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Man.....

What part of 'so the wheels don't lock up' do you not understand???

I remember when my Dad bought a new wagon and he was really proud of the anti-lock rear brakes, especially for winter stops.

No more sideways slides, just pushes through intersections because you couldn't lock the rear wheels with a rear wheel drive automatic.

He learned real quick to use neutral to stop which is the big downfall of the modern 4 wheel ABS.

The 'only' reason for the proportioning valve is to provide rear anti lock brakes.

It serves no other purpose.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Mike, that isn't ABS per se - it's a simple proportioner valve that modifies the amount of braking you can get to the rear wheels. On my MJ, there is a linkage between the axle and the bed that senses the load as the distance between the axle and the frame and allows more braking on the rear end as the load increases. Damned thing must work

- I forgot to connect the link rod when I changed the diff fluid one day so the rod was hanging all the way down making it think it had a full load. Locked the rear brakes as soon as I hit them to remind me to hook it up. It knows zilch about wheel rotation/skid so I wouldn't call it a real ABS.

It's also a PITA to bleed the rear brake lines if you ever get air into the proportioning valve!

They did advertise it as rear anti lock brakes back in the 70's. I remember it very clearly when my Dad bought a new Wagon with that 'feature'.

That acronym 'ABS' didn't exist then from what I remember.

Same for 'RTS' or radial tuned suspension made 'especially' for the new radial tires.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

So 'sure track' was the first generation of an 'ABS' system I guess.

I still was more talking about the proportioning valve part of the combination switch where the front/rear pressure balance occurs.

This proportioning valve is a dynamic balancer between front to rear. It varies according to how much pressure the pedal is sending.

If you are slowing down slowly, the pressure is close to equal. Panic stop it and the rears won't get enough pressure to lock up so you at least track straight, even if you can't steer.

Which goes back to what I first said. In a panic stop situation, there is usually no place to steer to, so full bore on the brake pedal is best for 'most' people. Lock up the front brakes. If you have time to steer, then likely you have time to threshold brake the front wheels and use engine braking.

If you have never practiced threshold braking, you 'will' hit something by trying to not lock up the front brakes.

Telling folks to never lock the brakes up isn't a good thing to do in a public forum. Better to tell them to go to a braking or skid school and learn how to skid and brake properly or at least hit up an empty parking lot and try to wipe out and see just where you lose control.

That is one reason I always mention on our newsgroup winter snow runs. They are great for folks new to Jeeps to learn how they handle.

Mike

"L.W.(ßill) Hughes III" wrote:

On 12 Dec 2003 11:59 AM, Mike Romain posted the following:

Where do the wires for the wheel speed sensors plug in? 8^)

---------------------------------------------------- Del Rawlins- del@_kills_spammers_rawlinsbrothers.org Remove _kills_spammers_ to reply via email. Unofficial Bearhawk FAQ website:

It was designed way back and is a purely mechanical valve.

It relies on how hard you are pushing down on the brake pedal. Push gentle for a slow stop and the pressure from to back is close to even. Mash the brake pedal down and the front only gets enough pressure to lock up, the rears stay turning right up to the last second of the stop where you might get a chirp out of them.

This was all new shit when I worked in garages in the 60's and 70's.

They did have fancy stuff before electronics eh. Like the mechanical multi port fuel injection systems Volvo and VW used. No electronics needed. They even still had breaker points.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Actually, they all ENDED off the road :-)

1 Jeep :-( 1 Ford wagon

Don't know what they called it, but the MJ had both proportioners - one up front as usual then the second one that modulated the rear end. The only time I ever really climbed on the brakes that hard on dry pavement was one of those OH SHIT! situations where some clown in a ricer decided it was his time to go no matter what was coming. Now, I'm no puny weaklings, but I never did get a full lock on either end at 50 mph. The BFG ATs were essentially still brand new and you could just see the tracks they left. Traffic was pretty heavy and fortunately the 2 guys behind me had slowed to turn off so that I had room but I stopped a lot shorter than I figured on and even with the extra space I still almost had a little Ford hitching a ride on my rear bumper. I didn't get out to look (getting dark and lots of traffic), but I would swear I saw evidence of all 4 wheels making marks. I did stop in a straight line, so there is that to say for it.

Not that it's germane to the t> So 'sure track' was the first generation of an 'ABS' system I guess. >

That's the old Bendix system with the accumulator, that are not used on Jeep vehicles anymore.

• * * Matt Macchiarolo
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First I have to spend some time trying to make sense of what you wrote....

• * * Matt Macchiarolo
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I can't say I'm 61 but I have also been legally driving since 14 and have never had an accident on a public road as well. (Knocking on wood.)

In over 20 years of driving I've had exactly 2 traffic citations, both for speeding and both before the age of 22. Can you say the same?

The second one shouldn't count, it was in a Dukes of Hazzard style speed trap in Dubach, LA at about 3am. Had to pay the fine on the spot in cash.

• * * Matt Macchiarolo
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The brakes are pulsed off and then back on as the wheels approach lockup. Missing is the note that the system automatically shuts off the ABS at low speed so the vehicle can come to a halt. As for it being a simple mechanical pump, only on the really old systems--modern ABS uses electronic control with feedback from the wheels, with the electronics pulsing the pressure release solenoids in the hydraulic control unit at a rather impressive noise-creating speed.

I do, but it pretty much says you are full of it. Chapter 5 in the 1995 FSM to be specific claims that the control is electronic using solenoids in the HCU.