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Installing ABS, specifcally on a pre-ABS Fox rear - Greg_M solution

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abs anti-lock brakes fox axle tone rings
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31K views 109 replies 29 participants last post by  6t8dart  
#1 · (Edited)
NOTE/UPDATE: On 3/15/2011, I posted this detailed summary of the project with procedures for testing the ABS components off the car, installation, troubleshooting, and many tips:
http://www.ffcars.com/forums/showthread.php?t=268018

Feel free to continue reading from here and see the learning process and what it took to get there.

I'm starting a new thread on ABS because I have been posting all over the place recently gathering data to make this happen.

This weekend I cleared a major hurdle in the process of installing ABS brakes on the FFR with a '91 Fox rearend. I came up with a clean solution to mounting tone rings on the narrower Fox axle using only hand tools and no machining costs.

I have details and photos posted at the end of my buildsite if you are interested. I will update this thread as I progress over the next few weeks.

Here is the link for the work this weekend.
http://www.worldisround.com/articles/123897/photo509.html
Select next in the upper right corner to see the progression. The photos I took blow up hi-res if selected.

Here are a few teaser shots:

Stock SN95 rear and tone ring for referrence
Image


My solution for the Fox rear
Image


Image


Image


Greg
 
#4 ·
Sure. It simply keeps the wheels from locking up.

Thanks for the kudos,
Greg
 
#5 ·
Excellent writeup and photos. Very creative solution.

Will you be able to provide before and after brake system performance data / stopping distances?
 
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#6 · (Edited)
I'm installing an ABS defeat switch so with/without ABS braking performace can be as simple as a click away.

Greg
 
#7 ·
Very nice work, as usual. your photo work is exemplary.

You've managed to overcome the single biggest challenge to this upgrade, now for all the grunt work of bending lines and adding wires etc.

I'll be very interested in the before and after 60-0 stopping numbers when you are done.

Sean
 
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#8 ·
canuck1 said:
Very nice work, as usual. your photo work is exemplary.

You've managed to overcome the single biggest challenge to this upgrade, now for all the grunt work of bending lines and adding wires etc.
Sean
Click to expand...
Thanks Sean,
I can't get enough of this kind of work.

Greg
 
#9 ·
Great job Greg... I am surprised nobody's thought of it before... JJ
 
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#11 ·
JJ'snakepit said:
I am surprised nobody's thought of it before... JJ
Click to expand...
I needed something to keep the front brakes from locking too easily and maintain full steering control around corners on mountain roads where traction could be compromised. The mother of invention and all......

David,
Drawings? You can't be serious :). This is prototyping in uncharted territory. I could come up with some in the near future when I get to the point I know this is going to perform correctly.

Greg
 
#10 ·
Greg,

Fantastic work! Thanks a ton for creating a single post for your project. I think this will be a bit help for those who will try this in the future.

If you have drawings or dimensions, I could machine some of the parts for folks that want to try this out. Just looking at that working from your idea, I think it would be possible to create the whole thing without the need of getting used tone rings.

David
 
#22 · (Edited)
David Borden said:
Greg,

If you have drawings or dimensions, I could machine some of the parts for folks that want to try this out. Just looking at that working from your idea, I think it would be possible to create the whole thing without the need of getting used tone rings.

David
Click to expand...
No drawings but here's some more data for you:
Image

The edge of the tape marks the point where the oil seal meets the axle. The caliper indicates 0.355" is the available flat area on the axle. Knowing the axle must move inward 0.25" to release the C-clip, there is no way I could fit the tone ring here even if I machined a bushing to support it. There is simply not enough room.

Image

Taking the thought process a step farther, if I made a bushing that fit over the curved part of the welded shoulder, the clearance is still not there. The available lateral travel would be 0.229" or 0.021" less than required.

Image

To further illustrate the clerance issue, I placed the spoke edge at the edge of the tape. The spoke is 1/4" thick. Note how little room is available between the spoke's lower edge and the start of the curved part of the axle. There is simply inadequate clearance for a ring to mount here

Image

This shot indicates 0.600" is the spot to cut the spoke.

