Front wheel speed sensor retrofit ideas?

[Map63Vette]

Hi all, I'm gearing up to swap my MS2 setup to a full blown MS3X at some point in the near future and am trying to plan ahead as much as I can for all the extra inputs and outputs and options I'll get to play with using the new computer. One of the things that I find the most novel to potentially include in the build would be some traction/launch control. I'm planning to completely remake my engine harness when I put the MS3X in the car, so the more I can build in from the start, the better.

I've already got a T56 in the car with a VSS and tone ring, so that takes care of the back wheel speed sensing (admittedly not as accurate as true wheel speed sensors since there is a rear end between them, but at least it's a posi unit). What I'm trying to figure out now is how I might get some front wheel speed sensing on the car. I saw Goody's setup on his Cuda that sensed the vanes on his rotors, which I think is a really cool idea and gives some nice resolution, but he's also got an aftermarket brake kit on his car, so it's maybe not the best apples to apples comparison with my setup, which I believe is actually factory E body disc brake parts (I thought they were F body originally, but when I went to buy brake hoses I found out the F body ones didn't fit). So that being said, has anyone else retrofitted a front wheel speed sensor on their car that has some pics to share? Just curious to see what other people have done and if anyone has a setup that works on stock-ish parts. I have a few random VR/Hall style sensors sitting around I should be able to use, but haven't held them up to the car yet to see where they might fit. Looking for ideas on brackets and whatnot. I read about potentially reading off the back of the wheel studs as one option, though it wouldn't be the best resolution at only 5 per rev. I might see if I could read of the vanes on my rotors as well, but could be interesting with the smaller stock rotors. Not sure if I'll have enough room in there or not.

 

[Dana67Dart]

Can you read the vanes from the inside of the rotor? Like where you would read the lug studs?

You could also have the top inside edge of the rotor machined (outside of where the pads ride) with a series of notches or shallow holes.

Heck for that matter you could have your rotors drilled (vented) and read there

 

[DionR]

There is a guy working on something similar, pretty sure he is running the same system you want to run, @racerjoe

12:05 Garage- ’70 Duster build

 

[DartGTDan]

An optical speed sensor?

 

[Map63Vette]

Can you read the vanes from the inside of the rotor? Like where you would read the lug studs?

You could also have the top inside edge of the rotor machined (outside of where the pads ride) with a series of notches or shallow holes.

Heck for that matter you could have your rotors drilled (vented) and read there

I'm planning to take the wheel off tomorrow and look around. I have one spare sensor that's the same as what is in my transmission I'm thinking would be good. I'm just not sure how much space I'm going to have between the knuckle and the rotor with the stock rotors. Feels like that is going to be pretty cramped, but I might be surprised. Not sure how the stock vanes are set up either, but will find out soon enough.

An optical speed sensor?

That's actually a pretty interesting idea. Wonder if you could clean up a surface enough to reflect where you want it and not where you don't so it would register well.

 

[Dana67Dart]

How about the wheel??

 

[1WildRT]

take what the OE's do and copy it... Find a tone ring that is close to the OD of the inner hub of the rotor, a few minor lathe operations & the tone ring will give you the optimum signal, then mount a OE sensor, they are compact & designed to reach into the close confined area behind a brake rotor...

 

[Map63Vette]

I had half considered that as well, but the main reason I was hesitant was 1. I don't have machine tool access (I know I could just take it somewhere, but I prefer to do what I can myself since it might be a lot of trial and error) and 2. I'd have to redo it if I ever replace suspension parts. Not a huge deal to redo as those parts should last a long time, but I'm not even really that sure what the hub looks like off the top of my head. I agree though that it would be the "best" answer as far as quality and fidelity of signal. Guess I'll just have to take some pictures and do some brainstorming. Would be easier if I actually knew the parts that made up my car, lol. It was so kludged together when I got it that every trip to the part store is an adventure. At minimum I know it's a big bolt pattern setup that I think is E body calipers. Beyond that it's hard to say as I think some of the parts swap somewhat freely between bodies. My car more or less came out of a junkyard though, so guessing they would have taken whole pieces and not mixed and matched stuff, so I would guess it's at least a full E body knuckle and spindle setup as well.

 

[CudaFish1968]

Hi all, I'm gearing up to swap my MS2 setup to a full blown MS3X at some point in the near future and am trying to plan ahead as much as I can for all the extra inputs and outputs and options I'll get to play with using the new computer. One of the things that I find the most novel to potentially include in the build would be some traction/launch control. I'm planning to completely remake my engine harness when I put the MS3X in the car, so the more I can build in from the start, the better.

