Jump to content

Brake Issue - any theories?


tneker
 Share

Recommended Posts

Back at the Road America in October we were struggling a bit with brake issues.  Our car is tucked away in storage so I haven't been able to do an autopsy yet.

 

The collective opinion of the drivers from Saturday was that the brakes were spongy at times, inconsistent, not terrible, not great, didn't seem to be just a hot brakes / brake fade issue, so as a precaution we bled the brakes Saturday night.

 

On Sunday, brakes continued to deteriorate, kind of.  First stint driver reported again some inconsistency, but without any noticeable patterns.  Next two drivers reported brakes were inconsistent for first ~45 minutes of the stint  and then got better and were "just fine".  But now a pattern was emerging during the brakes not working great time, there was one spot that braking seamed to be the worst.  Coming out of the carousel and into the bend, the brakes needed a pump or two in order to firm up.  It was noticeably worse as compared to anywhere else on the track.

 

Assuming the long right hand turn of the carousel was amplifying what ever issues we were experiencing, I have been trying to use that as a clue as to were to look first when I get access to the car again.

 

My original thought was that perhaps we had a loose wheel bearing that was allowing a little rotor movement under the high cornering load of the carousel that was pushing the piston back into the caliper requiring some pedal strokes to get a firm pedal.  That doesn't help explain why it seemed like twice the brakes got better during a stint.  I also at least tugged on the wheels prior to putting car in storage and bearings were not obviously loose.

 

Any other thoughts or ideas?

 

 

 

 

 

Link to comment
Share on other sites

I think you probably have a couple different issues going on at once which makes things like this tricky to diagnose.  Assuming a pin-slider type caliper?  Check the pins, calipers and the caliper carries for wear.  It does sound like a knock-back issue or some type of misalignment (dynamically?).  Its likely that something is hollowed/worn out but with heat comes expansion and that is lessening the issue as everything settles into its "race" temperature.  Check for things like weird pad taper indicating the caliper is not staying centered/aligned on the disc and/or shifting under braking.  Could also be a wheel bearing/hub issue, or a combination of both.  That's where I would start at least.

Edited by Bremsen
  • Like 1
Link to comment
Share on other sites

  • Technical Advisory Committee
9 hours ago, tneker said:

Back at the Road America in October we were struggling a bit with brake issues.  Our car is tucked away in storage so I haven't been able to do an autopsy yet.

 

The collective opinion of the drivers from Saturday was that the brakes were spongy at times, inconsistent, not terrible, not great, didn't seem to be just a hot brakes / brake fade issue, so as a precaution we bled the brakes Saturday night.

 

On Sunday, brakes continued to deteriorate, kind of.  First stint driver reported again some inconsistency, but without any noticeable patterns.  Next two drivers reported brakes were inconsistent for first ~45 minutes of the stint  and then got better and were "just fine".  But now a pattern was emerging during the brakes not working great time, there was one spot that braking seamed to be the worst.  Coming out of the carousel and into the bend, the brakes needed a pump or two in order to firm up.  It was noticeably worse as compared to anywhere else on the track.

 

Assuming the long right hand turn of the carousel was amplifying what ever issues we were experiencing, I have been trying to use that as a clue as to were to look first when I get access to the car again.

 

My original thought was that perhaps we had a loose wheel bearing that was allowing a little rotor movement under the high cornering load of the carousel that was pushing the piston back into the caliper requiring some pedal strokes to get a firm pedal.  That doesn't help explain why it seemed like twice the brakes got better during a stint.  I also at least tugged on the wheels prior to putting car in storage and bearings were not obviously loose.

 

Any other thoughts or ideas?

 

We had the EXACT same issue in the 2013 chumpionship. It was amplified the same way going into the bend as well. 

I was the first driver, and told everyone they may want to give a test pump at the 5 marker of all the breaking zones and to go easy as we just wanted to get through the day so we could redo the breaks saturday night (it was a 2 part race) and make a hard push Sunday. 

Our final driver needed to do a panic stop going into the bend to avoid a car, and for whatever reason the breaks coming out of the carousel were basically non-existent. First pump went straight to the floor, our car and an E30 ended up getting wrecked :( 

I ended up changing to an entirely new brake system for the next build so I don't know what the problem was. I am curious why the problem is, as it sounds like the exact same as what we had. 

  • Like 1
Link to comment
Share on other sites

On 12/5/2019 at 7:45 AM, red0 said:

 

We had the EXACT same issue in the 2013 chumpionship. It was amplified the same way going into the bend as well. 

I was the first driver, and told everyone they may want to give a test pump at the 5 marker of all the breaking zones and to go easy as we just wanted to get through the day so we could redo the breaks saturday night (it was a 2 part race) and make a hard push Sunday. 

Our final driver needed to do a panic stop going into the bend to avoid a car, and for whatever reason the breaks coming out of the carousel were basically non-existent. First pump went straight to the floor, our car and an E30 ended up getting wrecked :( 

I ended up changing to an entirely new brake system for the next build so I don't know what the problem was. I am curious why the problem is, as it sounds like the exact same as what we had. 

 

On 12/5/2019 at 8:13 AM, Gkuhn41 said:

The 350Z we tested Friday at road america had an identical issue around the carousel into the bend. took 2 pumps to get a solid pedal. Ill be following to figure out what you find, our initial review showed nothing alarming.

 

Interesting - I figured folks would have some thoughts, didn't anticipate others would have experienced similar issues at the same track.  If I find anything definitive I will let you know.  

 

 

  • Like 1
Link to comment
Share on other sites

I have ran into a nearly identical problem in one of the neons i race(d). 

 

Failed brake booster. Either bent slightly internally or broken spring. The pedal would not always fully return thus not fully returning the master to the "open to inlet port" configuration. This can cause a variety of issues, if left long enough your pedal will get longer and longer as the brake system will not be able to draw fluid from the reservoir to make up for pad wear. Short term you may find the brakes return to a position where the fluid is able to go past the MC seal during pad knockback events but is able to be pumped back up.

 

Boosters and MC on our cars are cheap, swap em both if in doubt and check your brake sliders. An extra return spring isn't a bad idea either, and check your booster rod length into the MC (adjust it so there is slack, i think spec is about .050")

Edited by Black Magic
  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...