Thoughts On Tone Rings

SLO MO · Jan 28, 2003

I was thinking, this would be for aftermarket applications. If you increased the diameter of the tone rings incrementaly(sp) with the increase in tire size would they still read the same?
Say if you increased the diameter with the same number of teeth would they read just the same.
I did some calculations with machining equations to figure out the outside speed (SFM) of the tone rings at stock dia. with stock tires, and with larger tires and a larger tone ring.
I would think in theory that if you increased the dia of the tone ring that everything would read as stock?

Thinking out loud here, if anyone wants to add in feel free, or call me an idiot go ahead :grin: .

SLO

Timzjatl · Jan 28, 2003

Actually, since the tone rings count the teeth as they pass, you'd have to increase the number of teeth, therefore the ABS and speedometer would read correctly. Larger tires rotate fewer times per mile than stock, so you'd have to speed the rings up to compensate, hence more teeth
Tim

SLO MO · Jan 28, 2003

Doesn't the computer have to read a certain number of pulses though for its calculations?
It would be nice to figure out the mystery of tone rings :?

I'll keep racking my brain with ideas :gears:

SLO

Timzjatl · Jan 28, 2003

Yes, the computer does read a number of pulses, so you'd need more teeth, not necessarily a larger diameter ring. a larger ring with no change in the number of teeth would have no effect.
Tim

David Luckadoo · Jan 28, 2003

OK, here we go. Let's see if we can simplify this mysterious contraption.

The tone rings themselves are just a bunch of teeth on a metal sleeve. The magnetic pickup generates an electrical pulse each time a tooth passes by it. Therefore, more teeth equals more signal pulses.

Now that we know how we get a signal, what is it used for? It seems that it is used by both the ABS system and the speedo. These are two completely separate functions, with one exception listed below.

The speedo uses it to display the actual speed that the axle is traveling. And it only gets this info from ONE of the sensors on the rear axle. If you want the speedo to display accurate information then you need to increase the number of teeth on the tone ring to compensate for larger tires than stock size.

As for the ABS, it doesn't care if the signal it is receiving is accurate in regards to actual speed. It is in essence only looking at the differential speed between the wheels. There are a couple of other things in play though. The following conditions must be met before the ABS will activate:

* The vehicle must be traveling faster than 5 MPH(I'm not positive about this number, but I think it is correct. Also the ABS doesn't receive the absolute speed value, just a status flag from the speedo system that it is above 5 MPH )
* The brakes must be applied(This keeps it from activating if the wheel slippage is due to acceleration)
* The measured speed difference between wheels exceeds X %(I'm not sure what the actual threshold value is)

Hope this helps.

David Luckadoo

SLO MO · Jan 28, 2003

So what you're saying is I can make new bigger tone rings for the front to fit over manual hub spindles and the rear tone rings would need to have more teeth, correct?
If so, would it be just a guessing game as to how many teeth it needs to have? :idea:

chadjans · Jan 28, 2003

David Luckadoo said:
The speedo uses it to display the actual speed that the axle is traveling. And it only gets this info from ONE of the sensors on the rear axle.

Hope this helps.

David Luckadoo

So are you saying that after I put in the 8.8 axle of mine and get rid of the abs system from the rear axle the spedo won't work. I just thaought the spedo signal came from the t-case spedo gear....

Chad

SLO MO · Jan 28, 2003

chadjans said:
David Luckadoo said:

The speedo uses it to display the actual speed that the axle is traveling. And it only gets this info from ONE of the sensors on the rear axle.

Hope this helps.

David Luckadoo

Click to expand...

So are you saying that after I put in the 8.8 axle of mine and get rid of the abs system from the rear axle the spedo won't work. I just thaought the spedo signal came from the t-case spedo gear....

Chad

Chad, I think that the ZJ comes off the T-case but on the WJ everything runs from the tone rings.

prIapIsm · Jan 28, 2003

You can either keep the same diameter tone ring, and increase the number of teeth by the ratio of tyre sizes (so that the spacing decreases), or you can increase the diameter of the tone ring (by the same ratio as above), while keeping the same tooth spacing. Tim is right, you have to increase the number of teeth. So you can decide if you want to have them closer together on a smaller diameter, or further apart on a larger diameter. As long as the total number per revolution is increased by the ratio of tyre diameters.

SLO MO · Jan 28, 2003

prIapIsm said:
You can either keep the same diameter tone ring, and increase the number of teeth by the ratio of tyre sizes (so that the spacing decreases), or you can increase the diameter of the tone ring (by the same ratio as above), while keeping the same tooth spacing. Tim is right, you have to increase the number of teeth. So you can decide if you want to have them closer together on a smaller diameter, or further apart on a larger diameter. As long as the total number per revolution is increased by the ratio of tyre diameters.

