95 Miata M: Disabling Anti-Lock Brakes?

Is disabling the ABS as simple as pulling a fuse and throwing away a light bulb or is there more to it than that?

Disabling is as easy as pulling the fuse. The light bulb is only an annoyance.

Out of curiosity.... why do you want it disabled? If it's a proper 4 channel ABS system (I don't know if it is, hopefully someone can provide insight) that can pulse one wheel individually, I'd be okay with ABS. Every Miata I've ever driven has had some serious "front right" lockup issues. ABS would be a nice way to mitigate that. I can only remember driving one ABS equipped NA Miata, and I don't know that I had any complaints about it acting weird that would make me want it disabled.

In reply to srduck:

ABS calibrated for all seasons often engages too early with stickier tires that reach peak grip with a higher amount of slip. In that situation, the ABS will kick in before you reach maximum braking.

rslifkin wrote: In reply to srduck: ABS calibrated for all seasons often engages too early with stickier tires that reach peak grip with a higher amount of slip. In that situation, the ABS will kick in before you reach maximum braking.

While this is theoretically true, you would need four feet and four brake pedals to achieve what ABS can do electronically. (well, three feet and three pedals for the '95 Miata ABS, since it's only a 3-channel system).

Yeah, but "Maximum braking" in a Miata, even on Hoosiers or one of the super-sticky 200tw street tires, is still super easy to hit and exceed those limits. Most AutoX guys and some track guys are putting aggressive pads like Hawk HP Plus in the rear, and whatever cheapo AutoZone stuff they can get in the front trying to even out the brakes and prevent that front lockup that's such a pain.

Unless there's a really, really good reason to do away with ABS... and you're pulling the whole system out to save weight... I'd seriously reconsider leaving it enabled.

I am pretty sure the 95 and most NA ABS are 2 channel and NBs and late NAs are 3 channel. I looked for and kept the 3 channel ABS from my 99 Miata donor on my Exocet for the benefits. It is a good system tuned well and adds safety and saves dollars by preventing lock up. I primarily track my car and even with the Exocet/Miata differences in chassis stiffness,grip,balance etc the ABS works great. I also had it on my 99 10AE which also was tracked and street driven with no issues.

I have done track days and raced with Erich Heuschelle from SRT and a couple track days with Mark Steilow and spoke with both about ABS since Mark added ABS to his track 1st gen Camaro. Both thought it was a benefit and are excellent drivers and engineers that work in the performance area of 2 different OEMs. There are poorly set up/designed systems for performance work or with drastic changes to a vehicle but I don't see the Miata being one. One tire saved from flatspot damage is worth the weight of the system to me and the ability to brake at maximum without thought while maintaining steering in an emergency is worth a lot more. It has saved my life on at least 2 occasions without doubt in emergency situations on road.

srduck wrote: Out of curiosity.... why do you want it disabled?

I plan to use this car for Wintercross and possibly for ice racing.

Zeitgeist wrote: I am pretty sure the 95 and most NA ABS are 2 channel and NBs and late NAs are 3 channel. I looked for and kept the 3 channel ABS from my 99 Miata donor on my Exocet for the benefits.

All NA and NB systems are 3-channel. NC and newer are 4.

The newer NB systems are better, in that they react faster, pulse faster, and some of the latter NB2 systems supposedly do electronic proportioning rather than using a static prop valve.

2 channel ABS is a piece of junk, AFAIK it was really only used in some mid-90s Chryslers after they decided they were going to put ABS in everything as a marketing move, but couldn't afford a decent system in Neons and the like.

Woody wrote:

srduck wrote: Out of curiosity.... why do you want it disabled?

I plan to use this car for Wintercross and possibly for ice racing.

And yes, I agree with this reason for doing it. :) When I transplanted ABS into my NB1, I wired up the power to the control logic to a spare switch on my dashboard (I used the cruise control switch, since that was no longer installed). Cut power to the ABS computer and you're back to straight hydraulic braking. The ABS light in the cluster comes on to remind me that I've done it as well. There are three power wires going to it -- computer, solenoids, and pump. The computer has a 10 amp fuse, that's the easiest one to interrupt with a switch.

Woody wrote:

srduck wrote: Out of curiosity.... why do you want it disabled?

I plan to use this car for Wintercross and possibly for ice racing.

I haven't tried my Fiesta on the ice to see how it works on the ice.

With my ZX2/SR did not have ABS, so it was threshold braking. Theoretically , ABS does it for you.

Any reason not to just yank the module and connect the appropriate lines to make a normal brake system?

Since that is what I am doing.

I was thinking about putting a switch in the mr2 so I can disable it at will, I bet you can cycle the key and it'll work again.

Woody wrote:

srduck wrote: Out of curiosity.... why do you want it disabled?

I plan to use this car for Wintercross and possibly for ice racing.

95 M's are my favorite. Hope it's a crusty one! (If not, I may be interested in trading you a decent, but not pristine 94 M)

Curious, what is the reason behind wanting to disable the ABS.

Think you can do it better ?

Remember, a sliding wheel has almost no traction.

You can't steer with a sliding wheel.

This from one who got his first ABS equipped vehicle in 2010.

I had a '95M & pulled the fuse for the 1st couple of seasons. Was advised by a race shop to pull the pump assembly because "you're still pushing fluid through that restriction". Pulling the pump did open some much needed space for access to the coolant bypass thermostat. Other than saving a few pounds, I noticed little or no improvement in brake feel on a road course.

