Staggered fitment fix

[GetMeMyStogie]

Well, not really a fix, but I had a thought about equalizing the size of the tires on an MM. It's probably been brought up before, but I don't recall reading about it since becoming a member here.

The ABS and traction control computers in the MM get their 'wheel rotation' signal from the sensors on each wheel. The sensors work by sensing the teeth of a small, toothed wheel (ring/crown) that spins with the wheel. The sensor produces a high signal as one tooth nears the 'pickup' followed by a low signal as the valley before the next tooth approaches (or vice-versa). So, as the wheel spins, the toothed ring also spins, which produces a series of high-low signals - basically a sine-wave, or square-wave - that the computer reads and interprets as a particular RPM.

Assuming that the number of teeth on each ring is the same at all 4 corners, the two rear wheels would produce slightly fewer pulses at a given forward speed than the front wheels, since the rear wheels turn slower to go the same distance. If this assumption is true, the computer must be looking for the front wheels to have a higher frequency than the rears (by the 3-6% margin we're well aware of).

The other option is that the frequencies produced by both front and rear wheels are the same. In order to do that, the rear wheels would have to have more teeth than the fronts, so that as they spin slower, they produce more pulses than the fronts. The computer then only has to look for the same frequencies from all 4 corners (give or take a small margin to account for varying tread depths, turns, etc.)

In the first case, if the same tire is run at all four corners, the rears would spin faster (than before) and the fronts would no longer produce the higher frequency the computers look for. The frequency of the signal coming from the rears has to be decreased (or the fronts increased). This could be done with a speed sensor ring with fewer teeth on the rear axles, or a set of front hubs with more teeth on their sensor rings.

In the latter case, the rears would again spin faster, this time resulting in a higher frequency than the fronts. The rear frequency again has to be decreased, or the fronts increased. The solution is the same as the previous case.

:confused:

In other words, it doesn't matter how the computer reads and interprets the signals, installing a speed sensor ring with fewer teeth on the rear axles, or front hubs with more teeth would allow us to run different tire sizes. The question is how many teeth would need to be removed (or added) to allow same size fronts and rears. The next question is did Ford make such things for the Panthers?

And if not, is there anyone out there who would be willing to produce them?

[Mike M]

Really?

The wheel/tires stagger are perfect in my world, one of the neater features of the car so I wouldn't want to change it.
I cant imagine anyone even thinking of producing another ring for our cars as the demand is not there...then again I couldn't imagine Obama winning again so what the hell do I know.

[screamn]

Would be nice to be able to rotate my tires from front to back and vice versa to get the most out of all of them.

Sounds like a good idea but the million dollar ? is will it work & what will it cost....

Only downfall....as stated by Mike M, "the demand is not there" and I have to agree.

[WhatsUpDOHC]

Would be nice to rotate tires.

[ChiTownMaraud3r]

If i'm not mistaken the speed sensor O ring is mounted at the back of the transmission/drive shaft? Not at each rear wheel..with that being said, I find it harder to find custom, other than OE-sized rings for replacement.

I would have liked to have an option in case tires become harder and harder to find. But I do love the staggered stance.

[MyBlackBeasts]

Well, if this was Class 8 all we'd do is change the tire size in the programming and then run any size we'd want. No ABS or traction control issues, working as designed.

Are you not able to do with a car??? :confused:

[ChiTownMaraud3r]

Well, if this was Class 8 all we'd do is change the tire size in the programming and then run any size we'd want. No ABS or traction control issues, working as designed.

Are you not able to do with a car??? :confused:

When I was running 17s on shorter tires, I tried changing my revs/mile on my xcal3 and the TC light still kicks on at 35mph. No go.

[EMAS]

The ABS doesn't care about the difference in the frequency between the front and rear sensors, it is concerned with the rate of change of the signals.

The traction control does compare the frequency of the front and rear sensors and does care about the difference. That difference is programmed into the ABS/TC computer.

That is why with the 300a car you can use tires with the same size front and rear. Of course you have to change the programmed tire diameter in the computer to keep the speedo reading properly and the transmission shifting at the correct point.

Lesser Panthers did use the same size tire front and rear so their ABS/TC computer is programmed for the appropriate frequencies between their sensors which read the same tone ring as our cars. So in theory you may be able to switch the ABS/TC computer with one from the same year CV or GM. The wiring diagrams I've compared show the basic systems to be to be the same except for a notation on a different connector for the traction active light in the instrument cluster.