I've already got a T56 in the car with a VSS and tone ring, so that takes care of the back wheel speed sensing (admittedly not as accurate as true wheel speed sensors since there is a rear end between them, but at least it's a posi unit). What I'm trying to figure out now is how I might get some front wheel speed sensing on the car. I saw Goody's setup on his Cuda that sensed the vanes on his rotors, which I think is a really cool idea and gives some nice resolution, but he's also got an aftermarket brake kit on his car, so it's maybe not the best apples to apples comparison with my setup, which I believe is actually factory E body disc brake parts (I thought they were F body originally, but when I went to buy brake hoses I found out the F body ones didn't fit). So that being said, has anyone else retrofitted a front wheel speed sensor on their car that has some pics to share? Just curious to see what other people have done and if anyone has a setup that works on stock-ish parts. I have a few random VR/Hall style sensors sitting around I should be able to use, but haven't held them up to the car yet to see where they might fit. Looking for ideas on brackets and whatnot. I read about potentially reading off the back of the wheel studs as one option, though it wouldn't be the best resolution at only 5 per rev. I might see if I could read of the vanes on my rotors as well, but could be interesting with the smaller stock rotors. Not sure if I'll have enough room in there or not.

I use a hall effect gear tooth sensor for my speed activated switch. I needed 5vdc pulse input. I used a 12vdc to 5vdc power supply feed the + vdc and - vdc and +5vdc pulse output. I used the front wheel studs for the pulse. You could easily use the same style sensor on the rear and front to feed a hall effect signal into mega squirt for traction control.
I experimented with Hemi Goldbox and found out quickly I do not have engineer tuning skills for ignition and fuel. I purchased the gear tooth sensor from Digi Key, $25.00 plus shipping.

 

[DionR]

If you didn't already have the rear solved, a swap to an 8.8 might offer an option. Or a cut down 9.25 out of a van or truck if you wanted to keep it Mopar. The 8.8 (I think) has tone rings on the axles, but the 9.25 has one one the carrier so it isn't any different than using a pickup in the trans.

Just ideas.

 

[DionR]

...but I'm not even really that sure what the hub looks like off the top of my head.

The link I posted to racerjoe's build has a picture of what he is doing. Pretty sure he cut down stock rotors for his DIY BBK, so it might give you an idea of when your hub looks. Just be aware that it looks like he used the HD rotors for his kit, and those have a cast in gusset to brace the wheel flange surface so yours might be more uniform than his is.

 

[Map63Vette]

I use a hall effect gear tooth sensor for my speed activated switch. I needed 5vdc pulse input. I used a 12vdc to 5vdc power supply feed the + vdc and - vdc and +5vdc pulse output. I used the front wheel studs for the pulse. You could easily use the same style sensor on the rear and front to feed a hall effect signal into mega squirt for traction control.
I experimented with Hemi Goldbox and found out quickly I do not have engineer tuning skills for ignition and fuel. I purchased the gear tooth sensor from Digi Key, $25.00 plus shipping.

Yeah, I think that is going to be the easiest way, I just wasn't sure if only 5 studs per revolution was going to work as well for traction control and stuff. Mostly just because I have a 10 tooth wheel in the transmission and a 3.55 rear end, which means I really have something closer to a 35/36 tooth wheel at the rear wheels from the input standpoint. If I'm trying to compare slip between the front and rear where one reads 5 pulses per rev and the other is reading 35, I'm not sure I'll be able to effectively measure something like 5% slip between the front and rear or whatever the number is going to be.

 

[Map63Vette]

The link I posted to racerjoe's build has a picture of what he is doing. Pretty sure he cut down stock rotors for his DIY BBK, so it might give you an idea of when your hub looks. Just be aware that it looks like he used the HD rotors for his kit, and those have a cast in gusset to brace the wheel flange surface so yours might be more uniform than his is.

Yeah, I had looked through that build and thought it was pretty slick. I think that's the first idea I'm going to try when I take the wheel off and look at things closer. That would be minimal work to implement as well since it's pretty literally just a bracket to hold a sensor. I wouldn't have to add any tone wheel or triggers or anything like that. I guess I missed that he did a DIY kit. I had thought it was more of an off the shelf full system, so that gives me a little more hope. I think his spindles looked quite a bit different though. I think finding where to attach the bracket might be the interesting part, though maybe I can pick up the lower ball joint attaching bolts or something. Not sure I want to attach anything to caliper bolts either as I wouldn't want to have to remove it whenever changing brakes or anything. Better to keep it solid so I'm not worrying about alignment all the time.

