Brake upgrade, proportioning valve? 95 LT1
04-30-2004, 05:10 PM
#1
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Brake upgrade, proportioning valve? 95 LT1
I read an interesting article in the new Car&Driver boost magazine, that called into question the wisdom of just slapping on a set of larger rotors and bigger calipers.
"TECH DEPARTMENT
Big-Brake Upgrades: More Than Just Eye Candy
Why those sexy rotors and calipers migh actually be doing more harm than good."
The jist of the article was that by adding larger rotors and bigger more efficient calipers on the front, then over all brake line pressures would be lowered, and this would result in a longer stopping distance than with stock brakes in a panic situation.
Though at first blush, you would be thinking ... "holly mother of god", this thing really stops now ... that perception is based on the amount of force you apply with your leg to the brake pedal.
The maximum deceleration is still controlled by the limits of adhesion of the tires. Normally the front tires. You are able to get to this limit of adhesion with less leg power and thus less brake system line pressure. It only feels as if the brakes are working better.
This is because the front tires would still be operating as before and providing a certain amount of braking force irrespective of the braking system line pressure. That point being when the antilock feature kicks in ... ultimate braking force.
The rear brakes would actually be supplying less braking force than before because the entire system is now operating at a lower line pressure.
The Car&Driver article had it at about a 9% increase in stopping distance in a panic situation. Obviously in a race track situation things are different.
I'm more concerned about keeping proper brake bias/balance so I still keep my panic stop ability ... I just can't think of anything worse than running over little Mary or little Johnny ... know what I mean??
So my question ... what do you guys do to adjust the braking force to get more braking out of the rear wheels ... a different proportioning valve? An adjustable proportioning valve?? And if the adjustable valve is used, how do you set it up??
And of course, this pertains to a 95 LT1 with the standard ABS brakes.
Any input is appreciated
LWM
"TECH DEPARTMENT
Big-Brake Upgrades: More Than Just Eye Candy
Why those sexy rotors and calipers migh actually be doing more harm than good."
The jist of the article was that by adding larger rotors and bigger more efficient calipers on the front, then over all brake line pressures would be lowered, and this would result in a longer stopping distance than with stock brakes in a panic situation.
Though at first blush, you would be thinking ... "holly mother of god", this thing really stops now ... that perception is based on the amount of force you apply with your leg to the brake pedal.
The maximum deceleration is still controlled by the limits of adhesion of the tires. Normally the front tires. You are able to get to this limit of adhesion with less leg power and thus less brake system line pressure. It only feels as if the brakes are working better.
This is because the front tires would still be operating as before and providing a certain amount of braking force irrespective of the braking system line pressure. That point being when the antilock feature kicks in ... ultimate braking force.
The rear brakes would actually be supplying less braking force than before because the entire system is now operating at a lower line pressure.
The Car&Driver article had it at about a 9% increase in stopping distance in a panic situation. Obviously in a race track situation things are different.
I'm more concerned about keeping proper brake bias/balance so I still keep my panic stop ability ... I just can't think of anything worse than running over little Mary or little Johnny ... know what I mean??
So my question ... what do you guys do to adjust the braking force to get more braking out of the rear wheels ... a different proportioning valve? An adjustable proportioning valve?? And if the adjustable valve is used, how do you set it up??
And of course, this pertains to a 95 LT1 with the standard ABS brakes.
Any input is appreciated
LWM
05-02-2004, 12:17 AM
#3
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Join Date: Sep 2003
Location: The Wild West
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Sorry to interupt, but Bone, I need you address to send you $ for the front Hawk brake pads if you still have it. PM me or send it to Ladiesman@cutey.com
Thanks...continue...
-Dustin-
Thanks...continue...
-Dustin-
05-02-2004, 06:26 PM
#5
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Location: Calgary, Alberta, Canada
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Originally posted by Bone Daddy
Yes, adjustable proportion valves are what you use. I use the WilWood rotary valve myself.
Yes, adjustable proportion valves are what you use. I use the WilWood rotary valve myself.
thx
LWM
05-02-2004, 06:45 PM
#6
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All you have to do is start the valve on the least amount of rear biast, test drive the car, then keep re-adjusting and testing until your done. Between each drive you want to turn the valve a 1/8 to a 1/4 turn. The goal is to make the rear brakes engage slightly after the front ones. The procedure is mostly trial and error and having the proper "feel" in the rear.
