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So I'm wondering if I can fix my ABS/TC by getting custom reluctor wheels machined or 3D printed to combat my difference in front and rear RPM from having taller rear tires. If my thinking is correct I could trick the wheel sensors by replacing the rear reluctor wheels with ones that have a proportionally higher number of teeth, making the sensors believe both wheels are moving at the same RPM while still activating with any slippage as normal.
If my math is right, and without taking actual physical measurements of my tires to confirm, the difference between the circumference on a 275/40r17 front and a 275/50r17 rear is around 8.44%. Carrying that over to the stock [front] reluctor wheel's 47 teeth tells me I'd need to have one in the rear of the same size but with 51 teeth. That way, the wheel sensor will read 47 teeth on both reluctor wheels when the front tire makes it's full rotation.
I'm not certain what material these are made of, it looks like aluminum... but since, as far as I know, it doesn't carry any sort of load, could it be made out of ABS or something and still function properly?
Does anyone know of any reason this wouldn't work?
Last edited by Richard_Strahl; 09-21-2019 at 04:51 PM.
It needs to be metal because the sensor uses the Hall effect, which I'm not an expert in, but needs to be metal to conduct. Aluminum for sure, or steel would work too but the exact size might need to change if it conducts more than AL.
Ah, I see, thank you! I wonder then if a steel or aluminum 3D print job would have enough metal in the resin to trigger the effect... CNC would be preferred, but I imagine a print would be a whole lot cheaper.
So I have this pic I found on the Z28 forums that list the OD, ID, and thickness. Would anyone be able to grab me a measurement of the diameter at that middle step down section, by how many inches the thickness steps down, and the length of the teeth? Once I get all the measurements I can get a 3D mock up and get started on this fix
Last edited by Richard_Strahl; 09-22-2019 at 12:38 PM.
Haha, well I appreciate your imagine, man, I learned a lot!
Oh, I see, what would be the thickness of the piece at the teeth, then? The depth, if you will And do you know how deep the counterbore is?
The diameter and depth/length of the counterbore is to be able to not interfere with the end of the rear end housing that sticks out past the dust shield / backing plate.
These are the measurements I still need before I can proceed to the 3D model and a print. Tooth depth/length, and how deep the counterbore goes Drawing is to scale, or at least within 3 SF
That 3 9/16" counterbore diameter comes from my 'notes' when I dimensioned them for the pic.The 'note' does not have a dimension for counterbore depth or for teeth.
But based on the pic, the counterbore depth appears to be 3/8 - 7/16 of the .580" thickness. The tooth (subtracting the 3 9/16 counterbore from the 4.245" diameter = .683" diameter difference = .342" radius difference ) appears to be about 3/8 of that .342".
My car is a 3 channel ABS only so I pulled the rings off axles and the 4 channel axles less the rings are useable in a 3 channel rear end. The rings are somewhere buried in the garage.
Ya, the unknown measurements I just kinda eyeballed, they aren't particularly to scale like the rest of it is, lol. But that measurement does make sense. I think I'll just buy one and do some measurements on the counterbore, they're only about 20 bucks from Summit: https://www.summitracing.com/parts/aly-11321
As the pic you posted in post #4 is showing rust starting to occur on the ID, steel. I'm assuming the Alloy USA 11321 part is also steel, plated to protect from the elements as it does sit at an unprotected area.
I see what you mean, now, I didn't notice that before. I believe you'r right about the Alloy USA wheel, then, they may have it zinc plated or something
Thanks for the confirmation, Chris!
I've got vacation coming up here in a couple weeks, once the dust has settled from that little trip I should be able to place the order for a 3D print.
Should be interesting. 47 teeth on the 13.336" circumference ( 4.245" diameter ) is a spacing of .284" for each tooth with an accompanying space. 51 teeth will equal a .262" spacing for each tooth with an accompanying space. Only a difference of .022", which is a .011" smaller tooth thickness. Should be adequate to properly trip the sensor.
I'm hoping so, if my math was right it would equate to rear tire height difference of about a millimeter. Tire pressure alone could create a change the slight
I'm wondering if this wouldn't also correct the speedometer deviation with running taller rears...
front to rear tire height distance is 2.17" difference and 51 teeth would be correct for that.
Speedometer is controlled by a reluctor and sensor in tranny tailshaft housing.
09-21-2019, 04:28 PM
Reluctor Wheel change, ABS/TC fix? 
