Spare Tires & AWD

[rlhdweman]

It's also a good idea to turn off the traction control if it doesn't automatically do so if you have to put on a donut or tire different size than the rest. One car I had there was a wire with a quick disconnect that was wired through the spare, you had to disconnect this when removing the 'space saver spare' because the traction control did not have a switch to turn it off (1990 model year).

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[Nw_adventure]

Do we know what the largest / tallest spare that will fit on the Eco without removing the shark teeth safety thing ?

 

[paneubert]

That's a good question. When I got my flat in Death Valley, I threw the flat tire in the bed. The donut spare doesn't have a sensor. The dash kept warning me that I had zero psi in one tire until I got the flat repaired. I don't know what warning I would have gotten if the tire was nowhere near the truck, but probably the same signal as a broken TPMS sensor.

Most modern TPMS sensors are only activated for a short time when spinning at a certain speed. I'm guessing the sensor has an accelerometer or gyroscope or other way to know when it is spinning. It saves/extends the TPMS battery. This is why a lot of troubleshooting guides talk about the need to drive above XXX MPH for XXX time before the sensors will update the vehicle as to the actual pressure.

 

[Kenny]

Most modern TPMS sensors are only activated for a short time when spinning at a certain speed. I'm guessing the sensor has an accelerometer or gyroscope or other way to know when it is spinning. It saves/extends the TPMS battery. This is why a lot of troubleshooting guides talk about the need to drive above XXX MPH for XXX time before the sensors will update the vehicle as to the actual pressure.

Good to know, thanks. One other thing I learned on this trip is the TPMS sensors are very inaccurate. After setting all the tires to 35 psi using a high quality Milton air gauge, I was getting readings on the dash from 32-37 psi. Even the manual says not to rely on the TPMS display when airing up tires.

 

[My Maverick and Me]

So if I have a spare tire that is the same size and kind as the other four will my AWD work properly if I put it on the truck in place of one of the other tires?

What if it doesn't have a TPMS sender in it? Will the AWD turn off and be unusable?

Should I have a TPMS sensor in the spare along with the 4 regular tires? How does the system know which is the spare and the other 4 tires? Movement?

If the spare has a TPMS in it will the system read the spare tire TPMS once it starts moving on the vehicle or will it still be trying to read the vibrating flat tire in the bed of the truck?

My concern is not having AWD available after changing a flat out in the boonies. It doesn't make sense if it gets turned off when you need it most.

Any added info would be appreciated.

 

[Kenny]

So if I have a spare tire that is the same size and kind as the other four will my AWD work properly if I put it on the truck in place of one of the other tires?
What if it doesn't have a TPMS sender in it? Will the AWD turn off and be unusable?
Should I have a TPMS sensor in the spare along with the 4 regular tires? How does the system know which is the spare and the other 4 tires? Movement?
If the spare has a TPMS in it will the system read the spare tire TPMS once it starts moving on the vehicle or will it still be trying to read the vibrating flat tire in the bed of the truck?

NO it will not affect the AWD whatsoever if your spare is the same size as the other 4 tires, and NO you don't want a TPMS in your spare. When you get a flat and put it in the bed of the truck, the dash will warn you every time you start the vehicle that you have zero psi in one tire. You just have to push the [OK] button on the steering wheel to make the message go away. That warning is your reminder to get the spare fixed. I have no idea what would happen if you had 5 TPMS sensors all communicating to the dash, but you don't need to know.

 

[My Maverick and Me]

NO it will not affect the AWD whatsoever if your spare is the same size as the other 4 tires, and NO you don't want a TPMS in your spare. When you get a flat and put it in the bed of the truck, the dash will warn you every time you start the vehicle that you have zero psi in one tire. You just have to push the [OK] button on the steering wheel to make the message go away. That warning is your reminder to get the spare fixed. I have no idea what would happen if you had 5 TPMS sensors all communicating to the dash, but you don't need to know.

Thanks Kenny

 

[Shakesbear]

Do we know what the largest / tallest spare that will fit on the Eco without removing the shark teeth safety thing ?

Someone on another thread said he got a 245/70/17 in the spare tire spot with the teeth in place. Just had to reroute a few wires that were getting pinched. Running the smaller spare tire shouldn't have any real impact on your AWD truck as long as you use it for its intended purpose: get you to the nearest place to fix your flat or replace your full size tire That said, I will probably look into finding an inexpensive 235/65/17 tire to put on the spare rim.

 

[Kenny]

Someone on another thread said he got a 245/70/17 in the spare tire spot with the teeth in place. Just had to reroute a few wires that were getting pinched.

I saw that article. What I see under my truck is not just some wires to reroute but a very large connection block the size of a small brick that cannot be moved that I can see. It's on one side up against the frame. The teeth that are towards the front I can see can easily be bent further away and then the only limiting factor is the front of the trailer hitch. Maybe the wiring is different with different models, mine is the FX4 with 4K.

I bought a Pirelli Scorpion ATR 225/65R17 to match the original 4 wheels, mounted it to a steel rim and it fits easily. I will probably run these tires until I need new ones, then do the lift and buy 245/70R17 tires then. Not sure if I'll keep the 225/65R17 spare or try and fit a bigger tire in there too.

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