 

[DionR]

Yeah, I had looked through that build and thought it was pretty slick. I think that's the first idea I'm going to try when I take the wheel off and look at things closer. That would be minimal work to implement as well since it's pretty literally just a bracket to hold a sensor. I wouldn't have to add any tone wheel or triggers or anything like that. I guess I missed that he did a DIY kit. I had thought it was more of an off the shelf full system, so that gives me a little more hope. I think his spindles looked quite a bit different though. I think finding where to attach the bracket might be the interesting part, though maybe I can pick up the lower ball joint attaching bolts or something. Not sure I want to attach anything to caliper bolts either as I wouldn't want to have to remove it whenever changing brakes or anything. Better to keep it solid so I'm not worrying about alignment all the time.

Spindles should be the same if you have a BB kit. Pretty sure the A-Body and E-Body spindle is the same. Far as I can remember, he doesn't have anything special going on with the spindle. Maybe just looks different based on the angle or side of the car?

I would look at using 2 of the splash shield bolts to mount the bracket. Ditch the splash shield, or bolt the bracket on top of it. There should be 2 holes opposite the caliper bracket holes that are wide open for this. Pretty sure that is what @racerjoe is doing.

Sorry, looks like I didn't link to the specific post when I did it last time. Meant it to point to post #300. [URL="https://www.forabodiesonly.com/mopar/threads/12-05-garage-%E2%80%9970-duster-build.297088/page-12#post-1973676459"]12:05 Garage- ’70 Duster build[/URL]

 

[Map63Vette]

Ah, that is a bit different than the one I was looking at before. I think I was thinking of Goody's build in my head that used an aftermarket disc brake kit and way different spindles. Racerjoe's setup is pretty much the exact sensor I have though, so nice to know that's one functioning option out there.

I was just out looking at the car and it is going to be interesting. Like you mentioned, pretty sure nothing is going to happen unless I ditch the dust shield or at least trim it out around anything I use. There is pretty much no opening for anything on the stock setup with that all in place. I really like the idea of trying to read off the rotor vanes on the inside, but I'm going to have to actually pull the whole rotor to figure out if that's possible, and that just wasn't something I felt like dealing with today. I wish the rotor just popped off and left a hub under it, but this is an old all one-piece type deal that has the bearings in the rotor assembly and actually has the rotor behind the hub flange instead of sandwiched between the hub and wheel. Something kind of like this I think:

Reading off the back of the studs on that is probably not too bad. Not sure if I could get a sensor turned sideways to read off the vanes though. They are just mighty small diameter compared to brakes today. I think I'm just going to have to bite the bullet and take the rotors off to get a better look though. Guess it wouldn't hurt to repack bearings anyway since I haven't touched them in all the years I've owned the car.

Here's a better view of the back of the rotors:

Might be tough to read the vanes with the sensor I have now. I think it might be too wide to get a good signal. I've got a narrower VR style one, but then I'd need a different signal conditioner, so I'd prefer to use the Hall style one I have now. Looks like I'd have a good shot at reading the lugs though. Guess I'll just have to do the math and see how bad 5 pulses per rev actually is

 

[DionR]

...I think I was thinking of Goody's build in my head that used an aftermarket disc brake kit and way different spindles.

Do you have a link? I remember Goody and his car but didn't know he had done anything like this.

 

[Map63Vette]

Here was what I was looking at: Just Sharing - MegaSquirt Hemi w/Traction Control
Looks like that might actually be a stock knuckle and spindle, but with the dust shield removed. Definitely an aftermarket rotor and caliper bracket, but maybe I'm not as far off as I thought I was going to be. I think my tiny rotor might still cause some issues, but won't really know until I dig all the way in and have a closer look. Would be a real pain to remove if I needed to though, lol.

 

[DionR]

Here was what I was looking at: Just Sharing - MegaSquirt Hemi w/Traction Control
Looks like that might actually be a stock knuckle and spindle, but with the dust shield removed. Definitely an aftermarket rotor and caliper bracket, but maybe I'm not as far off as I thought I was going to be. I think my tiny rotor might still cause some issues, but won't really know until I dig all the way in and have a closer look. Would be a real pain to remove if I needed to though, lol.