Disclaimer I've not done this myself and although someone here has postulated that it would work in the past I've not seen a post confirming it.

You'd still need to reprogram the PCM with the correct tire diameter to correct the speedo and shift points.

[SC Cheesehead]

Just punch off the TC button when you start the car, and you're good to go.

I ran 245/55s on all four corners for a couple of years without problems doing the above, but ended up going back to the staggered set up with aftermarket replacement tires (OEM BFGs don't wear worth a crap, even when you rotate them).

[H_M_T_81]

Couldn't you just run front hubs from a MGM or CV??? Assuming it is the rings that are different and not just the programing
I personally hate the staggered tires on these things. Its a major pain to find a matching set of tires for a decent price and then you can't even rotate them so your expensive tires wear out twice as fast. Stupid design if you ask me.

[Mike M]

I like the fact that they are staggered, I want bigger tires in the back of my cars, I don't care to rotate. That's why you need a daily driver.

[Mike M]

I like the fact that they are staggered, I want bigger tires in the back of my cars, I don't care to rotate. That's why you need a daily driver.

Lots of cars can no longer be rotated.

[MyBlackBeasts]

Couldn't you just run front hubs from a MGM or CV??? Assuming it is the rings that are different and not just the programing
I personally hate the staggered tires on these things. Its a major pain to find a matching set of tires for a decent price and then you can't even rotate them so your expensive tires wear out twice as fast. Stupid design if you ask me.

Rings are same, just different programming.

These cars are all about looks & fun. :burnout:

Rotating tires is for the DD. Enjoy owning & driving a unique & beautiful ride! :beer:

[EMAS]

Couldn't you just run front hubs from a MGM or CV??? Assuming it is the rings that are different and not just the programing
I personally hate the staggered tires on these things. Its a major pain to find a matching set of tires for a decent price and then you can't even rotate them so your expensive tires wear out twice as fast. Stupid design if you ask me.

Tone wheels are the same for GM, CV, TC and Marauder, it's all in the programming.

[H_M_T_81]

Well can you re-program for the same size tires all the way around somehow?

[SC Cheesehead]

Well can you re-program for the same size tires all the way around somehow?


Don't think so, at least nobody's figured out how to do it over the last ten years.

[a_d_a_m]

All this time, I thought the traction control module on the Marauder was set to accept factory stagger, or the same size (235/50/18) all the way around.

I guess I'm still learning things about these cars.

FWIW, I love the stagger on my car!

[MMcactusflower]

A really interesting and informative discussion here...I have wondered about these same things.

[babbage]

Just punch off the TC button when you start the car, and you're good to go.




^^^ This.

OR perhaps If you have an 04 and want to run same tires around, SPLICE the front ABS wires, and feed those wires into the ones it thinks it getting from the rears. Of course traction control won't work nor will ABS.

I don't think its a good idea but might work.

[Rockettman]

I don't I get it!

When you can just turn off the T/C with a switch; why would someone want to disable a safety feature?

If you don't want it...hit the switch.
If it's raining or snowing...you have some security.

[ChiTownMaraud3r]

I don't I get it!

When you can just turn off the T/C with a switch; why would someone want to disable a safety feature?

If you don't want it...hit the switch.
If it's raining or snowing...you have some security.


If your rear tires aren't detected to be 3%-5% larger diameter than the fronts, the car activates the TC to limit wheel spin when hitting 35MPH. This literally keeps you from going faster than that speed.

It is very annoying having to turn off TC before driving off, but you eventually get used to it.

EDIT: Ah I see..he was talking about deactivating the ABS, LoL.

[Agent M79]

...ended up going back to the staggered set up with aftermarket replacement tires...

Tell which! The BFGs are killing me... then reviving me and killing me again.

[EMAS]

Well can you re-program for the same size tires all the way around somehow?

I don't think the TC module has flash memory, if it does I'm not aware of anyone even attempting to hack the code to come up with a new program. So the best bet would be to try a module from a lesser Panther of the same year which would be programmed for the same size tires.

[Green96]

See the last post for a parts list and schematic for an "automatic button pusher". I have been running it for a year and a half, no issues. Traction control is always off.

http://www.mercurymarauder.net/forums/showthread.php?t=74997&page=2

[GetMeMyStogie]

The ABS doesn't care about the difference in the frequency between the front and rear sensors, it is concerned with the rate of change of the signals.

