Announcement

Collapse
No announcement yet.

Brakes went weirder

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Brakes went weirder

    Hi - Iím posting this in an effort to gain insight into a brake problem with my Camaro. Brake system is 12Ē front and 10.5Ē rear disk with Tilton prop valve in rear circuit. AND factory prop valve in place.
    When threshold braking from 200kmh to 150kmh it was Ok, from 150 down, rear end skips and bounces.

    So after much research, I remove the OEM prop valve and use just the Tilton in the rear circuit...

    It got worse! Now, the back end skips and bounces as soon as I touch the brakes at high speeds as well - what happened???
    In the video you can see that where I should be braking at 2 cones, Iím letting off at 3 1/2 cones and after the right hand kink, I tap the brakes and it starts a tank slapper.

    Any help would be greatly appreciated!!

    Matt

    https://youtu.be/L_fJLCCwGeo
    Last edited by mustturn..right; 06-17-2019, 05:41 PM.
    I'm sick of following my dreams. I'm just gonna ask where they're going and catch up with them later

  • #2
    Re: Brakes went weirder

    My first thought would be to dial off the rear brake as much as you can, then slowly put it back in. By eliminating a prop valve, I would assume you just sent a bunch more fluid to the rear than you were getting before.
    Andy
    Mobil 1 Time Attack - #96

    Comment


    • #3
      Re: Brakes went weirder

      So, I can't really say 100%, because my only experience was with a 4th-gen Camaro, so I don't know whether the 3rd-gen uses the same style of master cylinder and/or proportioning system??

      I know that both Dave Barker and I both experienced lots of rear-wheel hop under heavy braking, and tried various options to manage it. Dave had a secondary proportioning valve in-line to dial down the rears. I never got to installing a prop valve, but it was on the shopping list (...prior to getting out of the Camaro).

      The best "band-aid" solution (that was relatively effective) was biasing the brakes via brake pad selection. Thus, I ran fairly aggressive pads (ie: Carbotech XP12's or similar) in the front, and CHEAP/CRAP street pads (often ceramics) in the rear. Between that, and learning to understand and anticipate the funky braking bias, were about all you could do.

      The chicane at Shannonville (Pro Track), between the Fabi back straight and the Nelson front straight, was always my Achilles' heel. It's bumpy, and you come through there HOT, so it was always a riot, but I just learned to "manage" the chaos!

      Understandably, the weight balance and brake bias between a 3rd & 4th-gen may be a little different.

      Another thing to consider would be upgrading to C5 or C6 brakes in the front (13"). That should be a significant improvement, and help add to the front bias. I had done the conversion in the last year that I owned my '02, and after that, had the ability to lock-up the fronts, which pretty much NEVER happened prior.

      The '93 Z28 track car I had, already had C4 brakes (also 13"), and that car could also lock the fronts no problem. However, when I first got it, the previous owner had Hawk Blues in all 4 corners .......... what a NIGHTMARE to say the least (would lock the rears ALL DAY LONG).

      I would suggest you reestablish the factory proportioning system, possibly leave the Tilton valve to dial down the rears even further, and go to the crappiest rear pads you can find, and see how that works .
      OMSC
      Current: 2011 Corvette Z06
      Previous: '06 Z06, '10 Corvette, '93 & '02 Camaro Z28's

      Comment


      • #4
        Re: Brakes went weirder

        Yes, putting a proportioning valve downstream of the ABS box worked very well on my 4 th gen Camaro and eliminated 95% of the rear axle hop. The car stood on its nose under heavy braking but was easy to drive. Like Pete, I used a lower coefficient of friction and cooler temp pad at the rear.


        I think you have too much rear bias
        Mobil 1 Time-Attack # 4, CCC Member

        Comment


        • #5
          Re: Brakes went weirder

          Originally posted by Cap'n Pete View Post
          So, I can't really say 100%, because my only experience was with a 4th-gen Camaro, so I don't know whether the 3rd-gen uses the same style of master cylinder and/or proportioning system??

          I know that both Dave Barker and I both experienced lots of rear-wheel hop under heavy braking, and tried various options to manage it. Dave had a secondary proportioning valve in-line to dial down the rears. I never got to installing a prop valve, but it was on the shopping list (...prior to getting out of the Camaro).

          The best "band-aid" solution (that was relatively effective) was biasing the brakes via brake pad selection. Thus, I ran fairly aggressive pads (ie: Carbotech XP12's or similar) in the front, and CHEAP/CRAP street pads (often ceramics) in the rear. Between that, and learning to understand and anticipate the funky braking bias, were about all you could do.

          The chicane at Shannonville (Pro Track), between the Fabi back straight and the Nelson front straight, was always my Achilles' heel. It's bumpy, and you come through there HOT, so it was always a riot, but I just learned to "manage" the chaos!

          Understandably, the weight balance and brake bias between a 3rd & 4th-gen may be a little different.

          Another thing to consider would be upgrading to C5 or C6 brakes in the front (13"). That should be a significant improvement, and help add to the front bias. I had done the conversion in the last year that I owned my '02, and after that, had the ability to lock-up the fronts, which pretty much NEVER happened prior.

          The '93 Z28 track car I had, already had C4 brakes (also 13"), and that car could also lock the fronts no problem. However, when I first got it, the previous owner had Hawk Blues in all 4 corners .......... what a NIGHTMARE to say the least (would lock the rears ALL DAY LONG).