Wow. I completely missed that thread.

BTW, he does have different spindles that you do. His kit appears to use drum brake spindles rather than the disk specific ones. But they are still an OEM spindle and not something aftermarket.

For me, I think I would rather find a way to press a tone ring onto my hub. Just feels more secure and less chance of wobble. More work and not sure it would give any different results, but I like that I could swap out my rotors without having to change anything (my hubs are like racerjoe's, rotor/hubs with the rotor cut off).

Are there options in the MS software to set different values for the front and back sensors? I agree that 5 pulses per revolution seems pretty broad, but if the software will take it and compare it accurately to the transmission sensor, seems like it could work.

 

[Map63Vette]

Yeah, you tell it what your tooth counts are, so they can be different as far as I'm aware. I just need to do the math and see what kind of resolution I'm looking at. I very well could be making a bigger deal out of it than it really might be. I built a cruise control kit for my 71 Vette years ago in college and learned that one pulse per rev at a wheel surely isn't enough as the math and response time of the sensor would only start reading at some minimum speed and would jump something like 2 mph at a time. Just two pulses per rev was enough to make it work for highway speeds at least, but still not great.

I agree on the tone ring as well, but only if I had an actual separate hub. I'd much prefer the more modern style rotor that sandwiches between a hub and the wheel, but don't know if there is a conversion out there for that or not that still retains the stock calipers at least.

 

[racerjoe]

Thanks for the shoutout @DionR!
My front spindle/brakes consist of a stock F,M,J spindle with the brake surface turned off of a 11" rotor to create a hub. The rotor is a 13.75" rear rotor off an SRT challenger and it has a Gen 1 Viper Brembo caliper. While reading the ribs on the back of the hub seems like a super easy solution, mine weren't evenly spaced. I don't know how much that would have freaked out the MS3. Secondly, there's no way I could have fit the sensor in there since my rotors overhang the hub quite a bit. I'm reading off the back of the studs. While I don't have it up and running yet, I'm sure it will be fine. I've seen a youtube video of a guy having 1 pulse for speed input. While I'm sure it works, the resolution has to be pretty crappy.
Dion was correct in stating the bracket I made attaches to the dust shield bolt holes in the spindle. I could have easily used a ball joint bolt hole if those weren't there.
You are lucky to have a trans speed signal. I have one of the older TKO500s and it doesn't have the provisions for an electronic speed sensor. Of course I could put one in the speedometer location, but I have a speedometer and want to keep it. I'll be making a bracket to mount the same sensor on the back wheel studs also. I've been waiting on Deutsch connectors to come in so I can get it all done in a day.
I also recently purchased an accelerometer for assistance in tuning the traction control. I also think it will be fun to make some autocross videos with overlay showing this data. If you don't want to spend $300 on a Holley or Fuel Tech accelerometer and don't have a problem "engineering' some things, Digikey has an accelerometer for $16. It's just a tiny circuit board (3/4" x 3/4"). You will need to come up with a little box and a way to mount it firmly in the car.

 

[Map63Vette]

Thanks for the extra pictures on the sensor setup! That's pretty much the exact same sensor I have, so nice to know there is some kind of way to make it work. I think my biggest challenge at the moment is figuring out the brake setup. From what I can find, it looks like the front drum brakes didn't include the wheel bearings on the E bodies, but I'm having a hard time finding pictures of a front drum setup with the drum off. My hope would be to use the drum hub and just find a different rotor that could fit over the top of it that would still work with the stock calipers I have, but that might be a tall ask and a lot of parts book searching. I'm still not even sure the front drum hub thing really exists at this point and what mods might need to be done on it to make it fit.

I was doing a little math with my tire sizes and the pulse counts as well and it's really probably not as bad as I think it would be. My tire size comes out to something like 3780 pulses per mile if I have 5 pulses per revolution. Going all the way down to 1 mph would still get me roughly 1 pulse per second, which isn't amazing, but would probably still work okay. Normally I'd say you would never really care about resolution at that low of a speed anyway, but with traction/launch control I think that's the one exception since you are leaving from a standstill. You would probably still get up to a speed that would give you several counts in a second fairly quickly, but hard to say how it might affect the tuning. The difference between 1 and 2 pulses at a low speed if you're right on the edge of one wheel stud or between them when you first launch would be my main concern and where the resolution really matters. I think my tire circumference was something like 80" roughly, so divide that by 5 and you'd have 16" of forward travel before you read the next pulse. I'm not sure if that's a problem or not. I think it would be a bigger problem for launch control than traction control though. If you're already rolling along and stand on it, I think it would be fine to catch wheelspin, but I'm not sure I'm convinced it would get you off the line very well.

