location: Roanoke, Virginia
Posts: 29
IMO I believe the reason so many think the braking is handled more by the rear is due to an issue that the ESP system pulsates causing the rear pads to wear at a quicker rate than the front pads. There was a TSB for my vehicle that took multiple dealer visits to correct in which a clockspring defect was making the issue worse due to it pulsing the rear brakes so often. Since then, my rear pads have lasted much longer but they still seem to wear quicker than I would expect.

I do agree that the front would have to control a majority of the braking duty but am sure the proportioning on the JK could be speed dependent as stated above although I doubt it would be higher than a 50/50 ratio in the rear.
Hittnthebz is offline   Reply With Quote Quick reply to this message
Unread 09-29-2014, 04:35 PM   #6
jwmbishop
Registered User
2011 JK Wrangler 
 
Join Date: May 2011
Location: corsicana, tx
Posts: 3,728
Quote:
Originally Posted by Hittnthebz View Post
I do agree that the front would have to control a majority of the braking duty but am sure the proportioning on the JK could be speed dependent as stated above although I doubt it would be higher than a 50/50 ratio in the rear.
I doubt it too - but its POSSIBLE that it would bias the back more (and in the case of ABS front lockup avoidance - obviously it does) - but when the thing weighs 2275 on the front and 1875 on the rear - equal force would have the back locked even BEFORE adding transferred weight to the front (and taking it off the rear) to the equation.
__________________
J Wm Bishop EA, ASADE
Alcohol - because great stories never run on gasoline...
jwmbishop is offline   Reply With Quote Quick reply to this message
Unread 09-29-2014, 08:04 PM   #7
HappyTrails
Registered Voter w/ID
 
HappyTrails's Avatar
2008 JK Wrangler 
 
Join Date: Nov 2008
Location: West Georgia
Posts: 2,150
Aside from the technical talk, I've noticed that my rear brake pads were shot at 50K, while the front pads still have at least another 20K.

Nevermind the occasional tire burnout (supercharger + caffeine = trouble).
__________________
2008 2-dr Rubicon, auto,
RK 2.5" Max Travel, Fox 2.0 shocks, 37" Nittos, 5.38's, RR skids, Warn VR8000-S.
RIPP Gen 2 Stg 2 Supercharger.
"Don't give up 5 minutes before the miracle occurs."
HappyTrails is offline   Reply With Quote Quick reply to this message
Unread 09-30-2014, 05:09 AM   #8
Wrigley
Registered User
2013 JK Wrangler 
 
Join Date: Oct 2006
Location: fLORIDA
Posts: 263
Quote:
Originally Posted by HappyTrails View Post
Aside from the technical talk, I've noticed that my rear brake pads were shot at 50K, while the front pads still have at least another 20K.

Nevermind the occasional tire burnout (supercharger + caffeine = trouble).
I got almost 51,000 on my 2013. Both my front and rear pads still have a decent amount of meat left on them. I was surprised!

Mike
Wrigley is offline   Reply With Quote Quick reply to this message
Unread 09-30-2014, 09:54 AM   #9
jwmbishop
Registered User
2011 JK Wrangler 
 
Join Date: May 2011
Location: corsicana, tx
Posts: 3,728
Quote:
Originally Posted by HappyTrails View Post
Nevermind the occasional tire burnout (supercharger + caffeine = trouble).
Okay we have a volunteer to test a theory!

Go as fast as you can in reverse and stomp the brakes to see if the brake system will bias 60R40F to avoid lockup!
(This - swapping the bias - is a common demolition derby trick - as most of the derby is run with your car in reverse so you use the trunk to inflict damage rather than the engine)

Lets us know....
__________________
J Wm Bishop EA, ASADE
Alcohol - because great stories never run on gasoline...
jwmbishop is offline   Reply With Quote Quick reply to this message
Unread 10-03-2014, 12:16 PM   #10
smcutter
Web Wheeler
 
smcutter's Avatar
2012 JK Wrangler 
 
Join Date: May 2010
Location: Broomfield, Colorado
Posts: 1,162
Quote:
Originally Posted by jwmbishop View Post
(This - swapping the bias - is a common demolition derby trick - as most of the derby is run with your car in reverse so you use the trunk to inflict damage rather than the engine)
It seems like you could get a competitive advantage out of driving a Chevy Corvair or VW Beetle in a demolition derby...
__________________
2012 Rubicon (Black, Soft Top, Heated Seats, 6spd)
Rugged Ridge XHD Front Bumper and a Warn PowerPlant HP Winch
ACE Rock Sliders

More of a Tinkering Thread than a Build Thread (smcutter)

Colorado Jeep Club Member #302
Keep Calm and Chive On!
And for the record, I'm probably judging you for your bad grammar or spelling.
smcutter is online now   Reply With Quote Quick reply to this message
Unread 10-03-2014, 12:19 PM   #11
smcutter
Web Wheeler
 
smcutter's Avatar
2012 JK Wrangler 
 
Join Date: May 2010
Location: Broomfield, Colorado
Posts: 1,162
Also, my Jeep is at 55,500 miles and I'm having the rear brake pads replaced today. Rotors are getting resurfaced, and the mechanic said the front brakes still have 50% left in them. I'd be very curious to know how much more brake life I get than if I were driving an automatic, since I tend to use compression braking pretty aggressively.
__________________
2012 Rubicon (Black, Soft Top, Heated Seats, 6spd)
Rugged Ridge XHD Front Bumper and a Warn PowerPlant HP Winch
ACE Rock Sliders

More of a Tinkering Thread than a Build Thread (smcutter)

Colorado Jeep Club Member #302
Keep Calm and Chive On!
And for the record, I'm probably judging you for your bad grammar or spelling.
smcutter is online now   Reply With Quote Quick reply to this message
Unread 10-03-2014, 01:24 PM   #12
jwmbishop
Registered User
2011 JK Wrangler 
 
Join Date: May 2011
Location: corsicana, tx
Posts: 3,728
Quote:
Originally Posted by smcutter View Post
It seems like you could get a competitive advantage out of driving a Chevy Corvair or VW Beetle in a demolition derby...
Not enough weight to bring to the impact. Lighter car looses. A big ol Cadillac rear wheel drive (we ran a 57 in one - rules said "stock bumpers" so we put the front bumper with the big "bullets" on em in back and the rear to the front).... THAT was a bruiser.

You do save brakes quite a bit with a standard - but not everyone. Some folks don't downshift they just clutch when RPM gets low.
__________________
J Wm Bishop EA, ASADE
Alcohol - because great stories never run on gasoline...
jwmbishop is offline   Reply With Quote Quick reply to this message
Unread 10-09-2014, 02:41 PM   #13
Bobbb
Registered User
2012 JK Wrangler 
 
Join Date: Oct 2014
Posts: 3
Thanks everyone for your well thought out answers. I feel better that my break wear falls within the probably normal range but a little earl range.
Bobbb is offline   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Thread Tools






Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.