          I would suggest you reestablish the factory proportioning system, possibly leave the Tilton valve to dial down the rears even further, and go to the crappiest rear pads you can find, and see how that works .
          this is great to know - thanks Pete! its nice to know i'm not crazy and this happens elsewhere. The 4th gen is similar to the my 3rd gen and i just picked up the 4th gen 11.65" rear disk set up and was going to try that - but i'm really glad you told me to go with low-end rear pads for the rear because i had a set of Hawk Blue's queued up all around - i'll just keep them in the front! i had thought about this earlier but didn't because i thought the street pad would be "grabbier".

          and also Dave - i think you are correct; it appears that removing the OEM Prop valve added more rear bias despite the tilton rear prop valve being dialed completely out to remove as much rear as possible.

          the C5 /C6 swap is interesting and i'll have to look into that. but this year i have to step up to bigger tires because i'm only running the 245-45/16 and i really need the 275-40-17.

          it makes me wonder what the players challenge and firehawk cars did - i mean did every one of those cars bounce the back end as well??

          thanks again!!
          Attached Files
          I'm sick of following my dreams. I'm just gonna ask where they're going and catch up with them later

          Comment


          • #6
            Re: Brakes went weirder

            In 1989 and 1990 I co-drove a 1LE out of the showroom Firebird in the Firehawk series.
            The brake system was stock GM 1LE. As the car was Endurance road raced, we used whatever pads where available back then that wouldn't fade and would last at least 3 hours.
            I don't remember the car having too much rear brake but it would certainly hop the rear axle if a downshift wasn't perfectly rev matched. This would also bend the transmission rear cross member and then third gear couldn't be selected as the shifter hit the end of it's travel in the console.
            As brake pads are probably so much better than they were back then, I think I agree with the suggestions of way less grippee pads in the rear.

            Comment


            • #7
              Re: Brakes went weirder

              Man, that looks awesome!! That front aero looks aggressive! I'm assuming it's fully gutted inside?? What's the weight? Are you under 3000lbs with it?

              I would question whether the "upgrade" to bigger (LS1 or LT1??) rear brakes is even necessary, but if nothing else, stick with cheap pads. For the cost, experiment a little and see whether standard "metallic" pads vs. ceramic are any different. I feel like I had my best luck with ceramics, but it's been a few years now (...2009) since I was racing either F-body.

              I'd also seriously consider the C5 or C6 upgrade, but it's not "necessary" either, as long as you have the brake pad compounds (bias) correct. Bigger brakes are the natural progression though.
              OMSC
              Current: 2011 Corvette Z06
              Previous: '06 Z06, '10 Corvette, '93 & '02 Camaro Z28's

              Comment


              • #8
                Re: Brakes went weirder

                Thanks DEK - that is excellent insight - thank you, i had no idea it got that destructive!!!!

                Hey Pete - thanks! This week i am going to make time to find the shittiest rear pads i can - I'll let you know what i come up with. I started to put the OEM prop valve back in on the weekend, gotta do it in stages because bending over and flaring takes its toll on my back lol!!

                The car has no carpet or roof liner, or heater...but it has the OEM dash, console, door panels and still has the power windows. seats are a pair of corbeau reclining seats.
                With no driver and 1/4 tank of gas it scaled at 2990. i might take the power windows out and i just picked up an OEM "SMC" hood that weighs 15 lbs less than the current one. The motor is a GMPP crate motor, SP350, 385hp and with the T56 its never gotten out of 4th gear lol!
                the Splitter was my own design and manufacture (winter project!). its made of 1/4" honeycomb aluminum. The gold supports are 3/8" alum plate and its attached via the 5 struts on the front and two 3/8" pins into either side of the rad cradle underneath, so i can change the angle of the splitter and therefor the amount of grip as required by changing the length of the front attaching struts. the whole thing comes off to get it on the trailer with 7 pit pins in less that a minute and it weighs 5 lbs.

                thanks again!
                Matt
                Attached Files
                Last edited by mustturn..right; 07-03-2018, 08:47 AM.
                I'm sick of following my dreams. I'm just gonna ask where they're going and catch up with them later

                Comment


                • #9
                  Re: Brakes went weirder

                  ...so I put the OEM prop valve back in, put crappy rear pads in rear and Hawk Blueís up front. I got my brother in Tucson looking for a wrecked C5 to replace the stock 1LE 12Ē with the C5 13Ē fronts. I found a really weird pattern on the rotors in the back - never seen this before, extra weirdness! Anyway, Iím supposed to be on track tomorrow but Iím gonna miss this event and will hopefully have the new aero upgrades ready for event 4 on 17 Aug.
                  Thanks again for all the great information!!
                  Matt
                  Attached Files
                  I'm sick of following my dreams. I'm just gonna ask where they're going and catch up with them later

                  Comment


                  • #10
                    Zombie thread? Maybe...but itís my Zombie lol!! I just wanted to update and say thanks to those who helped out, Capín Pete I took your advice - twice! I put crap pads (as DEK and Dave Barker also concurred) in the back and Hawk Blueís up front and it was waaaay better, then I collected parts over the winter and installed them over the summer. I just finished my first event with 2018 C7 Z51/SS Brembo Camaro caliper front brakes. This required a bigger wheels, which meant bigger tires also. I went to 18x10 Apex wheels and 295/30/18 Hoosierís. Nothing was off the shelf and like anybody modding an older car knows, thatís going to be expected.
                    After the first test day it was soooooo much fun, I just canít believe how much more stable the car was all around. It was a different car. I had a lot of fun and found new limits not previously considered.
                    So thanks again!
                    matt
                    Stock 1LE vs 2018 Camaro/Corvette hybrid
                    Attached Files
                    Last edited by mustturn..right; 08-22-2019, 10:35 PM. Reason: Typo
                    I'm sick of following my dreams. I'm just gonna ask where they're going and catch up with them later

                    Comment

                    Working...
                    X