The traction control does compare the frequency of the front and rear sensors and does care about the difference. That difference is programmed into the ABS/TC computer.


Ahh, my mistake. Then it's only the TC that causes the problem. Since the ABS looks for the rate of change of the signals, the specific signals do not matter, so changing the number of teeth on the tone rings should not affect ABS.

[GetMeMyStogie]

No, I wasn't talking about deactivating the ABS. I was talking about a way to make an MM with TC run with equal size tires all around, without having to disable the TC.

I wrongly assumed the ABS worked the same way as TC.

[GetMeMyStogie]

Well, after a bit of scrounging on the web, here's what I found:



The toothed ring I talked about is a called a "tone ring", as others have already mentioned.
A tone ring for a Ford 8.8" is 3.7" (diameter, I guess).
Ford produced 2 different tone rings for 8.8" rear ends - a 49 tooth, and a 50 tooth. It looks like the MM came with 49 tooth tone rings. Unfortunately, we need fewer teeth, not more teeth.
There are companies that produce custom tone rings, and the prices are reasonable (less than $100, I think).

So, in 1 km, with 245's, there would be (49*438=) 21,462 pulses, and that's what the TC computer needs to see. If you drop a 245/55/18 down to a 235/50/18, the wheel would rotate an additional 22 times per km (460/km for the 235 vs. 438/km for the 245). Therefore, 21,462 divided by 460 rotations of the smaller wheel equals a tone ring with.... 46.65 teeth. Hmm. Too bad it's not closer to an integer.


Repeating the process for another tire size, I'll start with another tire combination that produces the 5% difference, say way bigger: 400 rotations/km front and 380 rotations/km rear.

So, in 1km, with the given tires, the rear would generate (49*380=) 18,620 pulses, which is expected by the computer. If we equalize the tire sizes, we'd need a tone ring with (18,620 divided by 400 = ) 46.55 teeth.

Following through with much smaller tires, say 500 rotations/km fronts and 475 rotations/km rears, the rears would generate (49*475=) 23,275 pulses. That needs to be produced in 500 rotations after equalizing tire sizes, requiring a tone ring of... (23,275/500=) 46.55 teeth.


In my first calculation, I used 460 rotations/km for a 235/50/18 tire, and 438 rotations/km for 245/55/18. That's not exactly a 5% difference. But, in the following calculations, I used a difference of exactly 5%. If I repeat the initial calculation using a difference of exactly 5%, that is 460/km front and 437/km rears, I get the same result - 46.55 teeth.

95% of the 49 teeth on an MM tone ring is exactly 46.55 teeth. So, theoretically, a 46 or 47 tooth tone ring on the rear axles of an MM should allow you to run same size tires all around without deactivating traction control, and they could be any size you want.


FWIW, I like the staggered look too, a lot. But I hate the difficulty in finding tires.

[GetMeMyStogie]

Alternatively, an electronic circuit which reads the pulses from the rear sensors and drops every 20th pulse would also result in the correct number of pulses per km. It would be a lot easier and cheaper than getting custom tone rings installed. But, since the signal wouldn't be as steady, there's a chance one of the computers sees a problem and raises a fault.

I think this is worth a shot [leaves to search for his 555 timer circuit book...].

[EMAS]

Alternatively, an electronic circuit which reads the pulses from the rear sensors and drops every 20th pulse would also result in the correct number of pulses per km. It would be a lot easier and cheaper than getting custom tone rings installed. But, since the signal wouldn't be as steady, there's a chance one of the computers sees a problem and raises a fault.

I think this is worth a shot [leaves to search for his 555 timer circuit book...].

Yes that dropped pulse will cause problems and cause the traction control to activate once you reach a certain speed.

Years ago we had a Windstar that the transmission failed on. I called up my usual supplier and installed it my self. It did not work right so I called them up and they said bring it in. They replaced it. However who ever did it slightly smashed one of the teeth on one of the rings that is pressed on the axle shaft in that application. I went to pick it up and everything was fine until I hit about 55mph and then the traction control activated for a few seconds and then defaulted off and the light started flashing. They paid to take it to the Ford dealer who determined it was the slight dent in one of the teeth on the tone ring. It was enough shorter that it did not create a strong enough pulse.

As I said before the easy fix if you want to run the same diameter tires front and rear (within ~2%) is to get the ABS/Traction control module from a 03 or 04 CV or GM. Looking on car-part.com shows them as low as $25 plus shipping. One for $40 claims they drove the car and the lights were out.

