245/65R17 Tires On The Rear...

[Silver23]

My issue is that I've been around enough different worlds where theory pushers go on and on about things that don't actually manifest as an issue in the real world. I'm not saying that's the situation here, in fact that's the point, I'm looking for someone with actual real-world knowledge of it causing a problem, not just theoretical explanation for what could happen. I've had multiple AWD vehicles and have never rotated tires.... and never had an issue. So yeah, so far everything has been fine. But you might have noticed that I'm curious about this 1" different diameter issue, not ignoring that it could be a problem, and looking for some real-world feedback. I'm just not finding any of it.

this system is very sophisticated. Even though I don't THINK you will hurt it, I think you are playing with fire.
It seems the system would give an error and shut itself off when it detects a problem but at the same time you must remember it was engineered with the same size tires all around.
I guess you can tell us what if anything happens.....
Good luck.
https://www.google.com/search?q=how...&ie=UTF-8#kpvalbx=_z_TaZbK4HvzMkPIPsci72AE_26

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[Uhtred59]

Not sure I get your looking for real world data. It is possible your are the first one to think this might be a good idea, thus you are the test rabbit.

 

[Taildragger]

This thread is moving along exactly as I hoped it wouldn't, but people are people.

This article (with info directly form a Ford Engineer that worked on the Maverick AWD system) indicates that the AWD completely decouples the rear end when traction is good.
https://driving.ca/features/feature-story/deep-dive-2022-ford-mavericks-awd-system-explained

So it seems that the question here (which likely no one can answer) is do the tires being a slightly different size between front and rear prevent the AWD from decoupling when simply driving straight with good traction. If it does completely decouple, then it would seem that the small difference in size would have no affect for 95% or more of driving conditions.

The fact that at 41,000 miles my front tires were worn out, and the rear tires showed almost no wear at all would certainly indicate that the AWD Maverick does indeed function as a front wheel drive vehicle for the vast majority of its operation.

I don't say all this as evidence that I won't have problems with this new tire setup, but it does seem possible that it would not be a problem.

 

[gp1200x]

This article (with info directly form a Ford Engineer that worked on the Maverick AWD system) indicates that the AWD completely decouples the rear end when traction is good.

My AWD is almost always engaged whenever I start from a light....you can view it in the display showing your awd traction so you never know when it is truly going to engage versus no engagement...too many factors involved. He is probably right at a steady highway speed it is decoupled but for normal driving it is continuously cycling. Most all AWD systems and anti-lock brakes assume the same size tires front to rear unless the ECB/PCB is calibrated for staggered sizes. Maverick assumes all four tires the same size with rotation to minimize differences. An inch diameter is pretty significant.

 

[Taildragger]

This article (with info directly form a Ford Engineer that worked on the Maverick AWD system) indicates that the AWD completely decouples the rear end when traction is good.

My AWD is almost always engaged whenever I start from a light....you can view it in the display showing your awd traction so you never know when it is truly going to engage versus no engagement...too many factors involved. He is probably right at a steady highway speed it is decoupled but for normal driving it is continuously cycling. Most all AWD systems and anti-lock brakes assume the same size tires front to rear unless the ECB/PCB is calibrated for staggered sizes. Maverick assumes all four tires the same size with rotation to minimize differences. An inch diameter is pretty significant.

Turns out the difference in diameter between the 2 different sets of tires is measuring out at only 5/8", so it's looking like the risks are reduced quite a bit right there.

 

[40caliber]

Go big or go home!

 

[gp1200x]

Turns out the difference in diameter between the 2 different sets of tires is measuring out at only 5/8", so it's looking like the risks are reduced quite a bit right there.

I would be worried about the anti-lock braking if it tends to activate (pulse) at all on dry roads or lights up on the dash thinking there is a sensor issue. If it isn't sensing issues while braking then it's not enough to cause any mechanical issues with the braking. I had this issue on a Shelby when I went too far over the tolerance of the system with tire sizes....

 

[turbobill]

Turns out the difference in diameter between the 2 different sets of tires is measuring out at only 5/8", so it's looking like the risks are reduced quite a bit right there.

Measure the loaded radius. Then you'll know where you really stand.

 

[hdave]

I haven’t seen anyone else try this.
I know modern AWD systems are very temperamental. I was talking to a guy who was selling a single tire because his awd went haywire off two tires with vastly different tread amounts.

it’s an easy way to test if someone around you has a few hours to lend two wheels to test it out.

It will definitely be good for you (or someone) to test so we all know for sure and learn from this kind of test.

Glad you are ignoring the useless clowns in here who have a negative attitude towards everything.

 

[Taildragger]

Measure the loaded radius. Then you'll know where you really stand.

I'm away from the truck currently, but will check that later today

 

[Montana]

I haven’t seen anyone else try this.
I know modern AWD systems are very temperamental. I was talking to a guy who was selling a single tire because his awd went haywire off two tires with vastly different tread amounts.

it’s an easy way to test if someone around you has a few hours to lend two wheels to test it out.

It will definitely be good for you (or someone) to test so we all know for sure and learn from this kind of test.

Glad you are ignoring the useless clowns in here who have a negative attitude towards everything.

It's not a question of attitude. It's how the differentials spin when AWD is engaged. You do not have control over this. Any difference in size changes the ratio from front to rear.

The question has been answered indefinitely and it's very well known why not to do this. Op is just being stubborn and ignoring the information. Which is why I linked the most simplest form of an explanation I could find as to why different sizes are not a good idea in part time or full time AWD.

The answer would be the same on any AWD vehicle based forum. Even if OP had a FORD engineer directly tell him not to do it, he would go "people are just being people". You have not seen anyone try this because the information that exists explicitly says to avoid it or you will run into problems.

 

[Maverickman74]

Im not an engineer, and I did not stay in a holiday inn express lat night. I also love the look of a vehicle with fat rear tires. It just makes me feel good inside.

However, this will certainly play havoc on your wheel speed sensors duties. They have 2 jobs on a 2wd/hybrids the fronts control braking force and power output from the differential and on the rear its just the braking. On the AWD models it controls the individual braking force and power output of each wheel individually on the fly at the whims of how the computer interprets the input from the wheelspeed sensors. Yes the rear is solidly locked to the front like in a transfer case type vehicle. However the computer has parameters that dictate what it does with its abilities to keep your truck stable on the the road. If it senses the wheel speed differences are out of range it will want to send more power to the larger diameter tire and more braking force to the smaller diameter. If it does that your vehicle will lose control in certain situations. I believe it is smart enough to know something is not right. So instead of making your truck behave like a drift car, It will simply disable one or both of the safety programs that dictate braking force and power output at each individual wheel.

Basically it will reduce your ability to handle emergency braking situations, icy or very wet conditions, and offroad forward momentum. How much it hampers those programs is up for debate unless a Ford programmer chimes in here. But it will hamper them to some degree.

I will say that someone with programming ability and access to Fords computer designs could input the neccessary data to make it all play well. But you will still likely have premature wear one the power take-off units clutches.

Sorry.

Edit: get out the measuring tape and the air compressor and you could maybe get the circumference of the two tires to meet in the middle with air pressure.

 

[fossil]

guys, OPie has the idea locked in his brain and you should stop trying to beat it out of him.

providing he gets past the electronics the failure will be the PTU trying to reconcile the 2 different circumferences. when the slippage causes the clutches to fail he'll be in a FWD Maverick and blaming Ford.

 

[Bob The Builder]

That is so not a good idea to do.

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