magnet placement for probe

So I have a 2000 ford focus with drum brakes and I need to attach magnets for the odometer probe. Anyone have any suggestions on where I should place the magnets and sensor?

Thanks
Chris

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ChrisKobi
So I have a 2000 ford focus with drum brakes and I need to attach magnets for the odometer probe. Anyone have any suggestions on where I should place the magnets and sensor?

Thanks
Chris

Chris, you should have chosen an odo that uses proximity sensors.
Somebody has been leading you astray.

Magnets was ancient technology when I started 27 years ago.

I have no idea where to find, where to place 'em

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Yeah that's pretty ancient technology. I think we used to glue them with either marine tex or hi temp sillycone. Don't think either is reliable tho. Magnets worked ok on drivelines but brake drums have such a temperature change it makes it harder to stick stuff.

Do they even really use odos on stage nowadays?

Quote
heymagic
Yeah that's pretty ancient technology. I think we used to glue them with either marine tex or hi temp sillycone. Don't think either is reliable tho. Magnets worked ok on drivelines but brake drums have such a temperature change it makes it harder to stick stuff.

Do they even really use odos on stage nowadays?

No, cause they have their own 2 pass recce notes cause it's safer to have notes!!!!! but the boys still have to get between stages, that does make some guys really nervous when they've not been on the roads in an area...

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
john vanlandingham

Quote
heymagic
Yeah that's pretty ancient technology. I think we used to glue them with either marine tex or hi temp sillycone. Don't think either is reliable tho. Magnets worked ok on drivelines but brake drums have such a temperature change it makes it harder to stick stuff.

Do they even really use odos on stage nowadays?

No, cause they have their own 2 pass recce notes cause it's safer to have notes!!!!! but the boys still have to get between stages, that does make some guys really nervous when they've not been on the roads in an area...

Exactly...on transit the brakes shouldn't get as hot...tires shouldn't be spinning and even a stock odo can be made to work.

If you are still running route book you need some kind of odo on stage. Sometimes notes are .7 mile or more apart...

If you can't get a proximity probe to work with your rally odo, can you attach your magnet (s) just like you would if you were using proximity? Many people pull a signal off the back of wheel studs, normally non driven wheels. you could glue your magnets there. Or deal with wheel spin and attach at a safe place like at the tranny output.

A few thoughts:

1) The odo is only looking for a voltage spike (normally 5v) so the actual sender isn't proprietary (although you might have to play with the wiring a bit) What kind of ODO do you have?

2) Hall senders that are commonly used to look at the backsid of studs, etc, work on a magnetic principle. Using magnets as a trigger allows a looser tollerance from the sender to the trigger and a clearer signal.

3) While taking a signal off of a non-driven wheel is best, using driven wheels, or the factory speed sender works fine. The VSS signal usually reads before the final diff, so it averages out the wheelspin, and is a bit better of a signal source.
I've seen a number of people use magnets on the inboard end of a half-shaft with a great deal of success. They use a bolt on the transmission to mount the bracket and sender and duct-tape over the glued on magnets. The obvious drawback is you have to prepare your replacement axles with magnets as well. (And since it's FWD you will be changing axles all the time )

4) when reading off of a driven wheel you have to think about what's happening with wheelspin. While less than ideal for TSDs or running on sparse tulips, it's perfectly fine for rallying on pace notes. One of the first pieces of advice I was given was to figure out what the average 'wheelspin' percentage was and to either make a note of that somewhere in the car or to actually use a different odo calibration on stage.

5) An odo on stage with notes is good if the co-driver gets lost, or for making a note of where a competitor is stopped on stage, but have much more value on transits. If your car's factory odo still works - that's good as a back-up, or even a primary on transits. (if you've changed your final drive and your odo isn't accurate, figure out the correction factor for it and calculate the distance to all of the major insutructions.)

6) also, if your focus had the radio that changed volume with the speed - I believe you can use that wire for the odo signal.

---

First Rally: 2001
Driver (7), Co-Driver (44)
Drivers (16)
Clerk (10), Official (7), Volunteer (4)
Cars Built (1), Engines Built (0) Cages Built (0)
Last Updated, January 4, 2015

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john vanlandingham
Blame is for idiots. losers.

Quote
heymagic
Do they even really use odos on stage nowadays?

I did most of my rallying in a car with an unreliable or not working rally odo.
That said, when I've had one that was working, I used it and it was a valuable tool, if you had the right odo.