Having a brain meltdown here at work :bang: . Henley, could you give an example of ratio of tyre size eg. from 29 to 35" tires?

prIapIsm · Jan 28, 2003

SLO MO said:
Having a brain meltdown here at work :bang: . Henley, could you give an example of ratio of tyre size eg. from 29 to 35" tires?

35/29 = 1.207

So unless you change things, your speedo will say you are going 20% slower than you actually are. Increasing the pulses from teeth by 20% will set that right.

prIapIsm · Jan 28, 2003

This article was quite nice

http://www.brakeandfrontend.com/bf/bf89920.htm

I know that the pulses depend on the speed that the tone rings are moving, and the induced EMF from the changing magnetic flux should increase as the speed goes up. But I was unsure as to whether the sensors were measuring the EMF (potential difference in volts, essentially), or just using the frequency from the spikes in the EMF. It makes sense that they would count spikes. In which case it should be easy to make some electronics that would generate perfect signals. You could even hook it up to your GPS to generate them if you like! It can even be done with a single magnetic pickup (like a bicycle speedometer), and anywhere you like, with electronics to create the pulses that the computer expects. Hmmmm. Tone rings are more likely to hold up to abuse over a long period of time, though.

SLO MO · Jan 28, 2003

Okay thanks. Just checked my calculations from the other night and I had 1.205 so I'm not far off the mark.
So, in theory, increasing by x number of teeth should get me to where I want to be.
I'll draw things up later and chime in with my results.
This might well be doable.

prIapIsm · Jan 28, 2003

You could machine up a few of those suckers and make a killing from all the lifted WJ owners, who desperately want to dump that rear axle!! :thumbsup: And the ones who want to rack up more miles than they are.

SLO MO · Jan 28, 2003

If it does in fact work out.... (Evil Voice)"I'll have the WJ world at their knees ha ha ha.... :lol:

Mike_Lib · Jan 28, 2003

Or, you could just buy a superlift truespeed ($150) and have an infinite amount of adjustability for tires from 20" to 66".

Keep in mind that if you change the outer diameter of the ring you'll need to reposition the sensors....and from what I've heard the sensors are very sensitive (no pun intended) to wrt their spacing from the ring.

SLO MO · Jan 28, 2003

Mike, is the Truspeed reliable though? Didn't yours just crap out? Was it covered under warranty. I was thinking if I just made new rings I could avoid the extra wiring of a Truspeed.
I will still need/want to put tone rings on the manual hubs so I will need to move the sensors anyhow.

Thanks everyone for your input, it is valued.
I will try and come up with something.

Mike_Lib · Jan 29, 2003

Yes, mine did crud out but it was replaced under warranty. I think the heat may have killed it since I mounted it too close to my block.

FYI - If you put tone rings on your stub shafts with manual hubs you won't get a reading while the hubs are unlocked. If you're totally set on keeping a signal up front then you'll have to adapt tone rings to the inside of your rotors and mount the sensor on the spindle. This is what dynatrac does to get a signal with manual hubs. I've got some pics in my temp folder in my sig.

Good luck

David Luckadoo · Jan 29, 2003

Mike_Lib said:
Keep in mind that if you change the outer diameter of the ring you'll need to reposition the sensors....and from what I've heard the sensors are very sensitive (no pun intended) to wrt their spacing from the ring.

The space between the tone ring and the magnetic pickup determines the voltage amplitude of the pulse(and to a lesser degree the waveform). The closer the two are the greater the voltage. So there is a limit to how far away the pickup is located. If you find that your new location isn't working due to the signal being below the threshold cutoff, you can swap in a different magnetic pickup with a higher sensitivity.

David Luckadoo

SLO MO · Jan 29, 2003

Actually Mike, I believe you posted those pics a couple of months ago and I saved them then. I've got a HP44 from a '78 Bronco I'm planning on retubing and using the knuckles and outers with manuals.
It was those pictures that gave me the inspiration to try this. And your rig of course.

Thoughts On Tone Rings

SLO MO

Timzjatl

SLO MO

Timzjatl

David Luckadoo

SLO MO

chadjans

SLO MO

prIapIsm

SLO MO

prIapIsm

prIapIsm

SLO MO

prIapIsm

SLO MO

Mike_Lib

SLO MO

Mike_Lib

David Luckadoo

SLO MO

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