05-02-2004, 10:05 PM
#7
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Originally posted by Bone Daddy
All you have to do is start the valve on the least amount of rear biast, test drive the car, then keep re-adjusting and testing until your done. Between each drive you want to turn the valve a 1/8 to a 1/4 turn. The goal is to make the rear brakes engage slightly after the front ones. The procedure is mostly trial and error and having the proper "feel" in the rear.
All you have to do is start the valve on the least amount of rear biast, test drive the car, then keep re-adjusting and testing until your done. Between each drive you want to turn the valve a 1/8 to a 1/4 turn. The goal is to make the rear brakes engage slightly after the front ones. The procedure is mostly trial and error and having the proper "feel" in the rear.
I've tried a few "panic stops" from around 40 mph with the stock ABS brakes and noticed ... nothing ... the car just goes into antilock mode and stops. The rear brakes are definitely not locking up first ... a good thing I suspect.
So, do you do the ... panic stop and adjust the valve untill the rear brakes start to make themsleves ... evident ... ?? Then back them down a notch? Makes sense to me.
Does the bias change with speed? Will a setting that works at 30 mph result in rear lock up at 70 mph in a panic stop??
Or the other way around??
Just trying to get a solid understanding of what is going on in the brake department.
Thx
LWM
Last edited by LWM; 05-02-2004 at 10:10 PM.
05-02-2004, 10:57 PM
#8
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Your Welcome...
Since (I assume) you still have the stock ABS system and rotors, the fact that your system works normally is a good thing. In fact, nothing is supposed to lock up on a ABS equipped vehicle. It does happen, but that's mostly road conditions (gravel, water etc.) or a fault in the braking system. Yours is doing what it is supposed to do.
When you have the larger brakes in place and the valve installed, you don't want to go around panic braking. You want to make the initial adjustments under "normal" braking conditions. When you get close to what you feel is the proper setting, adjust it as precisely as possible. If you drive around panic stopping and set the biast accordingly, your normal braking will be thrown off and the rear will fight the front. All the valve does is regulate more/less pressure to the rear. When you give the rear more biast by turning the valve, you gain pressure in the rear, which is what is lose with the larger front system (according to the article, me, and a large group of people). Once you adjust it as precisely as you can for normal braking, your done.
The ABS system does indeed regulate biast, hence the non lockup of the wheels. As to how much biast the ABS system (not the proport. valve) puts out, that is effected by speed, hence the wheel speed sensors. "Biast" is just a fancy word for force or pressure directed in a certain direction.
Since (I assume) you still have the stock ABS system and rotors, the fact that your system works normally is a good thing. In fact, nothing is supposed to lock up on a ABS equipped vehicle. It does happen, but that's mostly road conditions (gravel, water etc.) or a fault in the braking system. Yours is doing what it is supposed to do.
When you have the larger brakes in place and the valve installed, you don't want to go around panic braking. You want to make the initial adjustments under "normal" braking conditions. When you get close to what you feel is the proper setting, adjust it as precisely as possible. If you drive around panic stopping and set the biast accordingly, your normal braking will be thrown off and the rear will fight the front. All the valve does is regulate more/less pressure to the rear. When you give the rear more biast by turning the valve, you gain pressure in the rear, which is what is lose with the larger front system (according to the article, me, and a large group of people). Once you adjust it as precisely as you can for normal braking, your done.
The ABS system does indeed regulate biast, hence the non lockup of the wheels. As to how much biast the ABS system (not the proport. valve) puts out, that is effected by speed, hence the wheel speed sensors. "Biast" is just a fancy word for force or pressure directed in a certain direction.
Last edited by Bone Daddy; 05-02-2004 at 11:01 PM.
05-03-2004, 10:43 AM
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What is with all the ass3s not posting or helping in threads and just correcting (or trieng to) spelling? And bias can be used, but with fluid engineering (brakes,hydraulics,water,sauldry,atonic pressure) the word is biast, so that's what I use. Plus during my years at Bendix, that's what I used. So... stop trieng to be a j/o and actually post to help people. 
Last edited by Bone Daddy; 05-03-2004 at 10:49 AM.
05-03-2004, 10:57 AM
#11
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Conceptually, the article makes sense, but it doesn't track to my experience with the Baer Track kit. On the street, panic stops were the same or a bit shorter, and on the track, the car still had a bit too much bias toward the rear. I don't think too many folks in 4th gen cars are adjusting bias for track events, maybe they should but I would have thought I'd be hearing a lot more discussion about it.