The Coralba is great as it tracks some good performance and can be 'programmed' somewhat. I can have it show elapsed time (good for marking split times if you have a history on the stage), distance from beginning, and distance to the finish (great to have at hand when you have a puncture) while on stage and set-up a button so when I cross the finish line it changes to TOD, elapsed time on stage and top speed or average speed. (top speed is an interesting one - I've often seen lower top speeds but faster stage times on the same stage) Then, on transits I can have it show ETA at the end of the transit at either current or average speed, current speed and distance from start.

There is a lot you can do with a working and calibrated odo but I wouldn't say you need one to rally, particularly on pace notes or jemba notes.

---

First Rally: 2001
Driver (7), Co-Driver (44)
Drivers (16)
Clerk (10), Official (7), Volunteer (4)
Cars Built (1), Engines Built (0) Cages Built (0)
Last Updated, January 4, 2015

Quote
john vanlandingham
Blame is for idiots. losers.

For the 2000 the Focus Ford already has the direct output unfiltered from the factory VSS in the dashboard running to the radio. I think it is a white wire with a green stripe if my memory is accurate, it is somewhat separate from the other radio harness wires. Why not use that it is easy to access, already basically in the correct location in the car, out of harms way, one less ting to fiddle with. I run the solid state box that terra trip sells between the computer and the factory harness to reduce the number of pulses the computer sees to keep it from clipping at higher speeds. I think a better computer would likely not have this issue. As Morrison said with the prevelance of pace notes it has been more than accurate enough.

Only thing to watch for on a Ford is if you update the harness/ ECU when they switched to CAN around '04 that wire becomes a digital CAN signal that will give some completely bizarre reading when trying to be interpreted by a rally odo. Since they did not change the sensor on the transmission you can still get the signal you just need to go just upstream of the ECU which is still down by the co-drivers legs.

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Andrew_Frick
I run the solid state box that terra trip sells between the computer and the factory harness to reduce the number of pulses the computer sees to keep it from clipping at higher speeds.

I've used both the Terratrip nad Brantz prescalers and teh Brantz is easier, by far, to set-up and works without problem. The Teratrip one was a pain - for me - and would 'go away' from time to time.
My Coralba simply hooked up and worked - no boxes, no fuss.

---

First Rally: 2001
Driver (7), Co-Driver (44)
Drivers (16)
Clerk (10), Official (7), Volunteer (4)
Cars Built (1), Engines Built (0) Cages Built (0)
Last Updated, January 4, 2015

Quote
john vanlandingham
Blame is for idiots. losers.

The odometer Is a Timewise, can't remember the model #, it actually belongs to RallyMech. It uses a magnetic probe. Haven't received the probe yet but was told that I needed 2 rare earth magnets to glue to whatever wheel, non drive, in the rear. I'm at work right now or I would look up the odo and info for you.

From what I see in the timewise manuals online you should be able to just use the factory VSS signal from the car. Both the 547B (page 49) and 798A (page 86) say they are looking for a 5v signal. You may need a pre-scaler as well.

---

First Rally: 2001
Driver (7), Co-Driver (44)
Drivers (16)
Clerk (10), Official (7), Volunteer (4)
Cars Built (1), Engines Built (0) Cages Built (0)
Last Updated, January 4, 2015

Quote
john vanlandingham
Blame is for idiots. losers.

You stupid fuckers are turning a perfectly simple question into a shit show. If can't or won't answer the question shut the fuck up.

Chris, you have three options:

1. Left rear wheel. Mount two magnets on opposite wheel studs. Bring the sensor through the backing plate. This can be a pain because you have to clear all the hardware inside.

2. Left rear wheel. Mount two magnets 180 degrees apart on the outside edge of the drum facing the backing plate. You can drill 1/16 deep pockets for the magnets to sit in. Mount the sensor in the backing plate.

3. Install 2 magnets 180 degrees apart on an inner CV joint. Make a little tab to hold the sensor. This method is not very accurate but it will work for your first rally or two.

If you need a real answer for a question just call or e-mail me.

---

Robert.

"You are way too normal to be on Rally Anarchy." Eddie Fiorelli.

Timewise is a good odo. I ran one in my focus off the stock speed sensor for about a year since the co-driver that was riding with me had one that he liked more than the terra trip I had wired up. I don't remember if we used the pre scaller or not for that computer.

And Robert, Wow. Your solutions are incredibly more complex and prone to failure than taking a wire that already has the signal you need in a form that your computer can likely interpret in the dash next to the computer. I find butt connectors much easier to install than rare earth magnets.

On my dirt bike, I glue the magnets with 5 minute epoxy. You can get nice magnets at Radio Shack. Tough to do on a drum brake I think...