All this new stuff and more at the end of the buildsite.

Greg
 
#12 ·
Greg.

How hard was it to drill and tap the axle flange? I'm assuming that the bearing area is hardened but I wasn't sure if the flange was too. If it's relatively easy to drill and tap then I can simplify my approach to be in line with yours and it will make things a lot simpler.

Nice work.
 
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#13 ·
Mike,
Not too bad. The metal is hard but not brutal. I used a 1/8" bit to start and gradualy worked my way up to a #7 (.201) bit. Use cutting oil and take it slow when you tap.

How far along are you?

Greg
 
#16 ·
Greg_M said:
Mike,

How far along are you?

Greg
Click to expand...
I have all the parts including the harness, the ABS unit is mounted, and I have SN95 front hubs installed with tone rings. I measured and made some drawings of rear axle spacers while I had the axles out for the Torsen install but the axles needed to go straight back in for an upcoming auto X. My plan is to pull the axles again in a few weeks and install the rings etc over the winter.

At the same time as re running the brake lines I will install a CNC dual master with 3/4 front, 5/8 rear. I have Carbotech pads on the car and with V710's the car stops amazingly well but I cannot lock the rear brakes so I know there is more performance to be had with more pressure to the rears and ABS. This should all really add to my confidence in driving the car deeper into corners and hopefully cut some meaningful time.
 
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#23 ·
I checked it today and happy to report it works like a champ!

Here's a shot of the fully completed driver's side. The axle is locked into place.
Note the 0.030" clearance between the ring and the sensor magnet and the ~ 1/8" gasp between the ring and the sensor body. Also note the distance between the MRI-grade non-ferrous stainless Allen bolt and the sensor. I took ferro-magnetics into account when I place the mounting bolts. Did not want them to induce a stray signal into the sensor as they swept past.
Image


I spun the axle by hand and measured the accelleration, constant speed, and decelleration by scoping the sensor's ouput. It was proportional, clean, and had no spikes or missing pulses caused by the mounting hardware.
This photo is the axle acellerating and covers 1/3 of a rotation.
Image


This trace shows the sensor output at a relatively constant rotational velocity. This trace was produced by 2/3 of the ring's teeth.
Image


The final 1/3 of the ring's pulse are shown here as the axle coasts to a stop
Image


This data is also at the end of the buildsite.

Greg
 
#15 ·
I considered that in the design. All the Allen bolts are MRI grade non-ferrous stainless steel and they are as far away as possible. The backing plate is aluminum which is of course also non-ferrous. I will check the output of the sensor with an oscilloscope and look for any irregularities in the signal.

Greg
 
#19 ·
And for my next trick

Greg:
Nicely engineered and fabricated. Another use of your system is for traction control. Not the brake application kind, but the cut the fuel or retard the timing type of traction control. The tone ring signal is used to show if the rear axle speed is out of sync with the engine rpm. I'm not smart enough to know how to do this, but I think on some cars a few years ago the traction control computer was a separate box.

Again, great job!!

Ron
 
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#21 ·
Mike,

Looking forward to your impressions of the car with ABS and the CNC brake unit. On more than one occasion Ive ruined $500 worth of tires in a split second from locking them up.

On another note, Ive been thinking about the use of the C5 Corvette ABS unit since it more closely matches the weight distribution of the Roadster. Just not sure if the tone rings produce the same type of signal as the mustang.

David
 
#48 · (Edited)
After I buttoned up the rear, added oil and put the tires on, I spliced 12' of new twisted pair cable onto each rear sensor. The sensors all have a black and a red wire. I connected the new black wire to the old one to keep the OEM phase consistent and zip-tied the wires (covered by a 1/4" plastic sleeve) onto the brake lines all the way to the front of the car.

For reference, all 4 wheel sensors read 1,650 ohms +/- 3 ohms.

RE phase, I connected the scope in dual trace mode and noted the rear sensor's phase was inverted even though the wire colors were consistent. This is probably because the tone ring is turning the opposite direction relative to the sensor on each side of the rear OR the sensors are wound differently. Each has it's own unique part number but I think that has more to due with the location of where wire comes out than how it's wound.