[SC Cheesehead]

Tell which! The BFGs are killing me... then reviving me and killing me again.


Cooper makes a direct replacement tire for both front and rear (OEM sizes). I'm not running them, but from what I hear, they perform well.

I'm running 235/50 Nitto NT555s size in the front and 255/55 General Grabber UHPs in the rear and like the combination.

I got better mileage out of the first set of Grabbers, second set went on right before the Eaton swap and for some reason I'm not seeing the same tire life this time around... :dunno:

[ctrlraven]

Sorry but I have to LOL at this thread.

A much simpler way around a vehicle that has a select-able on/off Traction control system is just to wire up a relay system that will automatically turn the traction control off when the car has been started and the key is in the ON position. If you want to turn the traction control back on just press the button. Think of the relay as doing what you could just do with your finger every time you start the car but automatically, it will cost you a few bucks for supplies and a little time for labor.

Years ago I had to run 235/50-18 all around for a period of times when there were no stock size rear tires for sale, I just got into the habit when I start the car I turn T/C and O/D off since at half or more throttle or above 45 mph the T/C would kick in. To this day, I still turn those two things off after the car is started and before I put my seat belt on.

[EMAS]

Sorry but I have to LOL at this thread.

A much simpler way around a vehicle that has a select-able on/off Traction control system is just to wire up a relay system that will automatically turn the traction control off when the car has been started and the key is in the ON position. If you want to turn the traction control back on just press the button. Think of the relay as doing what you could just do with your finger every time you start the car but automatically, it will cost you a few bucks for supplies and a little time for labor.



Sure that will automatically turn off your TC so you can drive with tires w/o the proper stagger but if you want to run the same diameter tires front and rear and still have traction control then swapping in a CV/GM ABS module should make everything work as intended.

[GetMeMyStogie]

Sure that will automatically turn off your TC so you can drive with tires w/o the proper stagger but if you want to run the same diameter tires front and rear and still have traction control then swapping in a CV/GM ABS module should make everything work as intended.

Yes, like winter tires for example. Having to buy a 2nd set of staggered tires for the winter is a bit... ludicrous. And I'm not going to turn traction control off in the winter.

The TC computer... it's a separate module? I was under the impression it was a function built into the main PCM.

Since the missing pulse trick would likely cause other problems, and my electrical engineering prowess is actually pretty lame, replacing a module sounds like the best option so far :)

[EMAS]

Yes, like winter tires for example. Having to buy a 2nd set of staggered tires for the winter is a bit... ludicrous. And I'm not going to turn traction control off in the winter.

The TC computer... it's a separate module? I was under the impression it was a function built into the main PCM.

Since the missing pulse trick would likely cause other problems, and my electrical engineering prowess is actually pretty lame, replacing a module sounds like the best option so far :)

Yes the ABS/TC module is separate from the PCM though the ABS/TC module does tell the PCM when to cut power when the brakes alone can't stop the wheel spin. For $25 or $40 plus shipping and few minutes to swap it out it's certainly worth trying. As I said above I have not tried it , just verified that the wiring diagrams are one in the same with the notation about the Marauder instrument cluster being different than the GM and CV.

[Chevyguy]

I got some staggered Blizzak WS-70's on 17" LX sport rims for my 04 works peachy with the TC 215/60/17 front 235/65/17 rear. Would get 225/60/17 for the front if doing it again. Drives fine but they look really small compared to the rears.

Hardly any 18" snow tires which would fit, plus the stock rims are a bit valuable for winter driving

[ctrlraven]

I got some staggered Blizzak WS-70's on 17" LX sport rims for my 04 works peachy with the TC 215/60/17 front 235/65/17 rear. Would get 225/60/17 for the front if doing it again. Drives fine but they look really small compared to the rears.

Hardly any 18" snow tires which would fit, plus the stock rims are a bit valuable for winter driving
I just bought a set of Goodyear WRT winter tires 235/50-18 front and 255/55-18 rear. No snow yet but they have been great on dry pavement for a soft tread tire.

[GetMeMyStogie]

I just bought a set of Goodyear WRT winter tires 235/50-18 front and 255/55-18 rear. No snow yet but they have been great on dry pavement for a soft tread tire.


Guys, I think you're in the wrong thread. This thread is about turning an MM with traction control and staggered tires into an MM with traction control and 4 identical tires.