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Discussion Starter #1
So, when the ABS block is removed, is there a need for a proportioning valve for the rear brakes to maintain the correct pressures? I have also read that the port in the MC closest to the firewall is rear and the one in front is the front brakes.

Thanks in advance.
 

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AFAIK the ABS valve body also handles proportioning. Please dont remove ABS on a street car. There are other ways to change brake balance.
 

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I’ve been thinking of removing mine also but only because it is rather sensitive and slowing me down at autocross. Even when I carefully modulate the pedal sometimes it likes to kick in and I know the car can handle more bite from the brakes. It’s usually on corners that have a rough patch in the asphalt in the braking zone.

Instead of removing it, could you just disable it? That way you still have the proportioning but just no ABS kicking in. And when you drive on the street you can turn it back on. Maybe as simple as unplugging it or wiring in some sort of bypass?


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... Even when I carefully modulate the pedal sometimes it likes to kick in and I know the car can handle more bite from the brakes....

Instead of removing it, could you just disable it?
That doesn't make sense. The ABS doesn't engage until the wheel starts to slip, and once the wheel slips you lose braking force because of the loss of traction. The way you get maximum braking is by forcing the ABS to engage on all wheels. There are exceptions. For example, if you are on a soft surface, you can get somewhat better braking by plowing it.

You can pull the fuse. There are people who disable the ABS so that they can make handbrake turns.
 

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So, when the ABS block is removed, is there a need for a proportioning valve for the rear brakes to maintain the correct pressures?
Yes. If you lock the rear brakes first, the car will spin. The worst case is a maximally steep descent, and if you lock your rear wheels when you are coming down from a mountain, you will probably kill yourself. You can do a lot to optimize braking on a track, but you need to make sure that a car in that setup will never leave flat land. That is why ABS is an advantage. You can get full rear braking on the level just by stepping harder, and still have a safe car on any road.
 

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Yah thats the problem, the ABS engages on the slightest wheel slip, especially once you increase spring rates, and then you’re stuck fighting the pedal with no feel coming right into a corner. Without ABS in the same situation the wheel would slip and you’d feel it and modulate the pedal accordingly, then be on your way.

To each his own obviously ABS is a state of the art system made to keep brakes from locking up in a panic stop. Not panicking on the track, just trying to stop very fast. I personally like to be in control of it. Traction control is the same concept but on the other end of the spectrum. Most people turn it off on the track (unless of course it’s a very overpowered car where it is advantageous to keep it on).


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I have not had a problem with the ABS in race conditions. People who have, either run skinny tires with aggressive aftermarket brake pads or a giant front swaybar that unloads the inside wheel.

Most people do not turn off ABS on track. Most track cars come standard with ABS. People turn of traction control but ABS is always on.
 
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... you’re stuck fighting the pedal with no feel coming right into a corner. Without ABS in the same situation the wheel would slip and you’d feel it and modulate the pedal accordingly, then be on your way.

... ABS is a state of the art system made to keep brakes from locking up in a panic stop.
That is a good point. ABS destroys all pedal feel, and that makes an entirely different driving experience. I think that it gives the maximum possible braking force, because it has quicker reflexes than I do, and I don't have four feet that I can use to modulate each wheel independently. However, I drive for the experience and not for numerical optimization.
 

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Both good points there. My problem is I got used to not having it when I developed as a driver so now it’s bugging me. Perhaps I should just learn to live with it.

On another note, I run a front TRD bar and a stock rear with 6K springs front and 8K rear. ABS kicks in when I late brake into a corner sometimes. It never did before when I had Tein springs (very soft in comparison) and TRD front and rear bars. Perhaps I’m just driving more aggressively? I attributed it to the increased spring rates. I also had no roll bar before so the chassis was a little more flexible too.

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I definitely would not do that. I do feel it kicking in sometimes when not needed, but ABS does provide optimum braking. I also highly doubt that you will actually gain any time without it, (maybe autocross? spin car a bit??? not sure. )
 

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Can confirm non ABS on autoX can improve things by allowing the rear of the car to slide. However, the flat spots on the tires are a bit annoying at anything over 10 MPH afterwards.
 

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Since ABS has sensors at each wheel, if one tire slips only it will get ABS: not all 4 tires. Unless you want to slip around a lot when braking, I am not sure why you would want to disable it. The best time I had (not times mind you) was with bald tires at autocross. I was sliding all over the place (and burning out for 50 feet at the start). What a hoot! But even then, when I wanted to stop, I wanted to stop.

There have been times when, on acceleration the back end swung out at just the right spot to get me around a turn faster. But that was only butt feel and I am not sure it was actually faster.

On the race track, ABS is a must. I was usually in ABS at every corner to some extent. One less thing to think about: consistent braking distances is always good.

And, yes, just pull the fuse and try it out! One advantage we have over Miatas is ABS. They didn't get it til 2003 or so.
 

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You might be experiencing what is often called ice mode. Usually happens if you get on the brakes too hard/sudden. If you encounter this release and reapply the brakes. Pressing harder will not make you stop any better.

From what I’ve gathered, it does this because when you unload the rear wheels it thinks you’ve locked up the rear brakes and it’s cutting power from the front brakes to try and stop you from doing what is essentially a hand brake turn. You can also try putting in a more aggressive front pad.


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Discussion Starter #16
These threads always turn into answering 'should ABS be removed' when people like me have asked 'how' instead. One answer requires knowledge, the other requires an opinion - we all know which one the internet is best at providing! ;)

For the sake of anyone actually looking for the answer to the 'how' as I was, I have purchased an adjustable valve for the rear lines and will be mounting this to the bulkhead - after that I will experiments with the adjustment.
 

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One answer requires knowledge, the other requires an opinion - we all know which one the internet is best at providing! ;)

For the sake of anyone actually looking for the answer to the 'how' as I was, I have purchased an adjustable valve for the rear lines and will be mounting this to the bulkhead - after that I will experiments with the adjustment.

Well let us know the end result and what you found to work for you. Then we’ll give you our opinion

No but seriously, I’m interested to see how it turns out.


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If you remove the ABS you definitely should install a front to rear proportioning valve for any kind of competitive driving
 

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I've also kicked around the idea of disabling/removing the ABS and replacing with a prop valve, since the system freaks out and ice-modes in certain track situations. Would like to hear thoughts of those who track a lot and have it removed.
 

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I have removed the ABS on my time attack build and installed a proportioning valve to the tunnel behind the shifter so it can be adjusted while seated if necessary (pic attached). I did a quick calculation based on master cylinder diameter, caliper piston diameter, and rotor diameters, that suggested the system is balanced at ~0.8 G decel, it’s front biased below that and rear biased above that. This isn’t an exact threshold for when ABS kicks in due to the calculation needing information which I couldn’t find and had to guess, like CG height and brake pad coefficient of friction. My personal opinion is that the Spyder’s ABS doesn’t offer enough control for racing slicks since it was designed around late 90’s tire technology, so I removed it to steal the wheel speed sensors for data logging and to develop better braking sensitivity. If it becomes a major time loss on the track I’ll put in a motorsports based ABS system.
7075B5B2-31A7-4565-966E-F02CE95C8392.jpeg
 
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