The scope trace varied in amplitude from L/R by about 20%. I think this is due to a minor distance variation in how close I got the sensor magnet to the tone ring. A few thousandths makes quite a difference.

I will install an 8-pole terminal strip next to the controller, ahead of the OEM connector. This allows wires to be swapped changing the phasing if needed to eliminate fault codes. It also provides an easy way to isolate and scope the sensors for troubleshooting.

I don't think phase relationship or peak amplitude (within limits) will alter the way the computer handles sensor data. IMO, the computer is looking for transitions/second in the AC waveform. The sensor's AC voltage generated by turning the rear end by hand is about 1V p-p. At speed it must be way up there.

RE; 3CH vs 4CH ABS; My car has one hard brake line from the MC to a special adapter fitting at the rear of the chassis. From there, a single soft line connects to a T-fitting on top of the diff where 2 hard line feed each rear brake. 3CH ABS is the best fit for my car since I have only one line feeding the rear brakes. 4CH ABS would require another brake plumbing scheme to the rear.

David, and Tom,
Thanks and always glad to share. I love this kind of challenge. Tom, I lived in Houston for 31 years before moving here. Do you know Steve Normam? He used to make custom cabinets and furniture in Pearland. I worked with Steve for years at the Arabian Amercian oil Co. in the 80's.

Today, the front sensors go on and get wired up.

Greg
 
#25 ·
I can't compare the polarity to anything else yet. The sensor produces an AC waveform so the real question is, will the computer care about relative phase or whether it's leading or trailing edge triggered. I suspect it won't care. As good measure, I'm gonna be consistant connecting the same color wire to the sensor-minus in the harness. This way they will be in phase.

Greg
 
F
#106 ·
Greg (or anyone else that can explain it) - excuse the daft question, but does this mean that the two wires from the sensor to the control unit can be plugged in however I like?

I have weatherpack connections coming out of the ABS control unit all labelled LF, LR, RF, RR, ABS Light, Brake light, and I am about to put weather pack connections on the two wires coming from the sensor on each wheel. I'm no electrician, but I think what you wrote means that as long as I plug the LF wheel sensor into the LF on the control unit it should all work regardless of how I put the sensor wires into the weatherpack?

Is that right?

Martin
 
#26 · (Edited)
Made the passenger side today. These are a lot of work and I'm glad they're finished. Need to mount the sensor and button up rear end.


Image


Greg
 
#28 ·
Congrats on the creative solution, this is awesome.

I spent some time mocking up different options over the past few years, taking pics, posting on the forum...I couldn't figure out a clean, safe solution. I ended up with the expensive option, IRS w/ ABS provisions. Still haven't installed the ABS!

Again...nice job. This should be logged under FAQ or something.
 
#29 ·
Richard,
Thanks for all your help over the years and for making a brake conversion kit that turned out to be one of the things that made this mod relatively easy to sort out.

Redfish,
Thanks for selling me those ABS sensors, rings, and for some of your ring/axle photos.

Greg
 
#32 ·
Hi Greg, awesome work!! Any reason you couldn't simplify things by using four small spaccers and bolting right through the hub into the ring? Should save you from having to tap the hub.

Image


Cheers, Rod
 
#33 ·
Rod,

I was thinking of something similiar, except having an alum adapter ring that would sit flat on the spokes(light blue area) with an OD that would just fit into the inside of the tone ring, and an ID that would reference on the bearing surface on the axle. There would be reference holes in the adapter ring for markinging/drilling through the rings and the axle.

Then use what you show for spaces and bolt it up.

David
 
#38 ·
David.

That is close to what I am doing but using IRS tone rings without the spokes. The IRS tone rings are also thinner so offer a little more space to play with. I have aftermarket axles that have a very beefy radius behind the axle flange so the ring I need may not be quite the same for a Ford axle. I expect to complete this over the next couple of months as a winter upgrade I'll post pictures when it's done.
 
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