As far as adjusting a proportioning valve. I've got one on my Radical, and notice two good ways to adjust. If you come into a hard braking zone and the rear wheels lock up, you've clearlly got too much bias to the rear. That's a low-resolution adjustment - you're at least a couple turns off. Once you're close, fine adjustments of the valve work best (for me) to balance the car's ability to trail brake well. If it spins during a trail brake, then you've got too much rear. If it understeers, too much front.
Dave
As far as adjusting a proportioning valve. I've got one on my Radical, and notice two good ways to adjust. If you come into a hard braking zone and the rear wheels lock up, you've clearlly got too much bias to the rear. That's a low-resolution adjustment - you're at least a couple turns off. Once you're close, fine adjustments of the valve work best (for me) to balance the car's ability to trail brake well. If it spins during a trail brake, then you've got too much rear. If it understeers, too much front.
Dave
05-03-2004, 11:35 AM
#12
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Originally posted by Bone Daddy
What is with all the ass3s not posting or helping in threads and just correcting (or trieng to) spelling? And bias can be used, but with fluid engineering (brakes,hydraulics,water,sauldry,atonic pressure) the word is biast, so that's what I use. Plus during my years at Bendix, that's what I used. So... stop trieng to be a j/o and actually post to help people.
What is with all the ass3s not posting or helping in threads and just correcting (or trieng to) spelling? And bias can be used, but with fluid engineering (brakes,hydraulics,water,sauldry,atonic pressure) the word is biast, so that's what I use. Plus during my years at Bendix, that's what I used. So... stop trieng to be a j/o and actually post to help people.
And help me along here.... what is "sauldry"?
Normally, I would classify the spelling correctors as ****, but when you define a term, its only reasonable that you try and get it right, so others can speak with the same knowledge that you shared.
05-03-2004, 12:15 PM
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Wasn't trieng to define a term, I'm just used to my particular field and the word tenses involved, so I throw them around in general speech 
(I hereby apologise to the thread starter for causing this off-topicness!) I am and have been for about 10 years a fluidic engineer. We deal with the total "range" of fluids (the more viscous fluids, and even viscid fluid) and liquids ("we" call these liquids as they flow well) that are used with "pressure point" systems and "forced" systems and equipment. In non "me" terms, 
hydraulic, brake, water jet, sauldric, ascopic, and desalinization systems. In my particular niche of the engineering world, biast is "our" term. It's on all our plot's, and it's on all our books, scales, and even equipment literature.
Oh, "sauldry" is the process of super heating a viscid (very "sticky") liquid so that the more liquid portions steam off and are collected in crystalized form for chemical synthesis.
As far as the "****" people the guy above maybe not so much, but in other sections I've seen a great thread die off many a time, after some *** tries to be a spelling profit. I should make them work at bendix for 5 years of hell, it would break them!
(I hereby apologise to the thread starter for causing this off-topicness!) I am and have been for about 10 years a fluidic engineer. We deal with the total "range" of fluids (the more viscous fluids, and even viscid fluid) and liquids ("we" call these liquids as they flow well) that are used with "pressure point" systems and "forced" systems and equipment. In non "me" terms, hydraulic, brake, water jet, sauldric, ascopic, and desalinization systems. In my particular niche of the engineering world, biast is "our" term. It's on all our plot's, and it's on all our books, scales, and even equipment literature.Oh, "sauldry" is the process of super heating a viscid (very "sticky") liquid so that the more liquid portions steam off and are collected in crystalized form for chemical synthesis.
As far as the "****" people the guy above maybe not so much, but in other sections I've seen a great thread die off many a time, after some *** tries to be a spelling profit. I should make them work at bendix for 5 years of hell, it would break them!
05-07-2004, 11:01 PM
#15
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No, the bigger aftermarket brakes/brake conversions are not stock, so the car has no way to meter them in that way. So nothing to remove.
The valve simply threads in-line on the rear main line somewhere before the rear end split. It should be somewhere easily reached, like the engine bay.
The valve simply threads in-line on the rear main line somewhere before the rear end split. It should be somewhere easily reached, like the engine bay.
Last edited by Bone Daddy; 05-07-2004 at 11:12 PM.