FYI - the brake proportioning valve has a higher rear bias in the ABS car than non-ABS. I had to mix pad compounds to compensate, but you may like this on the ice.

iceracer wrote: Curious, what is the reason behind wanting to disable the ABS. Think you can do it better ?

It depends on the tires. In the Jeep with all seasons on it in snow, the ABS stops almost as fast and with less effort that trying to threshold brake and avoid lockup. However, put snow tires on it and the game changes. It'll stop MUCH faster without ABS, as the ABS cuts in too early (the snows need more slip to generate max braking than the ABS allows).

Having a high pedal effort for the brakes helps a lot without ABS, as it's easier to stay out of lockup and not over-do it.

Seems that better traction of the snows would have less slip thus later ABS engagement.

A wheel has to be turning (slip) less than the others for ABS to engage.

Less traction, sooner engagement.

How can you threshold brake with ABS. Both do the same thing.

So if you brake to the point of ABS, then release an re apply you are defeating the purpose of the ABS.

In reply to iceracer:

All tires will have some slippage at their maximum grip point. If you exceed that slip amount, they'll lock up and let go entirely. Snow tires on snow and sticky rubber on pavement will often handle more slip before letting go (and will need more slip to generate max grip) than a typical all season (which is what the ABS is usually tuned based on).

With more traction, you'll get less slip at a given rate of deceleration. But if you're going for max stopping power, you'll want to be as close as possible to the max grip point for your tires.

In some vehicle / tire combos, it's not too hard to smoothly hold the tires at that point. In that situation, if that max grip point involves more slip on the front tires (assuming front-first lockup if you stomp the pedal) than the ABS allows, you'll be able to manually stop faster (assuming you're stopping in a straight line).

If the brakes can't be modulated well enough to hold the tires close to their max grip point (too easy to accidentally lock them up), then the ABS will probably stop faster.

rslifkin wrote: In reply to srduck: ABS calibrated for all seasons often engages too early with stickier tires that reach peak grip with a higher amount of slip. In that situation, the ABS will kick in before you reach maximum braking.

I read this statement three times with furrowed brow. As I understand it, the ABS computer is measuring the difference in wheel speeds from one to the others. If all wheels are turning at the same rate (no slip), then the ABS will never kick in no matter how fast you are stopping. If one wheel is turning at a slower rate than the others (or not at all), then the computer will pulse the brakes on that wheel alone in order to make it turn at the same rate as the others. Nowhere in that equation is it measuring the actual deceleration rate, so theoretically it shouldn't matter what type of tires you are running.

jstein77 wrote:

rslifkin wrote: In reply to srduck: ABS calibrated for all seasons often engages too early with stickier tires that reach peak grip with a higher amount of slip. In that situation, the ABS will kick in before you reach maximum braking.

I read this statement three times with furrowed brow. As I understand it, the ABS computer is measuring the difference in wheel speeds from one to the others. If all wheels are turning at the same rate (no slip), then the ABS will never kick in no matter how fast you are stopping. If one wheel is turning at a slower rate than the others (or not at all), then the computer will pulse the brakes on that wheel alone in order to make it turn at the same rate as the others. Nowhere in that equation is it measuring the actual deceleration rate, so theoretically it shouldn't matter what type of tires you are running.

Assuming the brake balance is perfect and all 4 tires are experiencing equal slip, that's correct.

However, in the real world, that's often not true and you'll have more slip at one end of the car than the other (and one end would lock up first if you slammed the pedal to the floor). In that situation, the end with more slip can trigger the ABS prematurely. If it's the front end triggering the ABS, it often shows up as a significant reduction in stopping power. If you'd get a rear-first lockup and it's the rear end triggering the ABS, the drop in stopping power is usually far less significant.

I do know in the Jeep that on a snowy road (with snow tires), it takes far more pedal force to lock the front tires with the ABS disabled than it takes to trigger the ABS.

jstein77 wrote: Nowhere in that equation is it measuring the actual deceleration rate, so theoretically it shouldn't matter what type of tires you are running.

AIUI, many ABS algorithms do look at deceleration rates on the wheels and have built-in tables with assumptions about the vehicle weight and type of tires. That said, I've data logged the NB2 ABS on my Miata (transplanted) and it works very well indeed on dry and wet pavements, even with super sticky Hoosier A6s, so as far as I'm concerned this is only a theoretical issue for road/track/autox use. ABS is a real money saver for autox because Hoosiers are really easy to flat-spot.

For use in snow/ice/gravel I have no personal experience. I have read that on loose surfaces like snow and gravel it's actually desirable to lock the wheel, because it will tend to build up a pile of that material in front of the tire. I dunno, I live in California and I don't rallycross, so neither of those applies to me.

Do not know if it is relevant to this conversation, but in the past I drove a Honda Civic on all season tires and that thing had the ABS pulsing all the time. Very annoying. If the ABS was defeated, there was no noticeable problem driving or stopping in the snow. It just behaved like a car that did not have ABS.

Putting snow tires on the thing solved the pulsing all the time issue.

Exactly what ABS is suppose to do. The all season tires were slipping, triggering the ABS.

The snow tires were not slipping, no ABS.

In reply to codrus: That only works sometimes and then in an emergency.