CASC Ontario Region Message Forums  

Go Back   CASC Ontario Region Message Forums > CASC-OR Divisions > Time Attack Specific Forum

Reply
 
Thread Tools Display Modes
  #1  
Old 06-25-2018, 09:41 AM
mustturn..right mustturn..right is offline
Registered User
 
Join Date: Oct 2006
Location: YWG - Canada
Posts: 55
Brakes went Weirder...

Hi - Im posting this in an effort to gain insight into a brake problem with my Camaro. Brake system is 12 front and 10.5 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, Im letting off at 3 1/2 cones and after the right hand kink, I tap the brakes and it starts a tank slapper...I had my balls in my throat for that one lol!

Any help would be greatly appreciated!!

Matt

https://youtu.be/L_fJLCCwGeo
__________________
I'm sick of following my dreams. I'm just gonna ask where they're going and catch up with them later

Last edited by mustturn..right; 06-25-2018 at 09:50 AM.
Reply With Quote
  #2  
Old 06-26-2018, 09:12 PM
G-ForceJunkie's Avatar
G-ForceJunkie G-ForceJunkie is offline
Registered User
 
Join Date: Nov 2004
Location: Bruce county
Posts: 972
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
Reply With Quote
  #3  
Old 06-27-2018, 12:06 PM
Cap'n Pete's Avatar
Cap'n Pete Cap'n Pete is offline
Registered User
 
Join Date: May 2007
Location: Oshawa
Posts: 1,875
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
Reply With Quote
  #4  
Old 06-27-2018, 06:28 PM
Dave Barker's Avatar
Dave Barker Dave Barker is offline
Registered User
 
Join Date: Feb 2001
Location: Whitby
Posts: 1,920
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
Reply With Quote
  #5  
Old 06-28-2018, 10:11 AM
mustturn..right mustturn..right is offline
Registered User
 
Join Date: Oct 2006
Location: YWG - Canada
Posts: 55
Re: Brakes went weirder

Quote:
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 Images
 
__________________
I'm sick of following my dreams. I'm just gonna ask where they're going and catch up with them later
Reply With Quote
  #6  
Old 06-28-2018, 01:09 PM
DEK DEK is offline
Registered User
 
Join Date: Mar 2004
Location: Toronto
Posts: 970
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.
Reply With Quote
  #7  
Old 07-02-2018, 10:09 PM
Cap'n Pete's Avatar
Cap'n Pete Cap'n Pete is offline
Registered User
 
Join Date: May 2007
Location: Oshawa
Posts: 1,875
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
Reply With Quote
  #8  
Old 07-03-2018, 08:30 AM
mustturn..right mustturn..right is offline
Registered User
 
Join Date: Oct 2006
Location: YWG - Canada
Posts: 55
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 Images
  
__________________
I'm sick of following my dreams. I'm just gonna ask where they're going and catch up with them later

Last edited by mustturn..right; 07-03-2018 at 08:47 AM.
Reply With Quote
  #9  
Old 07-20-2018, 07:35 PM
mustturn..right mustturn..right is offline
Registered User
 
Join Date: Oct 2006
Location: YWG - Canada
Posts: 55
Re: Brakes went weirder

...so I put the OEM prop valve back in, put crappy rear pads in rear and Hawk Blues up front. I got my brother in Tucson looking for a wrecked C5 to replace the stock 1LE 12 with the C5 13 fronts. I found a really weird pattern on the rotors in the back - never seen this before, extra weirdness! Anyway, Im supposed to be on track tomorrow but Im 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 Images
  
__________________
I'm sick of following my dreams. I'm just gonna ask where they're going and catch up with them later
Reply With Quote
Reply

Thread Tools
Display Modes

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

Forum Jump


All times are GMT -4. The time now is 06:37 AM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.