 

[pishta]

An optical speed sensor?

That would get dirty ASAP. I think some strategically drilled rotors would work. Hang the VR off the caliper bracket right next to pads and have it read the drilled holes.

 

[racerjoe]

Thanks for the extra pictures on the sensor setup! That's pretty much the exact same sensor I have, so nice to know there is some kind of way to make it work. I think my biggest challenge at the moment is figuring out the brake setup. From what I can find, it looks like the front drum brakes didn't include the wheel bearings on the E bodies, but I'm having a hard time finding pictures of a front drum setup with the drum off. My hope would be to use the drum hub and just find a different rotor that could fit over the top of it that would still work with the stock calipers I have, but that might be a tall ask and a lot of parts book searching. I'm still not even sure the front drum hub thing really exists at this point and what mods might need to be done on it to make it fit.

I was doing a little math with my tire sizes and the pulse counts as well and it's really probably not as bad as I think it would be. My tire size comes out to something like 3780 pulses per mile if I have 5 pulses per revolution. Going all the way down to 1 mph would still get me roughly 1 pulse per second, which isn't amazing, but would probably still work okay. Normally I'd say you would never really care about resolution at that low of a speed anyway, but with traction/launch control I think that's the one exception since you are leaving from a standstill. You would probably still get up to a speed that would give you several counts in a second fairly quickly, but hard to say how it might affect the tuning. The difference between 1 and 2 pulses at a low speed if you're right on the edge of one wheel stud or between them when you first launch would be my main concern and where the resolution really matters. I think my tire circumference was something like 80" roughly, so divide that by 5 and you'd have 16" of forward travel before you read the next pulse. I'm not sure if that's a problem or not. I think it would be a bigger problem for launch control than traction control though. If you're already rolling along and stand on it, I think it would be fine to catch wheelspin, but I'm not sure I'm convinced it would get you off the line very well.

My old small bolt pattern drum had a hub pressed in them. Unfortunately, the way the hub face was made with some notches, it prohibited me from re-drilling to the 4.5" pattern. It seems like most reproduction drums are one piece. If you have any junk yards around you with old mopars, look for a B-body with front drums. You may have a chance at finding a drum with the pressed in hub there.

I think you're over thinking control at slow wheel speeds relative to the front wheel. You should be looking at drive wheel speed instead of front wheel speed. Megasquirt is looking at difference in speed. If you dump the clutch from a standstill, the rear wheel speed will instantly go 10+ mph. If you have your table set up to start pulling timing at 25% difference, at 3mph (front wheel speed), you are cutting timing when the rear wheel reaches 3.75MPH. That's pretty darn quick if you ask me. Now, I have no idea how what my deviation will be set to, but I figured I'd start at 25% and ramp up from there.

 

[Map63Vette]

Yeah, that's a fair point on the difference and another math problem I probably need to actually do some numbers on before I worry too much. The real question is going to be what resolution the front wheel speeds sensors read and how much of a difference one tooth could possibly make at slow speeds. The main example I had where you might be just after one stud and waiting forever for the next one vs just catching the edge of one at the start of a pull is the "worst case" scenario I can think of. One extra tooth matters if you only have 5 to read from as it's a 20% difference, but then again if it's only 20% of 1 mph then it's only 0.2 mph and probably not a big deal and likely something I could just tune around.

I did find some B body drum brake hubs though, so that does seem to be something that exists (pictures below) and might be a way to get to the two piece rotor/hub idea more easily, though I still suspect getting rotors to fit over them and still fit inside the calipers could be a challenge. Probably easier to just go the full retrofit route at that point and change the caliper and caliper bracket to use a larger modern rotor.

 

[turbofreek]

i have aluminum hubs so i am able to use the bolts from hub to rotor disk. along with a hall effect sensor. dont use a vr sensor they are not as acurate and subject to all sorts of interference. need shielding wiring for them as well. hall effect isnt as sensitive to electrical scatter around the car in said area. i use a 5v cherry sensor on mine. hall effect only