Initial soft brake pedal? pad knock-back? - LS1TECH



Road Racing Road Course | Autocross

Initial soft brake pedal? pad knock-back?

Reply
 
Thread Tools Search this Thread
Old 03-17-2017, 09:20 AM   #1
TECH Fanatic
Thread Starter
 
Join Date: Feb 2012
Posts: 1,402
Default Initial soft brake pedal? pad knock-back?

This is not a "new" condition for me that I have noticed but maybe I'm getting a little more annoyed with it.

I have this condition even driving on the highway and getting off coming to a stop. The first time I hit the brake pedal it will feel soft and travel farther than expected. Once the first initial pump is done, the pedal travels less and grabs sooner.

I thought this only happens during racing for people but on the highway it's slightly unnerving when you have a "oh ****" moment and need brakes instantly (happened last night when someone didn't know how to merge...)

95 Z28
Ls1 Front brakes stock rear
Hawk HP+ pads front Duralast rear
pads and rotors are not worn out
no leaks in system
(will need to verify fluid level but this has happened when fluid level is OK)
Rocketman1 adapters with SKF hubs
No ABS lights or issues

Is this "pad knock-back"?? If so I thought this happened when hubs were deflecting and pushing pads back into caliper **while racing not DD**...but with the SKF hubs I figured this solves that issue.
smitty2919 is offline   Reply With Quote
Old 03-17-2017, 11:04 AM   #2
TECH Fanatic
iTrader: (3)
 
M4N14C's Avatar
 
Join Date: Apr 2013
Location: Redmond, WA
Posts: 1,120
Default

I assume you know how to properly bleed the system and have done that. How much play do you have in your rear axles? Might need new c clips if more than 1/8 of an inch or so.
M4N14C is online now   Reply With Quote
Old 03-17-2017, 11:10 AM   #3
Launching!
iTrader: (2)
 
Join Date: Jan 2004
Location: State College, PA
Posts: 281
Default

It can happen on the rears too, but to a lesser extent. I have a video of rear discs moving/angling around a lot more than I ever imagined.
Chris Paveglio is offline   Reply With Quote
Old 03-17-2017, 11:13 AM   #4
11 Second Club
iTrader: (18)
 
thunderstruck507's Avatar
 
Join Date: Mar 2008
Location: Northwest AR
Posts: 8,250
Default

I had this problem after a while with LS1 rear discs swapped onto my Chevelle axle housing. It was every time I turned right, axle would slide in the housing and push the piston back in the caliper.

I replaced the C clips and also put new clutches/shims in the Eaton and it went away. Not certain which cured it or if both helped.
thunderstruck507 is offline   Reply With Quote
Old 03-17-2017, 11:53 AM   #5
TECH Fanatic
Thread Starter
 
Join Date: Feb 2012
Posts: 1,402
Default

Car has a TruTrac (put in maybe 2 summers ago), original c-clips. Never thought that c clips would "wear" lol.

Now, I have put in longer ARP studs in the rear in which I tapped the old ones out with a hammer. I can't imagine this "flattening the c clips to the point it allows more axle movement.

So you guys thing it's coming from the rear more than the front given I have brand new SKF front hubs?
smitty2919 is offline   Reply With Quote
Old 03-17-2017, 11:57 AM   #6
TECH Fanatic
Thread Starter
 
Join Date: Feb 2012
Posts: 1,402
Default

Quote:
Originally Posted by M4N14C View Post
I assume you know how to properly bleed the system and have done that. How much play do you have in your rear axles? Might need new c clips if more than 1/8 of an inch or so.
I have not bleed the system for a while, but last time I did it was PS RR, DR RR, PS FR, DR FR.

I then cracked the bleeders on the distribution block as well.

Is there a "spec" to measure axle movement and if so what specifically are you measuring for wear if there is excess movement?
smitty2919 is offline   Reply With Quote
Old 03-17-2017, 12:03 PM   #7
TECH Fanatic
 
SoFla01SSLookinstok's Avatar
 
Join Date: Mar 2012
Location: South Florida
Posts: 1,006
Default

Not saying this "is" your problem. First thing that came to my mind is the master.
SoFla01SSLookinstok is online now   Reply With Quote
Old 03-20-2017, 07:05 AM   #8
TECH Fanatic
iTrader: (7)
 
1981TA's Avatar
 
Join Date: Nov 2010
Location: Saint John, IN
Posts: 1,306
Default

Check if your caliper sliders are functioning properly. These are the greased posts that the caliper mounting bolts connect to on the caliper mounting bracket. If these are not working properly, the calipers won't move with the axle when there is side-to-side movement, or center automatically as your pads wear.
1981TA is offline   Reply With Quote
Old 03-20-2017, 08:34 AM   #9
TECH Fanatic
Thread Starter
 
Join Date: Feb 2012
Posts: 1,402
Default

Great, thanks. I'll check those and or grease them anyways since I'll have them apart.
smitty2919 is offline   Reply With Quote
Old 03-22-2017, 09:14 AM   #10
TECH Fanatic
Thread Starter
 
Join Date: Feb 2012
Posts: 1,402
Default

1981TA I tore everything apart last night and found the fronts were OK with the amount of grease in them but replaced it anyways.

The rears were pretty dry and the grease that was there was more of a paste. Drive to work seemed much better. Will keep an eye on this.

Thanks again, so far the slider pins seem to be the issue.
smitty2919 is offline   Reply With Quote
Old 03-22-2017, 09:55 AM   #11
TECH Fanatic
iTrader: (7)
 
1981TA's Avatar
 
Join Date: Nov 2010
Location: Saint John, IN
Posts: 1,306
Default

Glad to see it worked out. I had a similar problem on one of my cars, and it can certainly be an attention getter.
1981TA is offline   Reply With Quote
Old 04-03-2017, 08:27 PM   #12
TECH Fanatic
Thread Starter
 
Join Date: Feb 2012
Posts: 1,402
Default

After driving this for a while now, seems the rear sliders were in fact the issue.

Lesson learned!

Thanks again 1981TA
smitty2919 is offline   Reply With Quote
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Factory ZR1 hubs vs SKF HD hubs t_raven Corvette Performance 0 05-01-2016 09:03 AM
front hubs, which brand n supplier? severancej LS4 Performance 50 12-23-2015 01:11 PM
hawk pad issues ToxicWS6 Suspension & Brakes 2 09-02-2015 01:40 PM
Hubs/Wheel Bearings GXP25 LS4 Performance 0 09-22-2013 02:50 PM
brake pedal feels soft, w/ more travel 69camaross Suspension & Brakes 1 12-07-2008 07:30 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 03:42 PM.


 
  • Ask a Question
    Get answers from community experts
What's your question?
Send